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C.OFflUGHT DEPOSHi
PRACTICAL TANNING
PRACTICAL
TANN ING
A HANDBOOK OF MODERN PRACTICE
AND PROCESSES AS APPLIED IN THE
MANUFACTURE OF LEATHER
AND ALLIED PRODUCTS
BY
ALLEN ROGERS, Ph.D.
In charge of Industrial Chemistry and Leather Courses
at Pratt Institute, Brooklyn, N. T.
Partly Based on the Third Edition of "Practical Tanning,"
by Louis A. Flemming
ILLUSTRATED BY ONE HUNDRED AND TWENTY- FOUR
ENGRAVINGS
NEW YORK
HENRY CAREY BAIRD & CO., Inc.
Publishers of Mechanical and Industrial Books
2 West 45TH Street
1922
Copyright, 1Q22, by
HENRY CAREY BAIRD & CO., Inc.
PRINTED IN U. S. A.
APR 29 1922
'CU601479
P R E F ACE
In presenting this book on leather manufacture I have en-
deavored to Arrange the text with as little repetition as pos-
sible. The various processes have- been taken up in the order
of their sequence, and where the same procedure is carried
out for various classes I have attempted to point out the most
satisfactory method for each classification. For example, the
processes of depilation are included in one chapter, and
the various ways of accomplishing this end are thoroughly
discussed.
Being intended primarily for those interested in the actual
production of leather, this book deals with the subject from
the practical rather than from the theoretical standpoint, and
it is hoped that by following the instructions given the tanner
may find suggestions which will serve to improve his product
or assist him in producing new varieties of leather. Where it
has been found necessary to discuss the underlying scientific
principles, these are stated in as simple a manner as possible.
A chapter on analytical methods has been included, not only
for the benefit of the works chemist and student, but also
in order that the practical man in the plant may be able to
obtain some idea of the methods necessary for the chemical
control of the material he handles.
In addition to the common standard methods of tanning,
a number of unusual processes are given, as well as descrip-
tions of some of the more recent products which have been
introduced as a substitute for the ordinary materials employed
in leather manufacture.
Much of the matter herein has been taken from the previous
volumes of "Practical Tanning," by Louis A. Flemming, and,
in addition, many processes have been included as a result
of my personal experience. In many instances also, material
viii PREFACE
has been drawn from trade papers and technical journals, as
well as from notes furnished by men who are well known in
the industry. In presenting this material it is desired to give
full credit to these sources of information, which will be found
in the text.
In a book of this character, covering so wide a range of
methods, there are always points where a difference of opin-
ion may exist, and it is hoped, therefore, that wherever this
occurs, the reader will feel at liberty to communicate with me,
as any constructive criticism will always be greatly appreciated.
Allen Rogers
Pratt Institute,
Brooklyn, N. Y.
April 10, 1922.
CONTENTS
Chapter I
HIDES AND SKINS ! - 55
Classification of pelts. Dry or flint hides. Dry-salted hides.
Green-salted hides. Salt stains. Packer hides. Stuck-throats.
Cut-throats. Flaying. Curing. Taking-up hides. Sweep tare.
Grubs. Grub allowance. Hide selections— Native steers: Spready
hides: Texas steers: Colorado steers: Cowhides: Bull hides: Coun-
try hides. Kips. South American hides. Anglo-American hides.
Swiss and Bavarian hides. Calfskins. Horsehides. Goatskins-
Curing: Spanish goatskins: German goatskins: Italian goatskins:
Southern Europe goatskins: Turkish goatskins: Russian goatskins:
North African goatskins: South African goatskins: Arabian goat-
skins: Indian goatskins: Chinese goatskins. South American goat-
skins. Hogskins. Sheepskins— Sheep kids: Sheep ticks: Lice: Fly-
blow. Other hides and skins. Disinfection of hides. Regulations
of the U. S. Government. Hide structure. Conservation of skin
substance — Zinc chloride: Formaldehyde.
Chapter II
SOAKING S6_7 °
Fresh or market hides. Green-salted hides. Dry-salted hides.
Dry hides— Stocks: Fleshing: Putrid soaks: Chemical soaks: Pad-
dle soaking. Kips. Calfskins— Green-salted skins: Dry skins.
Sheepskins— Fresh skins: Dry skins: Green-salted sheepskins: Dry
sheepskins. Goatskins— Dried skins: Dry-salted sk:ns: Sodium
bisulphite. Kangaroo skins— Soaking and softening. Pigskins-
Washing: De-greasing: Krouse process. Furs and hairskins.
Formaldehyde raw stock.
Chapter III
DEPUTATION 71 " 109
Sweating— Cold sweat: Warm sweat. Liming— Quicklime: Hy-
drated lime. Sodium sulphide. Arsenic sulphide. Caustic soda.
Calcium sulphydrate. Arazym. Unhairing. Methods of depila-
tion. Liming hides for upper leather— First day: Second day:
Third day: Fourth day: Fifth day: Sixth day. Sodium sulphide
process for dry hides. Notes on beam-house work — Arsenic sul-
phide. Liming for thin grain. Liming for sole leather. Sulphide
process for sides, kips, or calf — Sodium sulphide and calcium chloride
on sides and kips. Liming of calfskins. Lime and arsenic. Liming
x CONTENTS
of goatskins — Combination process. Depilatory compounds for wool
skins and hairskins. Depilating glove leather. Patented depila-
tories — Depilatory paints: Applying the depilatory paint. Liming
after removal of the wool. Liming for Mocha and castor gloves.
Method of using arazym on goatskins — Soaking: First day: Third
day: Fourth day: First liquor: Second liquor: Fifth day.
Chapter IV
DE-LIMING, DRENCHING, BATING, PUERING AND
PICKLING . . ' 110-133
De-liming — Test for de-liming: Sulphuric acid: Hydrochloric acid:
Sulphurous acid: Sodium bisulphate: Boracic acid: Carbonic acid:
Lactic acid: Formic acid: Formic acid and lactic acid drench:
Butyric acid: Ammonium chloride: Ammonium butyrate: Sodium
dichromate: Sodium bisulphite: Ammonium phosphate: Zinc sul-
phate: Coal-tar bates. Drenching — Method of de-liming (drench-
ing) with bran: Other bran drench ' formulas: Mild fermented
drench. Puering and bating — Bating with molasses: Bating with
glucose, sulphur, and yeast: Dog dung: Hen manure: Dermiforma:
Dr. Rohm's bate "oropon C" for regular packs: Bating process:
Dr. Rohm's bate "oropon AB" for limed goatskins: Bating, first
liquor: Temperature: Second liquor: Quantity of oropon for 100
lb. of skins: Temperature: Martin Dennis' "puerine": First pack:
Second pack: Third pack: Fourth and all following packs: Puerine
D. Pickling — Sulphuric acid and salt: Formic acid and salt: Hydro-
chloric acid and calcium chloride. Pressing grease from pickled
sheepskins — Gargoyle de-greasing fluid. De-greasing fluid — Recov-
ered grease. Splitting out of lime. Splitting out of aluminum
sulphate and salt pickle. Splitting after tanning. Splitting out of
acid pickle.
Chapter V
RAW HIDES: OIL AND ALUM TANNAGE .... 134-157
Raw hide. Lace leather — Shark-liver oil tannage: Latigo leather:
Alum-tanned lace leather No. 1: Alum tannage No. 2: Alum tannage
No. 3: Picker leather: Pyro tan. Chamois leather — Bleaching.
Rogers' shark-liver oil process. Sheepskin fleshers — Imitation
castor. White calfskin leather — Tannage: Fat-liquoring: Finishing:
Formaldehyde tannage: Kid glove leather. White pigskins. Tan-
ning snake skins with alum and salt. White splits. Splits for
white shoes. Tanning buckskins. White buckskin. Indian method
of tanning buckskins. Tanning with formaldehyde.
Chapter VI
CHROME TANNAGE 158-213
Two-bath chrome process. One-bath chrome process. Glazed kid
manufacture. Two-bath chrome on pickled sheepskins — Sodium
thiosulphate bath: Neutralizing. Tanolin. One-bath chrome on
CONTENTS xi
pickled sheepskins — Process for glove leather. Neutralizing and
washing chrome sheepskins. White chrome-tanned sheepskins —
Tanning' in a paddle-vat: Process of alum and chrome tanning.
New two-bath process of chrome tanning — Neutralizing and wash-
ing the tanned leather: Neutralizing with borax. Notes and sugges-
tions. Difference between one-bath and two-bath chrome-tanned
leathers. Chrome-tanned side leather — One-bath chrome process for
acid-pickled stock: Prqcess for alumina-pickled grains: Process for
unsplit sides: Neutralizing and washing. Chrome side glove and
mitten leather. Chrome-tanned sole leather — Soaking: Liming:
De-liming: Pickling: Tanning: Other tanning processes. Chrome-
tanned harness leather — Liming: Bating: Pickling: Tanning: Re-
tanning. Chrome-tanned belt and strap leathers — Strap leather.
White side leather — Treatment with flour: Finishing: Tanning with
aluminum sulphate: Fat-liquoring with acid fat-liquor: Finishing.
Chrome velvet leather. Chrome-tanned patent leather — Coloring
and fat-liquoring: Staking and finishing. White chrome. Tanolin
T — Pickling: First pack: Second pack: Third, fourth, fifth and
sixth packs: Seventh, eighth, ninth, tenth, eleventh and twelfth
packs: Tanning: First pack; Second pack: Third, fourth, fifth, sixth
and seventh packs: Eighth, ninth and tenth packs: Dissolving
. tanolin T: Neutralizing and washing. To increase suppleness.
Dissolving chrome-alum. Aluminum bisulphite reduction. Re-
covery of chrome residues. Chrome-tanned buckskin — White
chrome buckskin. One-bath chrome tannages. Theory of chrome
tanning. Calfskin glove and mitten leathers. Chrome lace leather.
Semi-chrome leather — Splitting and shaving: Stripping the tannage.
Vegechrome — Pickling: First pack: Second pack: Third, fourth,
fifth and sixth packs: Seventh, eighth, ninth, tenth, eleventh and
twelfth packs: Tanning— First pack: Second pack: Third, fourth,
fifth, sixth and seventh packs: Eighth, ninth and tenth packs:
Dissolving vegechrome: Neutralizing and washing. Chrome-tanned
wax calf leather— Re-tanning. Intestinal leather — Parchment-like
skin. Leather for organ pipes.
Chapter VII
IRON TANNAGE 214-224
Research in iron tannage.
Chapter VIII
VEGETABLE-TANNED LIGHT LEATHERS .... 225-262
Vegetable-tanned sheepskins — Quebracho tannage: Hemlock and
quebracho tannage: Hemlock tannage: Combination tannage:
Sumac tannage: Tanning with alum, sumac, and oak bark: Tanning
with chestnut' extract: Tanning with sumac, alum, and salt: Que-
bracho-tanned sheepskins. Skivers. Roller leather. Calfskin
leather — Quebracho tannage: Gambier tannage: Dongola tannage.
Velvet and suede leathers. Russia calf — Bleaching: Re-tanning with
quebracho: Drumming with sumac. Vegetable-tanned kangaroo
xii CONTENTS
leather — Quebracho extract tannage: Gambier and sumac tannage:
Other tannages. Vegetable-tanned side leather — Tanning with
hemlock and quebracho extracts: Tanning with qucbracbo extract:
Tanning with gambier, sumac, and oak extract: Tanning with
gambier: Combination process: Pressing and splitting. Re-tanning
with gambier and sumac — Re-tanning grains with sumac. Tanning
sealskins — Levant grain: Walrus grain seal: Tanning the splits:
Directions for finishing: Treatment for split linings. Tanning pig-
skins — Tanning with sumac, oak bark, and alum. Tanning snake
skins. Fancy leather calfskins. Combined vegetable and mineral
tannage. Vegetable-tanned patent shoe tipping — Another re-tanning
process.
Chapter IX
VEGETABLE-TANNED SOLE LEATHERS 263-291
Rapid tanning processes. Oak leather. Non-acid hemlock tanning.
Acid hemlock leather. Union leather — Extracting: bleaching.
Rapid sole leather tannage — Tanning with chestnut extract. Drum
tanning for sole and belting leathers.
Chapter X •
BELTING LEATHER 292-317
Necessary characteristics. Leathers used in belting — Raw ma-
terial. Manufacturing processes. Tanning agents. Practical con-
siderations. Tanning of belting leather — Rockers: Handlers: Lay-
aways: Bleaching: Oiling: Drying. Currying — Scouring: Skiving:
Hand stuffing: Wheel stuffing: Hot stuffing: Stretching.
Chapter XI
STRAP, WELTING, BAG, CASE, AUTOMOBILE, AND
HARNESS LEATHER 318-340
Strap leather — Stock: Soaking: Depilating: Unhairing: Bating:
Washing: Rockers or stick pits: Splitting: Layaways: Bleaching:
Re-tanning: Stuffing: Setting: Tacking: Whitening and snuffing:
Finishing. Goodyear welting — Tannage. Bag and case leathers —
Tanning. Vegetable-tanned splits — Softening and stuffing, heavy
splits: Stuffing for wax splits. Harness leather. Good color on
heavily stuffed leather. Automobile leather — Tanning: Finishing.
Chapter XII
PATENT LEATHER 341-351
Patent leather 1 — Linseed oil: Turpentine: Naphtha: Soluble or
nitrated cotton: Lampblack: Chinese blue: Prussian blue: Umber:
Litharge: Spirit black. Boiling the oil for the daub coat — Varnish:
Application of compositions to leather.
CONTENTS siii
Chapter XIII
DYEING LEATHER 352-418
Classification of dyestuffs. Natural organic dyestuffs — Indigo: Log-
wood: Brazil wood, peach wood, and Japan wood: Fustic: Osage
orange: Cutch. Mineral dyestuffs. Artificial organic dyestuffs —
Basic colors: Acid colors: Direct colors: Alizarine colors: Devel-
oped colors. Dissolving dyestuffs. Preparatory treatment before
dyeing vegetable-tanned skins. Dyeing vegetable-tanned leather —
Brush dyeing: Tray dyeing: Drum dyeing: Paddle dyeing. Dyeing
chrome-tanned leathers — Black on chrome leather: Dyes for
chrome-tanned calfskins. Coloring alum-tanned leather. Methods
of coloring chrome-tanned sheepskins — Coloring with acid dye-
stuffs: Coloring with basic dyestuffs: Gambier mordant: Fustic or
osage orange mordant: Sumac and titanium-potassium oxalate:
Combined dyeing process: Dyeing light shades- with acid dyestuffs:
Dyeing with direct colors: Acid colors and sodium bisulphate:
Coloring with phosphine dyestuff: Fustic and logwood bottom:
Sumac and acid color mordant: 'Practical formulas for popular
shades: Coloring after fat-liquoring: Flesh-finished chrome sheep-
skins: Coloring chrome-tanned sheepskins after fat-liquoring and
drying out: Blacking with hematin and direct chrome black: Black-
• ing with logwood and titanium-potassium oxalate: Blacking with
direct chrome black. Methods of dyeing vegetable-tanned skins —
Blacking vegetable-tanned skins: Dyeing with acid and basic dye-
stuffs: Coloring with- artificial dyestuffs: Ox-blood shade: Brown
shades: Dyeing with fancy effects: Marbled effects: Spray dyeing:
• Antique leather: Bronze dyeings (dyeings with metallic luster).
Coloring and finishing India-tanned skins — Washing: Re-tanning
with sumac: Coloring the skins: Dyeing the skins black: Ooze
leather. Coloring chamois leather. Dyeing chrome-tanned calf-
skins blaok — 1. Dyeing with logwood and direct leather black:
2. Dyeing with logwood, leather black' and titanium salt: 3. Dyeing
with acid-blacks. Coloring chrome-tanned calfskins. Dyeing vege-
table-tanned calfskins black — Logwood liquor: Dyeing with direct
leather blacks. Coloring vegetable-tanned calfskins. Coloring
velvet or suede leathers. Notes on ooze calf and Russia chrome
leathers. Dyeing chrome-tanned goatskins — Dyeing with acid
colors: Dyeing with basic colors: Sumac mordant for basic and
acid dyes: Gambier mordant for tan shades: Process for tan and
brown shades: Clearing the grain of grease: Dyeing with fustic
extract and direct or anthracene colors: Use of tartar emetic.
Notes and suggestions. Coloring with natural dyestuffs — Light
tan shade: Dark tan shade: Ox-blood shade: Chocolate shade.
Dyeing chrome-tanned goatskins black — Dyeing with hematin crys-
tals or logwood and direct leather black: Dyeing with logwood,
leather black, and titanium-potassium oxalate: Dyeing with chrome
leather black: Another method of direct blacking: Blacking with
logwood and iron liquor: Dyeing with logwood, potassium per-
manganate, and iron liquor. Dyeing chrome kangaroo black —
Yellow flesh and black grain. Chrome-tanned ooze calfskins.
Chrome bag and belt leathers. Dyeing chrome side leather — Direct
xiv CONTENTS
dyeing with acid colors: Tannin mordant for basic dyestuffs: Red-
brown shade. Dyeing chrome side leather black — Yellow leather.
Coloring vegetable-tanned upper leather. Dyeing sealskins — Black-
ing. Dyeing pigskins. Process for producing marbled suede,
leather. Pigment finish — Mill coloring: The finish: Hand season-
ing: Machine seasoning: Full grain finish. Blacking and stuffing
chrome harness leather — Finishing.
Chapter XIV
FAT-LIQUORING 419-446
Fat-liquoring process — Fat-liquors for chrome-tanned sheepskins:
Fat-liquoring chrome-tanned calfskins. Oiling the leather. Fat-
liquoring chrome-tanned kangaroo — Applying the fat-liquor. Fat-
liquors for chrome side leather. Fat-liquoring vegetable-tanned
side leathers — Fat-liquor formulas. Fat-liquoring vegetable-tanned
calfskins — Sulphonated oils: Casein: Egg-yolk: Potash soaps: Fig
soap. How to make and use sulphonated oils. Sulphonated oil
on chrome leather. Sulphonated oil on vegetable-tanned leather.
Sulphonated oil on sole leather. Castor-oil soap. Potash soap.
Oiling chrome leather. Waterproof filling for sole leather. Stuffiing
chrome lace leather.
Chapter XV
FINISHING LEATHER • . . . 447-500
Setting-out: Drying: Dampening: Staking: Buffing: Tacking: Strip-
ping: Seasoning: Rolling: Glazing: Ironing: Embossing: Boarding:
Measuring: Sorting. Finishing chrome-tanned sheepskins — Black
glazed finish: Seasoning for dull finish: Seasoning for colored
sheepskins: Finish for embossed sheepskins: Finish for black
embossed sheepskins: De-greasing sheepskins. Finish for India-
tanned leather — Black glazed finish: Smooth dull finish: Finish for
colored skins: Re-tanning with chrome liquor: Morocco finish:
Crushed levant grain: Ooze or suede leather. Finishing skivers.
Seasoning for chrome calfskins — Bright finish, smooth or boarded:
Glazed finish: Seasoning for black-glazed finish: Boarded or box
finish: Smooth dull finish: Seasoning for black dull finish: Gun-metal
finish. Finishing chrome goat leather — Clearing the grain from
grease: Blacking defective spots: Black glaze finish: Seasoning for
colored leather: Dull finish. Finish for kangaroo leather. Finishing
chrome side leather — Dull finish: Glazed finish: Boarded finish:
Gun-metal finish: Storm-grain leather: Finish for colored leather:
Heavy chrome grain leather: Black chrome oil grain leather:
Leather for sporting goods. Finishing vegetable-tanned grains
into black leather — Finish for bright boarded grain leather. Finish-
ing rough leather. Finishing imperfect grains into patent tipping.
Dressing for leather goods and furniture. Removing spots and
stains from leather. Bright blacking varnish for shoe leather.
A Waterproof leather dressing. A harness blacking. Blacking for
vegetable-tanned leather. Sigs for greasy leather. Finishing splits
— Chrome-tanned splits: Finish for the black: Soap black: Flour
CONTENTS xv
paste: Finishing splits into Goody ears, chair splits, etc.: Grain
leather from splits. Materials used in finishing leather — Blood:
Blood albumen: Egg albumen: Gelatine and glue: Gelatine: Glue:
Isinglass: Casein: Irish moss: Algin: Shellac: Button lac: Pyroxylin.
Chapter XVI
WOOLSKINS AND FURS . . . 501-524
Tanning woolskins — Soaking, washing and scouring: Liming: Tan-
ning: Bleaching: De-greasing: Tanning with formaldehyde: Tan-
ning with a mineral and vegetable tannage: Tanning with gambier:
Tanning with alum, salt and hemlock extract: Coloring: Dyeing.
Tanning furs and hair skins. Washmg greasy skins. Oil process.
Oiling alum-tanned skins. Deodorizing furs and rugs — Cleaning
furs: Liming. Chrome-tanned furs and woolskins. Tanning hair
skins with alum and gambier. Cleaning white fur rugs— Bleaching
skins with the hair on. Dyeing China goatskins black. Dyeing furs
with acid colors — Re-tannage: Chlorinating the furs: Dyeing. Dye-
ing with chromate colors. Dyeing furs black with furrol dyes —
Preparation of the skins: 1. Drum killing with soda solution: 2.
Drum killing with milk of lime: 3. Drum killing with caustic soda
lye: 4. Brush killing with caustic soda lye: Mordanting the furs:
Dyeing black: Raccoon (imitation skunk): Lambskins: Red-haired
fox: Seal rabbit (English imitation of seal). Tanning for robes,
coats, etc. — Alum and salt process: Softening and cleaning the
stock.
Chapter XVII
VEGETABLE TANNING MATERIALS 525-557
Grinding: Cone mill: Disc chipper: Secondary reduction. Leaching
— Sprinkler leaches: Autoclave system. Clarification. Concentra-
tion. Chestnut wood. Oak wood. Barks — Chestnut bark: Oak
bark: Hemlock bark. Quebracho. Valonia. Mangrove bark. Gall
nuts. Sumac (rhus coriaria) — Mascolino: Rhus Glabra: Rhus
Typhina. Gambier. Myrabolans. Divi-divi. Algarrobilla. Mimosa
bark. Wattle bark. Palmetto. Sulphite cellulose extract.
Chapter XVIII
SYNTHETIC TANNING MATERIALS 558-566
Chapter XIX
UNUSUAL TANNING PROCESSES 567-577
Electric tanning. Vacuum tanning. Seymour- Jones method.
Organ leather. Leather for player-pianos — Pneumatic pouches:
Substitutes. Shark-skin leather — Catching and handling: Treatment
of skins. Porpoise leather.
xvi CONTENTS
Chapter XX
ARTIFICIAL LEATHER, DOPE SPLITS, AND
PYROXYLIN FINISHES 578-584
Pyroxylin — Solvents: Procedure: Acid formula. Coating real
leather.
Chapter XXI
ANALYTICAL METHODS 585-664
Water analysis — Total solids: Ash: Organic matter: Sulphates:
Chlorides: Iron: Temporary hardness: Permanent hardness: Mag-
nesia hardness: Free carbonic acid: Alkaline carbonates. Soaks
— Stiasny's method. Lime — Available lime: Iron, calcium, and mag-
nesium: Alkalinity of saturated solution. Sodium sulphide —
Na 2 S.9H 2 0: Total alkalinity and NaOH in the Na 2 S. Analysis of
arsenic sulphide — Arsenic: Sulphide sulphur (Procter's method).
Lime liquors — Soluble lime and hide substance: Available lime and
CaC0 3 : Hide substance continued: Kjeldahl method for hide sub-
stance. Sulphide lime liquors — Sodium sulphide: Soluble lime and
hide substance: Available lime and CaCOs. De-liming test. Salt
— Calcium oxide (CaO): Sulphates (SO s ). Aluminum sulphate —
Aluminum oxide (A1 2 3 ) : Total sulphuric acid (H2SO1): Free
sulphuric acid (H2SO4) : Ferric oxide (Fe^0 3 ). Pickle — Sulphuric
acid: Sodium chloride. Formaldehyde — Romijn's method. Two-
bath chrome liquors — Determination of Cr as Cr 2 3 , Na 2 Cr 2 7 , or
NaaCrd: Acidity: (a) Assume bath is all Na 2 Cr 2 7 : Strength: (b)
Assume bath is a mixture of Na 2 Cr 2 7 and Na 2 Cr0 4 : Strength:
(c) Assume bath is all H 2 Cr 2 7 : Strength: (d) Assume bath is a
mixture of H 2 Cr 2 7 and Na 2 Cr 2 07: Strength: (e) When bath con-
tains free acid (HC1 or H 2 S0 4 ) : Strength: Na 2 S 2 3 in hypo bath:
Second bath when made up of NaHSOs. One-bath chrome liquor
— 1. Determination of chromium: (a) Determination of Cr in new
or spent liquor: Strength: (b) Determination of Cr in stock liquor:
Strength: (c) Determination of basicity for diluted chrome liquors:
(d) Determination of basicity of stock liquor: Strength: 2. Use of
above results to obtain correct basicity of one-bath chrome liquors:
(a) Assume the analysis shows the ratio to be 52:83.2: Surama r y:
(b) Assume the ratio is below 80, say 69:16: Summary. Vegetable
tanning materials — Unextracted materials: Extracts: Tan liquors.
Official method of the American Leather Chemists' Association for
the analysis of vegetable materials containing tannin. I. Raw and
spent materials — (1) Caution: (2) Preparation of sample: (3) Water
determination: (4) Amount of sample to be extracted: (5) Extrac-
tion: (6) Analysis. II. Analysis of extract — (7) Amount and di-
lution for analysis: (8) Total solids: (9) Water: (10) Soluble
solids: (11) Insolubles: (12) Non-tannins: (13) Tannin. III. Analy-
sis of liquor — (14) Dilution: (15) Total solids: (16) Soluble solids:
(17) Insolubles: (18) Non-tannins. IV. Temperature, evaporation
and drying, dishes — (19) Temperature, (20) Evaporation: (21)
Dishes. V. Determination of total acidity of liquors — (22) Re-
agents. VI. General. Official method for sampling tanning materials
CONTENTS xvh
—General- (1) Solid, powdered and pasty extracts: (2) Liquid- ex-
tractni barrels: (3) Liquid extract in bulk: (4) Liquid extract m
ank-cars: (5) Crude tanning materials (6) Spent materials from
1 u c n\ Tormina- liauors. Official method tor analysis oi
^ble-^ S^ Q ?1) Preparation of sample: (2) Moisture:
H) Fats: (4) Ash: (5) Water-soluble material: (6) Glucose solu-
ions-Copper sulphate: Alkaline tartrate *°^J£?^
acetate solution. Determination. Munson and Walker s table
( N Log en. Reagents-Standard acid solutions: Standard alkali
o Lion: Sulphuric acid: Sodium hydroxide solution: Jotassium
sulphate: Indicator. Determination. Chrome-tanned l^'-**;
Free sulphur: Ash: Chromium: Complete analysis: Water: Ash.
Chromium and aluminum: Fat and sulphur. Water solubles-
TarTns- Sugar: Sulphates: Chlorides: Barium. Water msolubles
-Sulphates- Barium and lead: Alkaline salts: Total so luble sul-
phats Alkaline sulphates: Hide substance. Provisional method
for the analysis of chrome leather-Chrome determination. Pro-
visional method for sulphonated oils-Moisture: Ash: Non-sapom-
fiable Combined SO s : Total fatty oil. Provisional method for
anaWsis of moellons-Moisture: Ash: Unsapomfiable: Oxidized
f£tv acids- Free fatty acids. Provisional method for analysis of
hard grea es-Titer twt; Unsaponifiable: Free fatty acids., Provi-
sional method for analysis of lactic acid-Free sulphuric acid:
VoStile acid. Table showing the relation of amounts of volatile
acid found in distillate obtained under standard conditions to the
amounts actually present in distilling flask in *f^^°™
distillation: Two distillations: Free acid and anhydude Official
form for report on extract analysis. Sulphuric acid in leather-
Procter and Searle method: Balland and Maljean method: Jeans
method Soap analysis-Water: Fatty acids: Total alkali: Insoluble
S alcohol: Free sodium hydroxide: Free oil. Oils. (A) Lubricating
oil-Soap: Rosin oil: Saponifiable oil (qualitative test): Unsapom-
fiables: Specific gravity: Cold test: Cloud test: Viscosity: Total
acidity Mineral acids: Flash-point: Burning point: Loss on evap-
oration and tendency to gum: Suspended matter: Anti-fluorescents.
(B) Oil numbers for other than petroleum and lubricating oils-
odine number: Method: Helmer number: Reichert Meissl number:
Maumene number: Acetyl number: Titer test: Acid number: E ster
number: Polenske number. Analysis of titanium-potassium oxalate
OTiCu)-Aluminum: Iron and titanium: Oxalate: Ash: Potassium.
Analysis of blood albumen-Water: Ash: Inso uble matter: Non-
albumen. Analysis of formic acid-Total acidity : Acetic acid
Mineral acids. Analysis of egg-yolk-Water : Ash Fat. Salt
Nitrogen or albumen. Analysis of acetate of iron liquor-Total
acidity: Iron oxide: Ash: Sulphuric acid: Acetic acid. Some simple
chemical tests for leather makers-Lime: Linseed meal (crushed
linseed): Dried blood: Gum arabic: Dyes: Cod-liver oil: Glucose.
Salt: Ammonium chloride (sal ammoniac): Caustic soda: Ferrous
sulphate (green vitriol): Sodium thiosulphate (hypo): Flour: Egg-
yolk- Ammonia or ammonium hydroxide: Borax Mineral acids:
Shellac: Soda: Carbolic acid or phenol: Sumac: Lactic acid: Soaps:
Indicators.
xviii CONTENTS
Chapter XXII
DISPOSAL OF TANNERY WASTE 665-669
Classification and nature of tannery wastes; Plain sedimentation:
Mechanical sedimentation: Activated sludge process: Other methods
of treatment.
Chapter XXIII
USEFUL DATA 670-682
Thermometer conversions. Boiling and freezing points of ther-
mometers. Comparison of thermometers. Specific gravity, degrees
Twaddell, barkometer and Baume. Weight and specific gravity of
liquids — Water. Weights and measures — Troy weight: Apothe-
caries' weight: Avoirdupois weight: Dry measure: Liquid measure:
Long measure: Cloth measure: Square measure: Surveyor's meas-
ure: Cubic measure. Metric equivalents — Linear measure: Square
measure: Weights: Volume: Capacity: Multiples for conversion of
quantities: Multiples for conversion of distances: Multiples for
conversion of capacities. Approximate metric equivalents. Ca-
pacities of vats in gallons for each inch in depth — Circular in form:
Square in form. Sundry calculations — Volume of a cube: Volume
of a parallelopipedon: Volume of a cylinder: Volume of a cone:
Volume of a frustum of a cone: Volume of a sphere: Diameter and
speed of pulleys. Heat, steam, evaporation and electricity. Evapo-
ration in vacuum. Boiling point of water at reduced pressure.
Temperature of steam at various pressures.
GLOSSARY OF TERMS USED IN TANNING AND RE-
LATED INDUSTRIES 683-687
LIST OF ILLUSTRATIONS
FIGURE PAGE
1.— Skinning the head and cheek. The knife should pass
along the hide, starting at the base of the right horn
and extending across to the left horn, and then
down through the left nostril 4
2. — Skinning the forelegs 5
3. — Skinning the side 5
4.— Skinning the hind legs to make a uniform pattern . 6
5. — Skinning the buttocks 6
6. — Skinning the rump
7. — Skinning the back 7
8. — Beating the fell over the rump and round .... 8
9. — Skinning the neck 8
10.— Dotted lines show ripping-open cuts necessary to pro-
duce a hide of good pattern
11. — Dotted lines indicate proper cuts in skinning the head 10
12. — A hide of good pattern and trim 11
13. — How to fold a hide • * 2
14. — Checking off a load of hides 13
15.—A hide cellar 14
16._Cowhide, showing character of grain 16
17 —Calfskin, showing grain on finished leather ... 20
18. — Horsehide, showing character of grain .... 21
19. — Goatskin, showing grain on finished leather ... 22
20.— Warehouse in a goatskin tannery; stock being re-
ceived and weighed 24
21. — Raw stock. Goatskins come from all parts of the
world. They arrive in a dry condition and before
tanning are sorted into various grades and weights 24
22. — Hogskin, showing characteristic grain 29
23. — Skinning out the legs of a sheep 30
24. — Skinning over the flank of a sheep 31
25.— Stripping-off over the back of a sheep .... 32
26. — Fisting off a sheepskin 33
27. — Sheepskin, showing characteristic grain .... 34
28.— Lambskin 35
xix
xx LIST OF ILLUSTRATIONS
FIGURE PAGE
29.— Kid skin 35
30. — Kangaroo skin 35
31. — Human skin 36
32. — Sealskin 36
33. — Alligator skin . 36
34. — Cross-section of calfskin 49
35. — Cross-section of cowhide 50
36. — Cross-section of calfskin 51
37. — Pin-mill, wash-wheel, or drum for washing fresh
hides 56
38. — Washing hides preparatory to soaking 57
39. — Fulling stocks 59
40. — Turner pneumatic fleshing machine 60
41. — Hides ready for depilation 61
42. — Lime plunger 79
43.— Beam knife 80
44. — Whitney model "S" unhairing machine .... 80
45.— Broad flesher 81
46. — Spring style fleshing knife 81
47.— Monitor flesher 81
48. — Automatic roller fleshing machine 82
49. — Unhairing on the Leidgen machine 93
50. — Hand fleshing on the beam 94
51. — Inspection for fine hairs 95
52. — Checking machine, used for splitting necks on calf-
skins ' 99
53. — A typical beam-house of a goatskin tannery . .-■ . 100
54.— Fleshing 108
55. — Bate beam-stone 117
56. — Belt-knife splitting machine 131
57. — Rubber roll putting-out machine 132
58. — Buffing machine, used for snuffing grain for ooze,
and flesh for suede leather 146
59.— Buffing wheel 148
60.— Knee-staker ,150
61. — Tan-room in a goatskin tannery. The operation is
carried out either in paddle or drum as shown . . 162
62. — Line of shaving machines used for producing a
smooth effect on the flesh side 163
LIST OF ILLUSTRATIONS xxi
FIGURE PAGE
63. — Shaving machine 164
64. — Slicker and handle 232
65.— Moon-knife . . . 232
66. — Union splitter. Formerly much used for furniture
and automobile leather, but now replaced by band-
knife machine 246
67. — Iron frame stoning- jack 249
68. — Cork arm-board 255
69. — Sole leather rolling- jack 268
70. — Mechanical transfer in the tan-yard, showing pack
going to rocker 272
71. — Mechanical hoist for moving hides 273
72. — View in the tan-yard, showing series of layers . . 274
73. — Cropping 275
74. — Cropped hides and bellies ready for final layer . . 276
75. — Quirin press or wringer 277
76. — Extract wheels 278
77.— Ready for the bleach 279
78. — Hides suspended in the bleach 280
79. — Bleaching machine . . . 281
80. — Placing in loading wheel 282
81. — Removing from loading wheel . . . . . . . 283
82. — Setting-out after tempering ... 284
83.— Rolling- jacks 285
84. — Drying-loft 286
85. — Applying the bright finish to sole leather .... 287
86. — Brushing machine for sole leather 288
87.— Currier's knife 308
88. — Whitening machine, used for cleaning-up flesh side
of various kinds of leather 309
89. — Serial table setting-out machine 313
90. — Heavy rolling-jack . . ; . . . . . . . 316
9.1. — Boarding machine •. . . 325
' 92. — Sheridan embossing press 337
93. — Embossing machine 338
94. — Turner hydraulic embossing and smooth-plate press 339
95. — Coloring goatskins 357
96. — Top pan blacking machine used for seasoning and
coloring . . . . . 386
xxii LIST OF ILLUSTRATIONS
FIGURE PAGE
97. — Exterior view of Proctor dryer 447
98. — Skins entering at the "wet end" of Proctor dryer . 448
99. — Skins leaving the "dry end" of Proctor dryer . . . 449
100. — Interior of a typical dry-room in a goatskin tannery.
The room is heated by steam pipes on the floor and
ventilated by means of fans 450
101. — Side view of Sturtevant dryer showing supply pipe,
heater and open tube 451
102. — Rear end of heaters, Sturtevant dryer, showing steam
and drip connections 452
103. — Sturtevant leather dryer, double tube, showing drying
trucks 453
104. — End of two tubes of Sturtevant dryer, showing skins
hanging from chain belt-conveyor 454
105. — Looking into the end of Sturtevant leather dryer,
showing skins on conveyor 455
106. — Standard staking machine . ;. . . ... . 456
107. — Staking, or softening and stretching the damp stock 457
108. — Perching goatskins, sometimes termed re-staking . 458
109. — Buffing room in a goatskin tannery 459
110. — Bower glazing machine 460
111. — Flat bed glazing machine 461
112. — A line of glazing-jacks for producing a bright finish
on glazed kid 462
113. — Segment measuring machine 463
114. — Sorting finished skins 464
115. — Eureka bark mill 527
116. — Chestnut trees; giants of the forest 538
117. — A flume on the chestnut wood operations .... 539
118. — Flume terminus for chestnut wood 540
119. — Carting quebracho logs to port of shipment; trees
in the background 548
120. — Hauling in netted sharks 574
121.- — Roping a shark 575
122. — Landing a shark. Note skins on pier 575
123. — Tea's extractor 613
124. — Combined evaporator and dryer ....... 619
ACKNOWLEDGMENTS
The illustrations appearing in this book have been kindly
furnished by the following firms and Government Depart-
ment :
Goatskin Tanning
Dungan, Hood & Co., Inc., Philadelphia, Pa.
Sole Leather Tanning
J. H. Ladew Co., Newark, N. J.
Chestnut Extract
Champion Fibre Co., Canton, N. C.
Quebracho Wood
A. Klipstein & Co., New York City
Leather Dryers
Proctor & Schwartz, Philadelphia, Pa.
B. F. Sturtevant & Co., Boston, Mass.
Skins and Hides
Bureau of Chemistry, U. S. Dept. of Agriculture, Wash-
ington, D. C.
Cross Section of Calfskin
Dr. George D. Rosenthal, New York City
Flaying
Farmers' Bulletin 1055, U. S. Dept. of Agriculture, Wash-
ington, D. C.
Tanning Machinery
Turner Tanning Machinery Co., Peabody, Mass.
G. W. Baker Machine Co., Wilmington, Del.
T. W. & C. B. Sheridan Co., New York City
Whitney Machine Co., Winchester, Mass.
xxm
INTRODUCTION
In presenting any book on a special subject it is customary
to commence with the history of that subject, and by gradual
stages bring it down to the present time. In attempting to do
this, the author encountered so many difficulties and so many
unauthentic, conflicting records that he gave it up as being
too uncertain. If, however, any dependence can be placed
upon the records of Scripture, we must conclude that the
manufacture of leather is the oldest of the industries, for in
Genesis III, 21, we read, "Unto Adam also and to his wife
did the Lord God make coats of skins and clothed them."
It is interesting to know that the first method for preserv-
ing hide and skin in a more or less pliable and imputrescible
condition probably consisted in treating the pelt with the
grease and brains of the animal itself, which were worked in
by a process of pounding and stretching. Following this
primitive method came the smoke treatment, then the appli-
cation of salts containing alum. The dyeing of this leather
no doubt led to the discovery of a few vegetable tanning ma-
terials. It remained, however, for the last fifty years to see
more done for the advancement of the industry than ever be-
fore, and in this wonderful development America has played
no small part.
PRACTICAL TANNING
CHAPTER I
HIDES AND SKINS
The hides and skins used in the manufacture of leather
are generally obtained from animals killed for food. The
coverings of large animals are classified as hides, whereas
those of small animals are known as skins. The production
of hides and skins in the United States during 1920 amounted
to 894,000,000 lb., green basis, when 1 lb. of dry hide equals
2 lb. of green hide. Hides and skins soon putrefy if allowed
to remain in a moist condition, so it becomes necessary to
treat them in such a manner that they may be kept undam-
aged until ready for the tanning processes. This operation,
known as curing, may be done in several ways, each one being
more or less peculiar to the locality from which the hides are
shipped. The cure has a decided influence upon the hide, and
largely determines the character of the leather.
Classification of pelts. — The pelts of animals come to the
tanner in four conditions: (1) green (fresh from the ani-
mal) ; (2) green-salted (where the salt has been rubbed on the
flesh side) ; (3) dry-salted (rubbed with salt and dried) ; and
(4) dried (usually stretched on boards in the sun). The pelts
so received are divided according to size into three general
classes, namely: hides, kips, and skins: Hides comprise pelts
from large and fully grown animals such as the cow, horse,
camel and walrus. These give thick, heavy leather for shoe
soles, machinery belting, harness, and other purposes where
stiffness and strength, combined with wearing qualities, are
necessary. They are also cut into splits for use as shoe uppers,
and bag, case, strap, automobile, carriage, furniture, and up-
holstering leathers. Kips are the skins of undersized animals
of the above species. Skins are obtained from small animals
such as calves, sheep, and goats. Kips and skins yield a
lighter leather than hides, which is suitable for a great variety
1
PRACTICAL TANNING
of purposes such as uppers for shoes, pocketbooks, bookbind-
ing, gloves, and fancy leather. Pelts vary in thickness and
texture in different parts, being thicker on the neck and butt
than on the flank and belly. Pelts of the same species vary
greatly according to the climatic conditions under which the
animals are raised, also their breeding and feed. They often
show injuries like cuts, brand-marks, grub-holes, and sores
caused by the bot-fly or warble. Diseased hides are some-
times found, and are a source of great danger to the tanner
on account of the contagious nature of some of the diseases,
especially anthrax.
Dry or flint hides. — The simplest form of cure consists in
drying the hides in the open where they are exposed to the
action of both sun and wind, a method commonly adopted in
most tropical countries. Although curing by this method has
the advantage of simplicity, it has disadvantages owing to
the condition of the hide substance. Too rapid drying results
in the contraction and hardening of the surface, and the mois-
ture, not being removed from the middle section, gives rise
to bacterial action deleterious to the hide substance. As the
damage thus caused can only be detected in the beam-house,
it is apparent that the practice should be discouraged. The
temperature at which hides are dried is of great importance.
The best conditions are a comparatively low temperature and
good circulation of air. The higher the temperature, the
harder the stock and the slower it will wet back in the soaks.
Dry-salted hides. — These differ from flint hides in that a
coating of salt has been applied to the flesh side, and, after re-
maining in packs for some time, they are spread out and al-
lowed to dry in the sun. Dry-salted hides have the advantage
over dry hides in that they do not contract during the dry-
ing and are much more readily softened in the soaks.
Green-salted hides. — The stock coming to the tanner in
this condition has been salted on the flesh with common salt
and placed in piles to cure. The hides are piled-down in such
a manner that the slope is toward the center. In this way the
brine formed is retained and the cure materially aided. The
HIDES AND SKINS 3
time necessary for a thorough cure is at least thirty days. The
hides are taken-up, and, after the salt has been partly removed
from them, they are folded into a bundle for shipment.
Salt stains. — In salting hides it is sometimes found that
iron, in the form of ferric chloride, is present. This iron
becomes deposited in the hide, and shows up during the tan-
ning as black spots known as salt stains. Clots of blood or
flesh are also likely to produce the same result.
Packer hides. — The slaughtering of cattle on a large scale
by the great packing-houses of the United States has resulted
in a process so efficient that these hides are obtained in nearly
as perfect a condition as their nature will permit. Thus the
term "packer hide" has come to mean the best hide that can
be bought. Skilled labor and attention to details have re-
duced the possible damage to a minimum.
Stuck-throats. — As the cattle arrive at the packing-house
they are allowed to rest and cool off. The killing beds are
usually arranged on the top floor of the building, and the cat-
tle are driven up through runways or elevators. Two animals
go into each knocking pen, there usually being half as many
pens as skinning beds. A "knocker" uses a light sledge ham-
mer, and strikes the animal a heavy blow on the forehead be-
tween the eyes; if the animal does not drop immediately, a
second blow is given. The skull is broken by this heavy blow
and the animal becomes unconscious. The gate is now lifted,
and by mechanical means the floor of the pen is raised to a
sharp angle causing the carcass to slide to the sticking bed. The
"sticker" inserts his knife vertically through the neck in such
a way as not to tear the pattern of the hide, and when the
knife has been entered sufficiently deep, it is turned crosswise
to sever the jugular vein. The animal is now shackled by
passing a chain around both hind legs, and the body raised
from the floor, head down, in order to drain off the blood.
Cut-throats. — When animals are killed "kosher," accord-
ing to the Rabbinical law, the steer is not knocked senseless,
but is shackled by the hind legs and raised to such a position
that the head just rests on the floor. By means of a muzzle
4 PRACTICAL TANNING
the head is turned back and the throat washed to remove grit.
The Rabbi blesses the animal and with a long knife makes
one downward cut back of the jaw, almost severing the head
from the spinal column.
Flaying. — Whether the animal is a stuck-throat or cut-
throat, the operation of flaying is similar in each case. In the
Figure 1. — Skinning the head and cheek. The knife should pass
along the hide, starting at the base of the right horn and
extending across to the left horn, and then down through
the left nostril.
large packing-houses, skinning is done by several men, each
performing a specific part of the operation. The "header"
sticks his knife in at the top of the head and makes a cut
across the left side of the animal's face, continuing downward
along the left side through the nostril. The cheeks are skinned
out (figure 1), and the under side opened from the sticking
cut through the center of the lower lip. This method leaves
the pate on the right side of the hide, and allows it to lie flat
when placed in the pack. The carcass is next lowered to the
HIDES AND SKINS
Figure 2.— Skinning the forelegs,
floor where it is laid on the back and held in position by a
pritch pole. The claws and feet are removed by the "legger"
(figure 2) and the sweetbreads are taken out. In skinning the
front legs the cut is upward on the right side and toward the
center of the knee. The same holds good of the hind legs,
Figure 3.— Skinning the side.
PRACTICAL TANNING
Figure 4. — Skinning the hind legs to make a uniform pattern.
Figure 5. — Skinning the buttocks.
HIDES AND SKINS
Figure 6. — Skinning the rump.
Figure 7. — Skinning the back.
PRACTICAL TANNING
Figure 8. — Beating the fell over the rump and round.
Figure 9. — Skinning the neck.
HIDES AND SKINS 9
except that the cut runs toward the center. The "ripper-open"
next follows, opening the steer along the belly (figure 3) from
the sticking cut to the tail. The "floorsman" or "sider" now
removes the hide from the belly (figure 4) and cuts along the
brisket and back to the inside of the hind leg (figure 5) close
to the tail. After cutting down the side of the animal he
makes the cut at the brisket and foreleg to joint, and, on the
Figure 10. — Dotted lines show ripping-open cuts
necessary to produce a hide of good pattern.
hind leg (figure 6), he connects with the hind-legger cut. The
hide is now carefully removed from the belly and down the
sides. The body is then lifted until only the forward quarter
remains on the floor, and the "tail-puller" pulls the hide off
the tail. The "rumper" (figure 7) cuts the hide away from the
base of the tail and rump. The body is again raised, and the
"fell cutter" removes the hide from the hind legs and "round."
The fell puller takes the hind shanks and pulls, while the "fell
beater" (figure 8) pounds away the hide by means of the back
10 PRACTICAL TANNING
edge of cleavers. The "backer" (figure 9) finishes the flaying
by removing the hide from the shoulders. Figures 10 and 1 1
show cuts required during skinning, while figure 12 shows a
hide of good pattern.
Curing. — As the hide drops from the carcass it is spread
on the floor and inspected for cuts, scores, grubs, and other
imperfections. It is then thrown into a chute leading to the
Figure 11. — Dotted lines indicate proper cuts in
skinning the head.
hide cellar. Here the hides are assorted into different grades,
classes and weights, each grade being assembled in its respec-
tive pack. The workmen in the hide cellar are usually about
two hours behind the killing gang, so that the animal heat may
be out of the hides before salting. As the cellar gang receive
the hides, they split the ears and then pile them down flat with
flesh side up. Over each hide is sprinkled about 40 pounds of
rock salt, and the outside hides in the pack are turned over
so as to retain the pickle in the stock and hold the pile in
HIDES AND SKINS
11
shape. The piles are low and fiat to prevent drying out. After
the back edge and corners are put in, the sides are built up.
When the back and sides have been made, the spreads are put
This is done in such a manner that the heads come into
in
the center of the pack. As the spreads are placed in, the front
is built up. Hides packed in the proper way will keep for one
or two years, but in practice they are never left for this length
Figure 12. — A hide of good pattern and trim.
of time, thirty days being the usual period. The danger of
standing too long is indicated by salt stains, but these may be
prevented by adding "cyco" powder to the salt. This powder
consists essentially of sodium bisulphite, and is sold under
the above trade name.
In putting down hides, the work is done by a gang consist-
ing of two spreaders, one salt thrower, and a salt trucker, who
should handle about 40 hides an hour. To obtain the best
results, the cellars should be kept at as even a temperature as
12
PRACTICAL TANNING
possible, which should not vary greatly from 65 degrees
Fahrenheit.
Taking-up hides. — In taking-np a pack of hides, the repre-
sentatives of buyer and seller are present. As the hides come
\
\r
Figure 13. — How to fold a hide: (a) first step; (b) second step; (c)
third step. The shading represents the hair side.
from the pack they are shaken and drawn over a "heaver"
(a kind of horse) to remove excess salt. They are then spread
on the floor, hair side up, and inspected for hairslips, manure,
and brands. They are next turned flesh side up and swept
free from adhering salt. Another inspection is made for cuts,
HIDES AND SKINS 13
scores, and grubs, after which they are sorted according to
grade, and classified as firsts and seconds, brands, cows, and
steers. The No. 1 hides are rolled up with hair out, and the
No. 2 with flesh out. After rolling (figure 13), they are tied,
weighed, and further classified as heavy, spready, medium,
light, and extreme.
Sweep tare. — In taking-up hides a tare allowance is made,
kIET''
51\j i
%?• •'" 1
v;f!. ""
a.*^
,1 U-«: %
;
^^^^^fi.
■
V i
g^BM
|l
%«&m»
Figure 14. — Checking off a load of hides.
determined by what is known as the sweep tare. Ten hides
are selected at random, weighed, swept thoroughly both on
flesh and hair sides, and weighed again. The loss in weight
is then taken for the whole pack. If this tare is not satisfac-
tory to either buyer or seller, another lot of 10 hides is taken,
and the average loss on the 20 hides indicates the tare allow-
ance. Since the time of year has some influence on the tare
allowance, it is usually determined before the hides are taken-
up. For instance, July hides, on account of short hair, are
given an allowance of I to 1$ lb., whereas March hides, hav-
ing long hair, are given an allowance of 2 to 2\ lb. Figure
14 shows hides arriving at a tannery, and figure 15 depicts
a typical hide cellar.
14
PRACTICAL TANNING
Grubs. — Among the defects found in hides, note should be
made of the damage caused by the "bot-fly" or "warble fly"
(hypoderma bovis). The grub deposits eggs in the animal;
but just how, is open to controversy. Observations by work-
ers in the Department of Agriculture, Bureau of Animal In-
dustry, both of the United States and Canada, indicate con-
clusively that the eggs are deposited in the hair while the ani-
Figure 15. — A hide cellar.
mal is in a reclining position. According to a report of Dr.
Seymour Hardwin, he observed a fly on the ground near a
recumbent cow. It ran backwards, reached upward from the
ground, and oviposited on the hair hanging down around the
coronet. On another occasion a fly on the ground ran back-
ward in the same manner, and oviposited about six inches
below the point of the ischium, where the cow's body came in
contact with the ground. From this point it laid eggs at in-
tervals all along the side near the ground, as far forward as
the elbow, without touching the animal except with the ovi-
HIDES AND SKINS 15
positor. This journey took some time, as the fly rested one
or two minutes after ovipositing. With regard to irritation,
Dr. Hardwin observed that while the animal was recumbent
no annoyance was apparent, probably because the fly was on
the ground, but when standing it was a different matter, as the
fly was forced to grasp the hair while ovipositing.
An extended series of experiments have shown conclusively
that the larvae enter the animal both through the skin and by
the mouth. In either case, the parasite travels along a pretty
definite route, passing down the gullet to the diaphragm, and
then through connective tissue along the sides and vertebrae
to the back. The larvae found in the oesophagus, spinal canal,
and subcutaneous tissue all had about the same dimensions.
Signs of their migration through the intervening tissue were
also found, proving that the process is continuous. On reach-
ing the back, the larvae develop, and here force their way
through the hide, first causing a swelling during their pupal
stage, and finally making a puncture, falling, an undeveloped
grub, to the ground where it matures.
In small numbers, warble flies do little injury to the health
of the animal, although cases are on record where an excessive
number of grubs have caused death. The holes produced by
the grub soon heal, but if the animal is killed before the heal-
ing is complete, they remain open and are a source of damage
to the hide. Preventive measures are being taken in some
States to overcome this nuisance, and it is hoped that they
may become general practice.
Hides from certain countries may be damaged by ticks, but
the injury, however, appears only in the shanks, and is not so
serious as that caused by grubs.
Grub allowance. — The grubbing of native steers is per-
mitted and a grub allowance made between January 1 and
June 1. This is done by sampling. The hides selected for
grubbing, twenty in number, are spread on the floor, and the
purchaser's agent, by means of a spade, finds as many grubs
as possible. When all grubs have been found to a limit of
five, another hide is examined, and so on. If the number of
16
PRACTICAL TANNING
grubs found is not satisfactory to either buyer or seller, an-
other 20 hides are taken, and the grub allowance based on the
40 hides so chosen.
Hide selections. — When purchasing hides, the buyer looks
for certain selections, depending on the kind of leather he is
Figure 16. — Cowhide, showing charac-
ter of grain.
producing and the market conditions. Figure 16 shows char-
acteristic features of finished grain.
Native steers. — Steer hides free from brands are graded
according to weight as heavy hides, above 60 lb. ; light hides,
between 50 and 60 lb. ; and extremes, between 35 and 50
pounds.
Heavy hides are usually kept separate and sold for belting
leather. Light hides sell for one cent less per pound, and ex-
tremes for two cents less, than heavy hides. Kosher hides
are included in regular lots, and are sold for \ cent reduction.
Spready hides. — Native steers going into this selection
must be perfect in all respects, free from brands and grubs.
In the Western States the measurement of a spready hide
must be 6 feet 6 inches across the shoulders just back of the
brisket, whereas in the East the measurement is 6 feet 8
inches. Hides of this class are used largely for furniture and
automobile upholstery. As winter-killed hides are likely to
HIDES AND SKINS 17
be very grubby, the tanner prefers to purchase stock killed
from June to January. These hides bring the top prices today,
while several years ago they went at lower figures than other
stock.
Spready native cows must be perfect and measure 6 feet 4
inches across the brisket, and go into the same trade as spready
steers.
Texas steers. — These hides are from branded range cat-
tle, and on account of their plump condition find a ready mar-
ket in the sole-leather trade. The cattle themselves, however,
are underfed, and are known at the stockyards as "bone cret-
er." Conditions, nevertheless, are changing, and the quality
of the beef as well as of the hides is improving. Texas steers
are butt-branded. The grubbing privilege extends from No-
vember 1 to June 1.
Colorado steers. — The hides from Colorado steers are side-
branded either on one or both sides. As a rule they are more
spready and have a more spongy feel than Texas hides. The
grubbing privilege extends from December 1 to June 1. They
are selected as heavies, over 60 lb.; lights, 50 to 60 lb., and
extremes, 25 to 50 pounds.
Cowhides. — The so-called native cowhides are free from
brands, and are graded as heavies, over 55 lb., and lights,
under 55 lb. Branded cows on the other hand are sold flat
for weights. Both selections are grubbed from November 1
to June 1, with the usual allowance of I cent off in case of
kosher hides.
Bull hides. — The hides known as native bulls are free from
brands and stags. They are not grubbed and are usually
sold flat. Branded bulls are also sold flat and not grubbed.
' Bull hides are recognized by their tough pate, thick and ribby
neck, and thin butt. As a rule, spready bulls are not sorted
out. Some tanners, however, prefer selection, and in such
cases the sorting is done by the broker.
Country hides. — Green-salted hides not taken off by the
large packers are known as country hides, but they may be
from the same kind of cattle as those killed by the packers.
18 PRACTICAL TANNING
The principal difference is in the flaying, which is poorly or
imperfectly done, the hides being badly cut, scored, and of
poor pattern. These hides come from farmers or country
butchers, who either salt them lightly or sell them green to
small collectors, who in turn sell them either direct to the tan-
ner, or, as is more often the case, to the large dealers. The
latter sort the hides into different grades and weights, so that
the tanner can obtain the selection desired. As a rule, the
hides have been salted and re-salted several times, which im-
parts to them a dark flesh color, with a consequent loss of
hide substance. The defects of country hides include scores,
grubs, hairslips, and poor patterns. Badly damaged hides are
thrown into glue stock.
Kips. — Hides from undersized animals or large calves are
sold as kipskins, and range in weight from 15 to 25 lb.
Branded or grubby skins go into seconds, and are sold at the
proper reduction.
South American hides. — River Plate hides, or "straight
hides" as they are known in the trade, come from South and
Central America. These are dry hides shipped from Argen-
tina and Uruguay, and are spoken of as "Buenos Aires" and
"Montevideos," taking their name from the point of shipment.
These hides are from range cattle and are considered the best
dry hides on the market. Other hides also take their names
from the point of shipment and are known as "Puerto Cabel-
los," "Maracaibos," "Caracas," "Costa Ricas," "Central
Americas," and "Orinocos." They vary in character as to
plumpness and quality of grain. Salted hides imported from
South America come in as "frigorificos," "saladeros," and
"metaderos." Frigorificos are hides from animals the meat
of which is shipped from Argentina as frozen beef; saladeros
are from the smaller packing-houses of Argentina and Uru-
guay; while metaderos are hides from the village butcher and
correspond to American country hides. Other dry hides come
into this market from China and India.
Anglo-American hides. — These are hides taken from cat-
tle shipped to England on the hoof. They have all of the
HIDES AND SKINS 19
characteristics of packer hides, except that they have a short
shank, and so bring a somewhat better price than packer hides.
Swiss and Bavarian hides. — Hides coming from this
source are in great demand for the manufacture of belting
leather. The reason for this is that they are from animals
. raised by peasants, who have given them the best of attention.
They are plump and heavy, and have a very clear grain.
Calfskins. — All skins under 15 lb., except slunks, are sold
as calfskins. The following is the common classification:
Slunk Weight, pounds
No. 1 and 2 light deacons (country take-off) 7 down
No. 1 and 2 heavy deacons (country take-off).... 7 to 8
No. 1 and 2 light calf (butcher take-off) 7 to 8
Calf
No. 1 and 2 veal hair 8 to 15
Kip (veal, 1st grade) 15 to 25
Kip (grasser, 2nd quality) 15 to 25
No. 1 and 2 runner kip (light kip, poor hair) 15 down
No. 1 and 2 extreme cows (known as extra light) 25 to 45
No. 1 and 2 buff or medium cows 45 to 60
Cows
No. 1 and 2 light steers 45 to 60
No. 1 and 2 heavy steers 60 up
No. 1 and 2 light bulls „ 45 to 60
No. 1 and 2 medium bulls 60 to 85
No. 1 and 2 heavy bulls „ 85 up
No. 1 and 2 stags are classed with bulls.
Trimmed calf and kip
Calf 4 to 5
Calf 5 to 7
Calf 7 to 9
Calf „ 9 to 12
Kip 12 to 16
Kip 16 to 20
Figure 17 shows the grain on finished calfskin.
Packer hides are thrown into seconds if they have one cut
or five grubs. Country hides are thrown into seconds if they
have one cut and one grub. A side or butt brand throws
a hide into second grade.
Horsehides. — These hides are obtained from domestic
sources, and come mostly from work horses which have died
in service. The best hides, however, are imported from
France and Russia. These hides are sold by the piece ac-
20 PRACTICAL TANNING
cording to size and condition of the butt. The butts are
cut off 21 inches from the tail, the cut being made clear across
the hide. These butts are used for making the leather known
as "cordovan," also for making a heavy leather worn in cold
countries like northern Russia. The remaining portions of
the hides, known as "fronts," are used for making shoe and
glove leather, and are usually not tanned by the same firm
handling the butts. No. 1 horsehides must be free from cuts,
scores, brands, or dragged spots. Seconds are those having
■> :f '
Figure 17. — Calfskin, showing grain on
finished leather.
these imperfections. There is also a difference between sum-
mer and winter hides : In the summer, many horses die from
exhaustion, and, as a rule, are not skinned promptly, some
even lying several days in the street before removal. De-
composition is going on all the time, and dragged spots occur.
As the animal had been in imperfect health, this disturbance is
reflected in the hide. Winter hides, on the other hand, are
taken from animals killed after an accident, such as slipping
on frozen pavements. The animals are in a healthy condition,
and the hide is full of life and much stronger than summer
hides, also much thicker. Even if the horse lies in the street,
there is comparatively no putrefaction of the hide, which,
HIDES AND SKINS 2I
consequently, does not show dragged spot, Figure 18 shows
rt* characteristic grain of finished leatheis.
GoatsWns -These come chiefly from those eountr.es m
Goatskins. ^ _ s nQt a popular
s:i«^ p-r iy no th°o es "
tic k ns ar available. We, therefore, depend upon the Or,
tic skins «e America fof QUr raw mate _
e "ai an S d as m 'goatkins are tanned in the United States
£ tan" olr Country, we have become the greatest im-
■ ' 1
Figure l8.-Horsehide, showing char-
acter of gram.
u ni«Tav«s have a few animals on their iarms.
a Llr'thered by small collectors, who pass them on
ri: arg r dealers. The dealer then brings them to the
I kt place where they are bought by the big exporter, who
Tn turn ships them to the United States or other countries .
' The picking up and shipping of skins varies g-J^JJ
ri^ZdeTwith skiL from an entirely different conn
trv The climatic conditions of a region, of course, attect
Z n Jure of the skin. Excessively wet or dry seasons have
22
PRACTICAL TANNING
their influence upon the raw material, and in cold climates the
skins take on a heavy growth of hair, while in warm climates
the hair is short. The longer the hair, or the more closely the
animal approaches the sheep, the poorer the pelt is for leather
purposes. Figure 19 shows the natural grain on domestic
goatskins.
Curing. — Skins are cured in the same manner as hides, but
inasmuch as they are thin and small, the details of the proc-
ess are somewhat modified. The simplest method consists
Figure 19. — Goatskin, showing grain
on finished leather.
of sun drying, where the skins are either spread out or hung
up in the sun until dry. If the sun is too hot they are hung in
the shade. Dry-salted skins are given an application of salt,
and then dried in the sun or shade. Wet-salted skins are
rubbed thoroughly on the flesh side with salt, folded into small
bundles, and packed in barrels or casks. The dried skins are
placed in bales, and a small quantity of naphthalene is put
between each skin. This prevents moths and bugs from dam-
aging the stock, and overcomes the tendency to heat. Skins
from some countries are arsenic-cured, but this should be
avoided as much as possible.
Goatskins, as they come to the tanner, are designated by
the name of the country or province from which they come,
HIDES AND SKINS 23
or from the point of shipment. They are graded according
to weights and selections somewhat as indicated below :
From China Average weight, pounds
Light 1.25
Medium 2.00
Heavy 2.50
Bulls over 3.00
From India Weight, pounds
Lights A's • 0.75
Regular B's 1.00
Large C's 1.50
Heavy D's 2.00
Bulls, BB's , over 2.00
Northwestern and Amritsars from India <
Lights 1.25
Mediums 1.50
Heavies 2.00
Bulls over 2.00
Regular South American
Light A's 0.75
Regular B's 1.15
Medium C's 1.50
Heavy D's 2.00 to 2.50
Bulls, BB's over 2.50
Brazilian
Light A's 0.75
Regular B's 1.00
Medium C's 1.50
Heavy D's 2.00
Bulls, BB's over 2.00
Figures 20 and 21 show goatskins as they arrive at a
tannery.
Spanish goatskins.. — These skins are noted for their fine
grain, plumpness, and freedom from imperfection. They are
cut open and folded down the back. The best are obtained
from Valencia, Catalonia, Barcelona, and Seville; good skins
also come from Leon and Castille, but those from the territory
near the Portuguese boundary are inferior. Spanish skins
come into market under the following selections :
Class Weight, pounds
No. 1 and 2 lights 1.25
No. 1 and 2 regulars 2.25
No. 1 and 2 heavies 2.50
No. 1 and 2 extra heavies , 3.00
24
PRACTICAL TANNING
Figure 20. — Warehouse in a goatskin tannery; stock being received
and weighed.
Figure 21. — Raw stock. Goatskins come from all parts of the world
They arrive in a dry condition and before tanning are sorted
into various grades and weights.
HIDES AND SKINS 25
In addition to these there are small kidskins used for glove
leather. The light skins are sometimes known as
"chevrettes."
German goatskins. — Most of the skins produced in Ger-
many are used by the domestic trade. In case of shipment,
however, the best skins are retained, and a selection of A, B,
and C's, corresponding to first, second, and third, are sorted
for export, and are known as American selections.
Italian goatskins. — Those from the northern part of Italy
are of the best quality, and come from the districts of Rome
and Tuscany. They are flat dried and selected for primes
and seconds, which yield a good-weight leather. Skins from
the southern provinces are of an inferior quality. They come
from Naples, Puglia, Calabria, and the Island of Sicily. The
Sicilian skins are known as Messinas and Palermos. These
skins weigh from 2\ to 3 lb. each.
Southern Europe goatskins. — Many skins originate in
that part of Europe comprising Austria, Hungary, and the
Balkan countries. Most of these skins are of good quality
with fine grain, and are usually taken off the animal in such
a manner that they remain "cased," that is, not cut open.
They are flint dried, and their weight averages from 3| to
3 1 pounds.
Serbian skins are limited in number, but are of the highest
grade. The Bosnian skins are somewhat inferior in character.
Other skins come from Greece, Montenegro, Macedonia, and
Albania. Skins coming from these provinces are usually
shipped from the port of Trieste, while some of those from
Macedonia and Greece come from Salonica.
Turkish goatskins. — Under the general name of "Levant
goatskins" are those originating in Asiatic Turkey. These
skins are dry-salted, cut open, and folded flat. They are in-
ferior to Balkan skins, being coarse in character and having
considerable long black hair. The weight of the skins runs
from 3^ to 3f lb. each. The stock coming from the Mediter-
ranean side is of about the same quality as Asiatic skins. From
the southern district of Bagdad comes a skin which, on ac-
26 PRACTICAL TANNING
count of defective grain, gives a low-grade leather. After
being taken off, the skins are cased, dry-salted, and stretched
lengthwise. Their weight runs from 3 to 3^ pounds.
Russian goatskins. — Taken as a whole, Russia, including
Siberia and central Asia, produces more goatskins than any
other country in the world. The skins are packed at various
points, and are brought to the animal fairs held at Tyumen
and Nijni Novgorod, when they find their way to the mar-
kets of Petropaulovsk, Orenburg, Kazan, and Semipalatinsk.
Russian skins reaching America are known from the place of
shipment, such as "Petropaul goat," "Turkestans." and
"Bokharas."
Petropaul skins are flint-dried and are mostly white-haired.
The summer skins are short-haired and plump, whereas win-
ter ones are long-haired and thin. They are classified as
"werchural," primes and seconds, 25 lb. per dozen ; "mittel,"
primes, seconds, and winters, 20 lb. per dozen; and "lack"
kids, 12 lb. per dozen.
These skins contain considerable natural grease, and al-
though they produce a high-grade leather, the tanner often
encounters trouble from spew.
Turkestan skins possess all the qualities of Petropaul skins,
except that they are somewhat lighter.
Bokhara goatskins are almost identical with Turkestans,
except that they are short-haired and mostly black. Many
Afghanistan and Persian skins also find their way to the
American market, and, as their quality is inferior, they have
detracted from the real value of Bokhara skins. Their weight
is about the same as other Russian skins.
North African goatskins. — The chief shipping ports for
these skins are Algiers, Constantine, and Oran. The leather
from all these skins is of fine grain and good quality. The hair
is short and mostly white. They are cased and dry-salted,
and are classified as heavies, weighing about 2 lb. each: mid-
dles, If lb.; and lights, 1| pounds.
Skins coming from Tunis and Sfax closely resemble those
&
HIDES AND SKINS 27
coming from Algeria, although they are slightly inferior in
grain and substance.
Tripoli and Bengari produce a large quantity of skins,
plump in character and fine of grain, which produce a very
good leather. Both salted and flint-dried skins come from
this district.
High-grade skins are obtained from Morocco. Those from
Tangiers and Fez are earthy salt-cured, cased, and of a brown-
ish color. The hair is medium in length and of a reddish-
brown color. Skins come into the American market also
known as "Casablancas," "Mogadors," and "Marrakesh."
The first mentioned are either red- or gray-cured, the red-
cured skins being mostly cased. From Mogador and Marra-
kesh the stock is identical in character and of good quality.
These skins are cut open, and cured with a mixture of salt
and camel manure, but on account of this treatment, they do
not keep well.
The Egyptian and Sudan skins are cased and salt-cured.
The summer skins are short-haired and black, and, like other
skins, are better during this season. The shipping points are
Cairo and Alexandria. The selection includes : No. 1 heavies,
2.3 lb. ; No. 1 mediums, 1.6 lb.; No. 1 lights, 1.25 lb. ; No. 1
smalls, 1 lb. ; and No. 2, 1 lb. to | pound.
South African skins. — The skins from this country are
known to the trade as "Capes." Depending upon the point
of shipment, they are classified as "Capetowns," "Algoabays,"
and "Kaffirs." Of these classes the first are considered to
be of the highest grade owing to their plumpness, fine grain,
and white hair. Their cure is a light brine, ■ and the skins
are packed flat. The Algoabays are cured somewhat heavier
than Capetowns; the hair is slightly longer and somewhat
inferior in character. The Kaffir skins are inferior to the
two grades first mentioned, being darker in appearance, hav-
ing much longer hair, and being more heavily cured.
Arabian goatskins. — The skins coming from the region of the
Red Sea include those from northeastern Africa and Arabia.
They are known to the trade as "Mochas," originate largely
28 PRACTICAL TANNING
in the Yemen province, and are shipped from Aden or Ho-
deidah. Skins of a similar character also come by the way
of Gataways. All of the skins are "cased and dry-salted. The
hair is short and is mixed black and white. The selections
include heavies, weighing from 2 to 2\ lb. each ; regulars,
about \\ lb.; seconds, from 1 to 1 1/5 lb.; and long hairs,
kids, and thirds.
Many skins coming from this- region and packed in Abys-
sinia, are known as "Herrar" skins; while skins are also ob-
tained from Massowah, Somali,. Mogdeshur, Mombassa, and
Zanzibar.
Indian goatskins. — The most important country in the world
for goatskins is India, which produces 30 per cent of the en-
tire supply. Not only are thousands of skins exported in the
raw condition, but many are bark-tanned by the natives and
come into the market as "India-tanned." The best known
and most highly prized Indian skins are the so-called "Patnas,"
which derive their name from the city of Patna in the Prov-
ince of Bengal, from which they are shipped. East of Patna
is a district furnishing the skins known as "Daccas." The
Patna skins are dry-salted and tacked, whereas Daccas and
Dinajpores are dry-salted and not tacked.
The best Indian skins are produced in the district around
the estuary of the Ganges, and are known as "Kushtias" and
"Calcutta daissees." These skins are classified according to
weight as follows :
Class Pounds per 500 pieces Class Pounds per 500 pieces
Extra heavies 850 to 950 Smalls 300 to 350
Heavies 700 to 750 Kids 250 to 300
Medium 500 to 575 Heavy seconds 750 to 850
Light 400 to 475 Medium seconds 450 to 500
Many skins are obtained from other provinces of India,
among which may be mentioned "Oudhs," "Agras," "Pun-
jabs," "Amritsars," and "Madras."
Chinese goatskins. — These are of about the same nature, re-
gardless of the port of shipment. They are classified as long
hairs, medium hairs, and short hairs, the last being the best
HIDES AND SKINS 29
Quality The principal ports from which the skins are shipped
are Tientsin, Chowching, Shantafoo, Pastingfoo, Hankow,
Honan, and Shanghai. J _'. „ .,
South American goatskins.— Argentina and Brazil are the
chief countries in South America furnishing goatskins. Those
from Brazil are more in demand and most highly prized by
the tanner. These skins, named from the port of shipment,
are known as "Buenos Aires," "Pernambucos," etc.
A considerable number of skins also come from Mexico and
the West Indies.
Hogskins.-These, as a rule, are not taken off by the
butcher, as the method of removing the bristles consists of
w
Figure 22.— Hogskin, showing charac-
teristic grain.
scalding and scraping the carcass. Figure 22 shows die char-
acteristic grain. . , « .
In some establishments, however, the skm is removed, but
even then the take-off is very poor. Hogskins are des.rable
for certain purposes, and there seems to be a growmg de-
mand for leather made from this raw material Skins from
loss the shoulders are the most desirable, and of course bnng
^unTof vears, bacon strips have been worked into
30
PRACTICAL TANNING
a marketable article, and find a growing demand in the trade.
Sheepskins. — Of all the pelts of animals used in making
leather that of the sheep exceeds all others. It is estimated
by Alfred Seymour-Jones that there are more than 600,000,-
000 sheep in the world, and of this number from 25 to 40
per cent is slaughtered every year. As sheep are raised for
their wool and flesh, and not for their skins, many of the lat-
Figure 23. — Skinning out the legs of a sheep.
ter are lost, but owing to the increased demand, this waste
is gradually decreasing. The decline in the number of sheep
— as well as cattle — being raised is a factor which is giving
the tanner considerable cause for alarm. Figures 23, 24, 25,
and 26 show some of the steps in flaying sheep.
Although sheep form a separate group of animals, they
pass by gradual stages into the goat classification. Thus the
pelt may range from one with wool to one with coarse hair,
while some sheep possess no hair nor wool.
HIDES AND SKINS
31
The character of sheepskins depends upon the condition of
the environment and method of feeding the stock. Soft-
wooled skins possess a fine grain, while long-wooled skins
have as a rule, a coarse, tough grain. Generally, the more
woolly a skin is the more fat is found on the pelt; on the
Figure 24.— Skinning over the flank of a sheep,
other hand the less wool the skin carries the nearer the pelt
approaches the character of the goat. _
Sheepskins are subject to numerous afflictions, all of which
worry the tanner when he tries to convert the raw material
into leather. The worst enemy to the sheep is the fly, or
parasite, which acts as a means of transmitting disease from
one animal to another. The diseases produced by parasites
are sturdy or giddiness, louping ill and scab, while other
damages are caused by fly-blow, and ticks.
32
PRACTICAL TANNING
Of these various afflictions, that of scab is the most for-
midable on account of its persistence and difficulty of eradi-
cation. The presence of the disease is indicated by the falling
of the hair from the part affected. If examined under the
microscope, it will be noticed that the surface shows an erup-
tion, and that numerous insects may be seen moving in and
Figure 25. — Stripping-off over the back of a sheep.
out among the hair roots. If the parasite is not killed, the
disease will spread over the entire body.
Sheep kids. — This pest is probably the most widely distrib-
uted of the parasites attacking sheep. It belongs to the same
HIDES AND SKINS 33
order as the common house-fly, but is wingless. The kid does
not lay eggs, but hatches them in the body of the parent in-
sect. When the maggot is deposited, the development is so far
advanced that it becomes a pupa under cover of the puparium.
Each female produces above five pupae, at intervals of a few
days, after which it dies. The mature insect sucks the blood
Figure 26. — Fisting off a sheepskin.
of the animal, causing great irritation at the point of attack.
Sheep ticks. — The eggs of this insect are laid in large num-
bers in swampy places ; the larvae, on hatching, attach them-
selves to sheep, and, after feeding, fall to the ground and
moult, after which they become nymphae. Again they attach
themselves to the sheep, and after feeding fall off and moult
a second time, then becoming adults. Once again as adults,
they gorge themselves with blood, and the females fall to the
ground for egg-laying. The ticks are found in sheep during
the spring and summer months. The injury caused by the
34 PRACTICAL TANNING
blood-sucking is. that minute holes are made through the grain,
thus causing a local inflammation, which destroys the grain
and even the skin for some distance around the puncture.
Lice. — These insects are very common on sheep, their pres-
ence indicated by falling hair, itching, irritation, and unrest.
The injury to the grain is somewhat similar to that caused
by ticks.
Fly-blow. — This is caused by sheep maggot-fly. The fly
deposits the eggs upon the- backs of the longer- wooled
.&
.if *v
^6
Figure 27. — Sheepskin, showing char-
acteristic grain.
sheep, as deep in the wool as it can reach. The act of deposit-
ing the eggs is termed "striking," by the sheepman. The
eggs hatch quickly, and the larvae burrow into the skin, caus-
ing excruciating pain, which, unless treated, may often cause
the death of the animal, a death due to the sheep being eaten
by the maggot while alive.
Sheepskins come to the tanner either in the hair or in a
pickled condition. The latter skins have been pulled by the
fellmonger for the wool. The largest number of skins come
from New Zealand and the British Isles, while, at the same
time, a considerable number of domestic skins are available
Figure 27 shows characteristic grain.
HIDES AND SKINS
35
Other hides and skins. — Although the hides and skins
enumerated constitute the bulk of the raw material from which
leather is produced, it must not be concluded that they are
the only source, as the covering of many other animals — even
the skin of fish — enters into the production of this commodity.
Without going into detail, it may be well to mention that a
large amount of leather is produced from the covering of the
deer, kangaroo, buffalo, dog, seal, walrus, shark, porpoise,
whale, sturgeon, alligator, crocodile, lizard, and many others;
Figure 28. — Lambskin.
Figure 29.— Kid skin.
Figure 30. — Kangaroo skin.
36
PRACTICAL TANNING
while furs are produced from a large variety of animals.
Figures 28, 29, 30, 31, 32, and 33, represent the characteristic
srrain of the various kinds of skins indicated.
Disinfection of hides. — The number of hides and skins
imported into the United States annually amounts to many
millions, (700,000,000 lb., exclusive of furs, in 1920, calcu-
lated on a "green" basis, when 1 lb. of dry hide equals 2 lb.
of green hide). Since these hides and skins come from all
parts of the globe, there is great danger of their bringing in
Figure 31. — Human skin.
Figure 32. — Sealskin.
Figure 33. — Alligator skin.
HIDES AND SKINS 37
infectious diseases, among the most dangerous of which is
anthrax. As the anthrax spore has great resisting power,
many methods of disinfection have been suggested. Among
the numerous processes which have been suggested, that pro-
posed by Seymour-Jones has attracted much attention. Other
methods have been investigated, among them being the treat-
ment devised by Schattenfroh.
Seymour-Jones purposes to use mercuric chloride and form-
ic acid. By this method it is claimed that the formic acid
causes the hide substance to swell, thus furnishing a favor-
able condition for the action of this salt. The dilutions rec-
ommended are 1 part mercuric chloride in 5,000 parts of
water, and 1 per cent of formic acid, and time of treatment
24 hours. After disinfection, the hides are placed in a 10°
Be. salt solution when they will fall, and thus be brought to
the condition of green-salted stock.
The Schattenfroh method consists in immersing the hide
for 48 hours in a 10° Be. salt solution containing 2 per cent
of hydrochloric acid. This method is being carried out in
many tanneries, and by replenishing the hydrochloric acid re-
moved by the hide, is much less expensive than the Seymour-
Jones process.
The above methods for disinfection in the case of anthrax
apply equally well for other infections, such as rinderpest and
foot-and-mouth disease.
Regulation of the U. S. Government.— The Government
regulations covering disinfection are set forth in the following
orders :
TTNTTED STATES TREASURY DEPARTMENT AND DEPART-
MENT OF AGRICULTURE
Pomll!lf ; nn , Governing the Sanitary Handling and Control of Hides,
Regulations ^°*f ™L n p aring s, and Glue Stock, Sheepskins and
r^cE Sd ? Parts thereof? Ha r, Wool, and Other Animal By-
Pr^ducts? Say Straw forage, or Similar Material Offered for En-
try into the United States.
Effective January 1, 1918.
Washington, D. C, October 15, 1917.
Under authority of the act of Congress approved October 3, 1913, en-
titled "An art to reduce tariff duties and to provide revenue for the
38 PRACTICAL TANNING
Government, and for other purposes" (38 Stat., 114), and the act of
Congress approved February 2, 1903, entitled "An act to enable the
Secretary of Agriculture to more effectually suppress and prevent the
spread of contagious and infectious diseases of live stock, and for other
purposes" (32 Stat, 791), the following regulations are issued for the
purpose of preventing the introduction of anthrax, foot-and-mouth disease,
and rinderpest from a foreign country into the United States.
Regulation I
HIDES AND SKINS (
Section 1. All hides of meat cattle, calfskins, buffalo hides, sheepskins,
goatskins, and deerskins offered for entry into the United States (except
abattoir and hard, sundried hides and skins as hereinafter provided for)
may be imported from any country maintaining an efficient veterinary
inspection system when accompanied by a certificate signed by an official
veterinary inspector of such country, or, in the absence of such official
veterinary inspector, by a United States consular officer, stating that
anthrax is not prevalent and that neither foot-and-mouth disease nor
rinderpest exists in the locality in which the hides or skins originated.
Those articles may also be imported from any country which does not
maintain an official veterinary inspection system when accompanied by a
United States consular certificate stating that anthrax is not prevalent, and
that neither foot-and-mouth disease nor rinderpest exists in the locality
in which the hides or skins originated. In lieu of a certificate showing
the non-prevalence of anthrax and the non-existence of foot-and-mouth
disease and rinderpest, a certificate signed by one of the aforementioned
officials stating that the hides or skins have been disinfected under his
supervision by any of the methods approved or which may hereafter be
approved by the Chief of the Bureau of Animal Industry, will be accepted.
Sec. 2. All hides or skins offered for entry into the United States
(except abattoir and hard, sundried hides and skins as hereinafter pro-
vided for) which are not accompanied by any of the certificates prescribed
.in section 1 of this regulation, or which are accompanied by certificates
which do not comply with the requirements or purposes of these regula-
tions, may be imported from any country upon the conditions that they
will be consigned from port of entry to an establishment having proper
facilities for their sanitary control and disinfection; that they will move
from port of entry to the establishment in cars or approved containers,
sealed either with customs seals or seals of the Department of Agriculture;
that they will be handled at port of entry and en route to such establish-
ment in accordance with the provisions of these regulations, and that
they will be disinfected by one of the methods approved, or which may
hereafter be approved, by the Chief of the Bureau of Animal Industry.
Seals of the Department of Agriculture shall be affixed to said cars and
containers only by inspectors of the Bureau of Animal Industry, or by
customs officers, and may be broken only by inspectors of the Bureau
of Animal Industry, by customs officers, or by other persons authorized
so to do by the Bureau of Animal Industry. Customs seals shall in no
case be broken except by customs officers.
Regulation II
HARD, SUNDRIED HIDES AND SKINS, AND ABATTOIR HIDES AND SKINS
Section 1. Hard, sundried hides and skins may be imported without
disinfection if certified as required in section 1 of Regulation I to be
from a locality where anthrax is not prevalent, if the bale? or hides are
HIDES AND SKINS 39
distinctly marked for identification, each shipment showing invoice num-
ber, names and addresses of consignee and consignor, as such hard, sun-
dried hides and skins so certified showing freedom from anthrax can be
considered as having been disinfected by the process of curing and need
not be submitted to any further treatment. Hard, sundried hides or skins
may be imported without being certified to be from a locality where
anthrax is not prevalent, upon the conditions prescribed in section 2,
Regulation I, for the importation of uncertified hides and skins.
Sec. 2. Abattoir hides and skins taken from animals slaughtered in
Sweden, Norway, Denmark, Australia, New Zealand, Great Britain,
Uruguay, Argentina, Brazil, and Venezuela when accompanied by a
certificate of an official veterinarian of the country where such animals
were slaughtered showing that such hides or skins were taken from
animals free from disease at the time of slaughter, may be imported
into the United States without disinfection. Abattoir hides and skins
from the countries specified, which are uncertified, and abattoir hides and
skins from countries other than those specified, may be imported subject
to the requirements of Regulation I,
Regulation III
GLUE STOCK
Fleshings, hide cuttings, and parings, or glue stock may be imported
without disinfection —
(a) If accompanied by a certificate signed by one of the officials
mentioned in section 1 of Regulation I, showing the non-prevalence of
anthrax in the locality of origin ; or
(&) If shown upon entry to have been disinfected by heat; or
(c) If shown to have been disinfected by acidulation; or
(d) If shown to have been disinfected by soaking in a milk of lime
or a lime paste; or
(e) If shown to have been dried by exposure to the action of the sun
and air for a sufficient time to render each piece of the hardness of a
sundried hide.
If the said materials are not accompanied by the certificate described in
paragraph (a), and are not shown to have been treated by one of the
methods above indicated, they may be imported, upon the condition that
the consignee or his agent files a satisfactory bond or agreement that said
materials and their containers will be handled or disinfected in a manner
acceptable to the Bureau of Animal Industry before distribution from the
factory or establishment to which consigned.
Regulation IV
BONES, HOOFS, AND HORNS
Section 1. Bones, hoofs, and horns which are clean, dry, and free
from pieces of hide, flesh, or sinews may be imported without disinfection.
Sec. 2. Bones, hoofs, and horns, with pieces of hides or tendons at-
tached, and also horn piths, may be imported upon the conditions that
said materials be forwarded to a factory or other establishment in cars
or approved containers sealed in the manner prescribed in section 2,
Regulation I, and that the consignee or his agent files a satisfactory bond
or agreement that such materials and their containers will be handled or
disinfected in a manner acceptable to the Chief of the Bureau of Animal
Industry.
40 PRACTICAL TANNING
Regulation V
WOOL AND HAIR
Section 1. Raw wool or hair clipped from healthy live animals, scoured
wool and hair, and noils of wool and hair which have been properly
scoured may be imported without disinfection or certification.
Sec. 2. Picked or pulled wool or hair, when accompanied by an affidavit
of the exporter designating the bales or packages thereof by their
markings, indicating the consignor, consignee, and number of the invoice,
and stating that all the wool or hair contained in the bales or packages
came from animals free from anthrax, may be imported upon the condi-
tions that the consignee or owner of the wool or hair, or his agent, files
a satisfactory bond or agreement assuring proper facilities of disinfection
at the establishment to which the shipment is consigned and that such
wool or hair will be disinfected by proper exposure to a temperature of
not less than 165° F. prior to any transfer or reshipment from such estab-
lishment. If such wool or hair is unaccompanied by the above-mentioned
affidavit it may be imported upon condition that the consignee or owner
thereof or his agent files a satisfactory bond or agreement assuring
proper facilities for disinfection at the establishment to which the ship 1
ment is consigned and that all of such wool or hair will be disinfected by
proper exposure to a temperature of not less than 200° F. for at least 15
minutes prior to any transfer or re-shipment from such establishment.
Sec. 3. Importation of abattoir pulled wool will be permitted without
restrictions from any country maintaining an efficient veterinary inspection
system, when accompanied by a certificate signed by an official veterinary
inspector of such country, of, in the absence of such official veterinary
inspector, by a certificate of a United States consular officer of the locality
from which shipped to the effect that said wool was procured from sheep
slaughtered therein and passed under Government inspection, and that
in the process of wet pulling and drying it has been subjected to a
temperature of not less than 165° F. Such certificate shall indicate the
number of bales, marks, names, and addresses of consignor and consignee,
locality of origin, date of shipment, invoice number, and transporting
vessel, and shall also show that the consignment consists of abattoir pulled
wool which, in the process of wet pulling and drying, has been subjected
to a temperature of 165° F.
Sec. 4. Wool or hair not otherwise provided for in these regulations,
or not complying with the provisions thereof, may be imported upon the
conditions that such articles be shipped from port of entry to destination
in cars or satisfactory containers, sealed in the manner prescribed in
section 2 of Regulation I ; that the destination be a factory or establish-
ment having satisfactory facilities for disinfecting the same, and that they
will there be disinfected by proper exposure to a temperature of not
less than 200° F. for at least 15 minutes, or in such mannef as may be
directed by the Chief of the Bureau of Animal Industry, prior to any
transfer or reshipment therefrom. Such wool or hair may be stored in
bond at the port of entry, subject to shipment and disinfection, as herein
provided, on being released from bond. The consignee, owner, or his agent
will be required to file a satisfactory bond or agreement to fulfill all
requirements as to shipment and disinfection.
Regulation VI
certificates from other than official veterinarians and consular
officers
Section 1. Whenever it shall be determined by the Secretary of Agri-
culture, after investigation, that in any foreign country or locality thereof
HIDES AND SKINS 41
in which no official veterinarian of the Government or United States
consular officer is located, there is a satisfactory qualified official, authorized
by the Government of such foreign country to sign and issue certificates
stating that anthrax is not prevalent and that neither foot-and-mouth
disease nor rinderpest exists in the locality from which articles enumerated
in these regulations are shipped, to sign and issue other certificates, to
make affidavits and other declarations, and to supervise the shipment of
hides and skins, glue stock, and other animal by-products, as specified in
the regulations, due notice will be given of such determination, and
thereafter such official may sign and issue the said certificates, make the
said affidavits and declarations, and supervise the shipment of hides and
skins, glue stock, and other animal by-products, in manner and form
prescribed in the regulations; and such acts performed by the said
official shall have the same force and effect as if performed by an official
veterinarian of the country of origin or by an United States consular
officer.
Sec. 2. The name of each foreign official authorized to do and perform
the acts specified in section 1 of this regulation, when submitted to and
approved by the Secretary of Agriculture, will be_ published, and the
Chief of the Bureau of Animal Industry shall file with each such official
a copy of these regulations and copies of amendments which may hereafter
be made thereto. No act specified in section 1, performed by a foreign
official, shall be recognized unless performed by an official whose name
has been published, as required herein, and whose authority to do such
acts has not been revoked.
Regulation VII
HAY, STRAW, ETC., AND MEATS PACKED IN HAY OR STRAW
Section 1. On account of the existence of foot-and-mouth disease in
the countries of continental Europe and South America, and the imprac-
ticability of disinfecting hay and straw used as the packing on meats
offered for entry without injuring the meats for food purposes, the entry
into the United States from any of those countries of any meats -packed
in hay or straw is prohibited.
Sec. 2. Bran, middlings, and mill feed may be imported from Argen-
tina without being disinfected as prescribed in section 4 of this regulation
if accompanied by- an affidavit of the shipper, showing that such bran,
middlings, or mill feed was conveyed by chutes directly from the mill
in which produced into the vessels transporting the same to the United
States.
Sec. 3. Because of lack of danger of the communication of disease
through the importation of hay, straw, forage, and similar materials,
including bran, middlings, or other mill feed originating in and trans-
ported directly from Great Britain, Ireland, the Channel Islands, Canada,
and Mexico, such articles may be imported into the United States from
these countries as long as the above condition continues to exist without
being disinfected as prescribed in section 4 of this regulation.
Sec. 4. Except as otherwise provided in this regulation, all hay, straw,
forage, or similar materials, including bran, middlings, or other mill
feed, offered for importation from any foreign country, shall be disin-
fected in a manner prescribed by the Chief of the Bureau of Animal
Industry, at the expense of the owner, before being unloaded from the
vessel or conveyance bringing the same into any port of the United States,
and when unloaded and landed shall be stored and held in quarantine for
a period of not less than three months at some place acceptable to the
Chief of the Bureau of Animal Industry, and under directions prescribed
by him.
42 PRACTICAL TANNING
Regulation VIII
CANADA
Because of the lack of danger of the introduction of disease into the
United States through the importation of the articles enumerated in
these regulations originating in and transported directly from Canada,
such articles may be imported from Canada as long as the above condition
continues to exist without being disinfected or certified as prescribed by
these regulations.
Regulation IX
PRODUCTS FROM DISEASED ANIMALS
Importation into the United States of any animal by-products, taken
or removed from animals affected with anthrax, foot-and-mouth disease,
or rinderpest, is prohibited.
Regulation X
METHODS FOR DISINFECTION OF HIDES, SKINS, AND OTHER MATERIALS
Hides, skins, and other materials, required by these regulations to be
disinfected shall be subjected to disinfection by methods found satisfactory
and approved from time to time by the Chief of the Bureau of Animal
Industry of the United States Department of Agriculture. The Chief
of the Bureau of Animal Industry is authorized to revoke from time
to time any methods which have been approved by him.
Regulation XI
DISINFECTION OF CARS, BOATS, OTHER VEHICLES, AND PREMISES
Section 1. Cars, boats, other vehicles, yards, and premises which have
been used in the transportation, handling, and storing of uncertified or
non-disinfected imported hides, skins, and parts thereof, hair, wool, and
other animal by-products, hay, straw, forage or similar material, permitted
entry subject to disinfection, shall be cleaned and disinfected under the
supervision of the Bureau of Animal Industry, as indicated in Regulation
XII, and in the manner provided in sections 2 and 3 of this regulation.
Except as hereinafter provided in these regulations, cars, boats, and other
vehicles which have been used in the transportation of uncertified or
non-disinfected imported hides, skins, and parts thereof, hair, wool, and
other animal by-products, hay, straw, forage, or similar material, per-
mitted entry subject to disinfection, shall not be moved in interstate or
foreign commerce until the said cars, boats, and other vehicles have been
cleaned and disinfected under supervision of the Bureau of Animal In-
dustry in accordance with sections 2 and 4 of this regulation.
Sec. 2. Paragraph 1. Cars required by these regulations to be cleaned
and disinfected shall be treated in the following manner: Collect all
litter and other refuse therefrom and destroy by burning or other ap-
proved methods, clean the exterior and interior of the cars, and saturate
the entire interior surface, including the inner surface of the car doors,
with a permitted disinfectant.
Paragraph 2. Boats required by these regulations to be cleaned and
disinfected shall be treated in the following manner: Collect all litter
and other refuse from the decks, compartments, and all other parts of the
boat used for the transportation of materials covered by these regula-
tions, and from the portable chutes or other appliances or fixtures used
HIDES AND SKINS 43
in loading and unloading same, and destroy the litter and other refuse
by burning or by other approved methods, and saturate the entire surface
of the said decks, compartments, and other parts of the boat with a per-
mitted disinfectant.
_ Paragraph 3. Buildings, sheds, and premises required by these regula-
tions to be disinfected shall be treated in the following manner : Collect
all litter and other refuse therefrom and destroy the same by burning
or other approved methods and saturate the entire surface of the fencing,
chutes, floors, walls, and other parts with a permitted disinfectant.
Sec 3. Paragraph 1. All hides, skins, and other materials ■ subject
to disinfection at destination under the provisions of these regulations shall
be entered at ports having docking and unloading facilities separate and
apart by not less than 100 feet, from yards, premises, roads, or runways
where cattle and other ruminants and swine are kept, held, conveyed, or
driven except for immediate slaughter. No animals of the species named,
except for immediate slaughter, shall be permitted on any dock or prem-
ises where imported hides or other materials subject to disinfection
at destination are being unloaded, stored, or handled within 24 hours
following the completion of such handling, unless the said hides or other
materials have been removed and the place or places where they were
unloaded, stored, or handled, or with which they were in contact, have
been cleaned and disinfected in a manner approved by the Chief of the
Bureau of Animal Industry.
Paragraph 2. Except as otherwise provided in these regulations, all
such hides, skins, and other materials subject to disinfection shall be
loaded and shipped under official supervision and under seals as prescribed
in section 2 of Regulation I.
Paragraph 3. Dust and refuse at docks, unloading places, and all ware-
houses and other establishments shall be controlled. All dust and other
refuse shall be collected and destroyed by burning or other approved
methods.
Sec. 4. Paragraph 1. The substances permitted for use in disinfecting
cars, boats, other vehicles, and premises are as follows :
(a) Compound solution of cresol, U. S. P., at a dilution of at least
4 fluid ounces to 1 gallon of water.
(b) A permitted "saponified cresol solution" at a dilution of at least
4 fluid ounces to 1 gallon of water.
(c) Liquified phenol (liquified carbolic acid) at a dilution of at least
6 fluid ounces to 1 gallon of water.
(d) Chlorid of lime (U. S. P. strength, 30 per cent available chlorin)
at a dilution of 1 pound to 3 gallons of water.
Paragraph 2. The use of "saponified cresol solution" as a substitute for
compound solution of cresol, U. S. P., as a disinfectant is permitted, pro-
vided that such "saponified cresol solution" shall conform to the following
requirements :
(a) The formula of the product shall employ not less than 28 per cent
by weight of linseed oil. Either caustic potash, caustic soda, or a mixture
of caustic potash and caustic soda may be used to saponify the linseed
oil. The cresol used shall be at least 95 per cent pure, and enough of
this commercial grade of cresol (cresylic acid) shall be employed in com-
pounding the disinfectant to bring the actual amount of cresol in the
finished product up to 50 per cent.
(b) The product shall remain a homogeneous liquid when cooled to
32° F. It shall contain substantially no unsaoonified linseed oil or excess
alkali. Tt shall be readily soluble in cold distilled water; the solution shall
be practically clear and shall contain no globules of undissolved oil or
cresylic acid.
(c) Manufacturers wishing to offer saponified cresol solution as indi-
cated above for use in official disinfection shall first submit a sample of at
least 8 ounces for examination, together with a statement of the formula
44 PRACTICAL TANNING
employed and a guaranty that the product will be maintained of a quality
uniform with the sample submitted.
(d) To prevent confusion, each product shall bear a distinctive trade
name or brand, together with the name of the manufacturer or distributor.
There shall be no mention of the United States Department of Agriculture
or the Bureau of Animal Industry on the labels, containers, or printed
matter accompanying products permitted to be used in official disinfection.
The permitted saponified cresol solution shall be used at a dilution of
at least 4 ounces of the solution to 1 gallon of water.
Regulation XII
■ PLACARDING CARS AND MARKING BILLING
.Section 1. Transportation companies shall securely affix to and main-
tain upon both sides of all cars carrying uncertified or non-disinfected
imported hides, skins, and parts thereof, hair, wool, and other animal by-
products, permitted entry subject to disinfection, durable placards not
less than 5s by 8 inches in size, on which shall be printed with permanent
black ink and in bold-faced letters not less than H inches in height the
words "UNCERTIFIED IMPORT ANIMAL PRODUCT." These
placards • shall also bear the words "CLEAN AND DISINFECT THIS
CAR." Each of the waybills, conductors' manifests, memoranda, and
bills of lading pertaining to such shipments shall have the words "UN-
CERTIFIED IMPORT ANIMAL PRODUCT, CLEAN AND DISIN-
FECT CAR," plainly written or stamped upon its face. If for any
reason the placards required by this regulation have not been affixed to the
car, or the billing has not been marked by the initial or the connecting
carrier, or the placards have been removed, destroyed, of rendered illegi-
ble, the placards shall be immediately affixed or replaced, and the billing
marked by the initial of connecting carrier, the intention being that the
billing accompanying the shipment shall be marked and the car placarded
as herein specified from the time such shipments leave the port of entry
until they are unloaded at final destination and the cars are cleaned and
disinfected as required by Regulation XI.
Sec. 2. If it is necessary to unload enroute any of the products specified
in this regulation, the car from which the transfer is made and any part
of the premises at the point of transfer which may have been contaminated
shall be cleaned and disinfected by the transportation company, in accord-
ance with the provisions of Regulation XI, and the transportation com-
pany shall immediately report the transaction by telegraph, to the Chief
of the Bureau of Animal Industry, Washington, D. C. Such report
shall include the information indicated as follows: (a) Nature of
emergency; (b) place where product was unloaded; (c) original points
of shipment and destination; (d) number and initials of the original car;
also number and initials of the car into which the product is reloaded in
case original car is not used.
Sec. 3. Cars required by these regulations to be cleaned and disin-
fected shall be treated in the manner specified in Regulation XI, under the
supervision of the Bureau of Animal Industry, by the final carrier at
destination as soon as possible after unloading and before the same are
moved from such final destination for any purpose except as otherwise
hereinafter provided.
When the products are destined to points at which an inspector of the
Bureau of Animal Industry and proper facilities are maintained, the cars
shall be cleaned and disinfected at such points under supervision of such
inspector.
When the products are destined to points at which an inspector or
other duly authorized representative of the Bureau of Animal Industry
is not maintained, the transportation company shall seal, bill, and forward
HIDES AND SKINS 45
the infectious cars to a point to be agreed upon between the transportation
company and the Bureau of Animal Industry, and at which an inspector
is maintained. The transportation company shall there clean and disinfect
the said cars under the supervision of the Bureau of Animal Industry.
When the products are destined to points at which an inspector of the
Bureau of Animal Industry is maintained, but at which proper facilities
can not be provided, the transportation company may, upon permission
first secured from the Bureau of Animal Industry, seal, bill, and forward
the cars to a point at which an inspector of the Bureau of Animal In-
dustry is maintained and proper facilities provided, and there clean
and disinfect the said cars under the supervision of the Bureau of
Animal Industry.
Regulation XIII
TERRITORIAL POSSESSIONS
These regulations shall be applicable to all hides, fleshings, hide cuttings,
parings, and glue stock, sheepskins and goatskins and parts thereof, hair,
wool, and other animal by-products, hay, straw, forage, or similar material
which is offered for entry into the United States from any place under
the jurisdiction of the United States to which the animal quarantine laws
of this country do not apply.
Prior Order Annulled
Treasury Department and Department of Agriculture Joint Order No.
1, of October 21, 1916, and all amendments thereto, shall cease to be
effective on and after January 1, 1918, on and after which date this order,
which for purposes of identification is designated as United States
Treasury Department and Department of Agriculture Joint Order No. 2,
shall become and be effective until otherwise ordered.
L. S. Rowe,
Acting Secretary of the Treasury.
D. F. Houston,
Secretary of Agriculture.
UNITED STATES DEPARTMENT OF AGRICULTURE
BUREAU OF ANIMAL INDUSTRY
Special Order Prescribing Methods for the Disinfection of Hides,
Skins, Fleshings, Hide Cuttings, Parings, and Glue Stock, and Other
Animal By-Products, Hay, Straw, Forage, or Similar Material Of-
fered for Entry into the United States, and the Containers of Glue
Stock, Bones, Hoofs, and Horns so Offered for Entry.
United States Department of Agriculture,
Bureau of Animal Industry
District of Columbia, December 14, 1917.
In accordance with the provisions of the United States Treasury De-
partment and Department of Agriculture Joint Order No. 2, of October
15, 1917, "Regulations governing the sanitary handling and control of
hides, fleshings, hide cuttings, parings, and glue stock, sheepskins and goat-
skins and parts thereof,, hair, wool, and other animal by-products, hay,
straw, ; forage, or similar material offered for entry into the United
States," the following methods for the disinfection of the above-named
materials and articles are hereby prescribed, effective January 1, 1918.
46 PRACTICAL TANNING
I. DISINFECTION OF HIDES AND SKINS PRIOR TO SHIPMENT
Hides and skins disinfected prior to shipment as provided by regulation
I, section 1, of said Joint Order No. 2, must be disinfected by one of
the following methods :
(a) By immersion for not less than 24 hours in a 1 to 1,000 bichlorid
of mercury solution.
(b) By immersion for not less than 20 hours in a solution containing
2 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent
sodium chlorid.
(c) By immersion for not less than 40 hours in a solution containing
1 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent
sodium chlorid.
(J) By immersion for not less than 24 hours in a solution containing
1 per cent formic acid, and mercuric chlorid in the proportion of 1 part
to 2,500 parts of the solution. Hides or skins treated by this process shall
be held for two weeks following the treatment before neutralization.
(e) By de-hairing and pickling in a solution of salt containing a definite
percentage of mineral acid and packing in barrels or casks while still wet
with such solution, provided the hides or skins are not neutralized within
30 days after being so packed.
II. DISINFECTION OF HIDES AND SKINS AFTER ARRIVAL IN THE UNITED STATES
Hides and skins required by Regulation 1, section 2, and Regulation 2 of
said Joint Order No. 2 to be disinfected on arrival at a United States port
of entry shall be moved to an approved warehouse at such port or in sealed
cars or containers to an establishment having proper facilities for their
sanitary control and disinfection. They shall be stored and handled prior
to disinfection in compartments set aside for that purpose, and all hides
and skins stored or handled in such compartments shall be treated in
accordance with the following rules :
1. All dust, litter, or waste arising from sorting, cutting handling, or
moving said hides or skins prior to soaking shall be burned or disinfected
by exposure to a temperature of not less than 100° C. (212° F.) moist
heat for not less than 15 minutes.
2. The hides and skins shall be subjected to disinfection by one of the
following methods :
(a) By immersion for not less than 20 hours in a solution containing
2 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent
sodium chlorid.
(6) By immersion for not less than 40 hours in a solution containing
1 per cent absolute hydrochloric acid (hydrogen chlorid) and 10 per cent
sodium chlorid. „
(c) By immersion for not less than 24 hours in a solution containing
1 per cent formic acid, and mercuric chlorid in the proportion of 1 part
to 2,500 parts of the solution. Hides or skins treated by this process shall
be held for two weeks following the treatment before neutralization.
(d) By immersion for not less than 48 hours in a 1 to -1,000 bichlorid of
mercury solution.
(e) By immersion for not less than 6 days in a 1 to 5,000 bichlorid of
mercury solution, plus not less than 5 days in lime of the usual strength
for de-hairing.
Or, in lieu of disinfection by one of the foregoing mentioned processes,
the effluent shall be subjected to treatment by one of the following
methods :
(/) Heat the effluent from soak vats, mill drums, breaking machines, or
other similar equipment to a temperature of 100° C. (212° F.) and main-
tain at that temperature for at least one minute.
(g) Treat the effluent from soak vats, mill drums, breaking machines,
and other similar equipment with chlorin in such manner and in such
HIDES AND SKINS 47
amount (not less than 250 parts per million) as to secure efficient
disinfection.
(h) Subject the effluent from soak vats, mill drums, breaking machines,
and other similar equipment to filtration, the effluent from the filters to be
treated with chlorin in sufficient amount and in such manner as to secure
efficient disinfection : Provided, however, That in this method of treatment
the sludge which collects on the filters shall be subjected to disinfection by
heating at a temperature of not less than 100° C. (212° F.) for not less
than 15 minutes.
(i) Treat the effluent from soak vats, mill drums, breaking machines,
and other similar equipment with 50 parts of chlorin per million parts of
effluent and heat at not less than 80° C. (176° F.) for not less than 30
minutes. .
(/) In the case of sheepskins and goatskins, until further notice, by
immersion for not less than 12 hours in a solution of milk of lime con-
taining the equivalent of 5 per cent of calcium oxid (CaO).
III. DISINFECTION OF GLUE STOCK
All fleshings, hide cuttings, and parings or glue stock shall be moved
from the port of entry to an establishment having proper facilities for
the sanitary control and disinfection of such materials, in cars or approved
containers sealed with either Department of Agriculture or customs seals,
and upon arrival at the establishment, disinfected before removal there-
from by one of the following methods :
1. By heating in water at a temperature of 100° C. (212° F.) for not
less than 15 minutes, or by heating in water at a temperature of* not less
than 82° C. (180° F.) for not less than four hours.
2. By soaking in milk of lime or lime paste for not less than 24 hours.
3. By soaking in water containing not less than 2 per cent of absolute
hydrochloric acid for not less than 20 hours.
4. By soaking in water containing not less than 1 per cent of absolute
hydrochloric acid for not less than 40 hours.
IV. DISINFECTION OF BONES
1. All horn pith and porous bones classed as glue stock must be moved
from the port of entry to an establishment having proper facilities for
their sanitary control and disinfection, in cars or approved containers
sealed with either Department of Agriculture or customs seals, and, upon
arrival at the establishment, disinfected before removal therefrom as
provided for glue stock.
2. Bones with pieces of hide or tendons attached and all other bones
not otherwise provided for shall be moved from the port of entry to an
establishment having proper" facilities for their sanitary control and disin-
fection, in cars or approved containers sealed with either Department of
Agriculture or customs seals, and upon arrival at the_ establishment,
disinfected before removal therefrom by one of the following methods:
(a) By heating in water at a temperature of 100° C. (212° F.) for not
less than 15 minutes. o
(b) By heating in water at a temperature of not less than 82 C.
(180° F.) for not less than four hours.
V. DISINFECTION OF HOOFS AND HORNS
Hoofs and horns shall be moved from the port of entry to an establish-
ment having proper facilities for the sanitary control and disinfection of
such materials, in cars or approved containers sealed with either Depart-
ment of Agriculture or customs seals, and disinfected before removal
from the establishment by heating in water at a temperature of not less
than 74° C (165° F.) for not less than 15 minutes. Bones removed from
48 PRACTICAL TANNING
horns and hoofs that are required to be disinfected shall be handled as
provided for glue stock.
VI. DISINFECTION OF CONTAINERS OF GLUE STOCK, BONES, HOOFS, AND HORNS
Containers of glue stock, bones, hoofs and horns, which under the pro-
visions of Regulations III and IV of Joint Order No. 2, are required to be
disinfected, shall be handled as follows:
(a) The containers shall be burned; or
(b) The containers shall be subjected to moist heat at a temperature not
less than 100° C. (212° F.) for not less than IS minutes.
VII. DISINFECTION OF HAY, STRAW, ETC.
Hay, straw or similar materials shall be placed in a compartment made
tight by sealing all crevices therein and then subjected to treatment with
formaldehyde gas applied as follows:
The formaldehyde gas shall be generated from solutions of formalde-
hyde containing not less than 37 per cent actual formaldehyde by pouring
the formaldehyde solution onto pulverized potassium permanganate, the
formaldehyde solution and the potassium permanganate being employed in
the proportion of 20 ounces of formaldehyde solution by weight and 16%
ounces of potassium permanganate by weight to each 1,000 cubic feet of
space in the compartment to be disinfected. Bales of hay, straw, or other
material shall be piled in block so that not more than 6 inches of any sur-
face of the bale is in contact with another bale, or if deemed necessary
by the inspector, the bales shall be broken and the straw or hay loosened,
so that a satisfactory penetration of the formaldehyde gas may be obtained.
The disinfection with formaldehyde gas shall be carried out in compart-
ments in which the temperature is not less than 65° F.
J. R. Mohler,
Chief of Bureau of Animal Industry.
Hide structure. — Although the skins of the various ani-
mals seem at first glance to have little in common, they pre-
sent, on closer examination, much similarity of structure. The
difference in texture and thickness, on the other hand, makes
their practical application vary greatly. The skins of lizards,
alligators, fish, and serpents differ from those of higher ani-
mals in that the epidermis becomes harder and forms scales.
Figures 34 and 35 show cross-sections of hide.
The skin is not merely a covering for the animal, it is at
the same time the seat of the organs of sense and of certain
important secretions. It consists of two principal layers, the
epidermis (epithelium, cuticle) and the corium (derma, cutis,
or true skin). The epidermis is very thin as compared with
the true skin which it covers, and is entirely removed prepara-
tory to tanning ; it nevertheless possesses important functions.
Its inner mucous layer, which rests upon the true skin, is soft
HIDES AND SKINS 49
and composed of living nucleated cells, which multiply by di-
vision and form cell-walls of keratin. These are elongated in
the deeper layers, and gradually become flattened as they ap-
proach the surface, where they dry up and form the horny
layer which is being constantly worn away, thrown off as dead
scales of skin, and renewed from below by the multiplication
of the cells.
It is from the epithelial layer that the hair, as well as the
sweat and fat-glands, are developed. Each hair is surrounded
Figure 34. — Cross-section of calfskin.
by a sheath continuous with the epidermis, and in which the
young hair usually grows as the old one falls out. Near the
openings of the hair-sheath upon the surface of the skin the
ducts of the sebaceous or fat-glands pass into the sheath, and
secrete a sort of oil to lubricate the hair. The base of the hair
is a bulb, enclosing the hair papilla, which is a projecting knob
of the true skin, and which, by means of the blood-vessels
contained in it, supplies nourishment to the hair. The hair
bulb is composed of round soft cells, which multiply rapidly,
and, pressing upward through the hair-sheath, become hard-
ened, thus increasing the length of the hair.
The process of development of the sudoriferous or sweat-
glands is very similar to that of the hair. They consist of
more or less convoluted tubes with walls formed of longitudi-
50 PRACTICAL TANNING
nal fibers of connective tissue from the corium, lined with
a single layer of large nucleated cells which secrete the
perspiration.
Besides the hair, and hair-sheaths, and the sebaceous and
sudoriferous glands, the epidermis layer produces other struc-
tures of a horny character, including horns, claws, and nails,
which, both chemically and anatomically, are analogous to ex-
aggerated hairs. This is apparent in the quills of the porcu-
pine. The whole of the epidermis, together with the hairs,
is separated from the corium by an exceedingly fine membrane
Figure 35. — Cross-section of cowhide.
called the "hyaline" or glassy layer. This forms the very thin
grain surface of tanned leather, which is of a structure dif-
ferent from the rest of the corium.
The structure of the corium or true skin is quite different
from that of the epidermis. It is composed principally of in-
terlacing bundles of fibers known as "connective tissue," and
cemented together by a substance more soluble than the fibers
themselves. These fiber bundles are loosely interwoven in the
middle portion of the skin, but become compact again near
the flesh. The outermost layer, just beneath the epidermis, is
also very close and compact. The skin is united to the ani-
mal by a network of connective tissue (pannicnlus adiposus),
HIDES AND SKINS
51
which is frequently full of fat cells and is then called "adipose
tissue." This portion, together with some actual flesh, is re-
moved in the process of fleshing.
Ordinarily, the corium or true skin is the only portion used
for leather. To obtain it in a suitable condition for the vari-
ous tanning processes, the hair or wool, together with the
epithelium, must be completely removed without damaging the
skin itself; and special care must be taken that the grain, or
portion next the epidermis, does not suffer injury during the
Figure 36.— Cross-section of calfskin, (a) Corne-
ous layer, (b) malpighian layer, (c) papil-
lary layer, (d) reticular layer, (e) hair
shaft, (f) hair follicle, (g) sebaceous gland,
(h) hair, (i) inner root-sheath, (o) outer
root-sheath.
treatment. Figure 36 shows a cross-section of a calfskin five
weeks old, prepared by Geo. D. Rosenthal.
Butt,
Shoulder,
per cent
per cent
4.14
5.16
12.31
16.74
4.81
2.29
58.83
39.66
19.91
36.15
52 PRACTICAL TANNING
Samples were taken from various parts of the skin, .which
on analysis gave the following results :
Belly,
Constituent percent
Coagulable protein 4.30
Elastin 19.43
Mucoid 1.24
Collagen 51.46
Keratin 25.73
A very exhaustive study of hide structure was conducted
by Dr. Rosenthal, the result of which appears in the 1917 vol-
ume of the American Leather Chemists' Association.
Conservation of skin substance. — It must appear evident
to anyone engaged in the hide and skin business that there is
continual loss of substance and depreciation of value in a skin
from the moment it is taken off the animal until it is finally
converted into leather. The principal reason for this loss is
the presence of liquefying bacteria, which bring the gelatine of
the skin into solution. The conservation of this material is
of vital interest to the tanner, and should also demand the at-
tention of the skin collector and dealer. With this end in view,
experiments were conducted for a number of years to dis-
cover some inexpensive method of conserving the substance
of skins, especially calfskins, without any detrimental effect.
Of all the materials tested, zinc chloride has been found to
prevent this liquefaction best, and consequent loss and deteri-
oration without producing any results, visible either in
the skin or in the finished leather, that are in any way
objectionable.
Zinc chloride. — The method of using zinc chloride, which
has given the most satisfactory results, is as follows: The
fresh skins are first salted in clean, coarse salt for the pur-
pose of withdrawing the blood from them, and are allowed
to remain in a low, narrow pile for 24 to 48 hours. They are
shaken out of this first salt, which is taken to the refuse pile
and thereafter used only for salting the trimmings, and placed
in a pack, and to the salt which is used for this second salting,
HIDES AND SKINS 53
zinc chloride is added. For convenience, a stock solution is
made of 1 lb. of zinc chloride to 1 gallon of water. To a bar-
rel of water, add 1 pint of this solution, and stir thoroughly.
The salt intended for the second salting is sprinkled with this
zinc chloride solution until a quantity, taken in the hands
and pressed, oozes moisture. The salt, treated as above, is
thrown on the skins in the usual way. Fresh skins treated
in this manner lose practically no gelatine and remain fresh
and clean as long as skins are ordinarily kept. The treatment
is also valuable in conserving skins that are shipped in. In
a case where skins show a tendency to hair-slipping or have
become heated, it is advisable to dip them first into a solution
of the zinc chloride made by adding 1 pint of the stock liquor
to a barrel of water, and salting as directed for the second
salt. The results obtained from handling hair-slipped skins
in this manner are remarkable. The zinc chloride instantly
checks the liquefaction of the bacteria, and the leather pro-
duced from the skins is the equal of that made from perfect
ones. Comparative experiments with cold-storage methods
have also been made. One lot of skins was kept at a tempera-
ture of 30° F., another at 0° F. ; at the same time, skins were
put in pack by the zinc chloride method, and all were held for
one year. Those treated in zinc chloride were in every way
equal to those kept in cold storage; and the leather produced
from the zinc-chloride treated skins was equal to that made
from strictly fresh stock.
A general following-up of • the above suggestions will do
much toward conserving the most valuable constituent of the
raw skin. The method is not an expensive one, zinc chloride
costing only about 30 cents a pound.
Formaldehyde. — The antiseptic and germicidal action of
this substance has long been known in medicine and found of
practical use, and its application for the preservation or dis-
infection of raw skins is therefore only natural. With its aid,
skins that have already undergone putrefaction may be steri-
lized, as well as such as it is feared may decompose during in-
terruption of the usual process. To effect this, for each 100
54 PRACTICAL TANNING
parts of the soak water, take 2 parts of 40 per cent formalde-
hyde, and use this solution for 6 to 8 days, when it should be
strengthened by the addition of a further 2 parts of formalde-
hyde. Dried skins should be merely soaked for 10 minutes in
a solution of formaldehyde of 4 per cent strength, after which
they should be laid in piles for 12 hours, and finally dried in
the air.
In 1902, Roberts, of Buenos Aires, patented a process by
which skins were subjected to the action of antiseptic gas —
that is, formaldehyde — for a time in order to preserve them.
The Conservadore Mercantile Co. of that city, according to
this patent, submitted skins after flaying and before salting
to the action of formaldehyde vapors in closed chambers. This
destroyed the putrefactive elements which were likely to be
present in the skins and sterilized them for a certain time;
finally the skins were salted and dried out.
Salting by itself does not sterilize skins permanently; it can
only retard and diminish the development and the activity of
the putrefactive organisms. The damage known as salt stains
is said by some investigators to be caused by micro-organisms
which resist the action of salt, and it may be presumed that a
treatment with formaldehyde would greatly reduce this form
of damage. Also, for skins which are preserved by means of
drying, formaldehyde may be of excellent service, the goods
not being exposed to the risk of decomposition setting in dur-
ing drying. Moreover, the pungent odor of the formaldehyde
repels flies and other insects, which, under other circum-
stances, are attracted to the skins during the drying process,
and thus the presence of larvae in the goods is very likely pre-
vented. Finally, it is possible by this means to disinfect the
skins from carrying disease germs, especially from places
which are often subject to this sort of danger. Complete dis-
infection by means of formaldehyde entails a very strong ac-
tion, and this causes several difficulties in the work of soaking,
liming, etc., which are nevertheless surmountable. In any
case, it is only recommended that this process be employed for
skins which have undergone slight putrefaction, and for
HIDES AND SKINS 55
those in which mere salting would not suffice for perfect
preservation. The strength of the solution should never ex-
ceed 5 per cent, as otherwise the skin substance will be greatly
hardened. If the skins are to be salted, they should not be
treated, previous to the salting, with a solution of formalde-
hyde, because they would absorb too much water, for the' re-
moval of which an excessive quantity of salt would be re-
quired. It is therefore necessary in this case to use formalde-
hyde in the gaseous form and not as a solution.
CHAPTER II
SOAKING
The processes that precede the actual tanning or conversion
of hides into leather are about the same for all classes, whether
the tannage be chrome or vegetable. The object of these proc-
esses is to bring the hide to the natural soft condition it
Figure 37. — Pin-mill, wash-wheel, or drum for washing fresh hides.
is in when removed from the animal's back, and in addition, to
remove the blood, manure, dirt, and salt.
Fresh or market hides. — This grade of hides, after having
been trimmed, simply requires washing to remove the blood
and dirt, and is usually accomplished by milling for about
a half-hour in cold, running water, using a pin-mill or drum
as shown in figure 37.
56
SOAKING
57
This treatment is absolutely necessary, as the adhering
blood, lymph, and dung, would soon set up putrefaction, with
subsequent damage to the stock.
Green-salted hides. — The hides are first trimmed — the
tails, shanks, and pates being cut off in the hide cellar — and
are then soaked. One of the most approved methods of soak-
'-■it*
■fly l^s|||L
: ,, j
'^- : '
Figure 38. — Washing hides preparatory to soaking.
ing is to hang the hides in the water, which should be soft and
clean. If the water is hard, 1 lb. of borax for each 100 gal-
lons of water, dissolved in hot water, should be stirred into
it to make it softer, and increase its softening and cleansing
powers. The hides should be hung in the water, from tail to
head, and left therein for 24 hours; they are then usually
taken out and cut into halves or sides. The water in the soak
vat is run out and fresh water run in, when the sides are put
back and soaked 24 hours longer. Splitting into sides can
also be done after the second soaking. The object of the
soaking process is to soften the hides and remove the salt,
58 PRACTICAL TANNING
dung, blood, and dirt adhering to them. It is important that
this be done quickly and thoroughly, so that the hides may go
into the lime clean and soft, yet retaining their substance in-
tact. Prolonged soaking of salted hides results in a loss of
gelatine and in loose and spongy leather. On the other hand,
if the hides are not soaked long enough, they do not go into
the lime in the right condition, and the grain may have serious
defects. It is usually best to change the water once during
the process. If the hides are very dirty, two changes are
necessary; if only slightly salty and dirty, one change is suf-
ficient. Figure 38 shows the stock out of the wash-wheel
and ready for soaking.
No exact rule for soaking can be given, as much depends
upon the thickness and condition of the hides and the temper-
ature of the water. Usually, however, ordinary hides are
sufficiently soaked by being hung in water 24 hours, then re-
moved and re-soaked another 24 hours. At the end of the
soaking process the sides are drained, fleshed, toggled together
in a chain, and passed into lime.
A common procedure for green-salted hides is to throw the
trimmed stock into fresh water for 24 hours, and then mill for
a half-hour in cold running water, when they are fleshed and
ready for depilation.
Dry-salted hides. — Those that have been dried after salt-
ing require a longer soaking to restore the natural soft condi-
tion. This is usually accomplished by soaking for 24 hours
in water to which 0.2 per cent of caustic soda has been added.
The hides are then removed from the soak and milled in run-
ning water for a half-hour. They are then cut into sides and
returned to the soaks for another day, when they are dry-
milled for half an hour, fleshed, and piled-down over night.
If not thoroughly soaked, they are returned to the soaks for
another day.
Dry hides. — Those that are received by the tanner in flint-
dry condition require longer soaking and more thorough work-
ing in order to get them into the soft, pliable condition which
is necessary before they can be fleshed and limed. The follow-
SOAKING 59
ing method of soaking dry hides usually proves satisfactory:
For every 100 gallons of water in the vat, dissolve 1 lb. of
sodium sulphide or -J lb. of caustic soda in hot water, and
pour the solution into the water, plunging thoroughly. Put
the hides into the water and let them soak 24 hours. At the
end of that time take them out of the water, put them into a
dry mill, and run them in it 30 minutes; next place them in a
pile or piles, covered up, and let them lie 24 hours; then put
them back into the water from which they were taken and let
them soak 24 hours longer. From this soaking, .run the hides
in the dry mill for a half-hour; then flesh them. After flesh-
ing, place in clean, cold water over night ; then lime them.
ff\
Figure 39. — Fulling stocks.
Formic acid is sometimes used in soaks to hasten the soften-
ing of dry hides, 1 lb. of the acid being added to each 100
gallons of water in the soak vat. The hides are first placed in
clean water for a day or two, and then hung in the acidified
soak. If they swell excessively, some salt should be added to
check the swelling. After the hides have been soaked two
or three days, they should be washed and placed in clean
water for a few hours and then placed in the lime. ■
Stocks. — In softening flint hides, some tanners resort to the
use of the stocks, or kickers, after the preliminary soaking.
This mechanical working takes the place of "breaking over,"
which was formerly accomplished on the beam with a blunt
knife. The stocks shown in figure 39 consist of a curved
60
PRACTICAL TANNING
metal or wooden box, in which two heavy hammers work
backward and forward on a cam, thus driving the hides against
the walls on either side. The treatment of hides by this
method is rather strenuous, and is being replaced by the drum
in most tanneries.
Fleshing. — In order to facilitate the depilation, hides and
skins are usually fleshed before entering the depilating liquor,
or may be so treated to assist in the soaking operation. This
fleshing consists in removing the excess of flesh or fat on the
under side of the hide, and may be accomplished over the beam
with a sharp knife or by means of machinery built for the
purpose. Figure 40 shows one of the many forms of such
Figure 40. — Turner pneumatic fleshing machine.
machines. It consists essentially of a spiral knife against
which the stock is forced by means of a heavy rubber-covered
roll. The machine may be adjusted to suit the thickness of
the hide and so regulated as to take off a light or deep cut as
desired.
Putrid soaks. — At one time the use of putrid soaks was very
common, but the modern tanner realizes that putrefaction
means loss of hide substance; and as he wishes to conserve
his hides as much as possible, this wasteful and dangerous
SOAKING
61
method has been almost entirely abandoned. Figure 41 shows
a pack of hides out of soak, and ready for depilation.
Chemical soaks.- — Various chemical products for hastening
soaking have been placed upon the market. They are all either
alkalies or alkaline salts, and have no advantage over sodium
sulphide or sodium hydroxide (caustic soda) ; in fact, expe-
Figure 41. — Hides ready for depilation.
rience has shown that of all softening agents .the latter is the
most satisfactory. For dry hides or kips, a 0.2 per cent solu-
tion of this chemical will reduce the time of softening for
even flint hide to about two days.
Butyric acid has been suggested as a softening agent, in
which case from 3 to 5 oz. are used for each 100 lb. of stock.
The advantage derived is that no hide substance is lost. It
has never, however, met with popular approval.
Paddle soaking. — In pit soaking, the stock is likely to pack
at the bottom, and thus be prevented from absorbing water
uniformly. To overcome this, the hides are drawn and thrown
62 PRACTICAL TANNING
back. By means of a paddle, the labor involved in handling
the stock is obviated, and by simply running the paddle at five-
minute intervals twice a day, the hides may be loosened up
and the position quickly changed. The use of a paddle is
especially advantageous for green-salted or market hides.
Kips. — The same methods as applied to hides hold equally
good for kips. As this grade of raw stock is used for the
same purposes as light hides, the processes employed need no
further elaboration.
Calfskins. — One of the most important processes through
which calfskins are passed before they are tanned into leather
consists in soaking, which cleanses and softens them. There
are also mechanical and manual operations, such as trimming
and fleshing to remove the superfluous and objectionable parts.
Green-salted skins. — The soaking of green-salted calfskins
should be done in clean, fresh water. As good a method of
soaking as any is to shake the skins free from salt, trim off
the useless portions, and then put them into the water for 24
hours. The remaining salt and dirt are next removed by
washing the skins for 15 minutes with running water. Light
skins are then fleshed and put through a liming process. Heavy
skins are re-soaked 12 hours and then passed into the lime
liquors.
Dry skins. — Calfskins that are received at the tannery in a
hard, dry condition require thorough softening before they can
be limed and unhaired. Caustic soda is an effective softener
for such skins. . Dissolved and added to the water in which
the skins are soaked, it hastens the softening and freshens up
the withered fibers and grain; 1 lb. of the alkali is used for
each 100 gallons of water in the paddle vat. When the skins
have become flexible in the soak they should be taken out and
run dry in a drum for half an hour, then put back into the
water and soaked 24 hours longer. If they are not perfectly
soft at the end of that time, they should be placed in piles over
night and then re-soaked in clean water for 24 hours. They
are next trimmed and fleshed, and put into the lime.
In place of caustic soda, formic acid and salt may be used
SOAKING 63
in the soaks. For 100 parts of skins, 5 parts of the acid are
used in 1000 parts of water; some salt may advantageously
be added. This process takes from 2 to 5 days, according to
the substance and condition of the skins. The softening can
be hastened by running the skins in a drum, but this should
never be done until they are soaked through and fairly pliable
in the soak. Upon coming from the acid soak, the skins are
fleshed and then put into the lime solutions.
Sheepskins. — In the soaking of sheepskins previous to the
removal of the wool, the tanner or the wool-puller has not only
to consider how the skin can best be brought back to its natu-
ral soft condition, but it is also necessary for him to consider
the effect the method of soaking adopted may have upon the
quality of the wool, since it may be greatly depreciated in
value by using the wrong materials to aid the softening of
dry sheepskins. In the case of skins received direct from the
butcher, all that is required before the depilatory paint is ap-
plied is to remove adhering dirt and blood by washing or
soaking in water. Simple treatment in this way for a short
time has no effect whatever upon the wool, but prolonged
soaking may remove much of its peculiar natural fat, which
should be retained, as otherwise the wool loses weight, and
felting is liable to take place, the luster of the wool being
also diminished.
Fresh skins. — For fresh skins, the method recommended is
to shake them free from adhering salt, and then place them
in fresh soft water to remove salt, blood, dirt, etc. They may
then, if necessary, be transferred to fresh water for a few
hours, after removing any clotted dirt and blood by beating or
breaking over the beam. They are then drained and treated
for the removal of the wool.
Dry skins. — In the soaking of dry pelts, something must
be used to shorten the time required for bringing the skins
back to the original soft condition. Of the alkalies com-
monly employed in soaking hair skins, few can be used on
sheepskins because of their injurious effect upon the wool.
The wool fats are saponified by the alkalies, and removed,
64 PRACTICAL TANNING
leaving the wool brittle and less elastic, and also injured as
regards luster. Caustic soda and sodium sulphide will, in a
fairly weak solution, completely dissolve the wool in a few
minutes, and therefore cannot be used as softening agents;
neither can caustic potash and washing soda be employed.
Ammonium carbonate and borax are the alkalies which have
the least effect upon wool. If the former is used, the skins,
when placed in lime, will become impregnated with calcium
carbonate (lime blast) unless the ammonium carbonate is first
entirely removed by washing.
Borax may be employed in weak solutions, using 1} lb. to
100 gallons of water; but in stronger solution it also tends to
dissolve the natural grease of the wool. It is not advisable to
use acids in the soaks, because of their swelling action on the
skin. Sulphurous and formic acids, preferably the latter, may
be employed in extremely dilute solutions. These acids are
more or less dangerous, however, in the hands of careless and
incompetent workmen. Acids are therefore not generally rec-
ommended on account of their action on the pelt.
Of the various soaking agents that might be used, sodium
bisulphite has been found to give the best results, without in-
jury to either skin or wool. This substance, which is best
used in the solid form, is only slightly acid, so that there is
no danger of swelling the pelt except in comparatively strong
solutions. It is inexpensive, and only a small quantity is
required for effective soaking. The wool is improved in color
by the bleaching action of the sulphur dioxide present; and its
quality, so far as strength, luster, and elasticity are concerned,
is in no way impaired. Sodium bisulphite also acts as an an-
tiseptic, preventing the growth of micro-organisms which
would produce decomposition of the skin with its consequent
loss of skin substance.
According to the Tanner's Year Book, the strength of bisul-
phite solution that has been found to give the best result in
the soaking of sheepskins is 1 lb. of dry commercial sodium
bisulphite per 100 gallons of water. The dry skins are placed
in this solution, and allowed to remain therein until they are
SOAKING 65
soft enough for breaking over the beam. After breaking,
they are transferred to fresh water to complete the softening,
and then treated in the usual way. Very hard skins may be
given a second treatment in the solution of sodium bisulphite.
Although bisulphite has an antiseptic action, the subsequent
removal of the wool is not prevented, and whatever disadvan-
tages it possesses may be easily overcome.
Green-salted sheepskins. — Clean water should be used. In
warm weather, 10 or 12 hours is generally sufficient time; but
in cold weather the skins may be soaked longer without in-
jury. When the skins have become soft and clean they have
been soaked enough. They should then be removed from the
water, and thrown over horses or otherwise allowed to drain
for several hours, or they may be passed through an extractor
and the surplus water removed from them. They should be
clean and soft before any depilatory is applied to them.
Dry sheepskins. — Sodium bisulphite is of much assistance
in soaking dry sheepskins. As stated above, it also acts as an
antiseptic and prevents the growth of micro-organisms which
would produce decomposition and loss of skin substance. One
pound of commercial sodium bisulphite is used for each 100
gallons of water in the soak vat. The dry pelts are placed in
the prepared soak, and allowed to remain therein until they are
flexible and can be broken over the beam. After they have
been either broken over the beam or drummed, for a short
time, they are put into a fresh soak to complete the softening,
and are then treated in the usual way. Very hard skins usu-
ally require a second soaking in the sodium bisulphite solu-
tion. Ordinary skins become sufficiently soft in 24 hours. It
is always advisable to place the skins in fresh water a few
hours after they have been softened to remove the sodium
bisulphite, as well as the last traces of salt and dirt. It is
also good practice to use fresh solutions of the chemical for
every two or three packs of skins. The next process is re-
moval of the wool.
Goatskins. — It is very important that dried and dry-
salted skins should be thoroughly softened and cleansed be-
66 PRACTICAL TANNING
fore they are put into lime liquors. Dried skins should be
soaked separately from dry-salted stock; and to get them soft-
ened in the shortest time possible, and the fibers and grain
freshened and cleansed, some caustic soda or sodium sulphite
should be added to the water, and revolving drums used as
soon as the skins become flexible in the water.
Dried skins. — The most efficient way to soak dry goat
skins is by the use of what is known among tanners as the
sulphide soak. This is prepared by adding 1 lb. of sodium
sulphide dissolved in hot water, to the water in the soak vat,
this quantity being sufficient for 100 gallons of water. If
the skins are heavy, and very hard and dirty, 2 lb. of the
material should be used. The skins are placed in the pre-
pared soak, and are left therein from one day until the next ;
they are then drummed in running water for a short time to
soften and cleanse them further. From the drum they are
placed in a clean soak, containing, like the first, 1 lb. of sodium
sulphide or caustic soda for each 100 gallons of water. The
next day they are taken out and drummed again in running
water. It is good practice then to shut off the water, and run
the skins dry in the drum for 15 minutes, after which they
should be placed in clear water until the next day. Some
skins require longer soaking and more drumming than others.
More or less sodium sulphide may be used, according to re-
quirements of the skins, an excess doing no harm. If it is nec-
essary to leave the skins in the last clear soak for some time
before liming them, 1 lb. of carbolic acid for each 100 gal-
lons of water should be added to prevent decomposition, the
acid being washed out in running water before depilating.
Dry-salted skins. — The softening of this class of stock is
accomplished by soaking them in a sulphide soak over night,
next drumming them in running water, and then re-soaking
them in a second sulphide soak for 24 hours. These skins
require thorough drumming in running water to rid them of
every trace of salt. Skins that were pulled off the animal
should be cut open after they are soaked and all skins should
be trimmed before they are put into lime.
SOAKING 67
Sodium bisulphite. — An efficient soak for dry stock is pre-
pared by adding 1 lb. of sodium bisulphite to every 100 gallons
of water in the vat, as already described for sheepskins. The
skins are placed in the soak, and when they have become flexi-
ble, they are run in a drum and soaked again in a bisulphite
liquor, then washed and limed.
Kangaroo skins. — On account of the practical exhaustion
of kangaroo (wallaby) skins, the manufacture of this type
of leather has greatly diminished in recent years. Kangaroo
skins are characterized by great suppleness, toughness, and
thick grain. The leather is very compact and resists the pen-
etration of moisture, and does not readily crack or peel off.
On account of its distinctive qualities it is a splendid shoe
material — in a class by itself — and is especially suitable for
shoes for tender feet. Excellent leather is made by tanning
the skins by a chrome process; also by tanning with quebracho
or gambier. Dull-finished kangaroo leather has long been a
favorite material for the tops of shoes, and glazed leather for
vamps.
Soaking and softening. — Kangaroo skins come from Aus-
tralia, and are received by the tanner in the dry condition.
It is necessary to use some chemical in the soaks, such as
borax, sodium sulphide, or caustic soda, to hasten the soften-
ing, and to bring the goods to as near the natural soft condi-
tion as possible. From 1 to 2 lb. of any of these chemicals
may be used for every 100 gallons of water in the vat. When
the skins have become pliable, they are taken out of the soak
and drummed some time, then re-soaked until they are thor-
oughly softened. The soak readily softens the skins and
freshens up the dried and withered grain. The loosened flesh
should be removed before the skins are put into lime.
Borax also softens the water and hastens the soaking of
the skins, 5 or 6 lb. being sufficient for 1000 gallons of water.
Dissolve with hot water; pour the solution into the soak and
stir thoroughly; then throw in the skins.
Pigskins. — From time immemorial these have been used for
many purposes; at the present time they are employed more
68 PRACTICAL TANNING
extensively than ever. When properly tanned, they are as
durable as goatskins, as pliable as calfskins^ and present a
peculiarly attractive appearance. They are finished in russet
and colors, and are used for inner-soling, saddles, traveling-
bags, pocketbooks, belts, jewelry cases, bookbindings, sport-
ing goods, shoes, slippers, suspenders, leggings, military equip-
ments, trusses, wall decorations, screens, for upholstering,
and for carriage and automobile trimmings. Various ways of
tanning them will be described later.
Washing. — Pigskins contain a grease that has to be elim-
inated before they are limed, or the leather will be greasy
and hard. After having been scraped out dry before soak-
ing, the skins are washed in a warm solution of sal soda
(sodium carbonate). Put about 5 lb., of sal soda into a barrel
of water heated to 95° F. Put the skins in one at a time,
and leave them in long enough to get soaked through,
and then put them on the beam and strike them out thorough-
ly with a dull knife, bearing on hard and forcing out as much
of the grease as possible. This should be done two or three
times. The skins are then rinsed off in warm water and
soaked several hours in cold water before they are de-haired
and limed. A great deal of grease can be forced out by thus
passing them through the warm solution of sal soda and then
working them out on the beam. The skins are next soaked,
fleshed, and de-haired.
De-greasing. — In recent years, pigskin and other stock con-
taining a large amount of grease, have been de-greased with
various solvents. One of the simplest methods consists in
running the pickled stock with kerosene, using about 3 gal-
lons for each 100 lb. of skins. After running the stock with
this material for about one hour, the kerosene is washed out
with salt water, finally finishing with a weak pickle solution.
A more effective de-greasing mixture is manufactured by the
Vacuum Oil Co., and is being used in considerable quantities.
Krouse Process. — A process for de-greasing sheep and pig-
skins has been patented by C. E. Krouse, and consists in treat-
ing the dry pickled skins with high test gasoline in specially
SOAKING 69
built containers. The solvent is pumped into the cylinder con-
taining the skins, where it remains for a definite length of
time. The solvent now carrying the removed grease is trans-
ferred to a special form of still, where, by distillation, the sol-
vent is removed for further application, while the grease from
the skin is recovered, and may be used as crude soap stock
or employed for other purposes.
Furs and hairskins. — Although the tanner, as a rule, is
not interested in the tanning of furs, there are occasions when
he does want to preserve the pelt in its natural hair cover.
Soft, green-salted skins to be tanned with the fur or hair
on them require but two or three hours' soaking in clean water
to become soft and clean. Dry skins are soaked and softened
most effectively in water to which borax, caustic soda, or
formic acid has been added. A solution of 2 lb. of borax in
100 gallons of water is a suitable soak for dry skins. Well-
cured skins can be softened in a soak consisting of 100 gallons
of water to which 1 lb. of caustic soda has been added. An.
excellent soak is also prepared by adding 1 to 2 lb. of formic
acid to 100 gallons of water. This is an approved method
of soaking, since the acid has antiseptic properties, and will not
allow decay to take place. The water used for soaking should
always be fresh and clean ; and the soaking should be done as
quickly as possible, to avoid decomposition and loosening of
the hair. When soft and clean, the skins are fleshed, and all
lumps of fat and flesh removed. The skins should next be
washed in a warm solution of soft soap, which makes the
hair and the skin itself clean and free from grease; they are
then ready to be tanned.
Another method of preparing the skins is as follows : They
are taken in raw condition, and beamed and scraped on the
flesh side until they are free from flesh and greasy matter.
They are not soaked at first. Softening is done with wet saw-
dust. Soak some sawdust in water; spread the skins out
smooth 1 , flesh side up, and spread the wet sawdust an inch deep
on the flesh side, and let them lie until they are softened.
In the case of greasy skins it is necessary to soak them in
70 PRACTICAL TANNING
borax water, and then wash them in warm sal soda solution,
omittinsr the sawdust treatment. When soft, fleshed, and
o
clean, the skins are ready to be tanned.
Formaldehyde raw stock. — It often- happens that formal-
dehyde is used as a preservative and disinfectant on skins, but
this chemical has a hardening effect on the fibers. For skins
partly disinfected by means of formaldehyde this does not
present any great difficulty, especially when the skins have
been salted, as the salt has penetrated throughout so that they
are not hardened at all. For dried skins treated previously
with formaldehyde it is necessary to add some activating sub-
stance, such as formic acid or sulphurous acid, to the soak
water. Naturally, this method of working is not without dis-
advantage as regards the quality of the glue stock, for it is
well known that one cannot obtain as good a quality of such
stock; but, of course, the main consideration for the tanner is
to obtain good leather, and although the value of the glue
stock is not negligible, it is not the principal thing to consider,
CHAPTER III
DEPILATION
Having brought the stock to a soft and perfectly clean con-
dition, as described in the previous chapter, the next step,
usually, is the depilation or removal of the hair and epidermis.
Accompanying depilation there is generally a swelling action
caused by the chemicals used, which makes the fibers separate,
and at the same time more or less of the cementing material
is dissolved. The natural fats occurring in the hide or skin
are also affected during depilation, being converted into solu-
ble and insoluble compounds, which are very largely removed
during the working processes.
Hides that have been improperly cured often present what
is known as hair-slips; that is, the hair falls out in patches,
and is likely to be accompanied by a damaged grain. The cause
of this slipping is putrefaction, the stock having become wet
in these spots, or perhaps locally overheated during
transportation.
Sweating. — The oldest method of depilation seems to have
been by means of incipient putrefaction, or as it is called,
"sweating." The hides were allowed to remain in piles in a
warm, damp room until the mucous matter connecting the epi-
dermis with the dermis had decomposed, which thus loosened
the hair without injuring the true skin. This method, how-
ever, often resulted in damaged stock, and so the process was
improved by allowing the hides to hang in a closed, damp room
or cellar called a "sweat-pit." Two general methods are em-
ployed, known as "cold sweat" and "warm sweat."
Cold sweat. — This method is still used in America to some
extent, especially for de-hairing dry hides for the manufac-
ture of sole leather. The sweat-pit is a structure usually built
above ground, and protected from outside atmospheric influ-
ences by means of a double wall between which is a filling of
tan bark or other material to prevent loss of heat by radiation.
71
72 PRACTICAL TANNING
The temperature of these pits is controlled by means of steam
pipes running under the false flooring and a sprinkler system
to provide moisture and lower the temperature if necessary.
The temperature is maintained at about 70° F. The hides are
hung on hooks, each chamber holding a single pack. The
sweating usually lasts 4 or 5 days. Near the end of the opera-
tion the stock is carefully examined, and those hides showing
the first signs of slipping are dropped to the floor in order to
retard putrefaction, it being cooler on the floor than higher
in the pit. At the end of the process the hides are thrown into
lime liquors for a short time in order to remove the slimy
feel, and to plump the stock slightly. The value of this process
depends upon the fact that the hides are left in a firm condi-
tion without any appreciable loss of hide substance, but even
if most carefully conducted there is great danger from ex-
cessive putrefaction, with resultant damage to the grain.
Warm sweat. — The warm-sweat method is very similar to
the cold-sweat process, except that a higher temperature, about
80° F., is used, and the time of treatment is somewhat shorter.
It is applied more especially to sheepskin and is known as
"staling." This process is not employed to any extent in the
United States.
Liming. — The first chemical method of depilation was that
in which slaked lime was employed. Although this material
has been used for many years, the methods of application do
not differ materially from those in vogue a century or more
ago. Lime used for de-hairing must be as free as possible
from magnesia, clay, or iron, as these materials not only
diminish the lime content, but cause the lime to slake with
much more difficulty; and the iron, being insoluble, becomes
fixed in the grain, with subsequent production of stains.
Quicklime. — The natural source of lime is limestone, in
which it occurs in combination with carbon dioxide, and is
known chemically as calcium carbonate. There are other nat-
ural forms of calcium carbonate, such as chalk and marble.
In order to make pure lime or calcium oxide (CaO), lime-
stone or chalk is heated in a kiln to a high temperature, when
DEPILATION 73
the carbon dioxide (CO2) is driven off, leaving what is known
as quicklime, according to the reaction :
CaC0 3 +heat=CaO+C0 2
On coming in contact with water, quicklime combines read-
ily with it, forming calcium hydroxide or slaked lime. In do-
ing this, the water should be introduced slowly, and the mass
well stirred after each addition. During the slaking a great
deal of heat is generated, and the lumps of lime fall to a pow-
der. When properly slaked, the resulting product should as-
sume the appearance of a smooth paste. It is necessary to se-
cure proper slaking, otherwise the unaffected lumps will col-
lect in pockets and cause serious damage to the stock.
Hydrated lime. — By the careful addition of just sufficient
water to bring about the reaction between lime (CaO) and
water (H2O), a dry powder may be produced according to the
following reaction :
CaO+H 2 0=Ca(OH) 2
»
This powder is now being largely used by the tanner, and
is known as hydrated lime. The advantage of this material
is that it may be kept indefinitely without change, and may
be used in the process of depilation without fear of damage
to the stock.
Attention should be directed to a statement which is often
made, that, owing to the limited solubility of lime in water
(1.3 parts per 1,000 at 70° F.), there is no danger of de-
stroying a pack of hides or skins by using an excessive amount.
This is misleading. There is probably no danger of destroy-
ing the stock, but there is great danger of damaging it by
improper lime treatment. That lime can be and is used
in various ways is proved by the fact that if we visited
100 tanneries we would find no two plants using the same
method of liming. Yet lime is a compound which is only
slightly soluble in water, and according to theory, its beneficial
effects can only come from what goes into solution ; and pro-
viding that we always have an excess present, the results
should always be the same, no matter how much we may care
74 PRACTICAL TANNING
to use. This is a case where theory and practice do not
coincide.
Many tanners claim that in de-hairing a hide properly it
is necessary first to treat the stock with old lime liquors, and
gradually bring the hides into fresh lime solutions. There
is some foundation for this belief, but there are limitations
which must be observed. There is no doubt that old limes
do have a 'softening effect upon dry hides, due to the putre-
factive action of the bacteria which they contain, as it has
been shown that putrefactive bacteria are present in old limes.
That they subsist upon mucous matter between the epidermis
and dermis as well as upon the connective material between the
fibers has also been shown. 'But are we sure that they care
only for the mucous matter and connective material ? We are
not safe in assuming that they will attack these materials only,
for they will also act upon the fibers or gelatinous matter.
Would it not be better to depend upon the soaks for securing
the soft condition we desire, and not upon the uncertain action
of putrid lime?
It is claimed by some tanners that it is impossible to de-hair
with fresh limes, but those who make such a statement have
evidently never tried to do so. It is not the intention, how-
ever, to try and convert those who are using putrid limes, but
rather to give some of the salient points which have devel-
oped as the result of a series of tests extending over several
years, and which were carried out at the suggestion of the
National Association of Tanners. The points that have been
paramount in all of these investigations were the determina-
tion of weight, measurement, and the condition of the leather
obtained when the various well known and commonly used
depilating agents were employed. In conducting the experi-
ments, actual working conditions were approximated as closely
as possible, and not only was the chemical action noted, but
physical changes were studied also.
For the purpose, however, of corroborating the analytical
data obtained during the large-scale tests, a series of parallel
tests were made in the laboratory on small samples of stock.
DEPILATION 75
The material used in these laboratory tests was shaved free
from hair at the start so that this factor of uncertainty might
be eliminated.
The first series of large-scale tests was for the purpose of
determining the effect of various quantities of lime on the
stock as well as the influence of the time of treatment. Both
fresh and bettered (strengthened) limes were employed. Sev-
eral packs of skins were treated with 5 per cent of lime, and
at the end of two days showed an increase in weight of about
40 per cent above the trimmed weight. The lime absorbed was
about 1.30 per cent. Several packs were then run with 10
per cent of lime, and gave an increase of 50 per cent from the
trimmed to the second day out of lime, with an absorption of
3.65 per cent of calcium oxide. One lot treated with 10 per
cent of lime gave an increase of 61 per cent, with an absorp-
tion of 3.09 per cent of calcium oxide. These results seem to
indicate that the larger amount of lime produces a greater
increase in weight and causes a greater absorption.
An experiment was made to see if one portion of lime would
completely depilate a pack of hides. For this test 10 per cent
of lime was added to the stock in the paddle, and without
changing was allowed to remain in the same liquor for 10
days. At the end of this time the hair was only partly loos-
ened, it requiring immersion in warm water and considerable
work in beaming before the hair was completely removed.
Thus an excess of lime was always present, but for some rea-
son the changes which had taken place greatly retarded the
depilating effect. An interesting point in connection with this
pack was that after 8 days the lime in the solution increased
again, showing that it was being drawn from the hides.
In conducting the analytical work, the loss of hide sub-
stance was always observed. In all cases where the lime was
applied fresh the loss was greater than when the lime was
strengthened. This would seem to indicate that new lime
has a greater solvent action upon what is called hide substance
than an old lime. May it not be possible that in the old limes
a protective colloid is formed? To illustrate this point: if a
76 PRACTICAL TANNING
pack was treated with fresh lime, run for a day, the lime dis-
carded, a fresh lime made up, and so on for a number of days,
the loss of hide substance was much greater than where the
stock had been strengthened with the same amount of lime.
In the pack cited abcve — being treated for 10 days — it was in-
teresting to note that the amount of dissolved hide substance
increased slightly from that found after the second day. From
the appearance of the resulting leather, however, there can be
no doubt that some action had taken place which had a de-
cided influence upon the character of the product.
The record of pack weights at different stages of liming
showed, without exception, that the greatest weight occurred
on the fourth day. This was due to the fact that up to that
time the lime was being absorbed, but the action was not suf-
ficiently great to cause the hair to drop off. The decrease fol-
lowing the fourth day was on account of the loss of hair. This
was shown fairly conclusively in the laboratory tests, where
the hair had been eliminated before treatment, these showing
no loss after the fourth day. It may be of interest to note
a typical increase from samples that were freed from hair and
depilated with 5 per cent of lime, which was made fresh each
day, and from a series treated with 5 per cent of lime
strengthened each day :
Fresh, Strengthened,
increase increase
Days percent percent
1 42.10 42.93
2 2.60 2.10
3 4.14 4.10
4 1.30 1.41
5 170 170
6 0.30 3.60
These results are of interest, as showing that about 80 per
cent of the total increase in weight occurred during the first
day. From this it might be assumed that the absorption of
lime should give a similar condition. To show, however, what
did happen to hides treated with fresh and bettered lime, the
following results may be noted :
DEPILATION 77
Fresh Strengthened
Ash Lime Ash Lime
in ash in ash
Original dry weight, per cent.... 0.66 33.67 0.51 32.80
After 1 day 3.15 59.82 3.14 ' 56.61
After 2 days 3.30 74.45 3.71 78.98
After 3 days 4.25 76.58 4.19 80.49
After 4 days 4.52 78.46 4.50 90.64
After 5 days 4.21 86.69 4.81 86.07
After 6 days 5.18 82.69 4.67 84.23
The large-scale tests agreed with these laboratory experi-
ments, showing that most of the lime was taken up during
the first two days ; and both show that the absorption of lime
is not wholly responsible for the increase of weight. In other
words, the absorption of lime and water do not bear any def-
inite relation to each other. The higher ash in the fresh lime-
treated stock would seem to indicate that the fresh lime has
a greater solvent action on hide substance than the bettered
lime treatment. This is shown by the fact that the ash is
higher in the former case, while the lime in the ash is less.
This would again indicate that possibly used lime may have
a protective colloid effect.
It is generally assumed that during the liming process fat in
the hide is saponified, thereby producing a lime soap, and that
the formation of this soap tends to open the fibers. That this
saponification is not complete is shown by the following re-
sults :
Fat on dry weight
Fat Fresh Strengthened
lime lime
Original, per cent 5.1 1 5.21
After 1 day 1.86 2.77
After 2 days 2.05 1.96
After 3 days 1.24 1.96
After 4 days 3.01 4.43
After 5 days 1.22 1.05
After 6 days 1.25 2.88
Although these results are not very concordant, they do
show that practically all of the fat which is saponified be-
comes so in the first 24 hours. This would perhaps account
for the increase in weight of the stock during the same period.
It seems fairly safe to say that 75 per cent of the fat was
saponified during the first day, and after that practically no
78 PRACTICAL,, TANNING
more saponification took place. This is closely related to in-
crease in weight, when it is remembered that practically 80
per cent of the increase in weight took place during the first
day.
Many tests were run in the laboratory as well as on a work-
ing scale to determine the loss of hide substance occurring in
the lime liquors, and the following examples will illustrate
what was observed :
Hide substance lost, per cent
Fresh Bettered
Days lime lime
1 0.51 0.S5
2.. 0.253 0.39
3 0.43 0.59
4 0.66 0.64
5 0.24 0.17
6 0.25 0.34
These data are of interest from the fact that if we add the
first column we will have a loss of hide substance amounting
to 2.143 per cent and if the second column is added it would
give about the same result. As a matter of fact, the second
series of tests are for solutions that had not been changed, and
indicate the amount of hide substance which had dissolved dur-
ing the time the stock was in the solution. In the first series
the solution was made up fresh each day ; and in the second se-
ries the same solution was used continuously, new lime being
added to the old solution. These results need some explanation :
Do they show again that after a lime has been used for one day
some change has taken place which protects the so-called hide
substance ? It may be possible that the hide substance that has
been dissolved changes rapidly into some form which does not
respond to the tests applied for hide substance. Similar re-
sults have been noted in the working tests, although in these
instances a somewhat larger amount of hide substance was ob-
served. The question now arises : What is understood by
hide substance? It is fairly well agreed that hide substance
does not necessarily mean gelatin, but rather the albuminous
material present as connective tissue between the fibers and
the layer between the epidermis and true skin.
DEPILATION
79
From the observations noted above it seems fairly safe
to assume that the proper manner to apply a straight lime
solution would be to put the stock into a lime liquor which is
only a few days old at most, and then work up through the
series to a fresh lime liquor. The lime that has been used
thus for the new pack should then be discarded. This does
not mean, of course, that a hard and
fast rule can be made which will
work for all classes of stock, but it
is to be interpreted as being general
procedure.
Lime is the most common agent
for de-hairing, although it also has
disadvantages. In preparing the so-
lution, a quantity of fresh lime is
slaked by placing it in a shallow
tank similar to that used by build-
ers, and adding sufficient water to
moisten it thoroughly. At the end
of one or two hours it becomes
heated and falls to a powder. Suffi-
cient water is added to form a thick
paste which may be kept for several weeks or even months
without much change. When required for use, a suitable
quantity is dug out, stirred with water to remove rocks, and
then run into the pits. It is necessary to provide a surplus of
solid lime to replace that taken up by the hide. It is impossible
to set any fast rule as to the proper quantity of lime, but a
safe margin is 10 lb. for each 100 lb. of hide.
The usual method of liming is to place the hides one at a
time into solution, taking care that each hide is well immersed
before entering the next one. The hides are taken out
("hauled") each day, the liquor bettered and well "plunged up"
with a lime plunger ( figure 42) in order to distribute the un-
dissolved lime throughout the pit. They are then thrown back
("set"Y, care being taken to spread them out fully. In some
yards the hides are joined by hooks ("toggled") and reeled
Figure 42. — Lime plunger.
80 PRACTICAL TANNING
from one pit to another, or to the same pit. Sometimes hides
are suspended in the liquor, and the limes are kept in motion
by means of a paddle, or by blowing in air. The most corn-
Figure 43. — Beam knife.
mon means, however, of agitating the liquor is by the ordinary
paddle-box run at intervals during the day.
The action of lime on the hide is to swell up and soften the
epidermis cells, dissolve the mucous layer, and loosen the hair
so that on scraping with a blunt knife (figure 43), or work-
Figure 44. — Whitney model "S" unhairing machine
ing on the machine (figure 44), both the epidermis and hair
are easily removed. The action on the true skin is very vigor-
ous, causing the hide to become plump and swollen, at the
same time dissolving the cementing material of the fibers, thus
causing them to become split up into finer fibrils. This swell-
ing is probably due to hydrolysis of the albuminous matter
DEPILATION
81
and to formation of a lime soap. Not only does the liming
process remove the hair and epidermis, but it is also of value
in the re-fleshing process, as it gives the hide a greater firmness,
very desirable when working with the knife (figures 45, 46,
47), or on the machine (figure 48). The time of liming varies
with the season of the year and with the kind of stock treated ;
it may run from 3 to 60 days. The age of the lime greatly in-
fluences the time of treatment as well as the character of the
Figure 45. — Broad flesher.
Figure 46. — Spring style fleshing knife.
Figure 47. — Monitor flesher.
finished product. Old limes de-hair much quicker than fresh
ones. It is often customary to place the hides in an old lime
for several days, or until the hair and epidermis have started
to loosen, then change them to a fresh lime which produces
the desired plumping of the fibers. Great care, however, must
be taken that the limes do not become too old, especially in
hot weather, as this condition will very likely produce a trans-
parent swelling of the tissue, with destruction of hide
substance.
The period of liming has a marked influence on the finished
product. Short liming produces a tight grain, while long lim-
ing produces a loose, open grain. The former condition is
82
PRACTICAL TANNING
necessary in the production of shoe leather, while the latter
effect is desirable in glove and fancy leathers.
Sodium sulphide. — This material is largely employed as a
depilating agent. It may be used alone or in conjunction with
other substances if desired. When used alone it has the prop-
erty of rapidly and completely dissolving the hair, but causes
the stock to plump excessively, with the production of a false
grain and loss of measurement. It has its advantages as a
Figure 48. — Automatic roller fleshing machine.
time-saver, produces more weight, and a tight grain. The
strength of the sodium sulphide solution commonly used is 20°
bk. (barkometer) at a temperature of 75 Q F. The stock is
then placed in this liquor, run for 2 hours, allowed to rest over
night, run for half an hour, washed, neutralized with sodium
bicarbonate, and then again thoroughly washed.
For some classes of leather the sodium sulphide is made into
a paste or a heavy liquor and applied to the flesh side. Skins
so treated are piled-down over night, and on the following day
the hair may be readily removed by hand. This method is
DEPILATION 83
the one commonly employed by wool-pullers and by tanners
of other grades of stock carrying valuable hair.
Sodium sulphide mixed with lime materially helps in the
removal of fine hairs. For this purpose, about 20 per cent of
sulphide on the weight of the lime is sufficient. The sulphide
should be added to the lime before slaking. For hydrated
lime and sulphide mixture the two should be boiled together.
Whenever sodium sulphide is used in conjunction with lime
it should be at the start of the de-hairing process. Many tan-
ners, however, use the sulphide after the stock has been limed
for several days, but this would seem to be poor policy if its
addition is for the purpose of removing fine hairs. This con-
clusion is based on the fact that sodium sulphide has no sol-
vent action upon hair which has once been treated with lime,
no matter how strong the sulphide solution may be made.
On the other hand, clean hair will dissolve rapidly even in
dilute solutions of sodium sulphide. A good system, and one
which has been found to give satisfactory results, is to use a
series of three of four pits, adding the sodium sulphide re-
quired to the oldest liquor when the new stock enters, the
head pit being straight lime liquor. No loss of hair occurs by
this treatment, although the stock is free from fine hair and
has the appearance of limed stock, except that it has a better
grain than is obtained with either sulphide or a long lime
treatment.
To determine the effect of the lime and sodium sulphide
mixture, several working tests were made with a 5 to 1 com-
bination. The gain in weight from the soaked to the first day
out of the liquor was 43.24 per cent; during the second day
the gain was 2.45 per cent; while after the third day there
was a loss of 0.55 per cent. The loss was caused by the com-
plete slipping of the hair. The amount of lime absorbed in-
creased from day to day, but no more sulphide was taken up
after the second day. The laboratory tests conducted along
the same lines did not agree very closely with the working
tests, owing to the previous removal of hair. Analysis of the
hide samples, however, gave results which may show that there
84 PRACTICAL TANNING
is a reason why lime stock is not so tight-grained as stock
treated with sodium sulphide. For example, note the fol-
lowing :
New 1 day 2 days 3 days
Percentage of fat 3.55 1.19 1.57 2.11
Percentage of ash 0.67 2.35 2.71 3.07
Percentage of lime in ash.. 31.60 68.20 69.10 75.92
These records show that the percentage of fat remaining
after the treatment was about the same as noted for lime stock.
The absorption of lime was somewhat greater after the first
day than was observed for straight lime treatment, but on the
third day it had increased to that of limed stock. It can be
fairly safely assumed that the lime would continue to be ab-
sorbed if a longer treatment had been given.
In the working tests with straight sodium sulphide solution,
the gain in weight after one day was considerably less than
with any of the previous treatments, being about 16.25 per
cent. This was due of course to the solvent action of the sul-
phide on the hair. One pack was treated for four days with
the sulphide, but showed little gain after the first day. The
hair-free laboratory samples, however, showed a gain of more
than 50 per cent after the first day. Analyses of the hide gave
6.70 per cent of fat when new 'and 1.90 per cent after one
day, and 0.44 per cent of ash when new and 0.94 per cent
after one day.
It might be expected that stronger alkali would saponify
the fat more completely, but the data obtained do not seem to
bear this out. Analyses of the liquor showed that the stock
at the end of 24 hours had absorbed 0.126 per cent of sodium
sulphide and 0.124 per cent of sodium hydroxide (caustic
soda).
Among several other methods of depilating which were
studied, the one in which a mixture of sodium sulphide and
calcium chloride were used should be mentioned. The ad-
vantages of this treatment were found to be in the freedom
from false grain, complete removal of hair, saving of time,
and better measurement than straight sodium sulphide. The
method consisted in running the stock in a 20° bk. sulphide
DEPILATION 85
solution, to which had been added one- fourth as much calcium
chloride as sulphide.
Sodium sulphide is produced on a commercial scale by
fusing together a mixture of sodium sulphate and carbon, the
reaction being essentially as follows:
Na 2 S0 4 +2C = Na 2 S+C0 2
The mass is lixiviated with water and concentrated to crys-
tallization. The product thus obtained is sold to the trade
as "crystal sulphide." By carrying the evaporation to the dry
state, a solid is obtained which is practically free from water
of crystallization, and is known in the trade as "double
strength."
Sodium sulphide is also a by-product from the manufac-
ture of other chemicals, barytes, for example.
When used in depilation, sodium sulphide ionizes into two
compounds as follows :
Na 2 S-f-H 2 = NaHS+NaOH
Arsenic sulphide. — When the red sulphide of arsenic
(AS2S2) is mixed with hot water and added to lime, or mixed
with quicklime during slaking, it increases the depilating ef-
ficiency of lime. It is especially good for fine leather to which
it gives the necessary stretch, softness, and clearness of grain,
without the loss of hide substance, and the loosening effect
caused by ordinary liming. The amount used varies some-
what, but may be said to run from 0.1 to 0.4 per cent of
realgar (arsenic sulphide) and 4 to 6 per cent of lime, reck-
oned on the weight of the green skins.
Caustic soda. — This chemical is produced by the electroly-
sis of sodium chloride, or common salt. By passing an elec-
tric current through a concentrated solution of salt, the water,
in decomposing, gives the hydroxyl ion to the sodium and
the hydrogen ion to the chlorine, thus :
+ _ + _ + _ +_
Na Ci + H O H > Na OH + H CI
Owing to the fact that the hydrochloric acid is also broken
86 PRACTICAL TANNING
up by the current, a further decomposition takes place, re-
sulting in the generation of chlorine gas. The final products
of electrolysis, therefore, are sodium hydroxide or caustic
soda, chlorine, and hydrogen.
When dissolved in water to the amount of 1 lb. per gallon,
caustic soda forms a solution which is known as above normal,
in which strength it will dissolve the hair very rapidly, but
will not plump the stock. By using such a strength, skins or
hides may be depilated in the course of half an hour. Such
strong solutions are of no interest in practical tanning, as
they are difficult to handle and very expensive. A small quan-
tity of caustic soda, however, added to lime, has a decided ad-
vantage, as it aids materially in plumping the stock and short-
ens the time of treatment, and is spoken of as "sharpening the
limes."
Calcium sulphydrate. — This compound -is a powerful de-
pilatory, but is little used on account of its unstable character.
It is probably formed to some extent when sodium sulphide or
arsenic sulphide is added to lime. It may be produced by pass-
ing hydrogen sulphide (a gas) into milk of lime until the
latter becomes saturated. This is the substance largely sold
as a patent depilatory for removing superfluous growth of
hair.
Arazym. — It has recently been discovered by Dr. Otto
Rohm that hides and skins can be de-haired and bated in one
operation by means of "tryptase" in an alkaline solution. This
process gives especially good results on goat skins, and as no
bating is necessary, the process is meeting with approval, al-
though rather slow in adoption.
Unhairing.* — When the process of depilation is complete,
the skins or hides are removed from the pits and allowed to
drain for half an hour or more. They are then placed on the
beam, and the hair is removed by means of a blunt knife.
Various machines have been devised to remove hair, and these
* Both "unhairing" and "de-hairing" are used in this book, the former
when referring to the mechanical operation, and the latter to the chemical
process or the removal of hair in general.
DEPILATION 87
have been brought to such perfection that hand work has been
almost entirely eliminated. The unhairing machine as shown
in figure 44 represents a common type. It is similar in con-
struction to the fleshing machine, but is provided with a blunt
knife which works against the grain of the stock.
Methods of depilation. — Having discussed the various ma-
terials employed for depilation in a general way, let us con-
sider a few methods which are claimed to give satisfactory
results :
Liming hides for upper leather. — 1. Green-salted hides
that are intended for soft, supple leather — chrome or vege-
table tanned — worked through a liming process according to
the following directions, will be found to be sufficiently limed
for de-hairing in six days. Exact quantities of lime and so-
dium sulphide should be used, namely, 8 lb. of the former and
2 lb. of the latter for every 100 lb. of hides.
To start the liming process, slake 1^ lb. of lime for each
100 lb. of stock, add it to the water in the vat, and plunge
up well. Reel the chain of hides into the prepared lime, tak-
ing care that each side is spread out flat and not rolled, folded,
or twisted. After the hides have been 24 hours in this lime,
reel them into the second lime, made by adding the same quan-
tity of lime to water that was used in the first lime. Leave the
hides in this lime 24 hours. Then make up the third lime the
same as the second, and allow the hides to remain in it 24
hours. Reel them into the fourth lime, which should also con-
tain the same quantity of lime, and leave them in it 24 hours.
The fifth lime should contain 1 lb. of lime, and the hides
should remain therein 24 hours, when they are reeled into the
sixth lime, which should contain 1 lb. of lime and 2 lb. of
sodium sulphide. This lime should be warmed to 75° F., and
the hides left in it 24 hours, when they are reeled into warm
water and de-haired after two or three hours. The positions
of the hides should be changed every day, and fresh lime used
every day, the hides remaining in each lime 24 hours.
After the hides have been de-haired, wash them with run-
ning water for 15 minutes; then place them in water at 90°
88 PRACTICAL TANNING
F., and work them over the beam or on the machine, and then
put them into the bating liquor. This process produces very-
uniform leather. The hair should come off easily and clean.
De-hairing out of new- lime gives hard, plump hides, a
desirable condition for chrome tannage and for splitting out of
lime. After de-hairing, the hides can be split, or they may
be bated and pickled and then split; or bated, pickled, and
tanned, and split after they are tanned.
Although 8 lb. of lime will de-hair 100 lb. of hides, softer
leather is obtained by using 10 lb. in 6 limes, starting with H
lb., and using 2 lb. each day until the hides reach the fifth
lime, which should contain 2\ lb. of lime and 1 lb. of sodium
sulphide. Either of these processes produces satisfactory re-
sults for chrome or vegetable tanning. If the hides are to be
split out of lime, they should be de-haired, put into warm
water, and worked by hand over the beam or on the machine,
and left in cold water over night to harden for splitting.
2. Sides that are intended for shoe leather and other soft
and supple stock may be limed and de-haired with excellent
results, according to the following instructions :
By calling the pits A, B, and C, and numbering the packs,
the method of procedure may be readily understood. The
quantities of lime and sodium sulphide are based on 100 lb. of
wet, fleshed hides. The temperature of the limes should be
maintained at 70° F. The process is as follows :
First day: Pack No. 1 is put into pit A, containing 5 per
cent lime and 1 per cent sodium sulphide.
Second day: Pack No. 1 is transferred to pit B, contain-
ing 5 per cent lime and 1 per cent sodium sulphide ; pack No.
2 is put into pit A, once used.
Third day: Pack No. 1 is put into pit C, containing 5 per
cent lime and 1 per cent sodium sulphide; pack No. 2 is trans-
ferred to liquor B, once used ; pack No. 3 enters pit A, twice
used.
Fourth day: Pack No. 1 is removed; pack No. 3 is drawn
from A, and new liquor consisting of 5 per cent lime and 1
per cent sodium sulphide is made up with that pit; pack No.
DEPILATION 89
2 is transferred to A; pack No. 3 is put into C, once used;
pack No. 4 enters pit B, twice used.
Fifth day: Pack No. 2 is removed; pack No. 4 is drawn
from B, and a new liquor is prepared as above; pack No. 3
is transferred to B; pack No. 4 is transferred to A, once used;
pack No. 5 is put into C, twice used.
Sixth day: Pack No. 3 is removed; pack No. 5 is drawn
from C, and new liquor prepared; pack No. 4 is transferred
to C ; pack No. 5 is put into B, once used ; pack No. 6 is trans-
ferred to A, used twice.
When once started, this cycle can be kept up, and it entails
only a small amount of handling of the stock. This method
gives a good grain and full feel. On removing the hides from
the lime liquor they should be thrown into water at 85° F.
for a half-hour, then unhaired on the machine or over the
beam. The next process is bating.
Sodium sulphide process for dry hides. — : The immersion
of hides in a solution of sodium sulphide removes the hair
quickly, freshens the grain and imparts great toughness to the
leather. This is an excellent process for heavy chrome
leather for winter and work shoes. The hides should be split
into sides, fleshed, and put into cold water over night.
The de-hairing solution is prepared in the following man-
ner: Put 200 lb. of sodium sulphide into a barrel two-thirds
full of water. Turn on steam, and boil slowly until the sul-
phide is dissolved. Let the solution stand until the foreign
matter has settled and the liquor is cold, which requires 12
hours, or over night. Only the clear solution should be used.
Put enough water into a vat to cover the sides, and add
enough sodium sulphide to make a 6 or 7° bk. liquor. The
exact strength, however, is immaterial ; the stronger the liquor
the sooner the hair is dissolved; but a good rule to follow is to
start with a liquor of 6°, which requires about three days to
accomplish the desired result. Put the sides, opened out well,
into the liquor, and let them remain 24 hours ; then haul them
out. Plunge the liquor up and put the sides back, for another
24 hours ; then haul them out again. Plunge the liquor again,
90 PRACTICAL TANNING
and return the sides for another 24 hours. At the end of the
third day the hair should have been reduced to a slimy mass,
which can be easily washed off, leaving the hides clean. Put
the hides into a wash-wheel with running water and wash
them clean. If there is any hair that does not come off, the
sides should be worked on a beam; and if this does not re-
move the hair, add some fresh sodium sulphide solution to the
liquor, and put the hides. back into it for another 24 hours.
After washing, the hides are limed.
Slake \ bushel of lime for each 100 sides in the pack, and
add the slaked lime to water in a pit, put the de-haired hides
into the liquor, and keep them therein two days, handling them
each day. A little more lime may be used to make a softer
leather. After the sides have been thus limed, wash them
in cold water, and then split them into grains and splits, and
bate and pickle them.
This process destroys the hair, but makes plump and tough
leather. Men who handle the hides through the sulphide
process must wear rubber gloves to protect their hands from
the caustic material. When hides are split out of the lime the
grains are bated, pickled, and tanned; if they are split out of
pickle or after tanning, they are bated and pickled whole.
Opinions differ in regard to the best time for splitting.
The condition of the flanks and the fineness of the grain
depend largely upon how the grains are bated and de-limed.
Notes on beam-house work. — In the process of liming
hides for sole leather, and other kinds of firm and solid
leather, much depends upon the condition of the lime liquors.
A new lime has great swelling and plumping effect upon the
hides. Such a lime, particularly if caustic soda is added to
it, is strongly antiseptic. A short liming in new, sharp liquors
is desirable in order that but little hide substance may be dis-
solved. The plumping effect of such a lime is considerable,
while an old lime liquor has a more solvent effect and does
not plump the hides so well. Caustic soda in the lime liquor
assists in getting the full plumping effect, but it must be used
carefully or it will cause rough grain.
DEPILATION 91
Where sodium sulphide is used in the lime liquors, the de-
hairing is hastened and the plumping effect of the lime in-
creased; but unless the sulphide is used rather sparingly, the
grain is liable to be coarse. An old lime liquor containing
considerable sulphide makes leather more pliable than a clear,
fresh lime liquor. An old lime dissolves hide substance,
which means pliable leather, but the swelling effect of such a
lime is less than that of a new lime. For sole leather, there-
fore, liming should be done in new liquors to get the full
plumping effect and to avoid the loss of hide substance.
If pliability is an essential in the leather, the best procedure
is to place the hides first in an old lime to get the softening
effect, and then place them in a fresh lime where they will be
plumped. The more mellow the lime liquors are the greater
the flexibility of the leather.
For some leathers, such as harness, fairly fresh limes con-
taining sodium sulphide should be used. Such limes accom-
plish the swelling and de-hairing rapidly, but do not dissolve
enough substance to make the requisite degree of flexibility;
and it is therefore advantageous to accomplish the latter effect
in the bates. Bacterial bates dissolve considerable substance,
and where pliability is desired, such bates should be used, es-
pecially when liming has been done in fresh limes.
Soft leather is obtained by somewhat long treatment in mel-
low limes, followed by thorough bating and rather heavy
pickling. This is the usual process for certain grades of up-
per shoe leather, glove leather, etc. For leather that is to be
finished dull, sodium sulphide is preferable in the limes ; and
for that to be given a fine, glazed finish, red arsenic is best.
Arsenic sulphide. — Where sodium sulphide is used in the
presence of lime, the chemical reaction produces caustic soda
and calcium polysulphide. Being soluble, this caustic soda has
a pronounced action in the liming operation. Where arsenic
sulphide is used in the limes, the reaction produces calcium
polysulphide and insoluble hydrate of arsenic, and conse-
quently differs from the results obtained with sodium sulphide
to the extent that the caustic soda may influence the operation.
92 PRACTICAL TANNING
Arsenical limes have a characteristic action, due to the cal-
cium sulphydrate which forms when red arsenic* is added to
slaking lime. Sodium sulphide should be dissolved separately
and added to the lime, but red arsenic should be mixed with
the dry lime and slaked with it, or else added to the lime
while it is slaking. Lime should, in every case, be thoroughly
slaked and stirred before it is used. Unslaked lumps should
never be allowed to pass into the lime liquor, as they are likely
to burn the hides. Caustic soda may be added direct to the
lime liquor. Its use can be recommended for heavy leather,
as it sharpens the lime, but not for light, soft, leather, the lat-
ter being benefited most by the use of sodium sulphide or red
arsenic. Caustic soda is useful in swelling and plumping the
hides quite rapidly, but it does not assist in making soft
leather. There is considerable bacterial activity in an old
and mellow lime, and such a liquor, on account of its solvent
effect, tends to produce a leather that is soft and loose, and
has a dull grain. Hides that have been passed through such
a lime should therefore be put into a fresh lime to be properly
swollen and plumped.
Sun-dried hides should be de-haired with sodium sulphide
in the limes, since such a process swells the fibers and freshens
up the withered grain more than does lime alone or lime and
red arsenic. De-hairing in a strong solution of sodium sul-
phide and then liming for a few days is another excellent
process for dried hides. Soaking in a sulphide soak, supple-
mented by working in a dry mill, is usually found to be the
most satisfactory process which can be used on dry hides for
upper harness, and sole leather.
Liming for thin grain. — Leather can be made with a thick
or a thin grain by certain manipulations in the beam-house.
Hides can be so treated that when they are tanned they have
a thick, solid grain, this being usually done by using sodium
sulphide and de-hairing the hides rapidly. On the other
hand by treating in only clean, white lime, the grain can
be made soft and flexible, and so thin that when the
leather is split after it is tanned the grains have consid-
DEPILATION
93
erable substance and strength, even when the hides are split
unusually thin.
By shaving the hides green, liming them for 8 days, bating
them until they are soft and low, and stirring them easily in
Figure 49. — Unhairing on the Leidgen machine.
the tan liquors, a thin grain is obtained. One process ac-
complishing this is carried out as follows :
The hides are first soaked 24 hours in clean water ; they
are then fleshed and re-soaked 12 hours longer, drained, and
passed into the first lime. This lime is prepared by using
1 lb. of lime in sufficient water for 100 lb. of hides. The
hides remain in this lime 24 hours, and are then hauled out
and the lime is strengthened by adding another pound of lime.
The hides are put back for 24 hours longer, then hauled out
and put into the second pit. The third lime liquor should
contain 2 lb. of fresh slaked lime for each 100 lb. of hides in
the pack. At the. end of 24 hours the hides should be hauled
out and placed in the third lime, prepared the same way as the
V-h
PRACTICAL TANNING
second lime. Twenty- four hours later the hides should go
into the fourth lime, which should be a little stronger in lime
than the preceding liquor. At the end of 8 or 9 days the
hides should be in condition to be de-haired. After they have
Figure 50. — Hand fleshing on the beam.
been de-haired, put them .into water warmed to 85° F. for
6 or 7 hours ; then work them over the beam by hand, and get
them as clean as possible.
Liming for sole leather. — In liming this grade of stock,
the hides are first treated with a mixture of 10 per cent of
hydrated lime and 2 per cent of sodium sulphide, and left
in the liquor for one day. On the second day they are trans-
ferred to another paddle or pit containing 10 per cent of hy-
drated lime and 1 per cent of sodium sulphide. On the third
day, the hides are changed to straight lime liquor containing
10 per cent of the weight of the stock. On the fourth and
fifth days they are also changed to straight lime. On the
sixth day they are thrown into the warm pool for half an
DEPILATION
95
hour, after which they are ready for de-hairing. On removal
from the warm pool, the sides are placed on a table, spotted
for white hair, and then unhaired on the machine, (figure 49).
Following the unhairing on the machine, the hides are re-
Figure 51. — Inspection for fine hairs.
fleshed on the machine and then hand fleshed on the beam,
(figure 50). They are then inspected for fine hairs as shown
in figure 51.
Sulphide process for sides, kips, or calf. — The well-
soaked and washed stock is put into a paddle containing a
20° bk. solution of sodium sulphide at 70° F. The paddle
is run for about 2 hours, when the wheel is stopped, and after
that run for 5 minutes each hour. The stock is kept in the
liquor over night, and turned from time to time during the
morning. At about noon, the plug is drawn and the spent
liquor let out. The paddle is filled with water and run for
half an hour. One per cent of sodium bicarbonate is now
added, and the wheel is turned for one hour. Fresh water is
96 PRACTICAL TANNING
next turned on, and the stock is washed for 3 hours. By this
time it should be fairly free from sulphide and in a fallen
condition. It is then removed from the paddle, and may be
bated and pickled as desired.
Sodium sulphide and calcium chloride on sides and kips. —
Put into the paddle a weighed amount of sodium sulphide suf-
ficient to make a 20° bk. solution. To this solution add one-
fourth as much calcium chloride as sodium sulphide used.
Raise the temperature of the solution to about 80° F., and
then introduce the stock and run at intervals during the day.
Allow the stock to remain in the liquor over night, and at the
end of 24 hours wash thoroughly in running water for 1 hour.
The stock is then neutralized with 2 per cent of sodium bisul-
phite, running 1 hour in the liquor. The hides or skins are
then thoroughly washed in running water, and are ready for
the bate.
Liming of calfskins. — After calfskins have been soaked
and fleshed, they are put through the lime process. For light
skins, liming according to the following directions will be
found satisfactory in every respect, the skins being brought
into condition for de-hairing in 4 or 5 days. For each 100
lb. of skins 5 lb. of lime is used. It is thoroughly slaked and
added to the water in the paddle, and 1 lb. of sodium sulphide,
dissolved in hot water, is added. The temperature of the
liquor is then raised to 75° F. ; the skins are thrown in, and
the paddle is run at intervals during the day. The next morn-
ing, 5 lb. of lime and 1 lb. of sodium sulphide are poured into
the liquor; and the skins, which have previously been hauled
out, are put back and left in the liquor with occasional stirring
1 or 2 days longer, when the liquor is again strengthened in
the same manner as before and warmed to 75° F., this tem-
perature being maintained during the entire process. At the
end of 4 days, the skins should de-hair easily, but it does no
harm to leave them in the lime a day longer. Heavy skins
require another addition of sodium sulphide and lime, and 2
days more or longer in the liquor. The hair should come off
easily without straining the grain. When taken out of the
DEPILATION 97
lime liquor, the skins should be thrown into water at 85° F.
for a half-hour, then de-haired carefully, washed and put into
the bate.
Another satisfactory process of liming calfskins is carried
out as follows : the quantities of lime and sodium sulphide
being for 100 lb. of skins. The first solution contains 2 lb. of
lime, and the skins are left in for 24 hours. The second so-
lution contains 2 lb. of lime and 1 lb. of sodium sulphide, the
skins also remaining therein 24 hours. The next day they
are hauled out, the liquor is thoroughly plunged, and the skins
are put back for 24 hours. The third lime is made up of the
same quantity of lime and sodium sulphide as the second
lime, and the skins are left therein 24 hours. The fourth lime
contains 2 lb. of lime, and is warmed to 80° F. The skins
remain in this for 24 hours, and then are put into clean water
at 85° F. After having been in this water for 2 or 3 hours,
they are de-haired.
Lime and arsenic. — In this liming process, lime and
red arsenic are used, and the skins are brought into good
condition for chrome or vegetable tanning. To start with,
use a new solution made by adding 2 lb. of lime, well slaked,
to the requisite volume of water in the paddle. Leave the
skins in this lime 24 hours. On the second day, haul them
out, plunge the liquor, and put the skins back. On the third
day, add 2 lb. of lime, stirring the goods at intervals during
the day. On the fourth day, haul the skins out, and after
plunging the lime, put them back. On the fifth day, add 3 lb.
of lime, well slaked, and 1| lb. of red arsenic, slaked with the
lime. On the sixth day, simply haul the skins out and put
them back, plunging the liquor well. On the seventh day, add
3 lb. of lime and 1| lb. of red arsenic, and warm the liquor
with steam to 75° F. On the eighth day, haul the skins out
of the lime, warm the liquor as before, and put the skins
back. The hair should come off easily on the ninth day.
After the hair has been removed, the skins should be washed
in warm water, re-fleshed, and all the fine hair worked out.
They are then washed and bated.
98 PRACTICAL TANNING
Red arsenic keeps the grain smooth and the skins flat; it
also produces fine grain on the leather which takes a fine
glazed finish. The lime and red arsenic should be mixed to-
gether dry and slaked with hot water. Place the limed skins
in warm water containing 12 oz. of borax to 100 gallons of
water to soften the grain and dissolve the lime on the surface,
so that the fine hairs and waste matter will come out readily
when the skins are worked. The quantities of lime and ar-
senic in the foregoing process are for 100 lb. of skins.
The use of a paste of lime and red arsenic is not customary
among tanners of calfskins; yet such a method of de-
hairing, followed by liming for a few days, gives smooth,
soft skins with fine grain and texture. The paste of lime
and red arsenic should be prepared a day or two before using.
Mix 50 lb. of lime and 2 lb. of the arsenic, and slake together
with hot water. The mixture should be stirred while it is
slaking, and enough water added to make it as thick as paint.
The skins are spread out on the floor or a table, and the pre-
pared mixture is spread upon the flesh side with a brush, the
skins folded down the middle lengthwise, and placed in piles
in a vat. When the vat is about three-quarters full, some
boards loaded with stones are placed on the skins, and the
vat is filled with water. After 5 or 6 days the skins are taken
out of the vat, washed, and de-haired. Some skins require
from 6 to 8 days before they can be de-haired. The next
process is liming.
For each 100 lb. of skins in the lot, use 14 lb. of lime and.
5 lb. of red arsenic ; 1 or 2 lb. more of lime and a little more
arsenic may be used for soft leather. The skins are limed
from 3 to 7 days, according to their thickness, being stirred
by the paddles 3 to 4 hours each day. Having been thus
limed, the skins are next washed and bated.
The following method of liming with lime and sodium sul-.
phide, described under side leathers, produces good grain and
full feel without much loss of skin substance, so it is a good
process to use in preparing calfskins, kips, etc., for chrome tan-
nage. When once started, the movement described entails
DEPILATION 99
only a small amount of handling of the stock. Calfskins
having a heavy neck are split on the checking machine shown
in figure 52.
Liming of goatskins. — After softening, as shown in figure
Figure 52. — Checking machine, used for splitting necks on
calfskins.
53, a liming process in which sodium sulphide is used, pro-
duces first-class results and does not make fine-hairing neces-
sary, is carried out as follows:
For 100 lb. of skins, 3 lb. of lime and If lb. of sodium
sulphide are used as a first lime, the skins remaining in it one
day. They are then hauled out and the same quantities of
lime and sodium sulphide are added. On the third day the
skins are hauled out, and put back after the lime has been
plunged. On the fourth day the lime is strengthened and
warmed to 80° F. ; the skins are put back until the sixth day,
when they are de-haired, washed, and bated. If they do not
de-hair easily, the liquor should be warmed and the skins left
in a day or two longer.
Liming with lime and red arsenic produces fine-grained
100
PRACTICAL TANNING
leather. To start with, the goods are put into a weak liquor,
containing 2 per cent of lime, calculated on the weight of
the raw stock. After being in this for a day they are hauled
out and put back. On the third day, 2 per cent more of lime,
Figure 53. — A typical beam-house of a goatskin tannery.
well slaked, should be given. On the fourth day the skins are
hauled out, the liquor is plunged, and the goods are put back.
To strengthen the lime on the fifth day, 3 per cent of lime
and 2 per cent of red arsenic, slaked together, should be added ;
and on the sixth day the goods are hauled out and put back,
so that those that were on top before are now on the bottom,
and those previously at the bottom are on top. On the seventh
day 3 per cent of lime and 2 per cent of red arsenic are added.
On the eighth day it is advisable to haul the skins out and
warm the liquor to 80° F., then put the goods back, and
after leaving them one day longer de-hair them. They are next
washed 10 minutes in cold water, re-fleshed, worked for fine
hairs, and then bated. The exact quantity of lime to use and
the number of days to leave the goods in the lime depends
DEPILATION 101
upon their thickness, heavy goods requiring longer liming
than light, thin ones. For the preparation of glazed kid, a
fairly long liming is required, usually 12 to 15 days. Either
lime and arsenic or lime and sulphide may be employed. After
the goods have been de-haired, they are re-fleshed, and passed
into the bating process.
Combination process. — Run 700 gallons of water into a
paddle, and add 100 lb. of sodium sulphide crystals dissolved
in hot water. Put a pack of skins into this liquor, and leave
them until the hair is dissolved, when they are ready to be
limed. The liquor swells the skins and dissolves the hair.
The next process is liming. Slake 100 lb. of lime, and add
700 gallons of water. Put the de-haired skins into this liquor,
and turn them in it 2 or 3 days, then wash them and scrape
the flesh side again. Some of the hairs which may be broken
on the grain should be removed from the flesh side, and much
of the remaining grease will come out at the same time. The
skins are then in condition to be bated.
Depilatory compounds for wool skins and hairskins. —
The present methods of removing wool from. sheepskins and
the hair from goatskins and other light skins are considerably
different from the old-time process of sweating and liming,
the latter having been replaced by the method of painting
mixtures on the flesh side, of which lime is mainly the base.
These usually contain lime and some sulphide, such as sodium
sulphide or arsenic sulphide (red arsenic). By mixing lime
with either of these substances, and adding water, a paste is
obtained which, when applied to the flesh side of the skins,
causes the hair or the wool to be loosened in a few hours.
Methods of mixing lime and sulphides vary. It is usually
considered good practice either to slake the lime with a solu-
tion of sodium sulphide, or mix the lime with the sulphide
first, and then slake with water; or in the case of arsenic sul-
phide and lime, to place the two in alternate layers and then
slake. The high temperature caused by the slaking of the
lime produces a reaction between the sulphide and the lime,
so that hair-removing compounds are formed
102 PRACTICAL TANNING
As a type of method, the following, which has been rec-
ommended by the Light Leather Trades Federation of Great
Britain, may be given (7-J lb. of sodium sulphide crystals to
every 40 lb. of dry lime, are the desired proportions for all
skins) :
Take the 40 lb. of lime, slake in 9 gallons of water, and
allow to stand for three days, so that all the hard substances
are well slaked. Pass the slaked lime through a sieve with
10 meshes to the lineal inch. Dissolve the 7^ lb. of sodium
sulphide in 1 gallon of water, and add the sulphide solution
to the lime, mixing well. The mixture is then ready for
painting the skins, which should be pulled not later than the
next day. As they are pulled they should be washed in clean
water before they are put into weak lime.
A suitable depilatory paint for all classes of skins is pre-
pared as follows: 60 lb. of unslaked lime, 25 lb. of sodium
sulphide, and 20 gallons of water. A wooden tub should be
used for slaking and mixing. A thin layer of the unslaked
lime is then placed on the bottom of the tub, and on this a
thin layer of sodium sulphide crystals, followed by another
layer of lime. The two ingredients are thus placed in alter-
nate layers until all has been placed in the tub. The necessary
amount of water to effect thorough slaking is now added a
little at a time (about 10 gallons of water will be. sufficient).
After slaking, the mixture should be left over night, the re-
maining 10 gallons of water are then added, and the mixture
is thoroughly stirred. Before being applied to the skins, it
is better to pass the mixture through a fine sieve to remove
any small lumps of unslaked lime, stones, etc.
For the finer grades of leather, such as lambskins and goat-
skins for glazed and glove leathers, upon which fine grain is
essential, the use of paint composed of lime and red arsenic
is preferred. It is better to mix the arsenic sulphide and the
lime before slaking, so that the heat produced by the slaking
of the lime produces calcium sulphydrate.
M. C. Lamb has given the following method: "The arsenic sulphide
is mixed with the unslaked lime in a suitable receptacle, in alternate
DEPILATION 103
layers of lime and arsenic, and the amount of water necessary to effect
the slaking is then poured a little at a time over the mixture. Suitable
quantities to use are 120 lb. of lime, 30 lb. of red arsenic, and 60 gallons
of water. After the slaking has been performed, the mixture should be
thoroughly mixed with a wooden spade, and diluted to the required
consistence by the addition of 45 to 50 gallons of water. The paint should
be allowed to stand over night before using, and may with advantage be
passed through a fine sieve before being applied to the skins. When
properly prepared, the paint should be pale green in color. Any trace
of red or pink color is evidence that the mixture is not satisfactory, and
that the necessary chemical reaction during the slaking process has not
been satisfactorily effected."
Depilating glove leather. — The modern glove-leather
manufacturer has to deal with all kinds of skins, but chiefly
with goatskins and sheepskins. Owing to the scarcity of raw
skins, he is not able to choose as much as he formerly did.
Cape sheepskins form the glove-leather dresser's main supply,
and these are now in general demand by tanners and leather
dressers for a great variety of purposes, including boot and
shoe uppers and bag work. The following information rela-
tive to glove-leather dressing is taken from an article in "The
Leather Trades Review" :
For painting fifty dozen average skins, 6 bushels of lime and 45 lb. of
red arsenic are required. In preparing this mixture, care must be taken
to get a perfect reaction between the lime and arsenic. This is best
obtained by first thoroughly mixing the two together and breaking the
lime into small lumps. The mixture should then be carefully and thor-
oughly slaked with water and made into a paste-like mixture which can
be painted on the skins in the usual manner.
The skins are spread out on the floor or on a table, and the mixture
is applied with a mop to the flesh side. As each skin is painted, it is
folded over, flesh to flesh, and placed in a pile and left until the next day.
When the painting is done in the afternoon, the skins are ready for
pulling the next morning. The wool is generally sorted into four grades.
The next process is liming, and the duration of this process varies,
according to the skins under treatment, from 7 days to 2 or 3 weeks. The
old one-pit method still obtains in many tanneries and is carried out as
follows : The pit is started with 5 bushels of lime, and the pelts remain
in the same for 2 days when they are withdrawn, and the liquor is
strengthened by the addition of 2 bushels of lime. In this liquor the
skins are left for a week, then withdrawn and a final addition of 3 bushels
of lime is made to the liquor. The goods remain 1 or 2 veeks longer,
as they may require.
The amount of lime given above is sufficient for 50 to 60 dozen Cape
sheepskins, but much latitude must be allowed, as so much depends upon
local conditions, the season of the year and the condition of the goods.
^During liming, the skins are drawn several times, and when the process
is completed, they are drained and allowed to soak in clean water for a
day or two. The addition of a pail or two of lime to the water is
recommended. When the liming is completed, the skins are trimmed and
fleshed, and left in water containing a little lime, after which they are
104 PRACTICAL TANNING
passed through water to which some lactic acid has been added to accom-
plish a slight de-liming.
Patented depilatories. — In addition to sodium sulphide
used for the purpose of removing hair and wool from hides
and skins and preparing them for tanning, patented depila-
tories are obtainable, largely made from the same chemical,
which have many points to recommend them, being very satis-
factory for both wool-pullers and tanners to use; and the
leather which is made from skins treated with them is char-
acterized by toughness, pliability, and fine grain. These de-
pilatories are used in various ways according to the kind of
skin being treated and the qualities desired in the finished
leather.
Depilatory paints. — Following are several more prescrip-
tions for making the paint :
Put 25 lb. of lime into a tub, and add just enough hot
water to cover it. Stir the lime until it is entirely slaked,
and add more water as it is needed. In another tub or barrel
dissolve 25 lb. of sodium sulphide in 10 gallons of hot water.
Mix the lime and the solution of sulphide together, and allow
the mixture to become cold before applying it to the skins.
A suitable paint is prepared as follows: Mix 60 lb. of lime,
30 lb. of sodium sulphide and 20 gallons of. water. Place
a thin layer of the lime upon the bottom of a clean tub or
vat, sprinkle on this a thin layer of the sulphide, and spread
the remainder of the lime and sulphide in alternate layers. Ten
or twelve gallons of hot water are next added, a little at a
time, the mixture is thoroughly slaked, and is then left over
night. The remainder of the water should be added, and
then stirred up to a paint-like consistence. It is always ad-
visable to pass a depilatory paint through a fine sieve to re-
move particles of unslaked lime, small stones, etc. Hydrated
lime is better than lump lime, and if the former is used, the
proportions should be 60 lb., 40 lb. of sodium sulphide, and
20 gallons of hot water.
A good depilatory is made by dissolving sodium sulphide in
hot water until the solution stands at 18 or 20° Be (Baume)
DEPILATION 105
test, and then adding 18 gallons of slaked lime. Apply this
mixture to the skins when it is cold.
A mixture of lime and red arsenic can be recommended
for loosening the wool on skins for glove or glazed leather,
since it makes fine, smooth grain. The proportions are 100
lb. of lime and 25 lb. of arsenic, the two being thoroughly-
mixed together dry, and then slaked with 50 gallons of hot
water, and passed through a fine sieve.
Applying the depilatory paint. — Spread the skins, one at
a time, upon a table and apply the prepared paint upon the
flesh side; then fold the skin with the wool on the outside,
and place in piles until the next day, when the wool can be
easily removed. Only enough of the mixture should be used
to saturate the skin and cover it evenly, and none should be
allowed to run off" into the wool. Rubber gloves should be worn
to protect the hands during this work.
When the weather is cold, 6 or 7 skins may be placed in
a pile ; but during warm weather not more than 3 or 4 should
be so placed, and if they are to be left for 24 hours or longer,
they should be singled out and each pelt should lie by itself.
7 The wool becomes loosened in a few hours, but it is best if it
is not removed until the next day. Very young lambskins,
however, should be "pulled" as soon as the wool is loosened,
and then put into cold water to which some sodium sulphide
has been added. They may be kept in this water for some
time without injury, although it is advisable to pass them
promptly into the lime.
Liming after removal of the wool. — To start the liming
of the skins, use 20 lb. of hydrated lime with 6 gallons of
water for 100 average skins. Put the lime into water in a
vat; put the skins in and leave them 1 day; then haul them
out, and add 10 lb. of lime with 5 gallons of water, and put
the skins in for another da} 71 , then haul them, add 7\ lb. of
lime, and return for another 2 days.
Liming for Mocha and castor gloves. — In the depilation
of skins for Mocha, castor, buff, and chamois leather, it is nec-\
essary to employ a long liming, which in some cases is pro- \
106 PRACTICAL TANNING
longed to 30 or 40 days. For this treatment strong limes
are also used, and a certain amount or arsenic sulphide is
usually added. The outer grain is then removed on a beam
with a round stick, the operation being known as frizzing.
Method of using arazym on goatskins. — Soaking: It
is very important that the skins be thoroughly milled and
soaked, and it is advisable to soak them for one day more than
is considered sufficient for the lime or sulphide processes. See
that the heads and necks are carefully worked out, that is,
freed from grease and flesh.
First day. — Make up the following solution for each 100 lb.
of skins, dry weight in hair:
Light weight Heavy weight
skins skins
Water, gallons 125 125
Caustic soda (76 per cent), pounds... 3i 4
Temperature, degrees F 80 to 82 83 to 85
Time to remain in caustic solution, hrs. 36 48
Heavy hard-natured skins may stay in the liquor for 60 hours.
Run the skins in the paddle one hour when first put in, and
then for 10 minutes each, in the evening before closing down
and in the morning when starting up.
When the skins are to remain in the caustic solution over
Saturday and Sunday, put them into liquor late on Friday,
and reduce temperature 5° (according to the nature of the
skins).
The pack that has to stay in the caustic solution on Sunday
and Monday is put into the solution as late as possible on
Saturday, with a drop in temperature of about 8° (according
to nature of skins).
Third day. — Run off the caustic solution, and put the skins
into a solution consisting of 10 lb. of bicarbonate of soda and
125 gallons of water for 100 lb. of skins, dry weight in hair.
The temperature after the skins are in is 80 to 84° F.
Run for one hour, then add, according to the nature of the
skins, for lights, 12 oz. of arazym, and for heavies, 16
oz. of arazym, per 100 lb. of skins, dry weight in hair. Run
DEPILATION 107
for 20 minutes more, then leave in solution until the follow-
ing morning.
When skins are to remain in the de-hairing bath over Sun-
day, drop the temperature 10°, and reduce the arazym 30 per
cent, which means 8 oz. for light skins, and 12 oz. for heavy
skins.
Fourth day. — Take the skins out and unhair. It is im-
portant that the skins from the unhairing machine be put
into tepid water (about 65° F.) at once. They should not
be left in dry condition either in a box or on a pile for
any length of time. Wash in tepid water for 10 minutes,
then flesh. If after fleshing the skins do not go into the
bate at once, put them into tepid water. Weigh skins and
then bate with "oropon A special" as follows (it is very im-
portant that the quantities of water and skins are in the right
proportion, and for each 100 lb. of skins there should be 400
lb. of water).
First liquor. — The skins are washed in the old bating liquor •
used for the previous pack over night at a temperature of 85°
F. for light skins, and 90° for heavy skins. The time of bating
is 10 minutes (paddle 5 minutes). If no old oropon liquor is
available for the first pack, substitute a solution of 4 oz. of
oropon per 100 lb. of skins.
Second liquor. — In the second bating liquor the skins are
bated over night. The quantity of oropon required is 16 oz.
per 100 lb. for heavy skins, and 12 oz. for that quantity of
light skins. The temperature should be 90° for heavy and
85° for light skins. Paddle 5 minutes.
The oropon necessary for the first pack is fermented in
five times its weight of water for 24 to 48 hours at 110° F.
(24 hours in summer, 48 hours in winter). From the sec-
ond pack on, that is when for the preliminary bate an old over-
night bating liquor is available, it is not necessary any more
to ferment the oropon, but it is simply added to the fresh
bating liquor before the skins go in.
After the skins are in the bating liquor, make certain it
is on the alkaline side, that is, you should get a fair reaction
108
PRACTICAL TANNING
with phenolphthalein, and if not, add £ per cent of soda ash
on the weight of the skins.
When bating over Sunday, either put the skins into the
bating liquor on Saturday afternoon, without the preliminary
washing in the old bating liquor, reducing the temperature
about 5° and the quantity of oropon about 25 per cent; or
do the bating on Sunday in the usual manner, taking care,
Figure 54. — Fleshing.
however, that the skins, over Saturday and Sunday, are left
in water made strongly alkaline by the addition of a solution
of saturated lime water.
Fifth day. — Take skins out, slate, wash for 5 minutes in
tepid water in paddle, and tan as usual.
For the swelling and de-hairing liquors it is advisable to
take into one paddle a comparatively small quantity of skins
with a large volume of water — about 125 gallons for 100 lb.
of skins in the hair, dry — because in these liquors the skins
are considerably swollen. After the skins are de-haired,
washed, and fleshed (figure 54), they do not take more room
DEPILATION 109
than in the ordinary bating process, and the quantity of water
(50 gallons per 100 lb. of skins, bating weight) is sufficient.
For the swelling and de-hairing liquors, take 3 reels for a
quantity of skins for which in the regular bating process you
would take one reel. For instance, if the regular bating packs
consist of 900 lb. of skins, divide this quantity for the swell-
ing and de-hairing liquor into 3 paddles each containing 300
lb. ; however, for bating in the oropon special put them all into
one paddle again.
The finished leather is improved by giving a somewhat
heavier bottoming with vegetable tan in the dyeing, so as to
fill it up. Care should also be taken to dry slowly at mod-
erate temperature.
CHAPTER IV
DE-LIMING, DRENCHING, BATING, PUERING AND
PICKLING
It is essential that the lime or other depilating agent should
be completely removed after it has done its work, since its
action on tanning is very injurious. Its presence has a ten-
dency to weaken the fiber or produce a harsh-feeling grain.
For sole and belting leather it is only necessary to de-lime the
stock, and for soft leather this de-liming should not only be
complete, but the stock should be brought to a flaccid and open
condition. Ordinary de-liming may be accomplished by weak
organic acids or certain chemicals, while bating, puering, and
drenching, all of which tend to produce soft leather, must be
brought about through fermentative, bacterial or enzyme ac-
tion. Pickling consists in treating the de-limed, bated, puered
or drenched stock with a combination of salt and acid, usually
sulphuric. Drenching, which consists of a fermenting in-
fusion of bran, sometimes follows bating or puering, but it is
often resorted to independently of the other treatment.
The two terms "bating" and "puering" formerly meant
two distinct processes, the former being applied where
pigeon or hen manure was used, and the latter where dog
manure was employed to remove the lime and open up the
stock. Today, however, bating is most commonly used, and
puering only in connection with the conversion of goatskins
into leather.
De-liming. — Where de-liming only is desired, this may
be accomplished by purely chemical means. Lime, being of
an alkaline nature, adheres tenaciously to the hide fiber, and
so cannot be readily removed by washing in plain water.
An excess of strong acid must be avoided on account of its
swelling effect upon the pelt, with subsequent damage dur-
ing the tanning operation. What is especially required is
that the de-liming agent should form an easily soluble com-
110
DE-LIMING, DRENCHING, BATING, ETC. Ill
pound with the lime. An excess of the reagent must not
have an injurious action on the pelt, and it must be obtainable
at low cost.
Test for de-liming. — A simple test to ascertain whether
skins are sufficiently bated and de-limed is to touch a cut
edge of the skin with phenolphthalein solution. If there is
lime still present, a violet coloration is produced, but when
the skin is entirely de-limed, there is no such coloration.
Sulphuric acid. — By exercising great care this acid may
be used as a de-liming agent for stock that is to be tanned
in acid hemlock liquors. The stock should be run in a much
diluted, slightly warm solution, until the lime is nearly neu-
tralized; it is then thrown into clear water to finish the de-
liming.
Hydrochloric acid. — This mineral acid is somewhat safer
than sulphuric, but must be perfectly free from even a trace
of iron, and the paddle should have no iron surface exposed.
Sulphurous acid. — The most satisfactory mineral acid is
sulphurous. It may be generated as a gas by burning sulphur
in a stove, and allowing the sulphur dioxide (SO2) to be
absorbed in water. An excess of this acid is not harmful
to the stock, and leaves it in a somewhat plump condition.
Sodium bisulphate. — Ordinary nitric-cake may be used in
place of sulphuric acid. This material is a by-product from
the manufacture of sulphuric acid, in which sodium nitrate
is treated with sulphuric acid to furnish the necessary amount
of nitric oxide required during the process Care must, there-
fore, be taken to guard against the presence of any nitric
acid in the product.
Boracic acid. — This may be used to advantage as a sur-
face de-liming agent on sole leather, the amount required
being about 2 per cent on the weight of the stock. Experi-
ence has shown that the treatment should be carried out in
a paddle, otherwise patches will appear giving irregular color
to the finished leather. Among the various chemical de-
liming agents and bates which may be used in preparing hides
and skins for tanning, boracic acid is one of the most efficient
112 PRACTICAL TANNING
for that purpose. The hides or skins are bated in the usual
manner, and are then immersed in a drench of boracic acid,
which removes the last trace of lime, and makes the grain soft
and clean. When the acid is used alone for the purpose of
de-liming it makes the grain soft and silky, hastens the tan-
nage, and prevents the grain from becoming contracted in the
tan liquor. Light skins for chrome and vegetable tanning
are sometimes given a drenching with boracic acid after they
have been bated, a paddle being used during the operation.
When soft, silky, leather is required, it is advisable first to
use a commercial bacterial bate, such as oropon, and then
drench with boracic acid, and pickle with formic acid and
salt. Excellent results as regards grain, texture, and color
are assured when skins are treated in this manner.
Carbonic acid. — The use of carbonic acid has been sug-
gested as a de-liming agent, in which case the carbon di-
oxide gas (CO2) is allowed to bubble through the water in the
paddle. The first action is to form the neutral carbonate,
but as more carbon dioxide is introduced, the soluble bicar-
bonate is produced and the stock consequently de-limed.
Lactic acid. — In recent years this de-liming agent has come
into general use. Lactic acid is formed when milk sours. On
a commercial scale it is produced by adding the lactic ferment
to a solution of glucose. It comes into the trade either in a
30 or 60 per cent solution. When employed for de-liming,
2 lb. should be used for each 100 gallons of water, at a tem-
perature of about 90° F. Like other de-liming agents, the
best results are obtained in the paddle. A slight excess of this
acid produces considerable plumping, which is a decided ad-
vantage in treating hides for sole leather or other heavy stock.
For 800 to 1000 average limed sheepskins, 20 lb. of lactic
acid and 20 lb. of salt are used. The water in the paddle
should be warmed to 85° F. ; if it is cooler than this, more
salt is required to keep down the plumpness. Half of the acid
and all of the salt should be added to the water before the
skins are put in, and the remainder of the acid after they have
been in 15 minutes. The time required for drenching should
DE-LIMING, DRENCHING, BATING, ETC. 113
be about 45 minutes in a paddle; in a still vat or tub, 2 or 3
hours, the skins being stirred two or three times during that
time. Several packs of skins may be put through this drench,
with a fresh addition of 15 lb. of lactic acid for each succeed-
ing pack, adding 5 lb. at first, and 10 lb. after the skins have
been in 15 minutes. When drenched, the skins should be
rinsed in warm water and pickled.
Lactic acid may be used for goatskins in the following man-
ner: After the skins have been bated, prepare a bath in a
paddle with warm water, and for 100 lb. of skins add -| lb.
of lactic acid and an equal quantity of salt. The water should
be at 90° F. before the skins are put in; they are paddled 20
minutes, then rinsed and pickled. This method is advanta-
geous for goods that are intended to be colored, as the acid
cleanses them thoroughly. The process can also be carried
out in a drum, in which case only a few minutes is re-
quired to remove the last trace of lime from the skins.
Formic acid. — This compound is prepared on a large scale
by heating sodium formate with sulphuric acid. The result-
ing acid comes to the tanner as a 60 per cent solution. It
is very effective as a de-liming and plumping agent, and many
tanners prefer it to lactic acid. It is used in the same pro-
portions as given for lactic acid.
Formic acid and lactic acid drench. — A mixture of 4 parts
formic acid and 1 part lactic acid is efficient in drenching
skins, less than -| pint of the mixture being sufficient for 100
washed skins. The goods are paddled 30 minutes or longer
in the drench at a temperature of 90° F., rinsed, and pickled.
This drench may also be used after a regular bate. Drenched
with formic acid, skins tan into clear-grained and uniformly
colored leather.
M. C. Lamb, of the Leathersellers' Technical College, Lon-
don, describes a method of de-liming and pickling with formic
acid, which he has used successfully, as follows :
The goods, after washing free from surplus lime in the paddle water
at 85° F. for 30 minutes, are ready for de-liming. The de-hming is best
done in the paddle-wheel; the goods are placed in a vessel, together with
sufficient water at 90° F.; paddling is commenced, and then the following
114 PRACTICAL TANNING
solution, previously prepared, is added: 2 lb. of formic acid (40 per cent),
and 5 lb. of common salt, for each 100 lb. of limed skins.
The goods are paddled until flaccid and fallen, which will generally
require about 30 minutes, when they are removed and are ready for
pickling. Pickling is best carried out in a drum, but it may also be done
in a paddle. The proportions recommended are 10 lb. of formic acid, 20
lb. of salt, and 20 gallons of water for 100 lb. of skins.
Butyric acid. — This is another chemical product of recent
introduction. It may be used in the pickling of calfskins
for chrome or vegetable tanning, especially for the two-bath
process, when it is used in the following manner: The skins
are bated with any satisfactory bate or in a bran drench,
and are then pickled in a drum with a solution of 10 lb. of
salt, and 10 oz. of butyric acid in 15 gallons of water for 100
lb. of skins. The skins are turned in this liquor for an hour;
they are then given the first chrome process, which in this case
is made of 4 to 6 lb. of sodium bichromate, 1 lb. of butyric
acid, and sufficient water, say 15 gallons. This method of
pickling and tanning is said to produce leather having a par-
ticularly soft grain and agreeable feel.
Ammonium chloride. — This material can be used to good
advantage for dressing leather. It is a strong bating agent,
converting the lime into calcium chloride, which is very soluble
and easily removed. The ammonia generated, according to
the Otto P. Amend process, may be neutralized with hydro-
chloric acid, and the bath used continuously. The amount of
ammonium chloride used at the start should be about 3 per
cent of the weight of the stock, and 1 per cent is added to
each subsequent pack. The temperature should be maintained
at about 90° F. to get the best results. This method is es-
pecially adapted to calf and side leather where a depleting
action is not desired.
The following process is said to be excellent for goatskins
for chrome tanning: Dissolve 20 lb. of sal-ammoniac (am-
monium chloride) and 70 lb. of salt in 700 gallons of water
at 95° F., for 50 dozen skins. Paddle the skins in this liquor
for two hours, then leave them in over night. Sal-ammoniac
acts upon the goods like a bate or puer, having, however, the
advantage that the workman can control this process while he
DE-LIMING, DRENCHING, BATING, ETC. 115
cannot always control the old-time puering. The next morn-
ing the skins are transferred to the pickle in a paddle-
wheel consisting of 10 lb. of formic acid and 8 lb. of salt, at a
temperature of 85° F. After an hour in this liquor the skins
are in condition to be tanned. This removes all the lime, and
strengthens the fibers so they will stand the corrosive action
of the chemicals and acids used in chrome tannage.
Ammonium butyrate. — One of the newer chemical prod-
ucts for de-liming and bating is made by neutralizing butyric
acid with ammonia. It produces the best results as a bate
when used upon skins that are to be put into the tanning
liquors in a soft or neutral condition. The skins become per-
fectly de-limed, white, and soft, and no injury results when
an excess is used. It may be used alone or with any other
bate. For bating calfskins it is used alone, the quantity rec-
ommended being 1 to 1^ lb. for 100 lb. of skins. The am-
monium butyrate is dissolved and added to warm water in the
bating paddle. The goods are put in and paddled for a half-
hour; then allowed to rest for 2 hours, and then paddled
another half-hour, when they are taken out and either pickled
or tanned.
Sodium dichromate. — The value of this process lies in the
employment of a chromium compound as a base, a solution of
it forming the main ingredient of the bate. The liquor may be
prepared as follows :
Prepare a saturated solution of 2 oz. of sodium dichrom-
ate in water, pour it into a vat containing 1,000 gallons of
water, and stir thoroughly. This quantity is sufficient for
20 to 40 hides, which are thrown into the prepared bate, and
left therein for 24 hours, being stirred occasionally. The
temperature of the bath should be about 80° F. The hides
may be run in the liquor a short time, and then left in it over
night or longer. They are then fine-haired, washed in warm
water, and are ready to be tanned. About 2 oz. of dichromate
are used for 2000 pounds of hides or skins, green-salted
weight. The use of sodium dichromate as a bate has been
patented by Henry Schlegel, of Lapeer, Michigan.
116 PRACTICAL TANNING
Sodium bisulphite. — This chemical has marked de-liming
action, but on account of its acid character it does not pro-
duce a true bating effect. For certain classes of leather, how-
ever, it may be employed to advantage.
Ammonium phosphate. — For sole leather the use of such,
materials as ammonium phosphate and ammonium oxalate are
said to have some value as de-liming agents. In using these
salts an insoluble condition of the lime is produced which,
remaining in the leather, helps to give it body.
Zinc sulphate. — When limed hides are thrown into a solu-
tion of zinc sulphate, a double decomposition takes place,
which results in the formation of calcium sulphate and zinc
oxide, both being insoluble in water. The hides are therefore
filled and added body is secured.
Coal-tar bates. — Several of the aromatic acids have been
suggested as de-liming agents, some of which have been used
with more or less success. Among these should be mentioned
crude cresotonic acid, a mixture of phenol and cresols; oxy-
naphthoic acid ; napthalene mono and disulphonic acid ; sali-
cylic acid ; as well as phenol and cresol sulphonic acids.
Several years ago the Martin Dennis Co., of Newark, N. J.,
put on the market a preparation known as "C. T. bate." This
compound consisted of a mixture of sulphonic acids, and
was used in a 1 per cent solution. All of these coal-tar bates
are more effective as de-liming agents than as true bates or
puers.
Drenching. — By drenching is usually understood a method
in which some form of fermentation is employed, the sim-
plest of which consists of fermenting bran infusion. Not only
is drenching employed to remove the lime and open up the
stock, but it is often applied after bating or puering to bring
the skin to a clean and acid condition. During fermentation,
the principal products formed are lactic acid and acetic acid,
together with some formic acid, butyric acid, hydrogen sul-
phide, and amines. Drenching takes place most satisfactorily at
a temperature of about 90° F., and is usually complete in from
12 to 18 hours. Unless liquefying bacteria have been intro-
DE-LIMING, DRENCHING, BATING, ETC. 117
duced during the bating, no injury to the stock can result.
The following suggestions may be . found useful :
Method of de-liming {drenching) with bran. — Take a half
barrel of bran, and add enough water to make it mushy; cover
it up, and let stand in a warm place for 48 hours to sour.
Into a vat large enough to treat 400 skins run the requisite
volume of water and empty the sour bran into the same. Mix
thoroughly, and heat to 90° F. Throw the pack of skins into
the prepared drench, and treat them for 3 hours, heavy skins
a little longer. The skins will be made soft and clean by this
treatment, and, if intended for black leather, will require no
working on the beam; but if for colored leather, it is advis-
Figure 55. — Bate beam-stone.
able to work them out on the beam so that the grain will be
clear and clean. Washing in warm water after drenching puts
the skins into the best condition for pickling and tanning.
Other bran drench formulas. — Take 50 lb. of bran; add
water to make a mush, and let it stand until sour; then put
the sour bran into a paddle together with 700 gallons of warm
water, and process the skins until they are soft and clean.
Rinse them in warm water; work them over the beam with a
bate beam-stone (figure 55), and then pickle them. If acid is
needed, 25 lb. of 28 per cent acetic acid should be added
A process of drenching which is especially recommended
involves the use of bran and lactic acid in the following man-
ner: Run water into a paddle-wheel and heat it to 120° F.
Put two pails of dry bran into the warm water and let stand
over night The next morning bring the temperature up to
95° F. Take one pint of lactic acid for each 100 lb. of skins,
and put about half of it into the bran liquor; throw the skins
in, and while the paddle is running, add the remainder of the
118 PRACTICAL TANNING
acid. Run the paddle for 2 to 4 hours, according to the thick-
ness of the skins and the amount of lime in them, then take
them out and rinse in warm water. This washing should not
be neglected, especially if the leather is to be colored. The
skins, after they have been rinsed, are ready to be pickled.
For the second pack of skins, lower the drench liquor down
about 12 inches, and run in an equal quantity of water. Heat
the liquor to 95° F. Do not use any more bran, but take a
pint of lactic acid for every 100 lb. of skins to be treated, and
proceed exactly as described for the first lot. Continue in
this way for 6 days; then run off the liquor and make up a
fresh drench with water, bran, and acid, and proceed in the
manner described. This method of drenching makes the skins
soft and clean, and in good condition for pickling and tanning,
no matter what the tannage may be.
The following also is a reliable bran drench : Take a half
barrel of bran, add enough water to make it mushy, and let
stand 48 hours to sour. When sour, empty it into a vat half
filled with water. Add 6 pints of acetic acid and 3 pecks (45
lb.) of common salt, and heat to 95° F. This quantity of
bating material is sufficient for 300 to 400 skins. Throw the
goods into the liquor, and paddle for 4 or 5 hours ; then wash
them in warm water if for black leather, or work them over
the beam and then wash them, if for colored leather. This
process produces soft and clean skins which can be pickled and
tanned by any tanning process.
Mild fermented drench. — A mild fermentation of an acid
has proved to be a most satisfactory bate and de-liming proc-
ess for hides which are to be tanned into soft, supple leather
by a chrome or a vegetable tannage. Excellent results as re-
gards full flanks, good break, and fine, even grain are obtained
by allowing grape sugar or common glucose to become sour,
and using definite portions of the same in combination with
lactic acid for each pack of hides or grains.
The process is a simple one, and is easily carried out: Dis-
solve 100 lb. of grape sugar or glucose in 35 gallons of hot
water in a barrel. Add several quarts of sour milk, and allow
DE-LIMING, DRENCHING, BATING, ETC. 119
to stand for two or three days at a temperature between 95
and 105° F., when fermentation should be completed. Pre-
pare a paddle-wheel with water at a temperature of 95°, and
put into it 2\ quarts of the sour sugar solution. For every
100 lb. of stock to be bated take 1 pint of lactic acid, and put
about half of it into the prepared bate in the paddle-wheel
before putting in the hides, and when the latter are in, add the
remainder of the acid. Three or four hours are usually suf-
ficient to run the goods in the paddle-wheel. On being taken
out, they should be thoroughly washed with water. The im-
portance of this simple washing is too often overlooked, and
its necessity cannot be over-emphasized if a good clear grain,
which will color evenly, is desired. For the second pack of
hides, the bate liquor is lowered about 12 inches in the paddle-
wheel, and the loss made up with fresh water. The tempera-
ture is brought up to 95° F., and 2\ quarts of the sour sugar
solution and 1 pint of lactic acid is added for every 100 lb. of
stock, as directed for the first pack. Continue in this way,
running off a little of the liquor for each pack, for 6 days ;
then run off all the liquor, retaining, however, about a barrel-
ful with which to mellow the new liquor, which is prepared
with fresh water.
It should be pointed out that the amount of sugar solution
used, namely, 2| quarts per pack, is based upon the volume
of liquor in the paddle-wheel. The average capacity of a
paddle-wheel is between 2000 and 2500 lb. of stock. The
action of the sour sugar is, however, so mild, that a wide
range in the weight of the stock bated with the given quantity
of the sugar solution is permitted without danger.
Puering and bating. — Under this head are included such
materials as give the results desired through bacterial or en-
zyme action.
The process commonly called bating or puering frees the
skins from lime and alkaline sulphides acquired during the
process of liming, and makes them soft and clean and in the
proper condition to be pickled and tanned. Hen and pigeon
droppings and dog dung have been used for many years and
120 PRACTICAL TANNING
although these materials are unpleasant, they produce results
difficult to obtain by the use of others, and many tanners con-
tinue to use them. Goatskins are sometimes puered with a
mixture of chicken droppings and dog dung, but the latter is
also employed alone.
To prepare the material, soak it in hot water for two or
three days before using. Mash it well, stir it occasionally,
and strain it through a wire strainer to get rid of pebbles,
feathers, etc. ; this, however, is not always necessary. The
skins should first be washed in warm water to remove sur-
face lime, then be placed in a used bate liquor which has been
warmed to 80° F., and left in the same for 12 hours. From
such liquor they are placed in a fresh bate warmed to 85°, and
paddled in the same for several hours, or until they are soft
and silky. They are next fleshed, scudded, rinsed or drenched,
and pickled or tanned.
Bating with molasses. — Sour molasses makes an effective
bate for hides for heavy leather. The molasses is soured by
putting 7 gallons into a barrel of water, adding 1 gallon of
milk to assist the souring, keeping the solution at 90° F., and
stirring occasionally until sour. More than one barrel is
required, so that more molasses can be souring while the first
is being used.
To use the sour molasses, fill a paddle-wheel with enough
water to cover 50 sides, and add 8 pails of the sour molasses.
The sides remain in the bate at least 30 minutes, and a longer
bating will do no harm, although there is always danger of
bating too low. Judgment must be used as to how long to
continue the process. When the bate becomes weakened by
the lime which works out of the hides, more sour molasses
should be added, say 6 pails to 200 sides. If the paddle holds
50 sides, put in 1^ pails of molasses after taking out each pack
of hides, and keep the temperature of the bate at about 80°
F. The bate should not be made fresh for each lot of hides,
but molasses should be added to it. When the bating is over,
withdraw the hides and rinse them in cold water in another
paddle-wheel for a few minutes, and then put them onto sticks
DE-LIMING, DRENCHING, BATING, ETC. 121
for the tanning liquors. The bated hides will contain consider-
able lime, but a few hours in the liquor will take it all out.
Bating with glucose, sulphur, and yeast. — In working
with this process, the skins are limed, unhaired, and washed.
A bath at 95° F. is next prepared, consisting of 5 per cent
glucose syrup and 1 per cent sulphur, computed on the weight
of the skins, and about 1 lb. of yeast for every 1000 lb. treated.
The bath prepared in this manner is allowed to stand 24 hours
to become thoroughly fermented. At the end of this period
the temperature of the liquor is raised to 100°, and the hides
or skins are put into it. v
In order to have a continuous bath, half the original quan-
tity of sulphur, glucose, and yeast is added at the same time.
In working this process, it is not necessary to keep the skins
constantly in motion, but only stir them occasionally. Heavy
hides will be free from lime and in soft and open condition
at the end of 8 hours; lighter skins in a proportionately shorter
period.
On removing the pack, the temperature of the bath may
be raised, and after adding half of the original quantity of
sulphur, glucose, and yeast, another pack may be treated, thus
making it possible to work two packs each day in the same
vat. It will be understood that a continuous bath would in
time become too concentrated from solutions of calcium com-
pounds, and thus prevent or retard fermentation. This dif-
ficulty is obviated by drawing off half of the solution every
time after treatment of the second pack.
The hides or skins show no trace of lime after treatment,
and they are soft and open, and have a smooth, silky grain.
As there is nothing in this bate to cause putrefaction, there is
no loss of hide substance, and the skins, without further
drenching, can go at once into the tan liquors. Where pick-
ling is part of the process, the skins can be pickled at once
and then tanned. This is the Oaks patented process of bating.
By adding 2 per cent of ammonium chloride in the first
bath, the efficiency of the bath can be improved.
Dog dung. — Despite the unpleasantness of its use, dog dung
122 PRACTICAL TANNING
is an efficient bate for leather that requires a soft, fine, and
silky grain. The material may be used alone or combined
with the droppings of hens and pigeons. If dog manure is
kept for some time, it becomes heated of itself, burns up, and
becomes useless; consequently, it is placed in barrels, covered
over with enough water to soften it, and allowed to ferment
for two weeks, or until it has resolved itself into a pasty condi-
tion. In this way it can be kept for months in covered bar-
rels without losing any of its bating action. When it is to
be used, it is stirred into boiling water (by this means a great
many of the bacteria are killed, but not the spores) until, after
decanting off several times, all of the soluble matter has been
removed, and only the waste portion remains behind; but all
sand must be allowed to settle again from the liquor, because
if any is allowed to remain it is likely to injure the grain.
This settling is best done in a large vat.
For 100 pieces of calfskins or 50 sides it is customary to
reckon about 10 to 12 quarts of dog durig, while for 30 dozen
sheepskins about 50 lb. of the material are used ; and for 1000
lambskins or goatskins, 100 lb. or more. The proper amount
of the bate is placed in the paddle-wheel in water sufficient for
the pack of skins to be treated. The temperature of the liquor
at the beginning should be about 90° F. The skins should re-
main in the bate for 2 to 3 hours, or at the longest, until the
flesh remaining on them can be readily removed. It is injur-
ious to the skins to bate them too long.
After the process is completed it is well to rinse off the
skins, and then place them at once on the beam or the flesh-
ing machine. By placing them in fresh water, the flesh be-
comes tender and is not removed as readily as when it is in
the mellow condition in which it comes from the bate ; conse-
quently, as little water as possible is used, so that the mellow-
ness of the skins is not lost.
In this process of bating it is easily possible for undesirable
fermentation to take place and injure the skins. The duration
of the bating in a normal case should occupy a definite time,
regulated by the temperature, strength of the liquor, and tex-
DE-LIMING, DRENCHING, BATING, ETC. 123
ture of the skins, as well as by the degree of fermentation
which the bate has developed. This method of bating is not
patented.
Hen manure. — For calfskins and side leather it is custom-
ary to employ hen or pigeon manure in place of dog manure.
The usual quantity used is a half bushel to 50 sides or 100
skins. The manure is placed in a barrel with warm water and
allowed to ferment for several days, when it is added to the
paddle liquor. Manure bates may be used for some time with-
out changing, but care must be exercised to prevent too violent
an action, which may damage the stock, causing what is
known as "bate runs "
Dermiforma. — This is a prepared bacterial bate which has
been introduced as a substitute for the old-time bates. The
methods of using it described below, have proved satisfactory
and the results desired have been obtained.
It should be remembered that bacterial action is governed
by different temperatures, and if it is desired to reduce or
deplete the hides or skins, the temperature of the bating liquor
should be kept close to 95° F. during the process. Experience
has shown that a different grain is obtained at different tem-
peratures; consequently, if the liquor is kept near this tempera-
ture, the skins will be reduced more quickly and the grain will
be finer. This applies to all classes of stock.
The quantity of dermiforma to be used for every 100 lb. of
skins varies. In the bating of goatskins, 4 lb. are used, and
the same quantity in bating calfskins. Sheepskins, however,
may be bated with 2 lb., and the same quantity bates hides and
kips, while sealskins require 3 pounds.
It usually requires about four hours to get calf, seal, and
sheepskin in condition to be pickled or tanned. It requires
good judgment to determine the exact time for the bating
process ; consequently, no general rule can be laid down, as
some tanners do not bate hides longer than two hours at 95°.
If it is desired to plump the stock, H lb. of the bate will be
sufficient for 100 lb., the time required being generally from
2 to 4 hours, and in some cases where hides are being plumped
124. PRACTICAL TANNING
for sole leather, they may remain in the liquor over night.
The temperature should be normal or not over 80° F.
In using dermiforma in tanning liquors — either sweet or
natural sour liquors — 1| lb. to every 100 lb. of green hides will
plump them, and the leather will gain in weight. Where ex-
tract liquors are used entirely, the result is better, and the tan-
nage more rapid with the above proportions. In all cases, the
hides must be thoroughly washed from the limes, or the pro-
portions given will not suffice. More bate is required when
an excess of free lime is carried into the bating process.
Bating is done most advantageously in a vat with paddles,
and not in a stationary tub, as the action of the paddles causes
the liquor to be stirred, thus de-liming more quickly. A
warm bate depletes or reduces the goods; a cold bate plumps
them. When de-liming is completed, and the skins are soft
and silky to the touch, they should be removed from the bath,
rinsed in warm water, and then either pickled or tanned.
Skins are bated most satisfactorily in warm liquor, while for
hides for plump and heavy leather a cold bate is best.
Dr.- Rohm's bate "oropon C" for regular packs. —
Treatment of the skins before the bate is the same as usual.
It is advisable to wash them thoroughly before the bate to
free them as much as possible from lime. In the case of
sulphide, neutralize as usual. For this bate the quantity of
water and temperature are as usual, and the time of bating is
2 to 4 hours for calfskins, and 4 to 6 hours for hides. The
quantity of oropon is always calculated on the weight of the
wet skin's and according to their nature thus :
8 to 10 oz. per 100 lb. for calf and split grains, and 10 to
12 oz. per 100 lb. for insplit hides (used for furniture, etc.)
The liquor can be re-used, and in this case add, for the
second and following packs, about half or even less of the
oropon used for making fresh liquor. It is advisable to warm
the old liquor over-night the first two days to accelerate fer-
mentation. After the liquor has been used two days it will
be noticed that fermentation grows stronger. To keep it in
DE-LIMING, DRENCHING, BATING, ETC. 125
control, run off each day about 6 to 12 inches of the liquor
(more in summer than in winter). Before running off, stir
the liquor well to get rid of as much dirt as possible. As a
rule make up the bate fresh once every two weeks, but in
doing so, leave about a fourth of the old liquor in the paddle.
Bating process.— Always heat the water first, then put the
oropon in undissolved. After stirring thoroughly put in the
skins The further treatment is the same as usual. Watch
the process closely to see how the skins fall, and do not take
them out until they are as low as desired. In case they fall
too quicklv, reduce the quantity of oropon proportionately the
next time.' If they do not fall enough, add to the bate 0.1 to
2 per cent of oropon (dissolved in a bucket of water and
added while the skins are paddled), at the same time raise the
temperature of the liquor in case it has cooled down too quick-
ly If, after one hour, the skins are still too high, repeat this
operation until a satisfactory result is obtained. The next
time a correspondingly higher concentration is used. If over
night bating is preferred, use about 20 per cent less oropon
than indicated above, and a temperature of from 80 to 90° F.
before skins are put in.
Dr. Rohm's bate "oropon A B" for limed goatskins.—
Use 30 gallons of water for each 100 lb. of skins, and the
usual quantity for regular packs.
Bating, first liquor.— -The skins are first washed in an old
bating liquor. If no old oropon liquor is available, substitute
a light solution of 4 to 6 oz. of oropon for each 100 lb. of
skins or better, wash the skins in the used dog-manure liquor.
Temperature.— For soft skins, 90 to 95° F. (before the
skins are in) ; for hard skins, 95 to 105° F. (before the skins
are in).
Second liquor.— In this liquor the skins are bated over night
(put in about four o'clock, paddled 10 to 15 minutes, and
left until the next morning). In the morning they are paddled
again for 15 minutes, and if low enough, are taken out. In
preparing the bating liquor, always heat the water first, then
126 PRACTICAL TANNING
put in the oropon without previously dissolving it, and, finally
put in the skins.
Quantity of oropon for 100 lb. of skins. — For South Amer-
icans, Brazils, etc., 8 to 10 oz. ; for Russians, 8 to 10 oz. ; for
Chinese, 12 to 16 oz. ; for Mochas and Patnas, 14 to 16 oz. ;
and for Northwesterns, 16 to 18 oz.
Temperature. — 95 to 105° F. (before skins are in), accord-
ing to the nature of the skins.
In case the skins are not reduced enough, add more oro-
pon, starting with about 20 per cent of the original quantity.
If, after about an hour, the skins are still too high, repeat
the operation until the skins are as low as desired. The next
time, of course, correspondingly more oropon is used. In
bating over night, fermentation will raise the skins to the
surface of the water, which action is desirable. It is probable
that the first two or three packs will not come up, as the
fermentation is too weak at the start. It will strengthen grad-
ually, however, and the fourth and following packs will rise
over night.
Martin Dennis' "puerine." — Take a clean 50-gallon barrel,
remove the head, put in 25 gallons of water and heat to 130°
F., then, while stirring vigorously, put in 100 lb. of puerine.
Cover the barrel with an old burlap bag to assist in retaining
the heat. After 24 and 48 hours, add 10 gallons of water at
140° F., stirring well each time. At the end of 72 hours the
puerine is ready for use. The barrel will be full, and each
gallon taken therefrom will contain 2 lb. of puerine. When
using the prepared puerine always stir thoroughly before tak-
ing any from the barrel.
First pack. — Have the desired quantity of water in the pad-
dle, heat to 95°, put in stock, and then add, for every 1000
lb. of stock, 12 lb. of puerine (6 gallons of the prepared
puerine).
Second pack. — Use 8 lb. of puerine (4 gallons of the pre-
pared) for every 1000 lb. of stock.
Third pack. — Use 6 lb. of puerine (3 gallons of the pre-
pared) for every 1000 lb. of stock.
DE-LIMING, DRENCHING, BATING, ETC. 127
Fourth and all following packs. — Use 4 lb. of puerine (2
gallons of the prepared) for every 1000 lb. of stock.
Once a week allow the puer paddle to settle for four
hours, then draw off from the top about a fifth of the bating
liquor. This is easily done by having a plug on the the side of
the pit at the proper distance from the top. Clean out the
pit thoroughly every three months by drawing another plug
from the bottom.
It is impossible to explain here how long the stock should
be bated, but it should be left in the bate until in the judgment
of the operator, it is "low" enough.
The puerine bating liquor improves with age, and it must
not be expected that the first few packs will be as well bated
as those which follow. In this respect it is the same as a
manure bate. When the bating assumes a bluish, slate color,
it is in prime condition. If, at any time, this puerine bating
liquor suddenly becomes yellow, it is an indication that too
little puerine is being used.
Puerine D.- — The Martin Dennis Co. of Newark, N. J., has
also on the market a bate which is used the same as oropon.
This bate, as well as oropon, is made from dry pancreas com-
bined with ammonium chloride and some inert material. Its
action depends upon the presence of tryptase and to some ex-
tent on lipase, the former acting as a solvent on the albumin-
ous material, while the latter has the tendency to break up
the fats.
Pickling. — After the stock has been bated or puered it is
necessary to drench or pickle it before tanning. Drenching is
usual where the stock is to be vegetable tanned and pickling
is employed where chrome tannage may follow. The sub-
ject of drenching has been covered above, and the same
methods as outlined may be applied after the bate. The fol-
lowing suggestions will be found useful when pickling is
desired :
Sulphuric acid and salt. — To 40 gallons of water, add 40
lb. of salt and 5 lb. of sulphuric acid ; this forms a stock pickle,
12 gallons being used for 100 lb. of skins. The pickling is
128 PRACTICAL TANNING
accomplished most rapidly in a drum, the skins being run in
the liquor at least 1-|- hours, then allowed to press and drain
over horses for several hours or until the next day.
Another formula calls for 2 lb. of sulphuric acid, 15 lb.
of salt, and 15 gallons of water for 100 lb. of skins. The
drum containing the skins is started, and after it has turned a
few times, the solution of acid and salt is poured in and the
drumming is continued from 15 to 30 minutes. Either of these
processes produces good results, and there is no guesswork
about the quantity of acid and salt to use, and therefore no
uncertainty.
Formic acid and salt. — The formula for this pickle is 10
lb. of the acid, 20 lb. of salt, and 15 gallons of water for 100
lb. of skins. The process is carried out in the same manner
as with the sulphuric acid. An excellent way to pickle the
skins, no matter which acid is used, is to put them into the
drum together with three quarters of the water needed. The
salt is dissolved in the remainder of the water, and the acid
is added to it. The drum is started, and the acid and salt
solution is poured in through the trunnion, and the drum al-
lowed to run 30 minutes.
Hydrochloric acid and calcium chloride. — In the manufac-
ture of white chrome leather, a decided advantage in color
may be obtained by using a pickle of calcium chloride and
hydrochloric acid. To prepare this pickle, make up a solu-
tion of calcium chloride by dissolving 40 lb. of the salt in 40
gallons of water, and add 8 lb. of hydrochloric acid. To
pickle, use 12 gallons for each 100 lb. of stock.
Pressing grease from pickled sheepskins. — The follow-
ing method of removing grease from pickled sheepskins has
been found satisfactory in many cases: Get a sufficient num-
ber of sheet-iron plates as large as the press (hydraulic) will
take, about 1/16 inch thick. Place one dozen skins on each
plate, and spread out flat with the bellies and shanks folded
in so as to have each plate of the skins about the same size.
Place the butt of one skin as evenly as possible over the other
until the press is full. It will be seen that the pressure comes
DE-LIMING, DRENCHING, BATING, ETC. 129
directly on the parts of the skins that need it most. After the
pressure has been applied and the- skins have been pressed,
throw them into a drum, together with warm salt water, and
drum them until they have come apart and are well opened
out. They are then in condition to be tanned.
It is advisable to plaee sawdust or bran between the layers
of skins to keep them from slipping, and apply the pressure
very slowly as the stock is easily damaged at this stage.
Gargoyle de-greasing fluid. — This preparation is used for
de-greasing pickled sheep, goat, dog, and other skins carry-
ing a large percentage of animal fats. The following process
produces satisfactory results when the pickled skins contain
a minimum amount of moisture but no dry spots. If there
are any dry spots they should be wet down when taken from
the casks in the drained pickled condition, then proceed as
follows :
Weigh the skins, separate each bundle by picking them apart
one by one, place them in a clean drum without any water or
other materials, and mill them in that condition for 5 to 10
minutes, or until they are opened up free from wrinkles and
quite plump. Then for each 100 lb. of pickled stock, take
from If to 2\ gallons of de-greasing fluid, and heat to 100°
F. in a steam-jacket ed kettle or over an electric stove, or by
similar means where it is possible to avoid introducing any
moisture. Add the de-greasing fluid to the mill with the skins,
and mill together for about 30 minutes.
If the skins are entered in the evening and they are very
heavy or greasy in the necks and backs, which will be the case
if many bucks are among them, it is advantageous to let them
lie in the drum over night, and then mill again in the morn-
ing for about 15 minutes. Then add through the gudgeon of
the drum sufficient (1 lb. to the gallon) salt solution at 100°
F. to allow the skins to become wet ; although without sufficient
solution to cause them to float. The process is most efficient
where there is no excess of water at this stage. The pickled
stock, put in a drum 4 feet high and 8 feet diameter, should
not exceed 400 lb. In this condition the skins should mill
130 PRACTICAL TANNING
about 15 minutes, when there should be added through the
gudgeon of the drum enough salt solution to float the skins
freely. Next, pull the plugs or put on a slat door to flush
out the salt solution and grease. Put on the tight door again,
and slowly feed enough salt solution at a temperature of
100° F. to float the skins; then again put on the slat door and
flush out. The skins are now ready for tanning.
During this operation, in addition to removing the animal
grease, a good deal of the acid is extracted, thereby leaving
the skins in the best possible condition for tanning. In this
way the necessity of drawing pickle is eliminated, also the
wringing and pressing of skins.
De-greasing fluid. — This attacks the "sheep grease" con-
tained in the skins, dissolving and diluting it, so bringing it
into solution; and when washed with warm brine (salt water)
the grease is all removed. Precaution must be taken that the
temperature does not exceed 100° F., and that the pickled
skins are kept in contact with the saturated brine while wash-
ing, or they will bloat and be destroyed.
By this process, which naturally makes a flat leather, there
is no danger of breaking the grain or distending the fiber. The
process is beneficial to the stock, whereas wringing or pressing
is detrimental; and perfect results are secured in the single
operation described.
Recovered grease. — The solution of fats and brine, as it
flows from the drum while washing, should be collected in
wooden tubs or a large vat, then heated to boiling point and
allowed to stand for 1 to 3 hours. The oil and fat will come
to the surface, and the brine should then be drawn from the
tank through a spigot or wooden faucet at the bottom of the
vat until it has all been drawn from under the oil. Then
more water should be run in with the oil ; boiled again to agi-
tate it perfectly, allowed to settle the second time, and the
water again drawn off. This operation should be repeated
until all of the acid and salt have been washed from the oil,
both of which are detrimental if the fats are to be used in the
production of leather. Tests for acid should be made with
DE-LIMING, DRENCHING, BATING, ETC. 131
methyl-orange and tests for salt with silver nitrate. Natur-
ally some Glauber's salt is produced, which is also eliminated
by this process. Two washings should be sufficient.
These recovered fats are valuable to the tanner, principally
for making fat-liquors or emulsions. For sheepskins, it is
recommended that one part of this recovered oil be added to
two parts of "moellon degras" ; then add an equal quantity of
water, and boil it until thoroughly incorporated. The recov-
Figure 56. — Belt-knife splitting machine.
ered fat may also be emulsified by the addition of soaps or
alkalies, although excellent results have been produced by using
it as suggested above.
Splitting out of lime. — To make good chrome leather,
hides should come from the unhairing machine firm and hard.
If they are soft and flabby they will make poor leather, as
there is nothing in chrome tanning that fills the hides or makes
up for lost substance. After the hair has been removed, the
sides should be washed in lukewarm water for 15 minutes and
then worked over the beam for short hair. This work is im-
portant, as all fine hair must be removed; and even if there are
no fine hairs, working out the grain opens up the cells of the
hides and makes the grain fine and clear. After this work has
been done, the sides should be put into cold water over night to
harden for splitting. The next morning they are ready to be
split. This is done on the belt-knife splitting machine, shown
in figure 56. In splitting the sides, a 6-oz. grain from the ma-
chine will finish up 4| oz. of leather, as it loses 1^ oz. going
132 PRACTICAL TANNING
through the various processes. All loose ends and pieces of
flesh should be trimmed from the sides before splitting is be-
gun, so that there will be nothing to interfere with the hide
feeding freely into the machine. After the sides are split,
they should be run in a wash-wheel with cold water for a few
minutes to open them up and to remove the glaze caused by
the belt-knife. The grains and splits are next bated.
Splitting out of aluminum sulphate and salt pickle. —
Where hides are split out of pickle, a good procedure is to
bate and pickle them with aluminum sulphate and salt in this
Figure 57. — Rubber roll putting-out machine.
manner: For every 100 lb. of sides, unsplit, and bated and
washed, dissolve 4 lb. of sulphate and 10 lb. of common salt
in 6 gallons of boiling water ; then add 6 gallons of cold water
and use the liquor after it has cooled to 70° F. Drum the
sides in this liquor for an hour ; then horse them up smoothly,
and let them press and drain until the next day.
Hides pickled in this manner should not be pickled pre-
viously with acid and salt. If the splitting machine has a
corrugated roll, the sides can be split right off the horse. If
the machine has a smooth roll, the sides should be hung up
to "sammie" (to become semi-dry), or pressed, or put out on
a putting-out machine (figure 57), to prepare them for split-
ting. The grains should be the same thickness that the finished
DE-LIMING, DRENCHING, BATING, ETC. 133
leather is to be, as they do not fall away like grains split from
limed hides. Hides pickled with aluminum sulphate and salt
split as easily as bark-tanned leather and the splits are as good
as those taken from the limed hides. After the sides are split,
the grains can be shaved while in the pickled condition, this
saving putting them out for shaving after they are tanned.
Both the grains and splits are then ready to be tanned.
Splitting after tanning.— Tanning the sides in a chrome
process and then splitting them is sometimes practiced. The
sides are tanned in a one-bath chrome process in a paddle-
wheel or by suspension, and when they are well struck through
with the tan they are pressed and split. The pressing removes
the surplus water and makes the leather drier and firmer.
After pressing, the sides should be run in a dry mill until they
are opened up and ready to be split, when they should be
jacked the same as bark leather, and split to the thickness the
finished leather is to be. After they are split, the grains are
shaved and re-tanned.
Splitting out of acid pickle.— When hides, are to be split
in acid-pickled condition, they are allowed to drain 24 hours
after being pickled, pressed to remove surplus liquor, and
milled to remove the press-marks; they are then split to the
required thickness. The grains can be shaved either after
splitting or after they are tanned.
CHAPTER V
RAW HIDES: OIL AND ALUM TANNAGE
Raw hide. — For certain purposes, such as drum-heads, sad-
dle-tops, bayonet scabbards, belt-pins and the like, a very
strong and stiff form of leather is required. To make such a
product, the hides or skins are soaked, de-haired, and bated
in the usual manner, and after thorough washing are carefully
tacked on boards, the tacking being strong and close. The
skins are then allowed to dry slowly, and as they dry contrac-
tion takes place, causing a more or less transparent condition.
When stripped, they are ready for market. When used, such
skins are dampened with warm water and stretched into what-
ever form desired. Parchment is usually made from selected
sheepskins treated in this manner.
For the manufacture of raw-hide pins, now used extensively
for joining machinery belting, the hides are cut into strips, and
while wet are twisted into shape and allowed to dry out under
tension. Raw hide is also pressed into various shapes, such
as hammer heads, washers, and the like.
Lace leather. — Raw-hide lace leather must be strong and
soft, so it is necessary to separate the fibers and lubri-
cate them so that they will remain pliable. This is accom-
plished by the following method : The hides are limed thor-
oughly and bated with ammonium chloride. They are then
given a light tawing by milling with 5 per cent of aluminum
sulphate and 5 per cent of salt dissolved in just sufficient water
to float the stock. When struck through, they are piled down
for 48 hours, and then split to weight. The sides are then hung
up to dry, and when well crusted they are dipped in lukewarm
water and packed down to sammie. The sides, which should
now contain about 30 per cent moisture, are placed in the mill
in a mixture of 5 per cent of cod liver oil, with 2 per cent of
tallow at 120° F. added: The drum is run for two hours, and
another portion consisting of 3 per cent of cod oil and 1 per
134
RAW HIDES 135
cent of tallow is added; and after another hour a similar quan-
tity is added. When the sides have absorbed most of this oil
they are set out on- the machine, and then well set by hand,
using a dubbing of 2 parts cod oil to 1 part of tallow. The
sides are then hung over sticks to dry. When the stock is
dry, it is dipped in lukewarm water and piled down, care being
taken that it does not become too hot. A certain amount of
heat, however, should be developed to cause oxidation of the
cod oil. The oxidized stock is now re-set by hand, again hung
up, and finally rolled.
In place of the cod oil and tallow, many tanners are now
using a mixture of 50 per cent oleostearine substitute, 40 per
cent of vacuum currier's wax, and 10 per cent of rosin, at a
temperature of 140° F., using a total of 15 per cent of the
mixture, and adding it in three portions as indicated above.
Lace leather made by this process does not oxidize as quickly
as that made from cod oil, and besides being less dangerous
is less expensive. The same mixture is used for dubbing as
for oiling, and the same procedure is carried out except in the
case of packing down to oxidize.
Shark-liver oil tannage. — Where cod-liver oil is used for
stuffing or for other purposes the author has found that the
oil from shark livers can be used with equally good results ;
in fact, a stronger leather is produced with this oil than with
cod or fish oils.
Latigo leather.— A very strong leather, and one used ex-
tensively .where strength and body are desired, is what is
known as "latigo leather." The process employed in making
this is essentially the same as for raw hide. The point of dif-
ference lies in the fact that the sides, after splitting to weight,
are run in a .paddle with a solution of . gambier of 15° bk.
strength until the color is struck through. They are then dried
out, sammied, and stuffed as described under raw hide. Some
tanners improve the color of the stock by milling with a solu-
tion of auramine or picric acid.
Another method for making latigo leather is as follows:
The hides are suspended in gambier liquor for a few days,
136 PRACTICAL TANNING
and then put into a solution of alum and salt. This process
produces a thick grain which presents an excellent surface to
the buffs. Stuffing is done with hard grease, degras, and cod
oil. The leather is then shaved, buffed, and finally set out, first
by machine, and then by hand. Tallow and oil are often used
in stuffing lace leather, and when the grain is buffed off, there
is, of course, no liability of its cracking and breaking when
in use.
Some tanners also run the stock in a paddle-wheel contain-
ing a 15° bk. gambier solution and then finish with salt and
alum ; while others run the sides in a mixture of alum, gambier
and salt. In all cases they are finished by stuffing as de-
scribed above.
Alum-tanned lace leather. No. 1. — Put 30 lb. of alum and
50 It), of salt into a clean barrel; add water, and boil with
steam until the alum and salt are dissolved. Dissolve 6 lb.
of sodium carbonate with hot water, and pour the liquor slow-
ly into the alum and salt solution, which has been added to
water in a paddle, plunging the liquor briskly Effervescence
takes place when the soda solution is mixed with the alum
liquor, and when it ceases, the liquor, to be in the right condi-
tion for use, should have a sweetish taste. If it tastes sour,
add dissolved carbonate of soda and salt in the proportions
stated until it tastes sweetish or neutral.
The liquor should be cold when the hides are placed in it.
The tan liquor having been prepared, place about 400 lb. of
washed sides into it. Run the sides 15 minutes after they have
been placed in the liquor, again at the expiration of half an
hour, and again at the end of the next half-hour, then at in-
tervals of two hours until the close of the day. Frequent motion
lays the foundation of an even tan and a uniform grain, two
important considerations.
On the second day the pack is in the liquor, run it 4 times
at regular intervals; on the third day run it 3 times; and on
the fourth day, twice ; and near closing time, haul the pack up
to drain over night, and finish it the next day.
Tanning may be done also by drumming the sides with the
RAW HIDES 137
liquor for one day, stopping the drum at intervals, and then
starting it again. The pack being tanned and drained, hang
the sides up for part drying. The spots that dry hard should
be wetted with water, and the whole of each side made uni-
formly moist and soft before grease is applied. Dampen the
sides uniformly; fold and pack them in a box and let them
remain 24 hours, when they are ready to be stuffed. The
dubbing used to stuff the leather is made of pure tallow and
neat's foot oil in the following proportions, according to the
season of the year: In summer time, 10 lb. of tallow and 1
lb. of neat's foot oil, and in winter, 10 lb. and 3 lb. respectively.
The leather may be stuffed with tallow only, but the addi-
tion of some neat's foot oil gives it a softer and mellower feel.
Half a pound of rosin to 10 lb. of dubbing helps protect the
dubbing from oxidation. The dubbing is applied in a fluid
state at a temperature little higher than the melting point of
the tallow, in the following manner :
Place on a table the number of sides the stuffing-wheel will
carry, and spread them out upon one another. With a swab
or suitable brush give each hide a light coat of the fluid dub-
bing on both flesh and grain. Place the batch in the cold stuf-
fing-wheel, and set it in motion. The wheeling should be done
in such a manner that the sides come into contact with the pins
of the wheel, in order that the grease may be worked into
the leather.
When the sides have absorbed the grease, take them out of
the wheel and hang them up until they are partly dry. Then
with a stone having well-rounded corners go over the sides
on the flesh side and straighten them out, when they are ready
for shaving. Shave them lightly and evenly. Then coat
both flesh and grain with melted dubbing, and run the sides in
the wheel again. Hang the leather up, and when it is nearly
dry, snuff it over with the currying knife on the flesh side;
set the flesh out; stone, slick, and glass the grain; oil lightly
on the grain, and hang up to dry. Then take the leather down
and glass it on the flesh and brush it on the grain, when it is
ready for use.
138 PRACTICAL TANNING
Alum tannage No. 2. — A tanning liquor for lace leather
may also be made of 15 lb. of alum, 30 lb. of salt, and suf-
ficient water to cover 50 sides, which are kept in this liquor
24 hours. The liquor is then run off, and the sides are given
25 lb. of alum and 50 lb. of salt, and handled twice each day.
They should remain in the liquor two days, and then be hung
up to dry. When dry, they are dampened down for 2 to 3
days, and then worked out on the staker. To grease the sides,
50 lb. of white tallow and two quarts of pine tar are mixed,
and applied hot to both sides of the leather. The sides are
then put into the drum, heated with steam to 85° F., and
drummed one hour. They are next staked on the flesh side,
stuffed again as before, and then set out lengthwise of the
flesh and grain, and hung up to dry. Tanning can also be done
in a drum in much less time than in a vat or a paddle.
Alum tannage No. 3. — A process which is a little different
from the preceding one is carried out as follows : After they
are tanned with alum and salt, the sides are hung up and partly
dried ; but are staked while a little damp, and then thoroughly
dried. They are next stuffed by being given a coat of hot tal-
low, applied liberallv until they will absorb no more. The
leather is then run in a dry drum, stretched, and after rub-
bing off the superfluous grease, is ready for use.
Picker leather. — This leather is used extensively in cotton,
woolen, and silk mills, and great care must be taken in its
manufacture. It must be soft and mellow so that it can be
tied into knots, and above all, it should be so tough that it will
not tear or rip out where loops are cut into it to fasten onto
the shuttle. The hides should be from good steer selection,
weighing from 50 to 60 lb. each. They are soaked in cold
water in the usual way, and when thoroughly soaked, are
limed. When sufficiently limed, that is to say, when the short
hair can be worked out, the sides are reeled into water at 95°
F. This temperature should be maintained ; and the stock
again reeled at the expiration of 24 hours. After remaining
in this warm bath 48 hours, the hides are ready to be de-
haired. Fleshing and bating follow, the hides being bated
RAW HIDES 139
down soft and silky. All the lime should be removed, and the
hides should be soft, low, and clean, before they are put into
the tan liquor.
Gambier is preferable as a tannage, since it tans quickly and
makes soft leather. Oak tannage also produces a soft, tough
leather. The coloring must be done in paddle-wheels. The
sides must be wheeled regularly, and the liquor gradually
strengthened until the stock is thoroughly tanned.
Lactic acid used in the first stages of coloring proves ad-
vantageous. Rapid tanning results, by the proper use of the
acid, and plump, yet mellow leather is obtained. This method
is known as the oak-bark tannage, and it is suggested that
when the hides fresh from the beam-house are put into the
liquor, the latter should not be over 2° bk., and lactic acid
is best employed for plumping after the third day of tanning.
Gambier-tanned picker leather is treated in the same manner
as oak leather in the first stages of tanning, or until the grain
and flesh are nicely struck through with tannin. The sides
are then ready for a special treatment, which forms a yellow
streak in the center of the hide.
The gambier liquor is made of about 4 per cent alum and 1
per cent salt, and sufficient gambier to give a bright orange
color. This bath is heated to 90°F. At the end of an hour,
draw the sides out and return them to the liquor, and in 2
hours repeat the treatment, and again in 3 hours. The fol-
lowing day raise the leather and put it back again, and let it
remain for 24 hours, then hang it up and sammie quickly.
Put the sides into a stuffing-wheel, together with all the tal-
low they will take — say, 4, 5, or 6 lb. — until all the tallow
has gone into the stock. The sides should now be set on the
machine, then re-set by hand, and given a good coat of dub-
bing made of tallow and sperm oil, about 60 per cent of the
former to 40 per cent of the latter. The tallow should be al-
lowed to cool until one's hand can bear the heat, or until a
slight skin arises on the surface of the tallow. The sperm oil
may now be added, the tallow being stirred constantly while
the oil is poured in slowly. This makes a fine, close dubbing,
140 PRACTICAL TANNING
and both oil and tallow will penetrate. Should the oil be
added while the tallow is hot, it will result in what curriers
call "fish eggs," and only the oil will penetrate the stock,
which is very undesirable. The leather is then dried and
worked out soft and clean.
Pyro tan. — A process recently introduced into the United
States consists of treating side leather, kips, or skins, with
a solution containing aluminum sulphate, salt, and sodium
pyrophosphate. The stock is de-haired, bated, and pickled in
the usual manner, and is then milled in a solution, sufficient
to float the hides, containing 10 lb. of aluminum sulphate, 5
lb. of salt, and If lb. of sodium pyrophosphate for each 100
lb. of stock taken. The mill is run continuously until tan-
nage is complete, which occupies from 5 to 10 hours, accord-
ing to the weight of the pelts. The leather may be finished
at this point by fat-liquoring, drymg-out, dampening-back,
staking, etc. The usual procedure, however, is to re-tan in
gambier or quebracho, and finish as indicated under vegetable
tanned leather.
In working with this process, the author has found that
it may be used as a pre-tannage for one-bath chrome treat-
ment. The leather thus secured has fine body and excellent
tensile strength. It may be finished as given later under
chrome tannage. The author has also found that the com-
bination may be used to advantage as a pre-treatment in the
manufacture of oil-tanned lace or glove leather.
Chamois leather. — At the present time this is made almost
exclusively from sheepskins. It is produced by the action of
oil upon the raw skins, and is distinguished from all other
classes of leather by remarkable softness and open texture.
After the wool is removed, the skins are limed long and
thoroughly; they are then split on a machine, the grains being
tanned and finished into fancy leather, and the flesh splits into
oil-tanned or chamois leather. The splits are de-limed,
washed, and pressed to rid them of the surplus water and to
make them as dry as possible.
To soften them, the skins are thoroughly beaten by a ma-
RAW HIDES 141
chine, after which they are sprinkled with cod oil, and again
beaten to force the oil into the leather. The best grade of
Newfoundland cod-liver oil is considered most suitable. Oil-
ing and beating the skins is repeated 2 or 3 times, or until
they have assumed a mustard color. They next undergo a
process of heating, by which the oxidation of the oil, begun
during the previous process, is completed. The heat is gen-
erated spontaneously. The skins must be watched closely and
should be turned over frequently. When the temperature gets
too high, the leather is seriously damaged. The highest tem-
perature allowable is 130° F. When oxidation ceases, and the
skins are no longer susceptible to heating, they are treated
to remove the oil. This is done by washing them in hot
water and then squeezing in a hydraulic press. The grease
squeezed out in this way, is called "degras," and is used by
tanners. The oil remaining in the skins is removed by wash-
ing them in a solution of soda ash, which causes the fatty
acids to saponify. This saponified oil is then neutralized
with sulphuric acid and forms what is known as "sod oil."
A certain amount of the oil should be allowed to remain in
the skins to give them softness.
The finishing process consists of staking and smoothing
down all unevenness on the surface. The skins may be
bleached or colored, as may be desired.
Bleaching. — Chamois skins may be bleached by exposing
them to direct sunlight. They are first treated with 2 per
cent solution of a neutral soap, then wrung out, rinsed, and
exposed to the sun for a day. A second washing with a 1 per
cent soap solution is given; the skins rinsed, and again ex-
posed to the sun. This process is repeated until the skins are
bleached satisfactorily. Washing may be done with soda, but
this has a tendency to make the leather harsh; soap is there-
fore preferable.
Chamois leather is bleached rapidly and uniformly by im-
mersion first in a solution of potassium permanganate and
then in sulphurous acid. Before it is bleached, the excess of
oil must be removed by washing in a lukewarm 2 per cent
142 PRACTICAL TANNING
solution of a neutral soap; the skins are then rinsed and wrung
out. The solution is prepared by dissolving 1 lb. of perman-
ganate in 5 pints of water. Enough of this solution is added
to water in a tub to color it a deep purple. The bath is then
warmed up to 100° F., and the skins are placed in it, one at
a time, and stirred for 20 minutes, after which they will be
found to be thoroughly permeated with the solution.
The first bath can also be prepared by using 1 oz. of
potassium or sodium permanganate for each dozen skins.
Then sulphuric acid to about one- fourth the weight of the
permanganate is added, and the skins thrown in.
After the permanganate bath, the skins are rinsed in cold
water and placed in a solution of sulphurous acid. The tub
should contain water into which gaseous sulphurous acid is
either conducted from a steel cylinder, or liquid acid is added
until the brown color of the stock has disappeared and the
skins are bleached. The goods are stirred in the acid for 15
or 20 minutes, or until they are white; they are next rinsed
in cold water to remove the acid, and are hung up to dry.
Sulphurous acid may be prepared as follows: Dissolve 14
lb. of sodium bisulphite in 15 gallons of water. Into another
vessel containing 2\ gallons of water, pour 6 lb. of muriatic
acid, and mix well. The skins are placed in the bisulphite
solution, and the diluted acid is added slowly until the skins
are bleached throughout. They are then washed thoroughly,
dried, and finished.
The second bath may be prepared by adding 3 per cent of
sodium bisulphite to sufficient water, or about 3^ oz. per
dozen skins, and after the goods have been in the solution
15 minutes, muriatic acid, one-third of the weight of the soda,
is diluted with water and added slowly to the liquor. After
the skins have been bleached and washed they are washed in
a solution of white castor-oil soap or olive-oil soap, and are
then dried and finished by staking and pumicing.
Rogers' shark-liver oil process. — In his work on shark-
liver oil, the author has found that this material may be used
to advantage as a substitute for cod-liver oil, and in many
RAW HIDES 143
cases gives even better results than this commonly used prod-
uct As previously mentioned, it can be used for straight
oil tannage, but a method which has given very satisfactory
results is covered by U. S. Patent No. 1,346,385, granted
July 13 1920. In working with this process, the stock is
depilated and pickled in the usual manner, and is then run in
a drum with 7 per cent of aluminum sulphate, 5 per cent of
salt and 2 per cent of borax. When well tawed, the stock
is h'orsed-up over night, set out, and hung up to dry. When
thoroughly dry it is dipped in lukewarm water and piled
down to sammie. When properly damp, the hides, splits or
skins are placed in the drum and run for 2 hours with 5
per cent of shark-liver oil. A second lot of 5 per cent of
this oil is then added, and after an hour, 3 per cent more
and after another hour, another 3 per cent. At the end of
the day the hides are placed in piles to temper. The follow-
ing day the stock is well set out on the machine. If to be
used for lace leather, the hides are given a dubbing of shark-
liver oil and tallow in the proportion of 3 to 1 ; if for chamois
leather, no dubbing is applied. In each case the stock is
huncr up to dry, and when thoroughly dry the stock is piled
down tightly to oxidize. Care must be taken that it does not
become too warm. To hasten the oxidation the skins may
be slightly dampened before piling. As the oxidation reaches
the limit the stock is milled in the drum or stocks, and again
hurtg up to dry in a warm room. If lace leather is desired,
the hide should be well set before drying and after drying
should be rolled on the jack.
For -love or chamois leather the skins are not set out,
but after drying are milled with a solution of sodium car-
bonate, well washed, and dried. The dried skins may then
be staked and buffed, and are ready for market. _
Sheepskin fleshers.— When sheepskins are split out ot
lime the grains are de-limed and tanned in bark, sumac, or
some other tannage, and finished into skivers; the splits or
flesh portions are made into chamois leather and used for
linings, gloves, and other purposes; they are also tanned in
144. PRACTICAL TANNING
other ways and used for various purposes where inexpensive
material is required. Any one of the alum tannages for
whole skins can be used in tanning the splits. Tanned with
alum, salt, egg-yolk, and flour, they make very soft stock
which can be used in the white or colored any shade. The
chrome process can also be used, the splits being fat-liquored,
dried, and staked in the usual manner. A formaldehyde tan-
nage can also be applied : For each 100 parts of pelt, 1 part
of commercial formaldehyde in the necessary quantity of
water is used. The skins are left in the liquor from 12 to 24
hours, and are then neutralized, washed, and fat-liquored with
6 parts of soft soap, thus making a very soft leather resembling
chamois skin. Yellow stock is obtained by using moellon in-
stead of soap as a fat-liquor.
Imitation castor. — A process for sheepskin splits, which
produces stock closely resembling castor or Mocha leather,
is carried out as follows, the quantities of materials being
sufficient for 2 dozen fleshers of ordinary size : The goods
are immersed, stirred, and pounded for 30 minutes in a solu-
tion of 1 lb. of alum, \ lb. of flour, \ lb. of oatmeal (or 1 lb.
of either alone), \ pint of olive-oil and sufficient water to
process nicely. Tanning can be done in a drum in about 50
minutes.
The goods are then immersed for a half hour in a solution
consisting of \ pint of ammonia, |- bar of soap, \ oz. of soda,
\ lb. of salt, and 2 oz. of whiting or ocher, all boiled in \\
gallons of water. To this solution is added either 1 lb. of
flour or 1 lb. of oatmeal mixed in 6 quarts of water. The
fleshers are drummed in this mixture for 30 minutes, after
which they are dried, worked soft, and finished on either
side. The skins dressed in this manner are very soft, pliable,
elastic, and strong. After having been treated by the first
part of the process, they may be dried and finished, yet it
is desirable to use the entire process, as they are thus given
a superior quality and capacity for a better finish.
Another excellent process is as follows : The splits, drenched
and free from lime, are put into a drum together with a
RAW HIDES 145
solution of 12 oz. of alum and 4 oz. of salt in a half pail
of water, and drummed 30 minutes. Then 1 pail of flour is
added for each 10 dozen skins, and 1 quart of fresh egg-
yolks, and the drum run for 30 minutes longer. Take the
skins out of the drum and hang them up to dry; put them
away in a dry, cool, place for a few weeks, then dampen and
mill them in flour, knee-stake them, and run them on a fine
emery wheel After this has been done, wash the skins, and
if they seem to require it, give them 1 to 2 quarts of egg-
yolk to 12 dozen skins; dry them again, and stake out soft.
The finished skins should be very soft and white. They can
also be colored any shade desired.
White calfskin leather.— Soft, tough white leather is
made by tanning calfskins by the following process: The
skins are limed, bated, and pickled in the usual manner and
are then allowed to drain 24 hours.
Tannage.— To prepare the tanning liquor boil 12 lb. of
aluminum sulphate in 10 gallons of water. Dissolve 24 oz.
of bicarbonate of soda in a pail, and pour the solution slowly
and with constant stirring into the sulphate solution. Allow
the resultant white liquor to cool to 80° F. Put the pickled
skins into a drum, together with 10 gallons of water, 1 lb.
of Glauber's salt, and 3 lb. of common salt for 100 lb.
of skins. Drum the skins 20 minutes with the solution, then
drain off the liquor. Put 10 gallons of lukewarm water and
6 lb. of salt into the drum together with the skins, and let
the machine rotate 10 minutes. Then pour half of the sul-
phate-soda solution into the drum, and drum the skins 3
hours. At the expiration of that period, take the leather out
and let it drain until the next day; then hang it up to dry.
When dry, put the skins back into the drum, together with
8 gallons of water, and run them 10 minutes; then add the
rest of the white liquor and run the drum 2 or 3 hours. Place
the leather over horses to drain at least 12 hours, then hang
up to dry.
Fat-liquoring.— -When dry, let the leather lie in the crust
state in a clean dry room for some time, the longer the better ;
146 PRACTICAL TANNING
then dampen it with warm water preparatory to fat-liquoring.
Sulphonated castor oil or acid fat-liquor is the material to
use, as it imparts softness without discoloring the leather
or making it greasy. For each- 100 lb. of dry leather use
7 lb. of the oil, and stir it into 10 gallons of water at 95° R
Figure 58.— Buffing machine, used for snuffing grain
for ooze, and flesh for suede leather.
until it is dissolved. Put the moistened leather into the drum;
start the machine, and pour the solution of oil through the
gudgeon, and drum the leather 40 minutes; then let it drain
over night. The next day strike out the grain and apply
a mixture of French chalk (talc), 2 parts of glycerine, and
4 parts of water. Apply this to the grain and then hang
the leather up to dry.
Finishing. — This process consists of moistening the leather,
staking, and tacking it on boards. If it is not soft enough
when dry and taken from the boards, re-stake it; if staking
does not soften the leather sufficiently, wet it and give it more
fat-liquor. The appearance of the flesh can be improved by
buffing on a carborundum wheel (figure 58) ; and the leather
RAW HIDES 1^7
can be finished on the flesh if such flesh-finished leather is
desired
Another process of making white calfskins employs an
alum tannage composed of aluminum sulphate, salt, flour, egg-
yolk, and oil. The proportions given are based on 100 lb. of
pickled skins. Make a paste of 5 lb. of flour and a little
water. Dissolve 3 lb. of sulphate and 5 lb. of salt in 10
gallons of water. Slowly add 4 oz. of bicarbonate of soda,
and then mix in 2 lb. of egg-yolk and 2 lb. of olive oil. Add
the flour paste and drum the skins 3 hours in the mixture.
Leave in the liquor over night, drum a few minutes the next
morning, and dry at a moderate temperature.
Finishing consists of staking and buffing the skins, drum-
ming them with 1 lb. of egg-yolk and 5 lb. of talc ; then set-
ting out, tacking, and drying. If colored leather is
desired, the grain can be colored by hand, leaving the flesh
white; or a drum can be used and the leather dyed through-
out. This class of leather is, as a rule, dyed with wood
colors, which may be shaded with acid colors. Another
method is to bottom the leather with wood colors and then
top with basic colors.
Formaldehyde tannage. — By a method of tanning with for-
maldehyde, white skins are obtained which are very similar
to alum-tanned goods. The beam-house processes are carried
out as usual ; the skins are next washed in tepid water, when
they are ready for the tannage. For this a solution of 2\
parts of commercial formaldehyde in 100 parts of water is
used. This liquor is prepared in a paddle, and the skins are
put in and left there from 24 to 48 hours; then withdrawn,
neutralized, washed, and fat-liquored with a liquor made of
100 parts of neat's foot oil, 25 parts of carbonate of soda,
and 500 parts of water. The skins are drummed in this for
an hour, then dried and finished. Sulphonated oil can be used
for fat-liquoring, with good results. Fat-liquoring with moel-
lon degras gives skins of a light yellow color.
Kid glove leather.— -The tanner who wants to make Mocha
148 PRACTICAL TANNING
or castor glove leather will find the following process satis-
factory : The skins, after they have been soaked and softened,
are fleshed and limed. Liming should be done in clean white
limes containing no red arsenic or sodium sulphide. The
first lime should be clean, white, and weak, the skins being-
passed from it into stronger lime and limed thoroughly; or
Figure 59. — Buffing wheel.
a gathering lime may be used by hauling the skins out each
day and adding fresh lime. The period in the lime varies
from 20 to 40 days according to the judgment of the tanner.
When the hair comes off easily, the skins should be de-haired
and the grain frizzed. After frizzing, put the skins in weak
lime water for 2 or 3 days, then wash them in warm water
and drench with lactic acid in a drum, 100 skins requiring
about 1 quart of acid in 10 pails of water at 90° F. Drum
the skins in this solution for an hour, and rinse.
Another process, using alum, salt, egg-yolk, and flour is as
follows: For each dozen skins dissolve 12 oz. of alum and
4 oz. of salt to make 1 pail of liquor, and drum the skins with
this solution for 30 minutes; then add 1 pail of flour for each
RAW HIDES U9
10 dozen skins and 1 quart of fresh egg-yolk, and drum the
skins 30 minutes longer. Take them out of the drum and
hang them up to dry. When dry, put them away m a dry,
cool place for a few weeks to give them time to become com-
nletely tanned. To finish the skins, dampen and null m flour,
next knee-stake them, dry again, and then run them on a flue
emery wheel. After this has been done, wash them with
emery wneei. e „„. yo lk to 12 dozen skins,
water and give them 2 quarts ot eg y"
Then dry them again, knee-stake and finish on the finest
emerv The skins should now be very soft, dry, and white
and can be used for white gloves without further treatment,
colored skins are desired, they can easily be colored any
shade, then dried and staked, and finished on a buffing wheel
as shown in figure 59, using the finest emery. This process
an also be us°ed for grain-finished skin. For. such goods
however, it is best to use arsenic with the lime and a dung
bate to de-lime the skins. The leather finishes soft and strong,
and has a fine appearance.
Another good formula for pickled sheepskins which pro-
duces nice white, soft, and "well-fed" leather is as follows ,
For 1 dozen skins, 1 lb. of alum, 1 lb. of salt, | pint of egg-
yolk, and 1 lb. of flour are used. The alum and salt are dis-
solved in hot water. The flour is mixed with cold water,
the egg-yolk is added, and the whole is thoroughly stirred.
The solution of alum and salt and the mixture of egg-yolk
and flour are put into the drum together with the skins, and
the whole drummed for 2 hours. The skins are left ,n the
liquor over night, then dried out. One to two gal ons of
warm water are used with the tanning materials for 1 dozen
skins. This tannage should not be used on skins in the
pickled condition, but if such skins are to be tanned with
it the pickle should be removed by a light sour drench of
bran and salt, or bicarbonate of soda and salt. ■
One dozen small lambskins for glove leather can be tanned
with i lb. of alum and * lb. of salt. Dissolve the alum and
salt together, making a half pail of liquor. Drum the skins
with this solution for half an hour: then add 1 pad of good
150
PRACTICAL TANNING
flour to each 10 or 12 dozen skins, and 1 quart of egg-yolk.
Run the drum a half -hour longer, then hang the skins up to
dry. After drying, lay away for a while to age. Next
dampen the skins and drum with a little flour, then knee-stake
them (figure 60), wash, and give them 2 quarts of egg-yolk
to 12 dozen skins. Dry again, stake, and finish. The skins
should be taken from the drench and tanned without pickling.
If pickled, drench them in sour bran or bicarbonate of soda
to remove the acid.
Sheepskins taken from the drench or
de-pickled in a bath of sour bran and
salt can be alum-tanned in the following
manner: For every 100 lbs. of skins,
3 ltf. of aluminum sulphate and 6 lb. of
salt are dissolved in 6 gallons of water.
This liquid is put into the drum with
the skins, and the drum is run 30 min-
utes. A solution of 10 lb. of sodium
hyposulphite in 5 gallons of warm
water is poured into the drum, and the
skins are drummed in the combined
solutions for 20 minutes. The hypo-
sulphite fixes the tannage on the fibers
of the skins, and also thins the goods.
In order to overcome this thinning,
another solution of 2 lb. of aluminum sulphate and 4 lb.
of salt in 3 gallons of water is added to the contents of
the drum, and the drumming is continued for another
half -hour, or until the skins have become plump. The next
operation is rinsing in clean water and allowing the leather
to drain several; hours, then drying it out. Skins of fine tex-
ture and grain are obtained by this process. It is very essen-
tial, however, that the skins be entirely free from acid and
perfectly neutral when the process is begun, otherwise they
will be imperfectly tanned. After the skins have dried, they
may be made softer by drumming in a warm solution of sul-
phonated oil. Flour may be added to the oil. The leather
gG^
Figure 60.— Knee-staker.
RAW HIDES 151
can also be washed back and tanned with a one-bath chrome
liquor, and finished in any manner desired. White chrome
leather is secured by bleaching the skins with borax and sul-
phuric acid, and fat-liquoring with sulphonated oil and flour.
Alum-tanned skins should be buffed on the flesh side on an
emery-wheel to get rid of all loose flesh and make them soft
and smooth. In any alum process, flour increases the soft-
ness and plumpness of the skins, and makes the grain less
liable to crack. The cost of tanning is of course increased
by using flour, but the better quality of the leather is suffi-
cient to offset the added expense.
White pigskins.— If white pigskin leather is required, the
skins should be tanned in an alum and salt tannage or with
aluminum sulphate. It is also practicable to tan them with
formaldehyde, as with calfskins. The white leather can be
finished in the white and can also be easily colored light and
fancy shades. Thorough work in the beam-house is im-
portant for such leather. Not only must the skins be soaked
in sal-soda water and worked over the beam to rid them of as
much grease as possible, but they should also be fairly heavily
limed and bated, and then worked out again so as to be as
clean as possible before tanning is started. If they are not
too full of holes, pickling and tanning can be done most ad-
vantageously in a drum. To pickle 100 lb. of pigskins, use
1 lb. of sulphuric acid, 15 lb. of salt, and 15 gallons of water,
and drum the skins in this liquor 1 hour ; then place them over
a horse to drain 12 hours before tanning.
Prepare the tan liquor by boiling 12 lb. of aluminum sul-
phate in 10. gallons of water. In a pail dissolve 1| lb. of
bicarbonate of soda by boiling in 1 gallon of water. Pour the
soda solution slowly and with constant stirring into the sul-
phate solution; care must be taken to pour the soda solution
in carefully, for if it is added too rapidly the tan liquor will
be spoiled. The mixture should be used cold.
Tanning is effected as follows: Put the pickled skins into
a drum, together with 10 gallons of water, in which 1 lb. of
Glauber's salt and 3 lb. of common salt have been dissolved,
152 PRACTICAL TANNING
these quantities being used for 100 lb. of skins. Drum them
with this solution 20 minutes; then stop the drum and drain
off the liquor. Put the plug back, and throw in 10 gallons
of water at 75° F., and 40 lb. of salt; start the drum and
run it 15 minutes. At the end of this period, pour half of
the sulphate-soda solution into the drum and run 3 hours.
Drain the skins over a horse until the next day, and then
hang them up to dry. When dry, put them back into the
drum, together with 8 gallons of water and run 10 minutes;
then add the other half of the sulphate-soda liquor and run
the skins in it 3 hours. Drain them 24 hours, wash in clear
water, and fat-liquor with acid fat-liquor. Drumming the
skins with flour is another way to make them white. The
leather is washed after tanning and then given the flour treat-
ment; about 50 lb. of flour made into a thin paste with water
being required for 100 or more skins. The leather is
drummed 2 hours in the flour, and is then fat-liquored and
dried.
Finishing consists of staking the leather and milling it with
powdered chalk or soapstone, after which it is ready for use.
The flesh should be buffed clean and smooth, and if a leather
without a grain is wanted, the grain should be removed either
in the beam-house or by burring on an emery or carborundum
wheel.
Tanning snake skins with alum and salt.— The skins of
snakes, like all other skins, should be soaked in water until
they are soft, then broken or fleshed on the beam, and put
back into the water for a few hours. They are then pickled
with sulphuric acid and salt, after which they are placed in a
solution of equal parts of alum and salt, in which they remain
over night or longer. A basic solution of aluminum sulphate,
as described for alum-tanned sheepskins, may be used for
tanning. The skins are hung up to dry, and then are run with
moist sawdust until ?11 the scr.les are off; they are then worked
out carefully and dried. Some tanners prefer to remove the
scales by liming in the usual manner.
White splits. — Where a soft white split is wanted, a tan-
RAW HIDES 153
nage of aluminum sulphate may be used. If the sides are
split out of the limes, the splits should be bated and pickled
with sulphuric acid and salt as with grains or whole hides;
they are then in condition to be tanned. The tanning liquor
is prepared and used as under white pigskins.
Finishing consists of drumming the splits with a solution
of sulphonated oil, 7 lb. being used in 8 gallons of warm
water for 100 lb. of dry splits. Some flour may be added with
advantage to the oil solution. When the leather has dried
again it is staked and run in a dry mill until it is perfectly
soft. The solution of oil may be added to the tanning liquor,
which saves the labor of the extra fat-liquoring.
Formaldehyde also produces white leather. The splits are
tanned in a formaldehyde liquor as with grains and sheep-
skins, then neutralized and fat-liquored with soft soap or sul-
phonated oil, dried, and finished.
Splits for white shoes. — For sporting and athletic shoes,
seal splits are frequently sold as a good imitation of the real
deerskin article. These goods are treated as already de-
scribed so far as soaking, liming, bating, and drenching are
concerned. Only the best and stoutest splits are selected for
this purpose. After drenching, the splits are washed in warm
water and placed in a pickle made as follows: For every 100
lb. of splits, thoroughly dissolve 20 lb. of alum and 14 lb.
of salt. Use at 95° F., and drum the goods with it one hour.
Then add a mixture of flour, egg-yolk, and china clay, made
as follows: Mix 35 lb. of flour with enough water at 95° F.
to form a fairly stiff paste, and add | gallon of egg-yolk and
about 5 lb. of clay. No oil or grease is necessary, as seal
splits are naturally greasy.
To apply this dressing it is best to stop the mill and add
about half of the paste to the goods. Drum 15 minutes, then
add the remainder of the paste, and run 2 hours. Next take
the splits from the mill, double them across, and spread them
out in a vat or tub. The liquor in the mill is then poured
over them and they are allowed to lie in this for 3 days, haul-
ing up once a day and allowing to drain. After the final
154. PRACTICAL TANNING
draining, tack on frames or boards and dry quickly. If this
is not done the result will be poor, as the alum and salt will
not be fixed properly, and the finished leather will be flat
and tinny.
The splits are now allowed to lie in a cool place for 2 or
3 weeks to feed and mellow, and they are then staked. Damp
down first by draining through the liquor they are in, after
making up a convenient quantity with water. Stack them in
a pile until they are in good condition for staking, which is
best done by hand, although machines do good work. The
splits are then dried and worked on the perch with the arm-
crutch stake. Next carefully run them on an emery wheel,
commencing at the butt and work about halfway across, and
then turn them and do the other side in the same manner.
Turn over, and repeat the operation as before, and a fine,
velvety fiber will result. After being again placed in the
perch, rubbed over with whitening, and finally worked out
well with the hand-scouring tool, the splits are ready for the
shoe manufacturer.
Tanning buckskins. — The preparatory treatment of deer-
skins is somewhat similar to that for sheepskins. Green
skins are soaked for a few hours and fleshed. As they are very
buoyant and will not stay under the water, it is necessary to
place a weight on them to keep them submerged. For dry
skins a sulphide soak should be used and the skins thoroughly
softened before they are put into lime or coated with depila-
tory paint.
Two methods can be followed for removing the hair : The
skins may be painted with a mixture of lime and sodium sul-
phide, or one of lime and red arsenic, as for sheepskins; then
de-haired and limed a few days. Another method is to place
the skins in lime as for calfskins, using lime and sodium sul-
phide; de-hairing in the usual manner, and then bating the
skins.
De-liming is effected by bating or drenching the skins with
the same materials used in de-liming sheepskins; the goods
then pickled and tanned.
RAW HIDES 155
White buckskin. — A well-tanned, soft, and white' buckskin
is obtained by tanning with a solution of basic aluminum sul-
phate, as under white pigskins. Dampen, stake, and dry the
goods, then buff and drum with 2 lb. of egg-yolk or sul-
phonated oil and 5 lb. of talc. Set the leather out, tack, and
dry. Any shade of color — gray, tan, etc. — can be obtained
by ordinary application of suitable wood dyes or artificial
dye-stuffs.
A white leather is also made by tanning the skins with
formaldehyde; and by adding a little moellon of the first
quality to the soap fat-liquor, very supple skins of a light yel-
low color are obtained. Neat's foot oil and cod oil, as well
as sulphonated oil, produce white skins. The skins are left
in the liquor from 24 to 48 hours, when they are neutralized,
washed, and fat-liquored with soap for white leather; or with
soap and moellon, or moellon alone, for a yellow shade.
Where the grain has been removed, the skins tan rapidly.
The leather resembles alum-tanned goods, being of good white
color, soft, and supple. Sulphonated oil serves as a fat-liquor;
so does soap and moellon. Finishing consists of staking and
working out.
Indian method of tanning buckskins. — The North Ameri-
can Indians have for ages dressed deerskins into leather, and
the leather made by them is renowned for toughness and
durability. A description of their method of dressing is of
interest :
According to John Motheral in the "Leather Manufac-
turer," the skins are fleshed and all flesh and membrane re-
moved. It is then soaked in water to swell and free it from
blood, when it is ready for graining, which is done with a
case-knife or a butcher's knife on a beam having a diameter
of 6 or 8 inches. This way of removing the hair and the
grain makes Indian-dressed buckskin of the highest class.
Another way of preparing the skin for graining is, after
the skin has been fleshed and soaked, to treat it with a weak-
lye for 2 or 3 days, and then grain it. But this does not
yield a product equal in toughness to that by the former
156 PRACTICAL TANNING
method. The skin being grained, is then ready for the tan-
ning or tawing process, which is done with the brains of the
deer or those of cattle, horses, hogs, etc.
Briefly, the brains are prepared by putting them into a bag
of loosely woven cloth, and boiling them an hour in soft
water. The water is then poured off into another container,
and cooled until one's hand can bear the heat. The bag is
rubbed between the hands under this water until the brains
are forced through the cloth. The buckskin is then kneaded
and stretched in the liquor for an hour, at intervals of 10
minutes; and is allowed to soak for 2 hours (over night in
winter) followed by more kneading and stretching. The
skin is then partly dried, after which it is stretched every way
until dry, folded, wrapped, and put away for 2 weeks or more.
The skin is now ready for the smoking process, which colors
and re-tans it, bringing it into condition whereby it may be
washed with soap, yet it dries soft. Smoking is done with a
slow fire of decayed wood, and is continued on both sides
until the color is light yellow to yellowish-brown. The In-
dian stretches the skin over the end of a barrel, and conducts
the smoke to it; but a smoke-house, such as used for curing
meat, will do as well. After being smoked, the skin is
scoured with soap in lukewarm water, rinsed, dried for a
week, dipped in water for a few seconds, folded, and covered
for a half day, stretched, and dried. The skin is then soft
and pliable.
Tanning with formaldehyde. — By the application of the
following process of tanning hides or skins, a leather is ob-
tained which will not lose its tannage through the action of
hot water or sweat. It is also very tough and resistant to
tension, being especially adapted for orthopedic and surgical
uses, such as belts, straps, linings, envelopes, gloves, and even
for saddlery and shoemaking.
The leather is prepared by a combined tannage of formal-
dehyde, grease or oil, and a watery emulsion containing mag-
nesium silicate. This emulsion contains the active parts in
extremely fine division, in order to favor as much as possi-
RAW HIDES 157
ble the contraction and binding of the surface. The skins are
prepared in the usual manner by liming, bating, and washing,
and are then placed in the drum, together with the emulsion,
which must be sufficient to cover them.
The tanning can also be done in stationary tanks, but this
takes more time. At the beginning, the emulsion is composed
preferably of 20 per cent oil, 5 per cent talc and \ per cent
formaldehyde. A durable fat emulsion is first prepared for
which any of the water-soluble (sulphonated) oils may be
used The addition of gum tragacanth or similar binding sub-
stances to the emulsion is not absolutely necessary, if care is
taken to neutralize the small amount of free oleic acid present
in the oils, by adding about 10 drops of soda solution to each
quart of the emulsion. About one or two times the quantity
of formaldehyde given, as may be required, is added in the
course of the tanning. The length of time needed to tan
the skins depends upon their thickness. Several days are
required for thin leathers where stationary tubs are used;
thick skins require from 2 to 3 weeks. Where a drum is
used thin skins can be tanned in 24 hours.
All kinds of skins can be tanned by this method; and it
may either before or after tanning, be used in combination
with any other tannage. Leather made by this process dif-
fers from chamois in its color and greater strength, and it
does not shrink even after repeated washing.
This leather, which is similar in appearance to tawed leather,
maintains-even when 3/16 inch and more thick, perfect pli-
ability and suppleness, together with great firmness, which
enables it to fit itself wherever worn.
CHAPTER VI
CHROME TANNAGE
The action of chromium salts upon hide substance was first
studied by Knapp in 1858, but his investigations led him to
conclude that their application was of no practical value. Al-
though other investigators took up the matter, it was not until
1884 that any really important advance was made. At this
time Augustus Schultz patented his "two-bath process," in
which skins or hides are treated with a solution of chromic
acid, produced by the action of hydrochloric acid on sodium
or potassium dichromate, and afterwards with a solution of
sodium thiosulphate and hydrochloric acid. The hide substance
takes up the chromic acid, which is subsequently converted
to the basic condition by means of the "hypo." In 1893,
Martin Dennis made a study of the action of chromium salts
as previously investigated by Knapp, and perfected a method
for "one-bath tannage," for which he was granted numerous
patents.
Two-bath chrome process. — While the details involved in
the application of this process vary, nevertheless chrome tan-
ning is uniformly carried out either in a paddle or drum.
Different kinds of leather require different percentages of the
chemicals. In the drum tannage, 6 per cent of sodium di-
chromate and 3 per cent of hydrochloric acid, regulated on
the weight of the wet skins, are mixed with sufficient water
for the proper handling of the stock. The skins or hides are
placed in the drum, and the chrome solution is added, while
the drum is kept in motion. The hides or skins are worked
in the solution until they have taken on a uniform yellow
color and are completely struck through. They are now re-
moved from the drum and freed from the superfluous liquor
either by horsing up over night or by putting out; the latter
operation may be done by hand or on the machine. After
standing for 24 hours, the chromed stock is returned to the
158
CHROME TANNAGE 159
drum and run for about 1| hours with a solution of 12 per
cent of sodium thiosulphate and 6 per cent of hydrochloric acid.
On removal from the drum the stock should have a blue-
green color and should be uniform throughout. If thoroughly-
tanned, no curling will take place when a strip is placed in
boiling water. The stock is horsed up for 24 hours to allow
the chrome to set. It is then neutralized by running for 30
minutes in a | per cent sodium bicarbonate solution, washed
in running water 30 minutes, horsed up, and allowed to drain.
The reactions taking place in this process are represented in
the following equation :
Na2Cr207-f-2HCl=2NaCl+2Cr03+H 2
The C1-O3 produced forms a compound with the gelatine.
The sodium thiosulphate now acts as a reducing agent upon
the chromic oxide, converting it from the acid to the basic
condition, the reaction taking place in two stages. The basic
chromium chloride held by the fiber is probably converted
largely to Cr 2 (OH) G by the action of the sodium bicarbonate
used in washing.
One-bath chrome process. — In this process the skins or
hides, after coming from the puer, are washed with running
water and run in a pickle for about 1 hour. The pickle is
made by dissolving 8 lb. of salt and 2 lb. aluminum sulphate
in a small quantity of water, adding 1 lb. of sulphuric acid,
and making up to a density of 40° bk. The object of this
treatment is to neutralize any remaining alkalinity of the
puer or lime, and to ensure the stock being in an acid condi-
tion before it enters the tan.
One-bath chrome liquor is made in many ways. A good
solution may be made by dissolving 10 lb. of sodium dichrom-
ate in 10 gallons of water, adding 6 lb. of syrup glucose (40°
Be.), and then slowly introducing 10 lb. of concentrated sul-
phuric acid. A wooden vessel should be used for making up
this liquor. A less violent action, however, is produced by
adding the glucose last, but in this case stoneware or other
acid-resisting vessels must be employed A liquor, when pre-
160 PRACTICAL TANNING
pared as above and diluted to 45° Be., will give a product of
such strength that 15 lb. will be required for each 100 lb. of
pickled skins treated.
In using this method, the necessary amount of reduced
liquor (15 per cent of above liquor, equivalent to 4 per cent
of dichromate) is dissolved in a sufficient quantity of water
for proper handling of the stock, and 5 per cent of sodium
sulphate added to the solution. The pickled skins are placed
in the drum, the door is closed, and one-third of the solution
introduced while the drum is in motion. At the end of 15
minutes another third is added, and in 30 minutes the re-
mainder. A half-hour after the last portion has been put
in, -J per cent of sodium bicarbonate in solution is added,
and the stock run for 15 minutes longer, or until tanned. The
hides or skins are then removed from the drum, horsed up
over night, neutralized with 4 per cent of sodium bicarbonate,
thoroughly washed, horsed up again, and allowed to drain.
The reactions taking place in the above liquor are as fol-
lows:
1. Na2Cr207+H 2 S04=Na 2 S04+H2Cr 2 7
2. H 2 Cr 2 7 +H 2 0=2Cr0 3 +2H 2
3. 2Cr0 3 +6H (reducing agent) =Cr 2 ( OH) 6
4. Cr 2 (OH) 6 +2H 2 S04=CR 2 (OH) 2 (S0 4 ) 2 +2H 2
The basic chromium sulphate thus formed is the tanning
agent, and is decomposed by the hide substance into Cr 2
(OH) 6 and Cr 2 (OH) 4 SC>4 with the liberation of free sul-
phuric acid. This free acid must be neutralized with some
mild alkali such as borax or sodium bicarbonate to complete
the tannage, otherwise a reverse action is likely to take place.
The resulting tannage is the same whether a one or two-
bath method be employed.
Chrome tannage by either of the processes given above may
also be carried out in the paddle, but in this case the time of
treatment is somewhat longer. The advantage of the paddle
tannage is that a smoother grain is obtained with less danger
of "pipey" leather.
CHROME TANNAGE 161
To understand the process of chrome tanning better we will
take up its application to the various grades of stock:
Glazed kid manufacture. — As previously shown, goat-
skins come to the tanner from many different countries, where
they are cured, in many various ways, such as sun-dried, dry-
salted, wet-salted, clay cured, etc. The first duty in prepar-
ing these skins for manufacture is to classify them and cure
into different sizes and weights, namely, "bulls," "heavies,"
"large," "regulars," and "kids" ; and for quality into "firsts,"
"seconds," and "culls."
The selected skins then pass to the first manufacturing
process, which is called "soaking," where the skins are placed
in tanks of fresh water for about 24 hours to become thor-
oughly soaked for the milling process. The skins are then
placed in large revolving drums with protruding wooden pins
inside, and milled in running water for several hours to beat
up and soften the skin to bring it as near as possible to the
condition of a green skin, as it was when taken from the
animal.
The skins are then trimmed to remove what is termed the
false weight, such as heads, shanks, and rough edges, which
cannot be worked into leather. Then they pass to the liming
process, where they are allowed to remain for 12 to 14 days.
On being removed from the lime liquor, the skins are un-
haired by machines, and then thrown into wash-reels with
running water to wash out the lime, leaving a clean, solid pelt.
They then pass through a machine to clean off the superfluous
flesh and fat which is not a part of the skin substance from
the flesh side of the skins. Then they are subjected to the de-
pleting process, called "puering," to render them free from
any trace of lime, and to make them soft and open for the
proper action of the tanning agents.
After puering, the skins are again thoroughly washed in
"twisters" in warm running water. These twisters are large,
square, perforated boxes, mounted to revolve on their opposite
corners, which gives a twisting motion to the skins as they are
thrown from one side to the other. The beam-house work
162 PRACTICAL TANNING
has now been done. The dry, hard skin has become a clean
pelt, free from hair and dirt, with flesh and fat removed, and
is soft and open for tanning.
Most glazed kid is tanned by the two-bath chrome process.
Figure 61. — Tan-room in a goatskin tannery. The operation is carried
out either in paddle or drum as shown.
The first bath is a solution of sodium dichromate and hydro-
chloric acid ; the second bath is a solution of sodium hypo-
sulphite and hydrochloric acid. Both of these processes are
performed in what are called reels as shown in figure 61, made
similar in shape to a half drum, but on the inside a paddle
is mounted, which engages the liquor within the reel, and
keeps the liquor and skins in motion. Great care is taken to
have the exact proportions of the chemicals to the quantity
of water, and the weight of skins to each reel. When these
operations are finished, the product is a perfectly tanned
leather, insoluble, and unaffected by boiling.
After being taken from the tan liquor, the skins pass
through what is called a "striking-out machine," to expel the
CHROME TANNAGE
163
excess tan liquor so that they can be easily handled in the
next process, which is called shaving. This work is also done
by machine, (figures 62 and 63), and consists in cutting down
the heavy parts of the skin to give a uniform thickness. The
Figure 62. — Line of shaving machines used for producing a smooth
effect on the flesh side.
skins are now at a point where it is decided into what color
they are to be finished, and they are sorted accordingly. The
finest-textured and finest-grained skins are selected for browns
and other colors, and the remainder are held for black stock.
In many factories only black glazed kid is made, in which case
this selection is unnecessary.
Two-bath chrome on pickled sheepskins. — 1. The bated
or pickled stock is weighed and placed in the mill, the door
closed, and the following solution prepared, estimated on the
weight of the stock:
Chemicals Per cent
Sodium dichromate 6
Salt 4
Hydrochloric acid 3
Water, 5 times the weight of the stock.
164
PRACTICAL TANNING
The mill being in motion, this solution is introduced through
the trunnion, and the stock turned for 1| hours, or until
struck through. The skins are removed from the drum and
horsed-up over night to allow for draining and fixation of
the chrome.
Sodium thiosulphate bath. — On the following morning the
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Figure 63. — Shaving machine.
skins are removed from the horse one at a time, dipped in a
10 per cent solution of sodium bisulphite, and thrown into
the drum. The following solution,
Chemicals Per cent
Sodium thiosulphate (hypo) 12
Salt 3
Hydrochloric acid 6
Water, 5 times the weight of the stock.
is added through the trunnion while the mill is in motion and
run for 1| hours, or until a robin's-egg blue color shows.
The skins are again horsed-up over night.
Neutralizing. — The skins, after standing over night, are
returned to the mill and run for a half-hour with -J per cent
sodium bicarbonate and water equal to 5 times the weight of
the stock. The plugs are now drawn, and the stock is washed
CHROME TANNAGE 165
for a half-hour with running water. The skins are then set
out and shaved.
2. The bated or pickled stock, having been weighed, is
placed in the drum and the following solution prepared :
Chemicals Per cent
Sodium dichromate 6
Sulphuric acid 2
Salt 4
with the necessary amount of water to give proper working
conditions. The skins being on the shelf, the solution is
placed in the bottom of the drum, the door is closed, and the
drum is started. The turning is continued for about 1^ hours,
or until the stock has become struck through. It is then
horsed-up over night and allowed to drain. The next morn-
ing the skins are returned to the drum with a solution of 6
per cent sodium bisulphite, mixed with sufficient water to
float the stock. They are treated in this' reducing solution for
about an hour, or until a robin's-egg blue color shows. The
stock is again horsed or piled for 24 hours, to allow hydration
to take place. To neutralize the excess of acid, run the stock
with ^ per cent of sodium bicarbonate, and finally wash well
with running water.
Tanolin. — The pickled stock is placed in a drum with 6 lb.
of salt and 8 gallons of water for 100 lb. of stock and
drummed 15 minutes. Six pounds of "tanolin," dissolved in 2
gallons of boiling water, is the tanning material used, and it
is divided into three parts. One part is poured into the drum,
and the stock run for 30 minutes ; the second part is then
added, and the machine run 30 minutes; then the last part is
added and the drum is run an hour. Eight ounces of bicar-
bonate of soda is dissolved in a little water and poured into
the drum, and an hour later another 6 oz. is dissolved and
added and the skins are drummed another hour. They should
then be completely tanned. When removed from the drum, the
skins should be horsed-up and allowed to drain 24 hours. They
are then washed and neutralized.
166 PRACTICAL TANNING
One-bath chrome on pickled sheepskins. — This consists
of first tanning them with aluminum sulphate and salt and
then tanning with chrome liquor. When this process is used
it is necessary to remove the acid from the skins. This is
done by stirring them for a few minutes in a warm drench
of sour bran and salt or bicarbonate of soda and salt. They
are then in condition to receive the sulphate and salt.
The usual formula for the preliminary tanning is 3 lb. of
aluminum sulphate and 6 lb. of salt for 100 lb. of skins.
These materials are dissolved in 6 gallons of warm water and
the skins are drummed in it 30 minutes. The sulphate does
not act as a tanning agent in this process, as it is washed out
before the leather is dried. It serves to plump the skins and
prevent contraction of the grain and fibers by the astringent
chrome liquor. After the skins have been drummed with the
sulphate and salt, 3 gallons of concentrated chrome liquor,
diluted with 3 gallons of warm water, are poured into the
drum in portions of 2 gallons at intervals of 30 minutes, and
the drum is run for 2 or 3 hours or until the skins are tanned
through. They should then be left in the liquor over night
so that the chrome salts may take full effect on the fibers. The
next day the tanned leather is washed and shaved .in the usual
manner.
Pickled sheepskins- may be tanned into plump, well-tanned
leather in the following manner: Dissolve 3 lb. of aluminum
sulphate and 3 lb. of salt in a few gallons of boiling water,
and add enough cold water to make 10 gallons of solution.
To this add slowly 8 oz. of bicarbonate of soda dissolved in
a little hot water. Drum the skins with this liquor one hour,
then hang them up to dry. When they are dry, wet them back
and tan them with one-bath chrome liquor in the usual man-
ner. The tannage is complete when a piece of chrome leather
remains soft in boiling water; imperfectly tanned leather
hardens and curls in boiling water.
Process for glove leather. — The following method of han-
dling pickled sheepskins for glove leather, although called a
two-bath process, is really a three-bath process. The skins
CHROME TANNAGE 167
are not taken from the drum until they are fully tanned, when
they finish out into soft, durable leather.
The pickled skins are given a fairly strong re-pickle so
that the grease will run well, and are pressed or wrung until
as much of the natural grease as possible has been extracted.
They should then be drummed in a salt solution until well
broken up. Care should be taken, after the skins have started
in the press, to keep the pressure steadily increasing. They
are horsed-up from the salt solution and allowed to drain be-
fore weighing. The skins are next weighed and thrown into
a drum, and 1 per cent of salt is put on them, and 3| to 4
per cent sodium dichromate is dissolved in 10 gallons of water
for 100 lb. pickled weight. This should be fed in two parts.
The skins are drummed in this from two to three hours. This
will be a short liquor, but for the leather desired it works well.
The next step is to put 3| per cent sulphuric acid in 10 gal-
lons of water for each 100 lb. of skins, and 4 lb. of salt for
2 lb. of acid. This is fed through the gudgeon and the skins
are drummed with it for 20 minutes. Then 12 lb. of sodium
hyposulphite are dissolved in 12 gallons of water for 100 lb.
of stock, and the solution is fed to the skins and drummed for
2 hours; this completes the tannage.
The leather, after it has been horsed-up 12 hours, is washed,
neutralized, and then fat-liquored. If it is to be finished in
the pearl or regular chrome color it should be given 2\ per
cent white chip soap boiled and made up to 10 gallons for 100
lb. of leather, and drummed 20 minutes, and then given 5
per cent of egg-yolk. Horse-up and allow to drain 24 hours,
and hang up to dry in a moderate temperature; then drum
the leather in warm water until it is thoroughly wet through,
set it out, and hang it up again. Finishing is done by staking
on the machine, dry drumming with talc, and staking again.
If it is desired to make colors, the fat-liquoring would neces-
sarily have to be done without the soap, and the skins would
be colored with suitable dyestuff and handled in the finishing
as regular chrome leather.
Neutralizing and washing chrome sheepskins. — In every
168 PRACTICAL TANNING
case of chrome tannage it is necessary to drain the leather
over horses or on smooth piles for 12 to 24 hours before pro-
ceeding to wash and neutralize it. . This is done to allow the
chromium hydroxide to become dehydrated and fixed in the
fibers.
The most efficient neutralizing substance for chrome leather
is bicarbonate of soda. From 1 to 3 lb. is used for 100 lb. of
leather. It is dissolved in 10 gallons of warm water, and the
leather is run in the solution 30 minutes. The plugs are next
pulled out and the leather is washed another half-hour with
running water; it is then set out, or pressed and shaved. Some
tanners shave their leather before they neutralize it. Borax is
also often used for neutralizing skins. Less is used, but in the
same manner as soda.
White chrome-tanned sheepskins. — For some purposes,
such as suspender trimmings, baseball covers, linings, etc.,
a soft white leather is required. The alum tannage can be
used, but there are also special tannages which produce such
leather. It is also practicable to take chrome-tanned skins,
and by a treatment with flour and bleaching with borax and
acid, finish them into soft, white leather. The tannage is the
same as for any other chrome leather. After the leather is
fully tanned it is washed and bleached. For each 100 lb. of
skins, use 1 lb. of borax or bleaching soda dissolved in hot
water, and wash the skins 20 minutes. Then drain out the
water, replace the plug, and put cold water to which some
sulphuric acid has been added into the drum, and run the
leather with it 30 minutes. The borax opens and softens the
skins and prevents the acids from doing injury. After the
leather has been washed in the acid solution it should be
washed in clean warm water, and then. shaved. The next proc-
ess is the treatment with flour, 50 lb. being used for 100 large
skins or 200 small ones. The flour is stirred into 10 or 12 gal-
lons of water for 100 lb. of skins, and the leather is drummed
in the liquor 2 hours ; it is then struck out, pressed, and given
some fat-liquor. For some purposes the skins work out suffi-
ciently white without th£ borax and acid treatment. Sulphon-
CHROME TANNAGE 169
ated oil dissolved in warm water is excellent fat-liquor for
these skins.
When the leather is dry it is moistened and staked, then
run in a clean, dry drum with powdered chalk or soapstone
for one hour and then arm-staked. Chrome skins in the nat-
ural greenish-blue color of the process are obtained by simply
washing, shaving, and fat-liquoring them; then drying, stak-
ing, and tacking on boards.
Tanning in a paddle-vat. — Where the skins are tanned in
a paddle-vat the procedure is as follows : The first bath con-
sists of 6 per cent of the weight of the skins of potassium or
sodium dichromate and 3 per cent of 20° Be. muriatic acid.
The chrome is dissolved in boiling water and added to the
water in the wheel, about 65 gallons for 100 lb. of skins. The
skins are paddled in the liquor for several hours and left in
over night. The next morning they are taken out, struck-out,
and dipped in a solution of sodium hyposulphite to which a
little muriatic acid has been added. After dipping, the stock
is thrown over a horse and allowed to remain for a short time
before it is placed in the second bath. This bath consists of
18 lb. of hypo and 5 lb. of muriatic acid in 65 gallons of water
for 100 lb. of skins. The hypo is dissolved and added to the
water; the acid is then poured in and the stock thrown in as
quickly as possible. Some tanners do not add all of the acid
at once, two-thirds being added first, and the remainder after
the skins have been thrown in. When the yellow color of the
stock has turned to light blue throughout the thickest skins
the treatment is finished. The skins are taken out, placed
over horses for 24 hours, and are then washed and neutralized.
Both potassium dichromate and" sodium hyposulphite are used
in excess, but without injury to the stock, a few pounds more
or less for a large pack of skins making no difference in the
quality of the leather.
Process of alum and ctyrome tanning. — Skins tanned by the
following process work out into a leather which possesses
the qualities of both alum and chrome leather. In appearance,
plumpness, fine grain, and feel, the leather resembles alum
170 PRACTICAL TANNING
leather, and chrome leather in softness and durability. The
first step consists of tawing the skins in a solution of alum-
inum sulphate and salt. In the second step the sulphate is
fixed on the fibers of the skins by means of a solution of so-
dium hyposulphite, and after this has been done another solu-
tion of sulphate and salt is given to the skins, by means of
which they are plumped and the thinness that follows the use
of hyposulphite is overcome. By these operations the skins
are thoroughly alum-tawed, and, if desired, may be finished
without further tanning. To complete the process and pro-
duce chrome leather, the skins after the final application of
sulphate and salt, are chrome-tanned. In practice the process
is as follows :
The skins, after drenching and washing, are drained and
weighed. For every 100 lb. a solution is prepared consisting
of 3 lb. of aluminum sulphate and 6 lb. of salt in 3 gallons of
water, boiled, and allowed to cool. The skins are drummed
in this solution for 20 minutes. Then 10 lb. of hyposulphite
are dissolved in 3 gallons of water, and this liquor is poured
into the machine and the drumming continued for 15 minutes.
To finish the first part of the process, a third solution is pre-
pared by dissolving 2 lb. of aluminum sulphate and 3 lb. of salt
in 3 gallons of water. This solution is added to the contents
of the drum, which is run 30 minutes.
The skins, now plump and full, are next rinsed off in clear
water, drained several hours, and then given the chrome liquor,
which is used without the addition of water or acid. From
3 to 6 gallons of the concentrated chrome liquor is required
for 100 lb. of skins. The chrome liquor is prepared as fol-
lows : 5 or 6 lb. of chrome-alum is dissolved in 5 gallons of
water without the aid of heat. To this solution is added from
2\ to 3 lb. of sodium sulphate and from 12 to 16 oz. of po-
tassium or sodium acetate, or its chemical equivalent. In a
liquor thus prepared, the skins are drummed one hour, or until
they are chrome-tanned. They are then allowed to drain 24
hours, washed in the usual manner, shaved and colored. For
thick, heavy skins, the quantity of chrome liquor used may
CHROME TANNAGE 171
be increased to 6 or 7 gallons for 100 lb. of stock. No free
acids whatever are used in this process. Free acid in the
solution, added as an element — that is, other than as produced
by decomposition of the chemicals — will retard, if not pre-
vent, the reaction necessary to produce leather. For this rea-
son the skins must be perfectly neutral when treatment begins.
After the tanning is completed, the skins should be left
in the liquor several hours, then thrown over horses to drain
for 24 hours, to allow for complete tannage of the fibers. The
leather is then washed in warm borax water, then in clean
water, and then shaved, colored, and finished. This process
was patented by George W. Adler of Philadelphia, Penn-
sylvania.
New two-bath process of chrome tanning. — This process
is similar in manipulation to the regular two-bath process. It
can be worked by a two-bath or one-bath method.
The directions for one-bath are as follows: For 100 lb. of
skins use 4 lb. of sodium dichromate and 3 lb. of 20° Be.
muriatic acid and sufficient water for the pack of skins to be
processed properly. When the skins are thoroughly impreg-
nated with this liquor and seasoned, add to the bath, while the
goods are in motion, 20 per cent of the weight of the skins of
"S. Z." solution* and 35 per cent of "S. K." solution," these
two solutions being mixed before they are added to the bath.
Then add, the skins being in motion, 5 per cent of 66° Be.
sulphuric acid ; but before adding the acid, mix it with about
30 times or more its weight of water. Then add this mix-
ture through a lead-lined wooden funnel, long enough to reach
a Use 80 lb. of sodium nitrate and 84 lb. of hot water.
b Use 48 lb. of fresh chloride of lime, 48 lb. of soda ash, and 384 lb. of hot water.
Dissolve the soda ash in hot water. When all is dissolved, add the chloride of lime
through a sieve, keeping the liquor always well stirred. When all the lime is stirred
in, let the liquor settle until it becomes clear — say in two days — then draw off
the clear liquor for use as above, and throw the sediment away.
Both S. Z. and S. K. liquors may be kept in one vessel — -carboy, vat, or hogshead —
provided the proportions are maintained, and when wanted, the proper quantity is
taken out. A wooden tank or hogshead should be 'ised for making the solution.
In place of S. K» and S. Z. solutions, sodium peroxide and sulphuric acid may be
used. To each 100 gallons of water in the vat add 5 lb. and 5 oz. of 62° Be.
sulphuric acid, and stir well; then sift a little at a time 4 lb. of sodium peroxide,
while stirring well; use lukewarm water for the bath. When this bath is ready, put
the previously chromed skins into it, and paddle them until they are tanned.
172 PRACTICAL TANNING
to the bottom of the vat, and placed at one corner of it, while
the goods are in motion.
The skins are finished after about 1^ days. No damage will
result should they remain longer in the liquor. When done,
wash and finish them. This tannage produces a finer grain,
less contracted, and besides, sulphur as in the hypo process,
is not present. Skins treated by this tannage are best for mak-
ing enamel or patent-finish leather.
Neutralising and washing the tanned leather. — The object
of these processes is to remove the acid and salts from the
leather and make it perfectly neutral for coloring, fat-liquor-
ing, and finishing. Chrome-tanned leather is unique in one
respect: that is, it will stand any amount of washing with
water without injury. Water alone, however, removes the
acid so slowly that it is common practice for tanners to add
a small quantity of alkali to expedite the work.
In all cases of chrome tanning, whether by the two-bath or
the one-bath method, the leather should press and drain from
12 to 24 hours to allow the chromium hydroxide to become
dehydrated and fixed in the fibers. It is then in the proper
condition to be washed and neutralized.
The use of sodium bicarbonate for neutralizing the leather
is recommended. It destroys the free acid, helps to fix the
chrome, is inexpensive, and does no damage to the leather.
An excess of the soda is used in enough water to wash well in
a drum. This excess does no harm to the leather. The leather
is washed 30 minutes, when the plugs are pulled out and the
leather is washed half an hour longer with running water.
The skins are then struck out and shaved.
Neutralizing with borax. — A common method of removing
the acid from the leather involves the use of borax, the quan-
tity required varying with the amount of acid present in the
leather ; but it should be remembered that only as much should
be used as to have the leather still show a very weak acid re-
action. As a rule, from 1 to 2 per cent of borax, calculated
on the shaver's weight of the leather, is sufficient. The borax
is dissolved in hot water and added to the water in which the
CHROME TANNAGE 173
leather is washed. The leather is drummed in this water for
40 minutes at a temperature of 80° F. After it has been thus
neutralized, it is better to wash it well with running water.
Insufficient neutralization of the leather, which is indicated
by blue litmus paper turning red when pressed against the
leather in the cut, may cause various difficulties. It may es-
pecially cause an unsatisfactory absorption of the fat-liquor,
or lead to the dyestuff being fixed too surficially (merely on
the surface; little penetration), or precipitated in the bath;
besides, leather insufficiently neutralized has a tendency to
spew. Some tanners shave their leather before they neutral-
ize it; others neutralize before shaving. In some tanneries
the leather is first washed in warm running water. The borax
is then dissolved in sufficient water to allow the leather to move,
freely in the drum, and the treatment in such water, prefer-
ably warm, should continue 30 minutes. The leather is then
rinsed well in warm water. Where the skins are shaved be-
fore they are neutralized and washed, and are fat-liquored or
dyed immediately afterwards, me last rinsing should be in
water at 125° F., thus raising the temperature of the skins in
anticipation of the coloring or fat-liquoring process which
follows.
Notes and suggestions. — It is not always practicable for
the tanner to follow set formulas and rules in chrome tanning,
on account of the difference in the raw stock he uses. The
skins should be given what they require and no more. In the
second or hypo bath it is best to add only about two-thirds of
the acid to the hypo solution, then, as the process proceeds,
add more acid until the prescribed quantity has been used.
The skins should come from the second bath as nearly neutral
as possible, and operations should be conducted to attain this
result. More chemicals than necessary are generally used,
and more than the skins take up. Experience has proved this to
be good practice, especially where a paddle-vat is used. The
liquors are never fully exhausted when the skins are taken
out, yet it is best to run them out and prepare new liquors for
the next pack of skins. It is best to let the goods drain over
174. PRACTICAL TANNING
night from the first bath, and strike them out before putting
them into the second bath. When a two-bath process is used,
there is no danger of contracted grain, and the leather works
out soft and silky and to the greatest possible area of meas-
urement. Skins pickled with aluminum sulphate and salt can
be tanned without being de-pickled; but if considered advis-
able to remove acid pickle, it can be done in a bath of whit-
ing (chalk) and salt, the skins being then washed in warm salt
water and tanned; but bicarbonate of soda is to be preferred
to whiting, as the latter produces calcium sulphate with slight
solubility.
It is feasible in using the two-bath process of chrome tan-
ning to pickle the skins with muriatic acid and salt, and then
give them the first bath, which is made of potassium or sodium
dichromate and salt without acid. When this is done, the
acid pickle serves to liberate the chromic acid in the bath.
Whenever pickled skins are being tanned, considerable salt
should be added to the first liquor. The first or chrome bath
is given most advantageously in a drum; the second or re-
ducing bath may be applied in either a drum or a paddle-vat.
There should always be sufficient water used to give proper
working conditions. The ratio of potash or soda to the weight
of the skins may vary considerably without affecting the result.
Some tanners put the skins into the solution of sodium
hyposulphite and then add the acid rather slowly. Others
add all the acid to the hypo-bath, and as soon as the liquor
turns milky, throw the skins in as rapidly as possible. It is the
opinion of the author that the latter method is the better of
the two. When the tannage seems to be finished, it is advis-
able to leave the leather in the liquor several hours or over
night, to ensure complete reduction and deposition of the basic
chrome salt. The quantity of sodium hyposulphite may range
from 10 to 20 lb. for 100 lb. of skins, but.it is the general rule
to use more than the stock requires, as an excess does no harm,
it being rather beneficial to the quality of the leather. It is
advisable to dip the chromed skins into a fairly strong solu-
tion of hypo before putting them into the second bath. This
CHROME TANNAGE 175
dip may consist of 5 lb. of hypo in 10 gallons of water, or
a 10 per cent solution of sodium bisulphite. This prevents
"bleeding" of the chrome into the second bath, and drawn
grain. Sodium hyposulphite is used with acid; in the second
liquor, sodium bisulphite without acid.
Difference between one-bath and two-bath chrome-
tanned leathers. — One of the main causes of the differences
between leather tanned by the one-bath method and that
tanned by the two-bath method, says the "Shoe and Leather
Reporter," is to be found in the fact that free sulphur is de-
posited on the fibers of the skins by the two-bath when hypo
is used for reducing, and not in the one-bath process. In both
processes, the chrome salt which actually converts the pelt
into leather is a basic one, so that the main difference is not
to be sought in the nature of the actual tannage, but rather
in some of the side reactions. One of these reactions in the
two-bath process, but not in the single-bath, is the liberation
of sulphur when sodium hyposulphite and muriatic acid are
used in the second bath. It is customary to add the acid, to the
solution of hypo until a slight turbidity or milkiness appears,
before introducing the skins. The sulphur dioxide takes part
in the reduction of the chromic acid in the skins, and the free
sulphur is precipitated both in the surrounding liquor and in
the fibers of the goods. It is the free sulphur that produces
the turbidity of the liquor. This sulphur produces softness,
gives the leather its white appearance, and acts as a kind of a
lubricant to the fibers, so that they slip over one another more
readily, producing the effect of softness or mellowness.
Free sulphur can be incorporated into leather tanned by the
one-bath process by a -special operation proposed by Eitner,
the German leather chemist. This operation consists of treat-
ing the skins, before tanning, with sodium hyposulphite and
acid. The goods are treated first with one, and then with the
other, 100 lb. of pelt being drummed for 45 minutes with 100
gallons of water, 20 lb. of salt and 4 lb. of muriatic acid.
The goods, after drumming, are allowed to drain, and are
again treated for 6 hours with 20 per cent hypo. The same
176 PRACTICAL TANNING
reaction takes place as that described for the two-bath process,
the acid liberating the sulphur from the hypo, but in this case
the precipitation of the sulphur takes place entirely in and on
the fibers. Skins treated by this process, and then tanned by
the one-bath method, have most of the properties of two-
tanned leather.
A simple test to prove whether leather has been tanned by
the one-bath or the two-bath process, consists in determining
whether there is any free sulphur in it. A silver coin is
cleaned and moistened, and then wrapped round with a piece
of the leather and put in a warm place. In the case of heavy
leather a slit should be made with a knife, and the coin placed
in it. After an hour or so, if there is free sulphur in the
leather, the coin will be found to be darkened or blackened by
the action of the sulphur on the silver.
Chrome-tanned side leather. — Hides that are intended for
chrome upper leather are split out of lime, and the grains are
washed, bated, and pickled. The processes of tanning such
grains are the same as for the grains of acid-pickled sides.
A fine chrome side leather is obtained by tanning the grains in
the two-bath process described. The process can be carried
out in a paddle-wheel as follows :
The first or chrome bath consists of 6 per cent of the
weight of the goods of potassium or sodium dichromate, 5 per
cent of salt, and 3 per cent of muriatic acid. The dichromate
is dissolved in boiling water and added to the water in the
paddle-wheel, about 65 gallons of water being used for 100
lb. of stock. The salt and acid are added and the liquor is
ready. The stock is run in the first bath for several hours,
then allowed to remain at rest over night. The next morn-
ing the grains are removed from the wheel, struck out, and
then dipped into a weak solution of sodium hyposulphite to
which a little muriatic acid is added. After being dipped, the
stock is thrown on a- horse, and allowed to remain a short
time before it is placed in the second bath of the process.
The second bath consists of 12 per cent of sodium hypo-
sulphite to which 6 per cent of muriatic acid is added, in 65
CHROME TANNAGE 177
gallons of water for 100 lb. of stock. When the yellow color
has disappeared and the leather is of a greenish-blue color
throughout, the tannage is completed and the leather is al-
lowed to drain at least 24 hours, when it is washed and
neutralized.
One-bath chrome process for acid-pickled stock. — The one-
bath process of chrome tanning is generally considered safer
and more economical than the two-bath for this class of stock.
The tanner can prepare his chrome liquor of chrome-alum and
soda, or of sodium, dichromate and glucose, or he can buy a
concentrated one-bath chrome liquor and use it according to
the instructions furnished by the manufacturer.
Process for alumina-pickled grains. — Grains that are split
from hides pickled with aluminum sulphate and salt may be
tanned in the two-bath process the same as acid-pickled stock.
They may also be tanned in the manner described for acid-
pickled goods with one-bath chrome liquor.
Process for unsplit sides. — Sides that are not split previous
to tanning are tanned most satisfactorily in one-bath chrome
liquor in a vat with paddles. They are bated, washed, and
pickled either with acid and salt, or with aluminum sulphate
and salt. For every 100 gallons of water in the vat, 35 lb. of
salt are put in and dissolved. The hides are then introduced
and the paddle run for half an hour. Concentrated chrome
liquor is then dissolved in warm water until the solution stands
at 50°, Be. scale. When the hides have been in the salt water
30 minutes, 2 quarts of the chrome liquor are added and the
paddle is run an hour. An addition of 3 quarts of the chrome
solution is then made to the tan liquor, and the paddle is run
3 hours. More chrome solution is then added, and the hides
are kept in the bath until they are tanned throughout.
The tan liquor can also be made by adding 3 gallons of the
concentrated chrome solution to the salt water to start with,
and then add 3 or 4 gallons more for every 100 gallons of
water as the tanning proceeds. When fully tanned, the hides
are taken out and pressed for splitting, milled in a dry mill
to open them up, jacked and split as desired. The grains and
178 PRACTICAL TANNING
splits are next put into the drum and re-tanned by being
drummed 10 minutes in a solution of salt and then for 2 or
3 hours with 4 quarts of the concentrated one-bath material.
The leather is then washed and shaved.
Neutralising and washing. — After being tanned, the leather
should be allowed to press and drain 24 hours before it is
washed. The first washing is done in a drum with ^ lb. of
bicarbonate of soda in 15 gallons of water for 100 lb. of
leather. The drum is run a half-hour, when the plugs are
pulled out and the leather is then washed another half-hour
with running water.
The neutralization can also be accomplished by using 1 lb.
of borax in 15 gallons of water; washing in this solution 30
minutes, then washing in running water another 30 minutes,
and setting-out and shaving the leather.
Chrome side glove and mitten leather. — Hides which are
intended for glove and mitten leather should be thoroughly
limed and bated in such manner that when tanned they are
soft and elastic. The tanning is done most easily with one-
bath liquor, the leather after tanning being allowed to drain
until the next day. The stock is handled most readily when
it is split after liming. Softer leather is made by not wash-
ing the leather until after it has been colored, fat-liquored,
and dried.
Chrome-tanned sole leather. — The following method of
manufacturing chrome sole leather is chiefly remarkable for
its simplicity. The raw stock is first of all graded, with the
object of securing a uniform system of treatment for every
hide. In each pack there should be no greater variation of
weight than 10 lb. This is a very important point, being one
of the secrets of the successful production of this class of
leather.
Soaking. — Five days are allowed for this process when dry
hides are used, and one or two days for green hides.
Liming. — This is usually accomplished with a sulphide lime
mixture, using a 5-day system. The hides from the limes are
hauled into a pit of lukewarm water for 24 hours. Coming
CHROME TANNAGE 179
from the water pit. the hides are unhaired and fleshed by
machine.
De-liming. — Before scudding or fine-hairing, the goods are
paddled in lukewarm water for 10 minutes, then cleared of
loose flesh and fine-haired. After this operation, the weight
of the hides is ascertained, and they are again paddled in cold
water for a few minutes, then removed and suspended in a
pit of cold water until the next morning. Neither acid nor
bate is used at this stage, nothing but pure, clean water.
Pickling. — On the following day the sides are taken to the
pickling-wheel. For every 1200 lb. of hides, take 10 per cent
salt and 2 per cent sulphuric acid, and put in just sufficient
water to allow the goods to move freely in the paddle-wheel,
running the same until by taking a knife and securing a cross-
cut from the butt there remains a thin amber line, soft, and
almost transparent. To get this effect, a run of one, two, or
three hours may be necessary, depending upon the stock and
the condition of the pickling solution. On leaving the pickle,
the sides are spread out in a smooth pile to avoid creases, and
allowed to remain until the next day.
Tanning. — The sides are now tacked on sticks and suspended
in liquors made of tanolin, chrome or other crystals of equal
strength. This process is carried out in 5 or 6 days, the liquor
and hides being moved periodically by means of mechanical
rockers. The original liquor may be started on a basis of 10
per cent of the chrome crystals dissolved in the volume of
water contained in each vat, bringing the liquor up to about
8° Be. The supplementary liquor for each pack is 2 per cent
of salt on the hide weight, added the day the sides are put into
the vat. The liquor is plunged up and the sides are suspended
in it. On the second day, 6 per cent of tanolin is boiled in
quantities of 35 lb., this usually being one pailful, well stirred,
and dissolved. It may then be poured into the vat in four
portions at intervals of half an hour, the rockers being allowed
to run for another hour after the last portion of chrome liquor
has been added. The goods should be tanned in 5 days. At
the end of the fourth day a crosscut should be obtained, when,
180 PRACTICAL TANNING
if sufficiently tanned, the hides may receive \ per cent bicarbon-
ate of soda, dissolved and poured on the surface of the liquor
in the vat. If the cutting shows incomplete tannage and un-
satisfactory color, the liquor may be made lukewarm by means
of a steam pipe boxed inside, the steam being circulated
through the vat while the rockers are in motion. When the
desired temperature is obtained, the soda may be added, and
the liquor agitated one hour. In either case, the addition of
soda causes a foam, denoting the acidity of the liquor. It is
seldom beneficial to heat the liquor, for although it may hasten
the tanning process and help the color, it reduces the sub-
stance of the finished product, and is therefore resorted to only
in an emergency.
The sides may now be removed from the vat and laid out in
a pile, grain exposed to the air, for at least an hour before
washing, this being effected in the wheel or drum. A good
plentiful supply of clean water is needed at this stage, as it
makes all the difference between a poorly and a cleanly fin-
ished product. Three or four hours are usually necessary for
each wash, when the sides are taken out and spread over a
horse to drip for a few hours. After tacking them on frames
without stretching, the hides are dried, and then well rolled.
For waterproof sole leather, the leather is partly dried and then
undergoes a process of fat-liquoring and filling. For this proc-
ess the method is to dissolve for each 100 lb. of leather —
squeezed or semi-dry weight — 2 lb. of white soap and 1 lb. of
neat's foot oil in 6 gallons of water. This liquor may be used
at 125° F., and the leather drummed in it 45 minutes. On re-
moving from the fat-liquor, the sides may be set out on the
table or by machine, tacked on frames and dried out. The
filling may consist of stearine, paraffin wax, glucose, or other
similar substances, mixed in different proportions for various
requirements. This filling process improves the impermeabil-
ity, tightness, and firmness of the leather.
Other tanning processes. — There are other methods of pick-
ling and tanning hides, for chrome sole leather. One con-
sists of pickling with aluminum sulphate and salt, and tanning
CHROME TANNAGE 181
in vats; and another of pickling with sulphuric acid and salt,
tanning in pits or rocker vats.
The hides, after pickling, may also be tanned either in the
paddle or mill as given under such leather. In cases of drum
tanning, however, the stock should be run for short intervals
only, otherwise a drawn grain may result.
Chrome sole leather is also given weight and filling after
it is tanned by being drummed with quebracho extract. It
is claimed that 7 to 8 lb. of quebracho liquor, 70° bk.,
for each side of leather should be drummed into the latter
after the chrome tanning is completed. Leather treated in
this manner resembles vegetable-tanned sole leather in appear-
ance, repels moisture, wears well, and can be sold by the pound
the same as the older tannage. This combination process takes
about 30 days from the raw hide to the finished product. A
combination tannage may also be obtained by suspending the
chrome-tanned hides for 10 days in a 40° bk. extract, and then
extracting and finishing as for vegetable-tanned stock.
Chrome-tanned harness leather. — In the handling of
hides for chrome harness leather, the methods of de-hairing
and bating should be such as not to deplete them, and pre-
serve the strength of the fibers. To get heavy leather, heavy
hides must be used, weighing from 60 to 80 lb. each, and they
must be plump, as there is no way of plumping chrome leather.
The hides are trimmed and hung in cold water to soak.
After soaking 24 hours, they are split into sides, put back into
the water, and soaked 24 hours longer; when they are fleshed
and soaked over night in fresh water. Splitting into sides and
fleshing may be done after the hides have soaked 48 hours;
they are then re-soaked over night to be made as soft and
clean as possible.
Liming. — The sides are next toggled together in a long chain
and put into the first lime. For this class of stock a fairly
long liming is necessary, and a small amount of sodium sulphide
at the start is desirable also. When the hides come from the
limes, they are passed into clean warm water, from which,
after 3 or 4 hours, they are unhaired on a machine. After
182 PRACTICAL TANNING
the hair has been removed, the hides should be washed with
running water for 15 minutes, then put into clean warm water
for 2 hours, after which they are fine-haired and worked on
the grain. Thorough working-out of the grain is necessary
to ensure clear, tough grain which will not crack.
Bating. — This may be done with lactic acid or with any
other suitable bate; the bacterial bates, of course, produce a
finer-grained leather than any acid de-liming process.
Pickling. — A paddle-vat is used for this process. To each
100 gallons of water in the vat, 30 lb. of salt are added, and
to this liquor, for each 100 lb. of hides, 2 lb. of sulphuric acid
and 15 lb. of salt. For succeeding packs, 15 lb. of salt and
1| lb. of acid are used.
The paddle should be run for an hour, and then allowed to
rest 2 hours, then run half an hour, and the hides left in the
liquor over night. The next morning they are removed and
placed in piles for 24 hours; they are then put into the tan
liquor.
Tanning. — A good way to tan the hides to get full flanks
and bellies, and a fine, smooth grain, is by the use of rocker-
vats, although paddles and even drums may also be employed.
The same method of chrome tanning may be used as described
under any of the one-bath processes.
When fully tanned, the leather is put down in smooth piles
for 48 hours. It is next washed for half an hour in water to
which 1 lb. of borax has been added for each 100 lb. of
leather, and then for one hour in cold running water.
Another practical mode of tanning consists of pickling the
hides with aluminum sulphate and salt, then drying, dampen-
ing, and softening with warm water, and finally tanning in
chrome liquor. This process produces well-tanned leather.
Re-tanning. — After being tanned and washed, the leather is
re-tanned with quebracho extract or with gambier, preferably
the former. For each average side, from 1 to 2 lb. of solid
quebracho extract is used. It is dissolved in boiling water,
enough water being then added to make 15 gallons of liquor
CHROME TANNAGE 183
for each 100 lb. of leather. The sides are run in the liquor
one hour, then placed in piles until the next day, when they
are either pressed or put through a wringer. If pressed, they
should be run in a dry mill for 15 minutes to remove the
press marks. The leather is then shaved just enough to re-
move the flesh and make the backs smooth and clean. When
gambier is used, the quantity is about 4 lb. for 100 lb. of
leather; otherwise the process is the same as with quebracho.
Chrome-tanned belt and strap leathers. — Hides for these
two classes of leather are treated in the beam-house in the
same manner as those for chrome harness and sole leathers.
For belting leather, however, they are trimmed into butts after
liming or after bating. The butts should each be about 4-|
feet long and 4 feet wide, though some may have a width of
4-J feet. The bellies and heads are tanned with extract and
are sold as offal. The butts are then tanned with chrome
liquor in a drum or in a vat. Tanning in a drum is effected
by pickling the butts and tanning them with one-bath chrome,
according to the procedure outlined for chrome upper leather.
When a vat is used, the process is the same as for harness and
sole leathers.
After having been tanned and washed, the butts are fat-
liquored with soap, oil, and degras — 1 lb. of soap, 5 lb. of
degras, and 2 lb. of neat's foot oil boiled an hour in water, to
which 6 oz. of borax have been added, being sufficient for
100 lb. of leather. There should be 12 gallons of fat-liquor.
The butts are first run in a drum, together with 12 gallons of
water at 160° F., and 4 oz. of salts of tartar (potassium car-
bonate) for each 100 lb. of leather. The water is drained
off and after the fat-liquor, at 140° F., has been put in, the
leather is run in it 45 minutes. It is then placed in piles for
24 hours, when it is taken and set out good and hard. The
grain is oiled with cod oil, and the butts are then hung up to
dry. The next operation is stretching, the object of this be-
ing to get all the stretch out of the leather. The butts are
soaked in hot water and piled down over night. The next
day they are stretched in belt stretchers as tight as possible
184 PRACTICAL TANNING
and allowed to get thoroughly dry ; they are then finished and
ready for cutting up into belts.
Good leather is also made by fat-liquoring the butts with
a solution of soap, drying and dampening them, and then stuff-
ing them with degras, paraffin, and paraffin oil. Drying and
stretching is effected in the manner that has been described.
A satisfactory stuffing mixture is made of 4 lb. of cod oil, 2
lb. of black degras, and 6 lb. of stearine for 100 lb. of leather.
No soap is used with this stuffing, which is applied at 165° F.
The butts are then dried and finished.
The trimmings taken from chrome belts may be re-tanned
with hemlock or oak liquor and sold as trimmings from oak
belts. They are first drummed in hot salt solution, next given
a light re-tan with hemlock extract, and then laid away in
strong hemlock or oak liquor, preferably the latter, until they
are colored throughout, when they are dried and sold.
Strap leather. — There are numerous uses for which soft
strap leather is suitable. The beam-house treatment and the
tanning are the same as for chrome harness leather. When
tanned, the leather is washed, shaved, and fat-liquored with
4 lb. of moellen degras, 2 lb. of cod oil, 2 lb. of wool grease,
1 lb. of soap, and 7 oz. of alkali, boiled, and made into an
emulsion with 12 gallons of water for 100 lb. of leather.
After the leather has been drummed in this fat-liquor 40
minutes, the liquor is drained off, and the leather washed in
warm water containing 1 pint of ammonia in 10 gallons of
water. This water is drained off at the end of 10 minutes,
and the leather is then re-tanned with gambier, 4 lb. dissolved
in 15 gallons of water being used for 100 lb. of stock. The
leather is drummed with this liquor for an hour; it is then
set out on the grain and hung up to dry. Any rough spots
can be buffed off before the leather is finished.
The finish is made by boiling 8 oz. of Irish moss, 8 oz. of
starch, 8 oz. of soap, and 1 pint of olive oil in 4 gallons of
water for 30 minutes. When cool, the solution is strained and
enough water is added to make 8 gallons of finish. The
leather is given a coat of this finish, staked on the flesh side,
CHROME TANNAGE 185
rolled, and hung up to dry or tacked in frames. It should
be rolled immediately after staking and before it is dried.
When dry, it is given a second coat of finish, dried, and rolled
again. This process makes tough, pliable, and durable leather
which outwears the best bark-tanned product.
White side leather.— A white leather which closely resem-
bles alum leather is made by tanning the grains of split hides
in a one-bath chrome process, and then either bleaching the
leather with borax and sulphuric acid, or treating it with flour,
or both. The hides should be split out of lime; the grains are
then bated and pickled with sulphuric acid and salt. When
the leather is tanned, wash it in a fairly hot 2 per cent solu-
tion of borax for a half-hour. Then prepare a solution of
sulphuric acid and water, made by adding acid to water until
the solution is 1 per cent in strength. Take the leather from
the borax bath and wash it in a drum in the acid bath; then
wash it in clear water to remove the acid; next fat-liquor it.
Treatment with flour. — Drumming the leather with flour is
another way to make it white. The flour treatment can be
used alone, or after the borax and acid process. The leather
is washed after tanning, and is then given the flour treatment,
50 lb. of flour being sufficient for 50 to 100 sides, according
to size. The flour should be stirred into a thin paste with
water before it is used. The leather is drummed with the
flour for 2 hours, and is then fat-liquored.
Acid fat-liquor dissolved in hot water is most suitable for
this leather, from 4 to 6 lb. of the soluble oil being sufficient
for 100 lb. of chrome leather. It is mixed with 10 gallons
of hot water and applied to the leather immediately after the
flour treatment. The leather is then dried, staked, and finished.
Finishing. — After having been staked, the leather is run in
a closed drum, together with powdered chalk or soapstone, for
an hour or longer; it is staked again, and then is ready for
use. Properly tanned and fat-liquored, the leather finishes up
soft and white, and is excellent material.
Tanning with aluminum sulphate. — White leather which is
suitable for various purposes is made by tanning acid-pickled
186 PRACTICAL TANNING
grains and flesh splits with a solution of basic aluminum sul-
phate. Splitting is done preferably out of lime, the stock then
being bated and pickled.
To prepare the tan liquor, boil 12 lb. of sulphate in 10 gal-
lons of water.; also dissolve 24 oz. of bicarbonate of soda in
1 gallon of hot water. Pour the soda solution slowly and
with constant stirring into the sulphate solution. When mixed,
let the liquor cool to 80° F. before using.
Put the pickled stock into a drum, together with 10 gallons
of water, 1 lb. of Glauber's salt and 3 lb. of common salt for
100 lb. of stock. Drum 20 minutes, then drain off the liquor.
Put 10 gallons of lukewarm water and 4 lb. of salt into the
drum, and run the sides in this brine for 10 minutes. Then
pour half of the sulphate and soda liquor into the drum and
run the sides in it for 3 hours. At the end of that period take
the stock out and place it over a horse to drain until the next
day, then hang it up to dry. When dry, put the leather back
into the drum, together with a few pails of water, and run
10 minutes. Then add the other half of the sulphate-soda
liquor and drum 3 hours. Now add sufficient one-bath chrome
liquor to give 2 per cent of dichrome on the weight of the
stock, and mill one hour. Horse-up the leather until the next
day, and then hang it up to dry.
Fat-liquoring with acid fat-liquor. — When dry, let the
leather remain in the dry condition in a clean dry room for
two weeks; then dampen it with warm water preparatory to
fat-liquoring. Sulphonated oil imparts the necessary softness
to the leather without discoloring or making it greasy. For
each 100 lb. of dry leather use 7 lb. of the oil dissolved in
10 gallons of water at 95° F. Drum the moistened leather
40 minutes with the solution of oil; then let it drain over
night. The next day strike out the grain and apply a mix-
ture of talc, 2 parts of glycerine, and 4 parts of water; then
hang the leather up to dry.
Finishing. — This consists simply of moistening and staking
the leather and tacking it on boards. When dry and taken
from the boards, if not soft enough, re-stake it; or if stak-
CHROME TANNAGE 187
ing does not soften it sufficiently, give it more fat-liquor ; and
if the leather does not appear to be entirely tanned it can be re-
turned to the drum and re-tanned with sulphate and soda
liquor, and then dried as before. The grain may be buffed
off if desired ; and the appearance of the flesh side can be im-
proved by buffing, on an emery wheel.
If it is desired to re-tan the leather into chrome stock, this
can be done by wetting the goods back and re-tanning with
one-bath chrome liquor, coloring, and finishing the same as
regular chrome leather.
Chrome velvet leather. — The chrome-tanned sides are fat-
liquored in the usual manner, some substance being added,
which, during the subsequent dyeing, isolates the fibers of the
leather in such manner as to allow its being soaked and soft-
ened without difficulty; dextrine, grape sugar, syrup, etc., are
used for this purpose. The leather is then dried and buffed.
In case of grain leather, either the flesh side is buffed or the
grain is snuffed. Flesh splits are buffed on the flesh side.
The snuffed leather is then drummed with warm water until
it has regained its original softness, and is dyed with acid dye-
stuffs and sodium bisulphate. During or after the dyeing, a
somewhat larger quantity of gambier or sumac is added than
is otherwise customary with chrome leather, in order to im-
part the necessary firmness to the leather. The velvet is then
raised by working the leather in the dry drum after it has
absorbed some moisture by treatment with wet sawdust.
Chrome-tanned patent leather. — Hides intended for
chrome patent leather should be carefully selected after they
have been de-haired. The grain must be as nearly perfect
as possible. Only small pattern and plump hides can be made
into patent leather, as large, spready, and thin hides are of
loose texture when tanned. After the hair and fine hair have
been removed, the hides should be washed in a wash-wheel.
They are then bated, which must be carefully done, because
if the hides are bated too much the leather is loose and breaks
coarse, and if not bated enough, the grain is harsh and tender.
A thin grain is to be preferred to a thick one. The former
188 PRACTICAL TANNING
has more elasticity than the latter, and is therefore less likely
to crack. After the hides are bated they should be washed a
few minutes in warm water to cleanse the grain. Pickling
then follows.
The one-bath process of tanning is to be preferred for
patent leather, as it gives the most measurement and there is
no sulphur to cause trouble after the leather is finished. Drum
the grains in salt water; then give them the tanning liquor
and continue drumming until the leather is fully tanned. The
leather can be washed, colored, and fat-liquored in the same
manner as other chrome leather.
Coloring and fat -liquoring. — Coloring is best effected with
logwood (hematin) and direct chrome leather black. Fat-
liquoring is done most satisfactorily with degras and soap,
or with the former alone. It is then struck out, oiled on the
grain, and hung up to dry in a warm room. Drying should
proceed rapidly so that the leather will dry as firm as possible.
Ordinarily, chrome patent leather requires de-greasing before
finishing.
Staking and 'finishing. — When the leather has dried, it is
dampened, staked, and tacked out as tight as possible. When
taken from the frames, it is usually sufficiently firm to be
finished, were it not for the grease in it, which must be re-
moved. Some of the grease applied in fat-liquoring, and
some of the oil applied to the grain, does not combine with
the fibers, and unless removed, causes the varnish to slip over
the leather, making finishing impossible. De-greasing is done
most satisfactorily with naphtha. Where a large quantity of
leather is being made, a naphtha plant is necessary or else
the leather must be sent to a de-greasing establishment, and
treated by those who make a business of extracting grease
from leather. De-greasing can also be done by soaking the
leather in naphtha for 10 hours, then pressing out the naph-
tha and drying, the leather. The action of the naphtha upon
chrome leather is harmless; and where the leather has been
well fat-liquored and oiled, no strength is lost through the
de-greasing operation.
CHROME TANNAGE 189
Sides for patent leather can be tanned with chrome liquor
and then split to the desired substance and re-tanned. This
improves the "break" of the grain and softness to feel. So-
dium sulphide should be used with lime in preparing the hides
for tanning. It gives the grain an appearance similar to colt-
skin, removes the fine .hair, and produces fuller and plumper
leather than lime alone or lime and red arsenic. All fine
hair must be removed, as it is one of the worst troubles to
contend with in making patent leather. Hides that weigh
more than forty pounds each are not suitable for patent
leather.
White chrome. — On wet pickled weight, run the stock in
a mill with 2\ per cent formaldehyde, 7\ per cent aluminum
sulphate, 10 per cent salt, and 12 gallons of water. Add this
in four portions at half-hour intervals, and run for 3^ hours.
Horse-up over night. Return the stock to the drum, and add
enough one-bath chrome liquor to give 2 per cent sodium'
dichromate on the weight of the stock. Run for an hour and
add \ per cent of sodium bicarbonate. Horse-up over night.
Then neutralize and wash, and fat-liquor with 1 per cent glyc-
erine, 5 per cent egg-yolk, and 10 per cent of flour. Dry
and re-fat with sulphonated oil, and finally dry, sammie,. stake,
and tack.
Tanolin T. — Calfskins and coltskins may be tanned with
"tanolin T" in a paddle-wheel, in the manner outlined below :
Pickling. — Weigh the skins after washing from the bate.
First pack. — For each 100 gallons of water in the tub dis-
solve 40 lb. of salt. Then for each 100 lb. of skins add 1^
lb. of 66° Be. sulphuric acid.
Start the paddle, throw in the skins and allow the paddle
to turn 3 hours. Then shut down the paddle and allow the
skins to lie in the liquor until an hour before stopping for
the night ; then run an hour, then allow the skins to lie in the
liquor over night. The next morning run the paddle one
hour and then haul the skins, and either horse up, smooth or
pile down flat for 24 to 48 hours. When hauling the skins
from the tub, arrange it so that the surplus liquor clinging
190 PRACTICAL TANNING
to them may drain back into the tub before horsing-up or
piling-down.
Second pack. — Strengthen the liquor by adding 10 lb. of
salt and 1| lb. of sulphuric acid for each 100 lb. of skins.
Then proceed in the same manner as for first pack.
Third, fourth, fifth, and sixth packs. — Strengthen the liquor
by adding 8 lb. of salt and 1^ lb. of sulphuric acid for each
100 lb. of skins, and proceed as for previous packs.
Seventh, eighth, ninth, tenth, eleventh and twelfth packs. —
Strengthen the liquor by adding 6 lb. of salt and 1 lb. of sul-
phuric acid for each 100 lb. of skins, and proceed as for pre-
vious packs.
After 12 packs have been pickled, clean out the tub and
start again.
This formula requires that each pack must contain enough
skins to make a full load for the size of the paddle-tub used.
If less than a full pack is to be pickled, a drum should be
used.
Tanning: First pack. — For each 100 gallons of water in
the paddle dissolve 50 lb. of salt. Then for each 100 lb. of
skins to be tanned, dissolve 9 lb. of tanolin T, as directed
below.
Warm the liquor to 75 or 80° F. Start the paddle and
throw in the pickled skins (never throw in the skins unless
the paddle is running).
Take half of the tanolin solution and add to the contents of
the paddle and run for an hour; then add the other half and
run the paddle for the remainder of the day. Two hours
before stopping for the night, warm the liquor to 85 or 90°
F. and add \ lb. of bicarbonate of soda or borax, dissolved
in a little water, for each 100 lb. of skirls. Leave the skins
in the liquor over night. On the second day run the paddle
2 hours in the morning and 2 hours in the afternoon ; warm
up the liquor again before stopping for the night, and again
leave in the liquor over night. When the skins have been in
the liquor 48 hours they should be tanned, but if any doubt
exists run the skins until they are tanned. When completely
CHROME TANNAGE 191
tanned they are removed and horsed-up smooth or piled down
flat, and allowed to drain 24 to 48 hours.
Never start tanning in the paddle-tub unless there is suf-
ficient time before closing for the day to run the paddle at
least 2 hours after the last portion of the tanolin solution has
been added. If the skins are completely tanned a piece cut
off from the thickest part should stand boiling. If this
shrinks materially, and becomes hard after boiling, the skins
are not thoroughly tanned, and should be left in the tan liquor
and run until the leather will stand boiling. Be sure that
the skins are completely tanned. There is no danger of over-
tanning the skins by leaving them too long in the tanolin.
Second pack : — Strengthen the liquor by adding 8 lb. of
salt and 9 lb. of tanolin T for each 100 lb. of skins, as directed
for the first pack.
Third, fourth, fifth, sixth and seventh packs: — Strengthen
the liquor by adding 6 lb. of salt and 7 lb. of tanolin T, for
each 100 lb. of skins, as directed for the first pack.
Eighth, ninth and tenth packs : — Strengthen the liquor by
adding 4 lb. of salt and 6 lb. of tanolin T for each 100 lb. of
skins, as directed for the first pack.
Two hours before stopping for the night of the first day,
for each pack add to the liquor \ lb. of bicarbonate of soda,
dissolved in a little water, for each 100 lb. of skins.
After 10 packs have been tanned, clean out the tub and
start again.
Dissolving tanolin T. — Dissolve this substance in boiling
water, using 1 gallon of water for every 3 lb. of tanolin.
The best way to effect its solution is to put the proper amount
of water into a barrel or tank, insert a steam pipe, and bring
the water to the boiling point. Then add the tanolin to the
water, stirring it constantly with a stick to ensure its being
well wetted, and boil vigorously until it is completely dis-
solved. This will take about 10 minutes. Allow the solution
to stand until the temperature is reduced to 100° F. Do not
put the tanolin in water and then let it stand before boiling
and dissolving.
192 PRACTICAL TANNING
Neutralising and washing. — After draining 24 to 48 hours
from the tan liquor, the skins are thrown into a drum with
a solution made of 2 lb. of bicarbonate of soda or borax, in
10 gallons of water for each 100 lb. of skins. Mill in this
solution for 45 minutes. Then wash the leather in running
water until neutral to the taste. The leather must be washed
long enough to remove all acid and salt.
To increase suppleness. — When heavy chrome leather is
required to be soft and supple, and yet must not contain much
grease, as, for example, for automobile tire leathers, the
method recommended by Eitner is satisfactory. In the or-
dinary method of chrome tanning by the two-bath process
sulphur is deposited in both the liquor and the fibers of the
leather, and when thus deposited in the fibers, it produces
softness and suppleness.
A method for increasing the amount of sulphur deposited
in the fibers is as follows : In the first bath, for every 100 lb.
of pelt, take 3 lb. of chrome-alum, 1 lb. of sodium bichromate,
and 2 lb. of hydrochloric acid. In the second bath only so-
dium hyposulphite is used to the extent of 8 lb. No acid
is added, as there is sufficient in the goods to produce the
desired effect. By this means the sulphur is deposited on the
fibers, the result being a soft, supple leather. It has a green
color, but if it is desired to make it whiter, the following
treatment may be applied : The goods are first pickled for
1 or 2 hours with 1 gallon for each pound of pelt in a solu-
tion containing 20 per cent of salt and 5 per cent of sulphuric
acid, and 4 per cent of sodium bichromate is then added.
This constitutes the first bath; the second bath contains hypo
only.
Ordinary one-bath leather can be made to represent two-
bath leather by incorporating sulphur in the fibers. Before
the goods are tanned, they are treated alternately with hypo
and hydrochloric acid, then tanned by the ordinary one-bath
process. This method produces a chrome leather with a large
amount of free sulphur, which makes it very supple. The
process can be carried out in either order, or even repeated
CHROME TANNAGE 193
more than once, that is, either hypo first, followed by hydro-
chloric acid and salt or the reverse.
Dissolving chrome-alum. — Several substances which are
used in the tannery have the peculiarity that while being fairly
soluble in water, they dissolve very slowly. For example,
chrome-alum is soluble to the extent of 1 part in 7 or 8 parts
of water, but it dissolves very slowly. If this salt is used
and some remains undissolved there is danger of stains or
uneven results being produced by the contact of the solid
particles with the skins. In this case it is better to make
up the solution some time in advance to be sure that all the
crystals are dissolved. When this is impossible, or where
the solution is required immediately, it is better to adopt
some other means than merely stirring the crystals on the
bottom of the vessel. A better way is to suspend the chrome-
alum in a basket, coarse bag, or some sort of strainer in the
water, so that the crystals are in contact with the water at
the top of the vessel. By this means the alum is much more
quickly dissolved, because, as it dissolves, the solution falls
away from it by gravity, thus exposing a fresh portion of
the crystals. If the solution of chrome-alum is to be used in
the drum, then, of course, it may be dissolved in the requisite
quantity of water by agitation in the machine. With some
substances that dissolve slowly it is possible to hasten the
solution by using hot or boiling water; but in the case of
chrome-alum, the solution thus obtained is different from that
in cold water, the latter being of a violet color, while that in
hot water is green.
The two solutions differ chemically to the extent to which
the chrome-alum is hydrolized, and theoretically, one would
expect the violet-colored solution to produce better tanning
results than the green one, but the tanning effects are gener-
ally the same in both cases. In experimental cases, two sim-
ilar packs of calfskins were tanned in the two different colored
solutions (made basic with soda), and after being tanned,
were neutralized, fat-liquored, dyed, and finished, but with
no apparent difference in the result. It was therefore con-
194 PRACTICAL TANNING
eluded that it is not worth the time and trouble to make the
violet-colored solution.
Aluminum bisulphite reduction. — The modifications of
the ordinary chrome processes of tanning are almost legion,
particularly so in connection with the production of one-bath
chrome liquors. For the production of the latter, there are
two general types of method, the first involving the use of a
chromium compound, such as chrome-alum, which is ren-
dered basic by the addition of some alkali, such as soda. The
modifications in this branch include the use of different alka-
lies for rendering the salt basic, and also the use of different
classes of chromium compounds. The most common, of
course, is chrome-alum, of which the active constituent is
chromium sulphate. Other chromium salts which have been
advocated are chromium formate, chromium acetate, and
chromium chloride.
In the second type of method for the production of one-
bath chrome liquors, potassium or sodium bichromate is taken,
and reduced by some reducing material. The chief modifica-
tion in this type of process rests in the agent which is used
for the reduction, both organic and inorganic materials hav-
ing been employed. Of the organic materials, probably the
most common and the most widely used have been cane sugar,
glucose, glycerine, and alcohol; while the inorganic materials
include sodium bisulphite and sodium hyposulphite.
According to a German patent taken out by M. F. Hirch,
the reduction is carried out by means of a solution of alumi-
num bisulphite, which, it is claimed, has the following advan-
tages over hypo or sodium bisulphite :
There is no deposition of free sulphur as with sodium hypo-
sulphite, and no great evolution of heat as with sodium bisul-
phite. The deposition of aluminum hydrate is formed in the
skin. The reduction should be carried out without the addi-
tion of acid. If a solution of aluminum bisulphite of about
14° Be. be added to a 2 per cent solution of chromic acid,
the complete reduction of the chromic acid is attained with-
out any precipitation. If, on the other hand, a solution of
CHROME TANNAGE 195
one-third the above concentration be used, the reduction of
the chromic acid is complete, but at the same time a precip-
itation is produced in the liquor.
The first treatment, that is, with the concentrated solution
of bisulphite, is suitable for tannage in one bath, while the
liquor produced by the use of the weaker bisulphite solution
is suitable only for the tannage in two baths. The following
is given as a practical example : The skins, de-haired, de-
limed, and pickled as usual, are submitted to the following
treatment: The bath consists of 5 per cent of sodium bi-
chromate, 2\ per cent of hydrochloric acid, and 180 per cent
of water, calculated on the weight of pelt. The goods are
allowed to turn in this liquor for 3 or 4 hours, and are then
placed in a pile for 12 hours. Finally they are transferred
to the second or reducing bath.
This bath consists of 36 parts of solution of aluminum bisul-
phite at 14° Be., and 220 parts of water for each 100 parts
of pelt. The goods are turned in this liquor for 4 hours,
when the tannage should be complete, with the grain even and
smooth. The leathers tanned by this method are more re-
sistant than those produced by other processes, and can be
dyed more easily and more regularly, partly because the de-
position of sulphur is avoided and partly because the alumina
forms a mordant which is very favorable to dyeing.
Recovery of chrome residues. — In the two-bath method
of chrome tanning, the first bath, which consists of an acidi-
fied solution of potassium or sodium bichromate, is never
fully exhausted. It has frequently been proposed to utilize
the residual chrome in this bath by making use of a stand-
ing bath, that is, never wholly discarding a bath, but adding
each time a quantity of bichromate and acid sufficient to re-
store its original strength. Unfortunately, this renewal of
the bath is an extremely complicated matter.
It is probably more practical with our present knowledge
not to try to utilize this chrome again in tanning, and by so
doing produce a poorer quality of leather, but to recover the
chrome in some form suitable for some other purpose.
196 PRACTICAL TANNING
Two processes have been proposed for the recovery of
chrome as a by-product, both of which can be worked profit-
ably, provided proper care is taken and operations are on a
sufficiently large scale to warrant the expenditure for
labor.
The first process consists of the precipitation of the chrome
as chromate of lead or chrome yellow. There is an exten-
sive demand for this pigment, and the particular shade is
not of great importance so long as it is strictly uniform.
In order to obtain uniformity, the precipitation should be
always made under as near the same conditions as possible
and to obtain brilliancy, the solution should be filtered before
precipitation takes place, and some alum added as a clarify-
ing agent. White sugar of lead (lead acetate) should be used
for precipitation, and a filter-press is essential for collecting
the precipitate. The product may be dried or sold in pulp
form to manufacturers of mixed paint. The price obtained
for the chrome yellow depends upon the care with which it
is made, but with ordinary precaution, this working-up of
a by-product is fairly remunerative.
The second method of utilizing the waste chrome is to
reduce it with sodium bisulphite or sulphurous acid gas, pre-
cipitate with soda ash, collect the chrome hydrate so formed
in a filter-press, wash it thoroughly, and use it in the manu-
facture of one-bath tan liquors. This method is in many
ways preferable to the manufacture of chrome yellow, as it
does not involve the worry of looking for an outside market.
Even in the profitable recovery of this chrome, the liquors
must be analyzed, and no great excess of reducing agents or
soda should be employed, otherwise these chemicals may be
wasted and no real gain obtained.
Chrome-tanned buckskin. — The skins after the final
washing are pickled either with sulphuric acid and salt, or
with aluminum sulphate and salt. The goods are then al-
lowed to drain until the next day, when they are tanned in
a one or a two-bath process. Excellent chrome buckskin is
obtained by tanning the pickled skins in a two-bath process,
CHROME TANNAGE 197
and good leather may also be made with any of the one-bath
processes.
White chrome buckskin. — An excellent white buckskin is
made by tanning with one-bath chrome liquor and then treat-
ing the skins with flour.
One-bath chrome tannages. — While a great many pre-
scriptions have been published for one-bath chrome tannages,
preparation of a proper one for any given purpose is still
considered a valuable trade secret. A little consideration of
the one-bath chrome tan liquor from the chemical point of
view should therefore be of some interest.
Of first importance is the source of the chromium. So-
dium dichromate is almost universally the cheapest raw ma-
terial. The exception is chrome hydrate, it being occasionally
possible to obtain chromium in the form of hydrate relatively
cheaper than in the sodium dichromate. This is so because
in some chemical operations the dichromate is used simply
for its oxidizing effect, and when the chromium is reduced,
its work is done; then it is precipitated with sodium carbonate,
washed and offered for sale as a* by-product. Only a limited
supply, however, can be obtained from this source in the
United States; but large quantities are secured from Euro-
pean coal-tar dye-works. The dichromate contains almost
exactly 50 per cent cf chromic oxide, and 100 per cent chro-
mic oxide in this form therefore costs just double the price
of the dichromate. As in the dichromate, the chromium is
present in the form of chromic anhydrite and as it must be
in the reduced or chromic oxide form, for use in one-bath
liquors, there has to be added to the cost of the dichromate
that of the acid required to set free the chromic anhydrite, as
well as that of the reducing agent used to get it into the
chromic oxide form. For example, the cost of a liquor con-
taining 100 lb. of chromic oxide made by reducing sodium di-
chromate with glucose, may be figured as follows :
200 lb. sodium dichromate at 7 cents per lb $14.00
280 lb. sulphuric acid at $1.10 per 100 lb 2.98
50 lb. glucose at 3 cents per lb 1.50
Total cost of chromic oxide. $18.48
198 PRACTICAL TANNING
Sodium bisulphite may be used as the reducing agent in
place of the glucose, in which case the cost shows as follows :
200 lb. sodium dichromate at 7 cents per lb $14.00
163 lb. sulphuric acid at $1.10 per 100 lb 1.80
600 lb. bisulphite at 85 cents per 100 lb 5.10
Total cost of 100 lb. of chromic oxide $20.90
These liquors, as calculated, include the cost of the acid
which is required to hold the chromic oxide in solution.
If chromium hydrate is used, the cost of this acid must be
figured; for example, the chromium hydrate is usually sold
in the form of a 20 per cent paste, and the cost of a liquor
containing 100 lb. chromic oxide is:
500 lb. chromium hydrate at 31 cents per lb $17.50
210 lb. sulphuric acid at $1.10 per 100 lb 2.31
Total cost of 100 lb. of chromic oxide $19.81
The cost of a liquor made of chrome-alum to contain 100
lb. of chromic oxide is readily calculated, as this salt contains
almost exactly 15 per cent of chromic oxide; therefore, it
requires 667 lb. of chrome-alum at 5 cents a pound to supply
100 lb. of chromic oxide, or a total of $33.35.
The cost price of the materials is based on normal market
conditions, and as the market fluctuates, new values can be
readily substituted in the calculation given.
Theory of chrome tanning. — The next step in this treat-
ment is to modify the liquor so that it will produce good
leather. This is a matter of so much importance and so
little understood, that a great many tanners find it good busi-
ness policy rather to pay an extra price for a liquor already
prepared, and which has been accurately adjusted to condi-
tions they desire, than to attempt to make a liquor of their
own. In general, this desired modification of a tanning liquor
is described by the rather vague term of "basicity." To un-
derstand properly what is meant by this, we must consider
the theory of the one-bath chrome tannage a little, that is, as
much as it is known of it: According to present knowledge,
salts of all descriptions, when in solution, dissociate, that is,
CHROME TANNAGE 199
break up into acid and basic radicals or ions, and the chemical
properties of these ions constitute the properties of the solu-
tion. In the case of salts of strong acids and strong bases,
such as sodium sulphate or sodium chloride, the strong basic
or positive character of one ion is in effect neutralized by the
strong acid or negative power of its opposite ion, and a neutral
solution results in a solution of such a salt. On the other
hand, with a salt of a strong base and a weak acid, as
sodium carbonate in solution, there is a condition in which
the strong positive character of the sodium ion far over-
balances the weak acid character of the carbonic ion, and
the solution has marked basic or alkaline properties. While
in the salts of weak bases and strong acids — such as aluminum
and chromium sulphates — the acidic or negative character pre-
vails, and solutions of these act in many ways as if they con-
tained free acid. In fact, the solutions may to a certain
extent be said to contain also free acid by the taking-on of
water — the phenomenon known as hydrolysis — which is con-
nected with the facts of dissociation already cited, in the
equilibrium, as it is called, of the solution. With these theo-
ries in mind, we can perhaps consider and explain better
some of the observations on the behavior of the chrome tan
liquor. An untanned hide or skin is strongly swollen or
plumped by both acids and alkalies. The reason for this
phenomenon has never been adequately demonstrated. Per-
haps as good a theory as any other is that both the acid
and alkali combine chemically with the hide fiber in such a
way as to reduce its permeability, and thus the fibers become
swollen by solution-pressure. Neutral salts deplete, reduce,
or prevent any swelling of the hide. This action also has not
been thoroughly explained, but it, too, is doubtless connected
with the increase of osmotic or solution-pressure.
If a chrome tanning liquor is made up of chromium sul-
phate and nothing else in solution, it will, from the con-
siderations above, be seen to possess strongly acid properties.
A skin immersed in such liquor will be excessively plumped ;
the tanning, however, will proceed very slowly, because as
200 PRACTICAL TANNING
treatment constitutes, the deposition of the chromic oxide will
continually augment the acid character of the liquor, and by
so doing the tendency of the chromic oxide to deposit will
be retarded, until finally a condition is reached when no
oxide at all is deposited, that is, the liquor will cease to
tan. If to the liquor containing only chromium sulphate,
common salt, (sodium chloride) be added, ionization will be
prevented, the percentage of acid, however, will not be re-
duced, but the plumping effects will be obviated. Such a
liquor will tan with the same degree of slowness as a pure
solution of chromium sulphate, a better leather being, how-
ever, produced, because the excessive plumpness is prevented.
If, in addition to the common salt, sodium carbonate be added
to the liquor to neutralize the acid formed by the hydrolysis
of the chromium sulphate, the third factor necessary to com-
plete the tan liquor will be present.
By combination with the acid, the sodium carbonate forms
sodium sulphate, and this being a "neutral salt, will assist
the common salt in keeping down the plumpness, at the same
time tending to form a basic chromium sulphate. The amount
of sodium carbonate that can be added, is, of course, strictly
limited, because an excess will cause the precipitation of
chromium hydroxide; and even before this point is reached,
so much of the acid may be neutralized that the solution will
be unstable and practically decomposed by the skin. A solu-
tion in this condition will be found to plump as much as
a strongly acid solution. It should perhaps be noted here
that there is a difference between the rapidity with which solu-
tions penetrate and the speed with which they tan. The acid
solutions penetrate more rapidly than neutral solutions, but
do not tan so fast; thus a skin struck through in a too acid
solution will be found to be under-tanned. In practice, only
the tan liquor made by the solution of the chrome hydrate
in sulphuric acid will be found simple enough to modify as
above described.
The liquor made by reducing the dichromate with glu-
cose will contain considerable sodium sulphate and some salts
CHROME TANNAGE 201
of organic acid, obtained from the incomplete oxidation of the
glucose. The influence of these latter, is, however, almost
negligible in regard to diminishing the plumping effect, but
they do retard the tanning. As the amount of such salts varies
according to the temperature at which the dichromate has
been reduced, they constitute an objection to the tan liquor
made by reduction with glucose, as they make its action
slightly uncertain. The liquor made by the reduction with
bisulphite is therefore slightly superior in its regularity, al-
though a little more expensive.
The concentration of the liquor also exerts a pronounced
influence upon its tanning properties. In the first place, all
the constituents of a liquor should be proportioned to each
other, and for sure results their ratio should not be changed.
It should be remembered that the neutral salts are a con-
stant factor, while, on account of the chromic oxide being
taken up by the skin, the amount of this and of the acid
present is variable, the one constantly decreasing and the
other constantly increasing.
Finally, of utmost importance is the condition of the skins
when they are put into the tan liquor. They may be acid
or neutral, plump or depleted, but their condition should al-
ways be the same, or allowance made for it in the tan liquor.
Calfskin glove and mitten leathers. — Glove leather of
durable quality is made by tanning calfskins with chrome. The
most suitable are those which are large and thin. During
the processes of liming, bating, and pickling prior to tanning,
the skins are handled in the same manner as those for shoe
leather, except that it is advisable to lime them somewhat
more thoroughly, so that the leather will be soft and durable.
Tanning is done by the two-bath or one-bath process in
the manner that has been already described. Another excel-
lent way to tan the goods is first to give an alum tannage,
dry them out, and then re-tan with one-bath chrome liquor.
Chrome lace leather. — Hides for lace leather are limed
and bated in about the same manner as those for upper stock.
A fine grain is not essential. Sodium sulphide is used in the
202 PRACTICAL TANNING
lime to hasten the de-hairing and give toughness to the hides.
De-liming can be done satisfactorily with lactic acid. The
hides are next pickled with sulphuric acid and salt, and are
then tanned.
Chrome lace leather is made by tanning the pickled sides
with one-bath chrome tanning material the same as chrome
upper leather, and then fat-liquoring and finishing in the
following manner: The tanned and neutralized leather is
split. The flesh splits can be finished into gusset splits, glove
leather, or lace leather. The split lace leather is just as dur-
able as the grain leather, but it does not look quite so good.
The sides may be split out of lime or out of pickle, and then
tanned with the chrome liquor. Where yellow lace leather
is wanted, it is colored with extract of fustic and some yellow
dye before fat-liquoring. If white leather is desired, it is
washed in hot borax water, and next in water acidulated
with sulphuric acid, and then thoroughly in clean water be-
fore fat-liquoring.
A satisfactory method of tanning chrome lace leather is
carried out as follows : The sides are de-haired, bated, and
washed ; they are then drummed with 2 lb. of pulverized alum
and 4 lb. of salt for each 100 lb. of hides. The goods carry
sufficient water from the last washing to dissolve the alum
and salt. When they have absorbed the materials, they are
allowed to press and drain, and, after having been partly dried,
are split and shaved. The tanning is then completed by drum-
ming the hides in one-bath liquor in the same manner as for
chrome upper; they are finally washed and partly dried for
fat-liquoring.
The fat-liquor is made as follows : 4 oz. of potash or other
alkali is boiled in -| gallon of water; then 2 lb. of any good
degras and 4 lb. of tallow are added, and the whole brought
to a quick boil. The compound requires thorough cooking.
Then 1 quart of neat's foot oil is added, and the mixture is
stirred until the temperature reaches a little below boiling
point. The fat-liquor, at 150° F., is applied to the leather,
the above quantity being used for 100 lb.
CHROME TANNAGE 203
When fat-liquored, the leather is struck out and oiled on
the grain side with neat's foot oil, then stretched in frames
until dry. After this it is moistened and staked, staking
and drying being continued until the leather is soft and dry.
Then it is painted on both sides with a light coat of paste
made with tallow, starch flour, soap, and water boiled to-
gether ; next it is dried again and finished. The chrome tan-
nage permits the leather to be stuffed at a high temperature,
thus ensuring thorough penetration of the stuffing grease, and
the leather is made very elastic and durable, and peculiarly
suitable for lace leather. Chrome lace leather does not harden,
but remains soft and pliable until it is worn out. It does
not burn when it goes over the pulleys. The tanning can be
clone in any of the various methods given for chrome leather.
Semi-chrome leather. — This class of leather, as the name
implies, includes those leathers which are tanned partly by
a vegetable tanning process and partly by a process of chrome
tanning. The two processes may be carried out together, or
consecutively, or the chrome process may be used as a re-tan-
nage for vegetable-tanned skins. Usually the chrome process
precedes the vegetable process, since this procedure gives the
leather its characteristic properties.
Among the skins that arrive in the United States in a partly
tanned condition are sheepskins from East India, South Af-
rica, South America, and Australia. It is these skins, par-
ticularly those from East India, that are given the chrome
re-tannage. The goods are sorted according to substance,
tannage, etc., and are marked. After marking, the skins are
equalized by splitting or shaving. The larger skins are split,
and, if necessary, are shaved. Before splitting or shaving,
the goods are dampened down by immersing the thick por-
tions in warm water and finally the whole skin. Very light
skins are dampened back by being treated with warm water
in the drum for 10 minutes. Finally they are laid in a pile
for a few hours to become uniformly soft and moist.
Splitting and shaving. — In splitting, the goods should be
left thicker than the final product is required, and then shaved
204 PRACTICAL TANNING
down to the required substance. The flesh splits are used for
welting purposes, heels, linings, etc. ; the grains are de-tanned
and then re-tanned with chrome liquor. Unless most of the
original tannage is removed, the leather will be hard and un-
evenly tanned.
Stripping the tannage. — Stripping or de-tannage is accom-
plished by means of the milder alkalies. Caustic soda should
not be used as it is too energetic. Borax may be used with
advantage, because it acts gently and gives a smooth grain to
the skins. For light skins, 2 per cent, and for heavy skins,
2\ per cent of borax is used, calculated on the weight of the
drained goods. If washing soda is used, not more than 2 lb.
should be taken for 100 lb. of leather. The drained skins
are placed in the drum with warm water at 100° F., the drum
is set in motion, and the borax or soda solution is run in
through the hollow axle. The drum is allowed to run 30
minutes, which is usually sufficient to remove the greater part
of the tannin. The washing should be continued until the
skins have a soft and slippery or semi-gelatinous feel. When
this has been accomplished, the liquor is allowed to run out
and warm water is run in to wash the skins. This washing
is continued until the water coming from the drum is clear,
showing that all dissolved tannin is removed. In order to
neutralize the alkali retained by the leather, \ to 1 per cent
of formic acid is added to the wash water. The progress
of neutralization may be followed by applying a piece of blue
litmus paper to a cut section of the skins; if the paper is
colored a feeble red, the process is complete. A final wash-
ing with pure water prepares the goods for the chrome re-
tannage.
Vegechrome. — Calf and kip skins may be tanned with
"vegechrome" in a paddle-wheel tub by the following
procedure :
Pickling. — Weigh the skins after washing from the bate.
First pack. — For each 100 gallons of water in the tub dis-
solve 40 lb. of salt. Then for each 100 lb. of skins add 1|
lb. of 66° Be. sulphuric acid.
CHROME TANNAGE 205
Start the paddle, throw in the skins, and allow the paddle
to turn 3 hours. Then shut down the paddle and allow the
skins to lie in the liquor until an hour before stopping for the
night; then run one hour, and allow the skins to lie in the
liquor over night. The next morning run the paddle one
hour, and then haul the skins and either horse-up smooth or
pile-down flat for 24 to 48 hours.
Second pack. — Strengthen the liquor by adding 10 lb. of
salt and 1| lb. of sulphuric acid for each 100 lb. of skins.
Then proceed same as for the first pack.
Third, fourth, fifth and sixth packs. — Strengthen the liquor
by adding 8 lb. of salt and 1| lb. of sulphuric acid for each
100 lb. of skins and proceed as for previous packs.
Seventh, eighth, ninth, tenth, eleventh and twelfth packs. —
Strengthen the liquor by adding 6 lb. of salt and 1 lb. of sul-
phuric acid for each 100 lb. of skins and proceed as for pre-
vious packs.
After 12 packs have been pickled, clean out the tub and
start again.
This formula requires that each pack must contain enough
skins to make a full load for the size of the paddle-tub used.
If less than a full pack is to be pickled, a drum should be used.
Tanning: First pack. — For each 100 gallons of water in the
paddle-tub dissolve 50 lb. of salt. Then for each 100 lb. of
skins to be tanned dissolve 12 lb. of vegechrome as directed
below.
Warm the liquor to 75 or 80° F. Start the paddle, and
throw in the pickled skins. Never throw in the skins unless
the paddle is running.
Take half of this vegechrome solution and add it to the
contents of the paddle and run for one hour; then add the
other half and run the paddle for the remainder of the day.
Two hours before stopping for the night, warm the liquor
to 85 or 90° F., and add 6 oz. of bicarbonate of soda or borax,
dissolved in a little water, for each 100 lb. of skins. Allow
the skins to remain in the liquor over night. On the second
day run the paddle 2 hours in the morning and 2 hours in the
206 PRACTICAL TANNING
afternoon; warm the liquor again before stopping for the
night and allow the skins to lie in the liquor over night. When
the skins have been in the liquor 48 hours, they should be
tanned, but if any doubt exists run them until they are.
When completely tanned, the skins are removed and horsed-
up smooth or piled-down flat, and allowed to drain 24 to 48
hours.
Never start tanning in the paddle unless there is sufficient
time before closing for the day to run it at least two hours
after the last portion of the tanning solution has been added.
If the skins are completely tanned, a piece cut off from the
thickest part should stand boiling. If the piece cut off shrinks
materially and becomes hard upon boiling, the skins are not
thoroughly tanned and should be left in the tan liquor and
run until the leather will stand boiling. There is no danger
of over-tanning the skins by leaving them too long in the
vegechrome.
Second pack. — Strengthen the liquor by adding 8 lb. of
salt and 12 lb. of vegechrome for each 100 lb. of skins, as
directed for the first pack.
Third, fourth, fifth, sixth and seventh packs. — Strengthen
the liquor by adding 6 lb. of salt and 9| lb. of vegechrome for
each 100 lb. of skins, as directed for the first pack.
Eighth, ninth and tenth packs. — Strengthen the liquor by
adding 4 lb. of salt and 8 lb. of vegechrome for each 100 lb.
of skins, as directed for the first pack.
Two hours before stopping for the night of the first day,
for each pack add to the liquor 6 oz. of bicarbonate of soda,
dissolved in a little water, for each 100 lb. of skins.
After 10 packs have been tanned, clean out the tub and start
again, as for the first pack.
Dissolving vegechrome. — Dissolve the vegechrome in boil-
ing water, using one gallon of water for every 3 lb. of vege-
chrome. The best way to effect the solution of this material
is to put the proper amount of water into a barrel or tank,
insert a steam pipe, and bring the water to the boiling point.
Then add the vegechrome to the water, stirring constantly
CHROME TANNAGE 207
with a stick, and boiling vigorously until it is completely dis-
solved, which will take about 10 minutes. Allow the solution
to stand until the temperature falls to 100° F. Do not put the
vegechrome in water and then let it stand before boiling and
dissolving.
Neutralizing and washing. — After draining from the tan
liquor the required period, the skins are then thrown into the
drum with a solution of antimonine (antimony lactate), using
4 oz. in 10 gallons of water not over 100° F. for each 100
lb. of skins. Mill in this solution for a half-hour, and wash
the skins in running water for 10 to 20 minutes. Then add 10
gallons of water to the drum for each 100 lb. of skins, and
in it dissolve 4 oz. of borax and run them in this borax water
for 30 minutes. Then wash the skins in running water until
neutral to the taste ( 1 to 3 hours, depending upon the thick-
ness of the skins). The skins must be washed long enough
to remove all acid and salt.
Chrome-tanned wax calf leather. — The tanner of chrome
calfskins finds many having defective grain which can be
re-tanned and finished into chrome wax leather. Heavy skins
are more- suitable for this leather than light ones, the light
stock being more suitable for ooze leather. All skins from a
medium up to 10 to 12 lb. can be worked into chrome wax
leather, provided that they are free from butcher cuts on the
flesh side. They are worked through the preliminary process
in the same manner as those for chrome leather, being tanned
with one-bath chrome liquor and shaved. After shaving, they
are washed and tanned.
Re-tanning. — This consists in re-tanning the skins with
hemlock extract, or with a mixture of hemlock and oak ex-
tracts, hemlock and quebracho extracts, or with other suit-
able tanning material. Two methods of re-tanning will be
described :
The first liquor is a 5° bk. hemlock liquor in which the skins
are hung 24 hours. This liquor is then strengthened to 8°, and
the skins are left in it for 48 hours, after which the strength
is increased to 10°, the skins remaining therein 48 hours. The
208 P-RACTICAL TANNING
next liquor is at 14°, and the skins are transferred to it and
remain in it 6 days. Handle them every 2 days, or give them
a 16° liquor for 4 days and handle every 2 days; then they
should be given 5 days in an 18° liquor, being handled every
other day. Re-tanning is now complete. The liquors may
also be made up of oak and hemlock extracts in the propor-
tion of 3 parts of the latter to 1 part of the former. Gambier
is about the only vegetable tanning material that does not
lose considerable of its tannin strength by precipitation in the
presence of salt. Synthetic tans do not lose their efficiency by
precipitation, but quebracho, hemlock, and most other vege-
table tanning materials do.
Re-tanning may also be done in a drum in the following
manner: The first liquor is made of 3 lb. of hemlock extract,
and 1 lb. of oak extract, and 5 lb. of salt in 25 gallons of
water for 100 lb. of chrome leather. In this liquor the skins
are run one hour, then they are piled-down for 24 hours. The
second liquor may be the same as the first, the skins being
run in it one hour, then piled-down for 24 hours. On
the third day the skins are given the last re-tanning liquor,
which is made up of 3 lb. of oak extract and 1 lb. of hemlock
extract and no salt. The skins are run in this liquor 2 hours,
then placed in piles for 12 hours. Re-tanning by hanging the
goods in the liquor is doubtless the better method of the two.
After the leather is fully re-tanned it should lie on a pile for
48 hours, and then be fat-liquored.
Intestinal leather. — This process makes leather from the
intestinal membrane, which, on being bleached, has the ap-
pearance of ordinary glove leather or kid. It is, however,
essentially different from such leather by the absence of pores,
thus rendering it impervious to moisture and gases, and by
its extreme thinness coupled with great toughness or strength
of fiber. It is distinguished from gold-beater's skin in that
it may be sewed, the seam being firm and the leather closing
tightly around the thread, and also by its extreme pliability
and softness. These properties render this leather peculiarly
suitable for the manufacture of gloves for those whose occu-
CHROME TANNAGE 209
pations render it necessary to protect the hands against infec-
tious matter and poisonous solutions. The extreme softness of
the leather permits free movement of the fingers, and its thin-
ness gives the sense of touch full play. Unlike gold-beater's
skin, it may be boiled without injury, so that a surgeon's
glove made from it may be dipped into a formaldehyde solu-
tion and then boiled for the purpose of cleansing, disinfection,
and sterilization, which is a matter of great importance.
This leather is applicable to a great variety of purposes.
For example, it is exceedingly well adapted for ink ribbons;
as a covering for balloons it has been found superior to the
ordinary silk covering by virtue of its greater lightness, less
bulk, pliability, softness, and imperviousness ; it is also used for
partitions in dirigibles; it can be dyed any color, and when
dyed, may be used in place of ornamental papers. This material
serves the same purpose as the outer peritoneal coating of the
caecum or blind gut of the ox, and is known as "gold-beater's
skin," being used by the gold-beater in making gold leaf. In
most of the slaughtering establishments in the United States
and Germany this membrane is now removed from the intes-
tine which it envelopes, and is supplied in this condition to the
manufacturers of gold-beater's skin, or to gold-beaters.
In order to convert this delicate membrane into leather, all
fatty substances and adhering impurities are first removed by
the following treatment : The membranes are rinsed in warm
water, preferably in three graded baths, each having a higher
temperature than the preceding one; for example, 77, 86, and
95° F. One hundred membranes are next immersed, and left
for about 5 minutes, in a bath composed of 10 grams of po-
tassium permanganate dissolved in 3 liters of water and hav-
ing a temperature of 80° F. They are then placed in a bath
of 20 grams of sulphurous acid dissolved in 3 liters of water
at 80° F. The skins must be left in this bath until they have
swelled up and attain a pure white color, whereupon they are
taken out and again submitted to three rinsings in warm water
as above. They are now ready to be immersed in a soap solu-
tion or bath. This is preferably prepared by boiling about
210 PRACTICAL TANNING
\ kilogram (1.1 lb.) of good pure white toilet soap, such as
white castile, in 1^ liters (2\ pints) of water, for 100 mem-
branes. The temperature of this bath has first to be reduced
to 95° F. by the addition of | liter of cold water. The mem-
branes remain in this soap bath for several hours, until the
soap has been completely absorbed; they are then put suc-
cessively into two baths of warm water having a temperature
of 80° F., for the purpose of completely washing them. The
membranes are now ready for the tanning process, which is
as follows : A solution is prepared by dissolving, for each 100
membranes, 100 grams of chromic acid, and 50 grams of alum
in 1 liter of water at 95° F. The membranes are placed in
a bath of 1 liter of warm water at 80° F., and the chromic
acid solution is gradually added to the water, the skins being
stirred in the bath. Preferably the following course is pur-
sued : First, about a sixth of the chromic acid solution is add-
ed to the membranes, then after about 10 minutes a further
eighth of the same, and after another 10 minutes a quarter
of the original amount of the chromic solution, and finally
after 20 minutes, the rest of the solution is poured into the
bath containing the membranes. In this final bath the skins
are allowed to remain for an hour, being constantly agitated
or stirred. They are then removed and rinsed twice with
warm water at 80° F. This completes the tanning process.
It is advantageous to immerse the tanned membranes in a
bath composed of 500 grams of egg-yolk and 100 grams of
glycerine added to 2 liters of water, and thoroughly mixed with
it. The membranes remain in this bath for about 10 hours.
They are then removed and drained by hanging over ropes,
and are next placed on suitable frames and allowed to dry.
After about 8 days they are stored in moderately damp cham-
bers and are then drawn over their entire surface across cres-
cent-shaped blunt knifes until they are smooth and pliable.
The leather is now finished and may be used in this condi-
tion, but for many purposes it may be found desirable to
finish or embellish it further. It can be dyed beautiful colors,
and for this purpose may be immersed in a bath containing the
CHROME TANNAGE 211
desired dye, such as aniline dye. A bath containing from 3
to 5 per cent of dye usually suffices. To this bath is added a
mordant consisting of 4 cubic centimeters of acetic acid of
50 per cent strength. The leather remains in this bath for
several hours. It is also claimed that by this process the
leather, whether dyed or undyed, may be still further finished
by passing it through calendering rolls. In some cases col-
ored talcum powder may be sprinkled or dusted over it, and
then calendered. It is also desirable in some cases to coat the
undyed leather with a thin film of a composition prepared by
mixing 8 parts collodion, 1 part castor oil and 1 part caout-
chouc solution. Leather so coated is suitable for gloves, ac«
cordion bellows, and the like. When it is desired to obtain a
thicker and stronger leather, which, however, is not so well
adapted for dyeing, a tanning bath consisting of 100 grams of
zinc sulphate, 40 grams of alum and 50 grams of wheat-flour
properly mixed with 1 liter of water, may be used to tan 100
membranes, the other conditions and steps of the process re-
maining the same. This tanning bath is used instead of the
chromic acid bath described. This treatment yields white,
lusterless leather of greater body than that produced by the
chromic acid method. This process was patented by Bruno
Trenckmann, of Berlin, Germany, who also has a patent on
the following process :
Parchment-like skin. — In the process as usually carried out,
the peritoneal membrane of the gut, after having been cleaned
of fat and soaked in a bath of soap, is immersed in a bath of
zinc sulphate, barium chloride, or any other similar mineral
salts which are able to produce pigments insoluble in water,
by double transposition with any organic salts, acids, or bases.
This process consists of alternately treating the skins in such
baths at certain definite temperatures. For example, the gut
membranes are first rinsed from 5 to 10 minutes in a solution
of zinc sulphate or other mineral salts of 15° Be., and at a
temperature of 40° F. They are then put into a solution pref-
erably of sodium carbonate of about 15° Be. and at the same
temperature, and are treated therein for about the same pe-
212 PRACTICAL TANNING
riod, raising the temperature to 60° F. They are then returned
into another solution of zinc sulphate and then into a solution
of sodium carbonate. This treatment is repeated once or
twice more until the skins have absorbed a sufficient amount
of the pigment, which is usually attained after two or three
treatments.
By this process a parchment-like, clear white, or well col-
ored, product is obtained, which may come into contact with
water and when again dry, will appear as before. The prod-
uct is capable of being extended when soaked, and will again
shrink while drying, thus making a tight cap, perfectly air-
tight, so desirable for closing bottles of all kinds.
Leather for organ pipes. — Leather made by the following
process is distinguished by its fineness, suppleness, lightness,
and durability. Such properties are required for many indus-
trial purposes, particularly for fitting organ pipes, and in the
manufacture of bellows and the like; and generally for pur-
poses where it is desired to have an air-tight, light, and flex-
ible material. The leather hitherto used for such purposes was
usually not air-tight or sufficiently flexible, while rubber sheets
or fabrics impregnated with a solution of rubber, although
air-tight, are difficult to fit snugly because they are not suffi-
ciently soft. They have also the serious drawback of being
liable to deteriorate and lose their flexibility, thereby becoming
brittle under the influence of cold. This is of great impor-
tance in church organs which are not heated during the winter.
This leather has none of these disadvantages, and is therefore
suitable for various purposes. It is manufactured from the
caecum or blind gut of the animal. This outermost skin of
the blind gut has hitherto been deprived of its fat and dried,
and used as the so-called gold-beater's skin. It has been pro-
posed to subject it to a tanning process, but the leather ob-
tained in that way alone is not sufficiently air-tight and durable.
By means of this process, the blind gut skin, well cleaned
and washed with potash or the like, is first tanned by mineral
salts such as chrome-alum, etc., or with vegetable products.
In practice, it has been found that for 200 skins of maximum
CHROME TANNAGE 213
size, 400 grams of zinc sulphate with 10 liters of water is suit-
able as a tanning solution; or about the same quantity of
chrome-alum may be used. The skin is then filled in a bath
of egg-yolk, flour, or the like, and permitted to remain therein
until it is thoroughly impregnated, whereby it is made thicker
and stronger. This bath is made by adding a small quantity
of flour to about 1 liter of egg-yolk. The skins are then rinsed,
stretched, and dried. The drying is effected by placing two
skins, one on top of the other, and allowing to dry together
in close contact. During this drying process they adhere firmly
to one another without any glue or cement being used. The
best plan is to place together the grain or outermost sides of
the two skins. More than two skins may be superposed, in
which case the similar sides are placed in apposition.
When a multiple skin treated in this manner has become
sufficiently dry it is de-greased or deprived of its fat by treat-
ing it with benzine, being rubbed and kneaded at the same time,
whereby it is rendered soft and supple. This treatment is
necessary to remove the oil incorporated in the skin by treat-
ment with the eggs, and make the leather soft and capable of
being cemented to wood and metal. This property renders it
suitable for gluing or piecing together, so that large pieces
of any size may be made from small pieces, and it can be ce-
mented to other materials, such as wood, etc., which is of im-
portance for organ pipes and other purposes. This process,
as stated, includes the process of tanning the stock, but if un-
tanned skins are subjected to the other steps of the treatment
— filling, superposing, and washing with benzine — a product is
obtained having many • advantageous characteristics over the
untanned skins previously known.
CHAPTER VII
IRON TANNAGE
The subject of iron tannage has been much discussed, and
many attempts have been made to obtain a satisfactory tan-
nage with this element. Iron belongs to the same periodic
group as aluminum and chromium, and naturally one would
expect it to lend itself to the same general reaction as the other
two elements. Of the three elements, iron is the most basic,
and, unlike chromium and aluminum, has no acid-forming
property. The tanning quality of iron, however, does not de-
pend upon this property, but rather upon the fact that it forms
basic compounds when its salts are treated with an alkali. Al-
though chromium and aluminum also form basic products,
these compounds are more stable than that produced from
iron. Any attempt to produce a compound of the formula
Fe2(OH)2S04 will result in the precipitation of the hydrated
oxide Fe2C>3. H2O which is a yellow powder and entirely in-
ert as a tanning material. This hydrated oxide differs also
from the corresponding aluminum and chromium oxides in
that it rapidly passes through the colloidal range and becomes
a crystalline substance.
In a series of papers which appeared in the Journal of the
American Leather Chemists' Association, beginning in the
February issue of 1921, Dr. Daniel D. Jackson and Dr. Te
Pang Hou set forth the early history of this important sub-
ject, and through their investigations have shown conclusively
why so many attempts to produce iron-tanned leather have
failed. They have also pointed the way to new processes
which open up a new field for investigation and should warrant
every consideration.
Having had Dr. Hou as a student at one time, and know-
ing the painstaking care with which the investigation was con-
ducted; the author can vouch for the thoroughness of the clas-
214
IRON TANNAGE 215
sic research, and desires to give him credit for the following
information on iron tannage :
Research in iron tannage. — Attempts to use iron salts as
tanning agents date back to the time when efforts were first
made to find a substitute in the form of metallic salts for vege-
table tannins. In the course of more than a century, efforts
were repeatedly made and interest was continually revived to
make iron tannage a commercial success, but without reward,
in spite of the great promise that inspired such investigators to
make a most determined effort. Within the last decade, partly
on account of the great war, new interest has been given to
iron tannage, and the properties and behavior of iron salts
as tanning agents are gradually becoming better understood.
The history of iron tannage begins from the latter part of
the 18th century. Many of these early investigators were
men who also helped to establish the present-day chrome
tannage.
In 1770, J. Johnson, an Englishman, patented a process
of tanning, using ferrous sulphate with an acid (sulphuric
acid, hydrochloric acid, or nitric acid). The pelt was tanned
in three operations, in the middle of which a vegetable tannin
was used.
In 1794, Sam. Ashton, another Englishman, recommended
for tanning a mixture of iron oxide and sulphuric acid, cal-
cined iron ore or iron ocher with pyrite, copper ore, and zinc.
The period of tanning was given as from 5 to 7 weeks. Some
alumina was added for calfskins.
In 1805, Sigmond Hermbstadt, in his book on leather tan-
ning, explained that solutions of metallic acid baths had simi-
lar action on the pelt as oak tannins. Among other salts he
mentioned the red iron sulphate, in which not only the grain
of the pelt was affected, but the pelt was virtually converted
into leather if soaked in it for some time. He prepared his
iron tan liquor by heating ferrous sulphate to a dry yellow
substance which was dissolved in 20 times its volume of boil-
ing water, and on cooling, the clear yellow-red solution was
decanted for use. He also treated iron oxide with acetic acid ;
216 PRACTICAL TANNING
or oxidized ferrous sulphate with concentrated nitric acid, or
with a mixture of concentrated nitric acid and sulphuric acid.
Sole leather as well as upper leather could be made in this way,
but it was de-tanned in contact with water.
In 1842, d'Arcet, a Frenchman, tanned the hides in a ferric
sulphate solution, but the sulphuric acid set free gradually de-
stroyed the hides. In the same year, Julius Bordier, of London,
patented a process (British patent 9,219, 1842) of oxidizing
ferrous sulphate with nitric acid and sulphuric acid, and with
manganese dioxide and sulphuric acid. It was said that he
had attained some success.
In 1853, Hylten Cavalin, employed a tanning liquor con-
taining 10 lb. of potassium dichromate and 20 lb. of alum in
180 lb. of water. The hides were tanned in this liquor for 4
days, and were next placed in a 10 per cent ferrous sulphate
solution for 12 hours with frequent stirring. The acidity re-
lation of these two liquors was not properly adjusted, and the
iron was not completely oxidized. The leather obtained was
hard and brittle.
In 1855, Rene de Kercado Molac and Jean Daniel Friedel,
both of Strasbourg, France, patented a process whereby the
hides were tanned in a basic ferric sulphate solution which
was later neutralized with metallic oxides, such as ferric
oxide, alumina, and zinc oxide to remove the sulphuric acid
liberated. They prepared the liquor with ferrous sulphate,
manganese dioxide, and sulphuric acid, and added ferric ace-
tate in varying proportions to the liquor. A. E. L. Bellford,
of London, patented their process in England. In this Brit-
ish patent (January 12, 1855) it was stated that the leather
treated by other mineral processes is "liable to tear in length
of time on account of the great quantity of acid remaining in
the leather corroding the animal fibers."
Dr. Frederick Knapp, Professor at the Polytechnic School
of Braunschweig, Germany, made a thorough investigation on
these mineral tannages and published the results in "Die Natur
und das Wesen der Gerberei und des Leders" (Munich, 1858),
and also in an article, "Uber Gerberei und Leder," in Dingler's
IRON TANNAGE 217
Polytechnische Journal, vol. 181, p. 311 (1866). He made a
satisfactory explanation of the tanning action. He had in mind
the possibility of reducing the length of time needed in the
vegetable tanning process, and eliminating costly materials
such as egg-yolk and flour used in alum tannage. He recog-
nized the plumping effect upon the hides by the acid liberated
during tanning, and the stiff and brittle character of the leather
obtained. He recommended neutralizing the tan liquor dur-
ing the process of tanning with sodium carbonate or caustic
soda, and pointed out the advantages in so doing, namely, that
the hides were more richly tanned, that the harmful acid ef-
fect was prevented, and that neutral electrolyte NaCl (in
FeCl 3 liquor) was produced in the tan liquor. His British
patent 2,716 (1861), through John H. Johnson, covered iron,
chrome, manganese, and other metallic salts in combination
with fatty acids to form insoluble metallic soaps, so that the
iron in the pelt might not be washed out. He also mentioned
the use of similarly insoluble silicates of alumina and alkaline
earths. According to his German patent No. 444 (1887), he
prepared his liquor by adding nitric acid in excess to oxidize
completely a boiling ferrous sulphate solution when brown
nitrogen dioxide (N0 2 ) fumes were seen. After all of the
iron was oxidized, he introduced more ferrous sulphate into
the resulting solution, as long as N0 2 fumes were evolved.
The liquor, after evaporation, becomes a varnish-like liquid.
Judging from this description; his liquid must have been too
alkaline through the loss of the nitric acid by boiling. In his
additional German patent No. 10,518 (1879), he used sodium
nitrate and sulphuric acid for oxidation instead of the nitric
acid. This method is far more economical, and involves no
danger of losing the acid by heating, so that the acidity of the
resulting liquor is under control. Furthermore, a neutral salt,
Na 2 S0 4 , is produced in the tan liquor.
In 1864, F. Pfannhauser obtained a patent for the prepara-
tion of a basic ferric sulphate solution and its use in tanning.
He roasted ferric sulphate to a red heat with continuous stir-
ring until it was reduced to a red powder, which was then
218 PRACTICAL TANNING
thrown into water while still hot. Most of this powder was
said to be dissolved. The colloidal matter was allowed to
settle, and the supernatant liquid was drawn off for prepara-
tion of tan liquors of varying strength. The skins were tanned
counter-currently and, when tanned, were placed in a soap
solution.
In 1877, Paesi proposed to use a ferric chloride solution
together with salt at 20° C. in the ratio of 100 parts of water
to 10 parts of FeCb and 5 parts of salt.
In 1881, E. Harcke obtained a German patent, No. 19,633,
according to which the pelt for making sole leather was treat-
ed with a mixture of a resinous body (such as rosin), coal-tar
creosote or carbolic acid, and an alkali, in water, until thor-
oughly penetrated. The pelt was then tanned, first in an
aluminum salt solution and then in a ferric chloride solution,
or other ferric salt solution. For making upper leather, the
hides were previously limed, and if softness and porosity were
desired, the rosin could be omitted.
In 1881, W. Eitner patented a process (Austrian patent No.
6,775) using a mixture of a basic chromic sulphate and ferric
sulphate solution. This process was used in Graz, Austria,
and the product known as "patentleder, marke elefant." By
changing the ratio of the chromic salt to the ferric salt, dif-
ferent gradations of color — from yellow (of the iron) to
gray (of the mixture) and to green (of the pure chrome) —
were obtained. When a mixture of the ferric and chromic
salts was used, the leather was colored black with logwood
alone; when chromic salt alone was used, the leather was
colored black with logwood and an iron "striker." When a
yellow color was not desired in the product, chromic salt alone
was used for tanning. Leather obtained in this way was stuff-
ed, after sammying, with mixtures of train oil, castor oil,
stearine, tallow, mineral oil, etc., with sodium bicarbonate,
soap, borax, casein, etc., as emulsifying agents.
In 1886, John W. Fries, of Salem, North Carolina, pat-
ented a process of tanning (U. S. patents No. 343,166 and
343,167), using ferrous carbonate (or ferrous sulphate), so-
IRON TANNAGE 219
dium carbonate (or sodium bicarbonate), and sulphuric acid.
The skins were tanned first in a dilute liquor for 2 or 3 days,
and then in a more concentrated liquor for the same length of
time. A small amount of liquor might be added. After the
tanning operation the skins were hung in the air to get the
iron oxidized. For currying, he used tallow with a paraffin
oil, lard, or cotton-seed oil ; and later, in his patent No. 343,-
167, he recommended an alcoholic solution of castor oil.
In 1892, Paul F. Reinsch of Erlangen, Bavaria, patented a
process (German patent No. 70,226) using a liquor prepared
by mixing 10 kg. (kilogram) FeCl 3 dissolved in 40 liters of
water, with 4^ kg. crystalline Na 2 C0 3 dissolved in 20 liters
of water, thus yielding a dark brown solution. He called it
ferric chloride-sodium chloride liquor, which he used for mak-
ing different kinds of leather, either alone or in combination
with alum-sodium chloride tannage. In 1912 he obtained an-
other German patent, No. 265,914, on the use of ferric chlo-
ride and magnesium carbonate. He prepared the liquor by
dissolving 1 kg. of ferric chloride in 4 liters of water, to which
was added a suspension of 225 grams of MgCO s in a liter of
water. To this mixture he added a solution of 8 per cent
aluminum chloride. Evidently his idea is to bring about the
required basicity by MgCOs- The A1C1 6 present was probably
meant to help keep the basic ferric chloride in solution.
J. Bystron, and Karl, Baron von Vietinghoff, obtained a
number of German patents, No. 255,320 et seq., in 1911, a
British patent, No. 13,952, in 1912, and two U. S. patents,
No. 1,048,294 in 1912 and No. 1,061,597 in 1913. They em-
ployed nitrogen dioxide (NO2) and nitrogen trioxide (N 2 3 )
for the oxidation of iron. The nitric oxide (NO), from the
oxidation reaction is collected and re-oxidized by contact with
fresh air to N0 2 and N 2 3 , which gases are used again for
oxidation. They thus proposed to utilize the N0 2 -NO-N0 2
cycle, making the oxides of nitrogen virtually catalytic agents
for the oxidation of iron. In British patent, No. 13,952 they
observed considerable precipitates formed in the tan liquor
and on the skin. According to them the presence of large
220 PRACTICAL TANNING
quantities of an acid causes the formation of a highly acid
and not completely insoluble iron oxide in the skin, so that
the leather made is brittle and cannot be stored. In this patent
and also in the U. S. patent No. 1,048,294 they proposed
placing the skin in a ferrous salt solution, and oxidizing the
ferrous iron by passing in NO2 gas from outside or by liber-
ating HNO2 from a nitrate added to the liquor. Thus they
attempt to complete the oxidation reaction and the tanning
operation in a single operation. It is true that HNO2 (from a
nitrate and an acid) has sufficiently high oxidation potential
to oxidize ferrous iron to the ferric state, but in order to oxi-
dize all the ferrous iron into the ferric state completely, the
presence of much acid in the solution and of an excess of
the oxidizing agent is needed. If the oxidation by HNO2 or
oxides of nitrogen is to take place simultaneously with the
tanning operation at the low acidity necessarily present in the
tan liquor, probably there will be much difficulty in getting
all of the ferrous iron completely oxidized. Bystron, in U. S.
patent No. 1,061,597, patented the use of a neutral alkali salt
such as Na2S04 or NaCl for treating the iron-tanned leather.
He claimed that by this treatment a more insoluble basic fer-
ric salt of a light color is formed in the leather, thereby yield-
ing a soft, elastic, and non-brittle product.
In 1917, O. Rohm obtained British patents No. 103,827 and
104,338 for a combination tannage using formaldehyde and
ferric chloride, or formaldehyde and a mixture of ferric chlo-
ride and chromic chloride or aluminum chloride. In his patent
No. 103,295 (not accepted) he mentioned the use of ferric
alum mixed with vegetable tannins to form iron tannate (ink)
for tanning. In his patent No. 103,827 he recommended tan-
ning with formaldehyde in sodium bicarbonate solution, fol-
lowed by a tannage with a ferric chloride solution; a mixture
of ferric chloride and chromic chloride ; a mixture of ferric
chloride and aluminum chloride ; a ferric chloride solution and
then vegetable tannins; or a ferric chloride solution with an
alkaline sulphide. He also mentioned the treatment of the
skin with an iron precipitant, such as NH3, alkalies, or alkal-
IRON TANNAGE 221
ine salts ; or phenols, naphthols, organic carboxylic acids, vege-
table tannins; or soap, sulphide, polysulphide, and the like.
He mentioned that the leather obtained would not become slip-
pery when wet, as is the case with a chrome leather. In his
patent No. 104,338 he stated that the aldehyde tannage could
be advantageously used to follow iron tannage after neutral-
ization, or together with neutralization. When the aldehyde is
introduced with the neutralization after the iron tannage, there
is, according to Rohm's observation, an advantage that the
grain-drawing, so common in mineral tannage, will be pre-
vented. His thought seems to be along the line that since aide"
hyde tannage is carried on in an alkaline solution, the intro-
duction of the aldehyde tannage after the iron will serve also
as a neutralization operation to fix the iron in the pelt. But
since formaldehyde is a tanning agent alone, to what extent
the iron salt has contributed to the tannage it is difficult to tell.
In his German patent No. 306,015 (1918), Emil Kanet in-
troduced an interesting feature in the mode of tannage. He
derived the tanning action by the hydrolysis of a ferric salt.
He treated the pelt at a low temperature with a ferric salt
solution of such a basicity that it would be unstable at the
ordinary temperature; and, after allowing the liquor to pene-
trate the pelt, raised the temperature to bring about hydrol-
ysis. To illustrate : He placed the skins in a basic ferric ace-
tate liquor containing from ^ to 2 J per cent of Fe203, prefer-
ably with the addition of some salt or other electrolyte such as
sodium acetate. After the skins were penetrated by the tan-
ning liquor he transferred them to a fairly concentrated salt
solution at a temperature of from 45 to 60° C, or exposed
them to heat in a warm chamber. The tanning action was
completed in a short time, but the stock was further laid aside
for some time to fix the iron. The acetic acid set free under
the influence of heat can be recovered from the skins by pres-
sure. If a filling material such as flour is used with the tan
liquor, it is, according to him, fixed in the leather with the
basic ferric acetate. Other mineral salts such as chromic salt
can be mixed with the iron. The advantage claimed is that
222 PRACTICAL TANNING
at a low temperature a more basic ferric salt solution can be
used, and that the oxidizing activity of the ferric iron towards
the skins is lessened.
In his Swiss patent No. 75,775 (1918), W. Mensing recog-
nized the ease with which ferric salt in solution is decomposed,
and mentioned the effect of ferrous iron on the skin when the
ferrous salt is present in the tan liquor. He recommended
the use of an excess of an oxidizing agent and patented the
use of a chlorate (Na, K, or Ba) as the oxidizing agent. He
also recommended a preliminary treatment of the skin with
borax or a basic aluminum or chromic salt solution for the
use of a slightly more acid or neutral ferric liquor. Accord-
ing to his idea, the tanned stock should not be washed with
water, but only wrung or pressed to get rid of the excess of
the tan liquor. On drying, the stock is oiled with a mineral
oil, paraffin, or ceresin, and then washed. To avoid reaction
of the iron in the pelt with vegetable tannins, he recommended
fixing the iron by treating the leather with a slightly alkaline
solution before vegetable re-tanning. He advocated the
bleaching of the leather by de-tanning the surface layers by
means of a reducing agent and then an acid. On the whole,
his patent marks a better understanding of the properties of
the iron tan liquor and the process of iron tannage.
Vittorio Cassaburi, in the articles, "Notes on the Tannage
of Skins with Iron Salts," published in the Journal of the
American Leather Chemists' Association in 1919, gave the
results of a series of his experiments, using a basic ferric
sulphate solution (from the oxidation of ferrous sulphate with
a mixture of nitric acid and sulphuric acid) ; a solution of a
mixture of basic ferric chloride and sulphate (from the oxida-
tion of ferrous sulphate by nitric acid and hydrochloric acid) ;
a basic ferric chloride solution, and a basic ferric acetate solu-
tion. He employed a strength of iron liquor containing 1 per
cent of Fe20s on the weight of the pelt in a little over 4 times
the weight of the water as of the weight of the pelt. Accord-
ing to him, 7.88 per cent of Fe20s in the leather on the basis
of the dry weight is sufficient to convert the pelt into leather.
IRON TANNAGE 223
He stated that he had started with a tan liquor having such
a basicity as to correspond to the formula Fe2(S04)s(OH)2
but his iron and basicity determinations of the liquor showed
that the liquor he used was more acid than this, the basicity
of his first liquor (basic ferric sulphate) being only one-half
of this value, and that of his second liquor (a mixture of
basic ferric sulphate and chloride) less than a half of this
value. (We have found that a sulphate liquor having so high
a basicity as to correspond to Fe2(S04)2(OH)2 is too alka-
line for use.) Throughout the course of tanning he strength-
ened the liquor with fresh portions of the strong liquor.
In his work, Dr. Hou devoted much time to the study of
proper methods for the oxidation of the ferrous to the ferric
conditions, and made a careful series of tests on the exact
point of neutralization. All of this work is set forth in his
treatise referred to early in this chapter, so it is hardly nec-
essary to repeat it in this volume. Dr. Hou's conclusions may
best be stated in his own words, showing that iron tan-
nage has possibilities when the processes are conducted along
scientific lines :
The character of the iron tannage seems to lie between that of alum
and chrome tannage. Iron seems to yield a more permanent tannage
(towards water) than alum, but like the alum tannage, iron-tanned leather
does not resist the boiling temperature of water. If we take the critical
temperature as that at which the sample under water begins to shrink or
to draw together under the influence of heat, that point generally lies
between 160° and 175° F. In the case of a re-tanned leather (in fish
oils or vegetable tannins) a somewhat higher test may be obtained; but
in no case can an iron-tanned leather stand boiling, unless a considerable
portion of the tannage is due to chrome as in the case of the chrome-
iron joint tannage.
It has often been reported that iron-tanned leather produces a brittle
grain, and rots on storing, but to do justice to the iron tannage it must
be declared that an iron-tanned leather, properly tanned, is not brittle on
the grain and does not deteriorate on storage. Samples of leather which
have now been kept for more than 10 months show no sign of deteriora-
tion. Sometimes the product obtained is somewhat stiff and "flat," but this
should not be ascribed to the inherent properties of the tannage. The
strength, the fullness, the elasticity, are, in our opinion, a matter of
proper tannage and not dependent upon the nature of the tannage.
As a considerable amount of salt (4 to 5 per cent of the weight of the
pelt) is needed in the liquor, and much of it is formed from neutralization,
it is important to rinse the tanned stock after neutralization to wash off
most of the neutral salts present (NaCl, Na 2 SC>4, etc.) ; otherwise their
presence in the leather may cause dampness or even salt stains or spues.
Iron tannage is much affected by the presence of grease or any imperfec-
224. PRACTICAL TANNING
tions in the skins, and when such is the case, unevenness of color and other
irregularities are liable to show up on drying; hence the necessity of
uniform softening of the pelt and of de-greasing.
Iron-tanned leather generally runs high in ash. The leather often has
a harsh feel, due probably to the presence of a large amount of iron
oxide (Fe 2 3 ) in the leather. On account of this harsh feel it is generally
advisable to give the leather a somewhat heavy fat-liquoring or an oil
treatment. The use of flour, egg-yolk, etc., may be practiced, if desired.
At the present stage of our knowledge it seems that to produce a satis-
factory tannage, at least for a light leather, an amount of iron, calculated
as Fe 2 3 , not less than 4 per cent of the weight of the air-dried sample
should be present.
The iron-tanned leather compares favorably with other mineral-tanned
leather. The red-yellow or brown-red color of the tannage, however, is
for some purposes an undesirable feature. The chemical activity of iron,
forming dark colored compounds in the leather, is another drawback. But
even with all these limitations there is much to be said in its favor. There
are certain classes of goods in which these features are of no consequence
and the saving in the cost of production is considerable. True, there
are difficulties in connection with the tanning operation and subsequent
treatment of the leather — difficulties which in other tannages either do
not exist, or are less serious. But the process, like any other new process,
necessitates a new set of conditions. To summarize, the following main
factors may be mentioned :
I. Completeness in the oxidation of iron and maintenance in its ferric
state by using an excess of a proper oxidizing agent, and by means of an
after-oxidation.
II. Adjustment of proper basicity by the addition of a proper amount
of an alkali, a basicity between the ratio of one OH-equivalent to every
5 equivalents of the mineral acid radical present, and that of one OH-
equivalent to every 3 equivalents of the mineral acid radical present, being
the proper range for tanning.
III. _ Gradual neutralization to be effected so that iron may be uniformly
fixed in the pelt throughout its thickness.
IV. Drying to the crust state before subsequent treatment to minimize
the chemical reactions between the iron in the stock and the substance
employed, which would react with iron to give an undesirable color.
It might be added that the subject of iron tannage presents
a broad and unexplored field, and this study is far from being
exhaustive. Other phases could have been taken up and it is
hoped that this work will serve as an indication for much
that remains to be done.
CHAPTER VIII.
VEGETABLE-TANNED LIGHT LEATHERS
The processes employed in the production of leather with
vegetable tanning materials vary according to the kind of
leather being manufactured, and with the nature of the ma-
terials employed. Time is also an important factor, and
several months may be consumed in the case of sole leather,
while with light leather the operation may be completed in a
few hours. In dealing with these processes the study of
light leathers will be considered first.
Vegetable-tanned sheepskins: Quebracho tannage. — ■
Soft and well-tanned leather is made by tanning pickled sheep-
skins with quebracho extract. This tanning material is used
alone with good results; it is also used in combination with
chestnut and hemlock extracts. It is recommended that for
the quebracho tannage the skins be pickled with formic acid
and salt. When so pickled and carefully tanned, they have
fine, soft grain, and there is no danger or difficulty in dyeing
owing to lime spots. The natural grease should be removed by
pressing the skins while they are in the pickled condition. It
is also advisable to press them after they have been colored
in the first quebracho liquor ; they are then put back into the
liquor and tanned thoroughly. The quebracho liquors should
always contain salt. A quantity of the extract is boiled with
water in a barrel, this forming a stock solution from which
the tan liquors are made and strengthened.
To make the first liquor, add enough of the dissolved
extract to water in a paddle to make a 3 or 4° bk. liquor.
Let the skins turn in this liquor until they have assumed
a uniform color and are well struck with the tan; then
either strengthen the liquor, or pass the skins into a fresh
and stronger liquor of 6 or 8° strength. After several hours
the liquor is strengthened to 10°, and the skins are left therein
225
226 PRACTICAL TANNING
until they are completely tanned. The skins can be taken
out of the paddle after the grain is set, and tanned out in a
drum, thus saving time.
When it is fully tanned, the leather is washed and fat-
liquored with a solution of sulphonated oil or some other fat-
liquor, and dried; or it is dried and fat-liquored after dyeing.
The skins can be tanned by being tacked to wooden strips
or frames, and suspended in the liquor. The tanner must be
careful to avoid drawn grain by having the liquors too strong
at the beginning. The liquor for the fresh skins should not
be over 6 to 8° strength; but as soon as the grain is well
set, the liquor can be strengthened. Colored and embossed,
the skins make fine leather for pocketbooks and bags, sweat-
bands for hats, and other purposes.
Hemlock and quebracho tannage. — In this process the skins
are started in weak hemlock liquor, and then passed into a
stronger liquor composed of hemlock, oak-wood and que-
bracho extracts, care being taken to handle the skins every
day until they are tanned. Hemlock and quebracho extracts
combined form a good tan for sheepskins. The liquor may
be two-thirds quebracho and one-third hemlock. The result-
ing leather is tough, firm, and pliable; and has good color
which is more satisfactory in every way than the color of
hemlock leather.
Hemlock tannage. — Large quantities of sheepskins are
tanned with hemlock-bark extract, and used for various pur-
poses. The tannage fills and plumps the skins, and the leather
has good color on which it is easy to apply dyes. Hemlock-
tanned skins are finished in the natural color of the tan; they
are dyed black or colored, and are finished with a smooth
or an embossed grain for fancy leather purposes.
Pickled skins should be pressed for removal of the grease,
and drummed in warm salt water to soften and open them
out, also to separate and prepare them for the tannage. There
should be considerable salt in the liquors. The tanning is
begun in weak liquor, which is gradually strengthened until
the skins are tanned through. When tanned, the leather is
VEGETABLE-TANNED LIGHT LEATHERS 227
horsed-up to drain, dried, then colored and finished. A mix-
ture of oak and hemlock liquors produces light-colored, well-
tanned leather.
Combination tannage. — A mixture of gambier, alum, and
salt can be recommended for making a soft, durable leather
from sheepskins. The skins are limed and drenched in the
usual manner, and are then placed in gambier liquor in a
paddle. From 3 to 5 lb. of gambier is sufficient for a dozen
skins, according to size and thickness. After the skins have
started to absorb the gambier, from 8 to 16 oz. of alum and
8 oz. of salt for each dozen skins are added to the liquor, and
the paddling is continued until the tannage is completed. The
leather is then washed in warm water to remove the adhering
tan, and then treated with acid fat-liquor, dried, wet-back,
colored or blackened, dried again, and finished.
After the alum and salt are added, it is customary to put
the skins and tanning liquor into a drum, and run a few
hours or until the skins are thoroughly tanned. Some soluble
oil may also be added to the liquor and applied to the leather
toward the end of the tanning process. Excellent leather is
also made by taking the skins out of the gambier liquor when
they are well struck through, striking them out, and then
drumming them in a paste of water, flour, alum, salt, and
either egg-yolk or sulphonated oil, drying, and then coloring.
Quebracho extract may be used in place of gambier, with
equally good results. The color of the tanned leather can
be greatly modified by adding a solution of fustic or other
dyewood to the gambier liquor. The entire process can also
be reversed. The skins can first be drummed in alum and
salt, dried out, and staked, and then re-tanned with gambier.
For glove leather, flour and oil may be added to the alum
and salt liquor, the skins drying out soft and full.
Heavy skins can be tanned with gambier, split, and shaved,
and then re-tanned with gambier, alum, and salt ; they can
also be alum-tawed, sammied, and shaved, and then re-tanned
in a drum with gambier or quebracho. There are numerous
variations of the process, these few suggestions being suffi-
228 PRACTICAL JANNING
cient to give some information about methods which may be
used. After the leather is dry, it can be colored, and, if not
previously fat-liquored, drummed' in acid fat-liquor or an
emulsion of oil and soap, dried, staked, and finished. The
product is a soft and durable leather, which is suitable for
gloves, linings, and various other purposes.
Sumac tannage. — Sumac makes soft, light-colored leather
which can easily be colored and finished in any desired man-
ner. The tannage is done in paddles ; the skins are then dried
and finished. The first liquor is rather weak and mellow ;
and as the tannage proceeds, the liquors are stronger and are
warmed. A mixture of oak bark and sumac is also some-
times used ; and a shorter tannage is obtained by drumming
the skins with the tanning liquor after the grain has been set
in a paddle.
The use of sumac after the regular tanning process is
complete is for the purpose of preparing the leather for
coloring. When the skins are completely tanned, they are
horsed-up over night and are then placed in sumac liquor.
This is prepared by adding water at 122° F. to 25 lb. of
best Palermo sumac. The liquor should be cooled to 90° F.
before the skins are put in, then they should be stirred more
or less and left in over night, drained, set out, and dried.
Sumacking can also be done in a drum. If soft leather is
wanted, the skins can be run in a solution of sulphonated oil
before they are dried. When dry, they should be kept in
storage-rooms for some time before being colored and finished.
Well-tanned leather is made by a tannage of gambier and
sumac. The skins are put into a 10° bk. liquor slightly acid-
ified with acetic acid. After they have been in this liquor for
a few hours they are placed in another and stronger liquor,
and from this they are passed into a third and still stronger
liquor to which acetic acid and oak-wood extract have been
added. From this third liquor the skins are passed into the
sumac bath, and are then oiled and dried out.
The application of an alum or kid tannage to skins tanned
with gambier or quebracho makes fine, soft dongola leather.
VEGETABLE-TANNED LIGHT LEATHERS 229
For 200 average skins, a mixture is prepared from 5 lb. of
alum, 9 lb. of salt, 24 lb. of flour, 10 lb. of egg-yolk or a
corresponding quantity of sulphonated oil and 8 gallons of
water. The alum and salt are dissolved in part of the water,
then the flour is stirred in. The egg-yolk or the oil mixed
with warm water is next added, and the whole mixture is
thoroughly stirred. The skins are drummed with the mix-
ture for an hour, then dried, colored, and finished.
Tanning with alum, sumac, and oak bark. — A soft, light-
colored skin which can be used in the natural color of the tan-
nage, or colored any desired shade, is made by tanning with
alum, Glauber's salt, common salt, sumac, oak bark, nutgalls,
and acid.
The pickle should be removed from the skins by drenching
them with whiting and salt, followed by washings in two
baths of warm salt water. To make the tanning liquor, dis-
solve 6 lb. of alum, 3 lb. of Glauber's salt, and 4 lb. of com-
mon salt in 5 gallons of water; and in another tub, boil 5 lb.
of ground sumac, 3 lb. of oak bark, and 1 lb. of ground nut-
galls, in 5 gallons of water. Mix the two solutions, then
strain while the mixture is hot. A small quantity of formic
acid is added to preserve the color.
The liquor is used lukewarm and the skins are drummed
with it until they are tanned, then allowed to drain 24 hours.
They are next struck out on both sides and oiled with neat's
foot oil, then dried. A solution of sulphonated oil may be
used instead of neat's foot oil; the skins can be drummed in
it, or it may be applied by hand. The skins tan quickly, and
when worked out can be colored any shade or left in the nat-
ural color of the tan. The leather is durable and quite mois-
ture-proof.
Tanning with chestnut extract. — Sheepskins, prepared as
for any other tannage, may be tanned by being hung in chest-
nut liquor, or drummed in liquor made direct from the extract,
or from a mixture of chestnut and quebracho extracts. If
the skins are intended to be colored after they are tanned,
it is best to tan them direct in the extract liquor, and then
230 PRACTICAL TANNING
re-tan them with sumac. Stock to be run in the natural
color is usually struck in the combination liquor, giving the
shade desired. With very thin skins, the main requirement
of the tanning material is that it be clean, bright, and quick
in action. Tanning may be started in a paddle and finished
in a drum, the leather being then dried, treated with sumac,
colored, fat-liquored with acid fat-liquor, dried, and finished.
Tanning with sumac, alum, and salt. — Sheepskins may be
tanned in sumac liquor and then placed in a solution of alum
and salt for one day. Taken out of the latter solution, the
leather is rinsed off, struck out, and oiled with sulphonated
oil, hung up, and dried. Coloring can then be done with
artificial dyestuffs — basic or acid — the skins are again dried,
worked out soft, and finished.
Quebracho-tanned sheepskins. — The pickled skins, being
weighed, are placed in the mill and a solution of 30 per cent
of quebracho extract on the weight of the stock is prepared
at a concentration of 30° bk. To this solution is added 10
per cent of salt on the weight of the stock, and the whole
added to the stock in the mill. The mill is now run for 1-|
to 2 hours, or until the stock is tanned. The plugs being
drawn, water is turned on, and the stock is washed until per-
fectly clean. If desired, washing may take place in a separate
mill, and a new lot of skins run in the spent liquor for
half an hour to utilize the unabsorbed tan. The plugs being
drawn, a new liquor of 25 per cent of quebracho at 30° bk.
with 10 per cent salt will be a sufficient quantity to complete
the tannage. The plugs are then returned, the above liquor is
added, and milling continued for 1-J hours. The washed stock
is now fat-liquored with 1 per cent of anhydrous turkey red oil
at a temperature of 110° F. for 30 minutes, washed again, set
out, shaved, and hung up to dry. When dry, it is de-greased,
buffed if necessary, and colored.
Skivers. — A skiver is the tanned grain side of a split
sheepskin. The skins are split either after they have been
limed or pickled. The grains are then tanned the same as
whole skins with sumac, bark, alum, or some other tannage.
VEGETABLE-TANNED LIGHT LEATHERS 231
Skivers are used in the manufacture of leather goods, for
linings, hat sweat-bands, etc. They can be tanned with any
material which is used in the tanning of sheepskins. Sumac
is in common use ; quebracho extract and quermos and hem-
lock extracts also make good skiver stock. If soft white
skins are wanted, alum is used. Little tanning is required.
It is generally sufficient to get the stock well struck through
with the tanning material.
A good tannage is a mixture of two-thirds quebracho and
one-third hemlock extracts. This produces a light and uni-
form color.
Coloring and finishing are the same as for skins; but
skivers, being very thin, require careful handling to prevent
them from getting torn.
Roller leather. — This leather is made from lambskins
tanned with bark. The qualities needed are level substance,
clear and perfect grain which has no scratches, scars nor cuts,
smooth feel and pliability, with a certain degree of firmness.
Only the best skins should be selected. The leather must be
perfectly smooth on the grain, or the cotton thread used by cot-
ton spinners — who use this class of leather — when it is drawn
between the rolls, one of which is covered with leather, will
keep breaking. As a light color is essential, only clean, light-
colored bark liquors can be used. The natural grease con-
tained in the skins must be removed since the edges of the
leather covering the rolls are cemented together before being
slipped over the roll, and if there is grease in the leather the
cement will not hold.
The preliminary tanning is done in weak bark liquor. The
skins are then subjected to hydraulic pressure in layers be-
tween iron plates, and are sprinkled with sawdust to remove
the grease. They are then taken apart and paddled in a
weak liquor, and drummed in warm salt water until all press
creases have disappeared.
The skins are tanned by being suspended in the liquor,
as a smoother grain is produced in this manner than when
a paddle or a vat is used. The liquor consists of oak bark
232
PRACTICAL TANNING
extract of increasing strength, in which the skins remain 2
or 3 weeks, when they are hung up and dried. When dry,
they are stored away until they are to be finished. The
longer the skins are kept in the dry condition the better they
are when finished.
When the leather is to be finished, the skins are sorted.
Those that are not as perfect as they should be are finished
into fancy leather. The roller skins are then dampened and
shaved. The shaving must be accurate so that the skins shall
be of even substance; however, the skins do not all have to
be reduced to the same thickness, as some of the roller manu-
facturers make three or four different substances. After
shaving, the skins are drummed in sumac solution and then
Figure 64. — Slicker and handle. Figure 65. — Moon-knife.
go back to the tan to receive a stronger liquor. After being
rinsed in water and drained, the skins are struck out on the
flesh with a slicker (figure 64), and tacked out to dry. When
dry, they are taken off the boards and softened, then trimmed
and seasoned with milk and albumen, dried and rolled, perched
by hand with the moon-knife (figure 65), and next re-sea-
soned and glazed. The finished skins are then marked with a
frame on the flesh side and trimmed with a pair of shears.
As every hair must be removed, the skins are wiped over with
a cotton-wool pad to find the remaining, hairs, which are re-
moved very carefully so as not to break the grain. The skins
are then ironed, and sorted into grades and sizes. The proc-
VEGETABLE-TANNED LIGHT LEATHERS 233
esses, of course, are not always followed exactly as outlined,
but are modified as found desirable.
Oak bark makes better roller leather than hemlock, since
it contains less filling matter and produces lighter-colored
skins.
Calfskin leather: Quebracho tannage. — Calfskins for
upper and fancy leather are tanned in numerous ways, and
quebracho extract in solid or liquid form is in common use,
producing a soft, tough leather.
A practical way to tan calfskins with quebracho extract is
carried out as follows : A quantity of the extract is dissolved
in boiling water. Solid extract should be dissolved in a tub
containing a false screen bottom which prevents the extract
adhering to a solid surface. Liquid extract should be dis-
solved in water at 180° F. The solution of extract should
be stirred well and allowed to cool gradually before using.
It is a mistake to chill the extract solution suddenly by run-
ning it into cold liquor. The tannage should be started in a
weak liquor. Having the liquor too strong, and thereby draw-
ing the grain, must be guarded against during the entire
process. The suspension method, by which the skins are not
violently agitated, produces the plumpest and best tanned
leather, especially along the sides and in the flanks. The
skins are tacked to wooden strips with galvanized iron or cop-
per nails, and hung in the liquor.
The first tanning liquor is usually weak, not exceeding 10°
bk. Where pickled skins are being tanned, salt should be
added to the tan liquor, to prevent the acid in the skins doing
injury. As the tanning proceeds, the strength of the liquor
is increased until it reaches 20 to 25° bk. towards the end of
the process. The period required to accomplish the tanning
depends upon the" thickness of the skins, and the strength of
the liquor. It is always advisable to tan slowly, and so get a
fine, smooth grain. When the tanning is completed, the
leather is washed, pressed, and fat-liquored. From 7 to 14
days is usually required.
Another method employs a liquor made of quebracho ex-
234 PRACTICAL TANNING
tract, alum, and salt for the first part of the process, and a
clear quebracho liquor for the second part. Prepare a liquor
by adding enough dissolved extract to water in a paddle to
make a 40 or 50° bk. liquor, and add 1 lb. of alum and 3
lb. of salt dissolved in hot water for every 100 gallons of
liquor. Plunge the liquor well and throw the skins in. Start
the wheel and turn the skins in the liquor for 36 hours or
longer, which strikes them a light oak color; then place them
in the second liquor, which should consist of clear quebracho
liquor. Add enough dissolved extract to the water in the
paddle to make a 6° bk. liquor. Turn the skins 36 hours;
then strengthen the liquor to 10° bk., and continue the turning
for 2 days, or as long as is necessary to complete the tanning.
A mixture of quebracho extract and hemlock extract may be
used in the same manner, also a mixture of hemlock and oak
extract.
When thoroughly tanned, the skins are horsed-up and al-
lowed to drain several hours or over night, and are then
placed in sumac liquor. This is prepared by adding water at
122° F. to about 25 lb. of sumac, using the liquor at 90° F.
The skins are thrown in and stirred more or less, and left in
over night, then drained, set out, and either fat-liquored and
dried, or dried without fat-liquoring.
Gambler tannage. — Calfskins can be made into fine, soft
leather by tanning with gambier. The skins, having been
limed and drenched, are put into a gambier and sumac liquor
of about 10° bk. The liquor should be slightly acid to pre-
vent thin leather, acetic acid being used to acidify it. After
the skins have been in this liquor from 6 to 10 hours, they are
placed in another liquor in a paddle, made up with gambier
to a strength of 20° bk., 1 quart of acetic acid being added for
each 5 dozen skins. The skins remain 10 hours in this liquor.
The third liquor should be made to a strength of 35° bk.,
and the same quantity of acid added as before. It is also
beneficial to the quality of the leather to add, after the skins
have been in it an hour, a pail of oak-wood extract.
When the tannage is completed, the leather is put into a
VEGETABLE-TANNED LIGHT LEATHERS 235
sumac liquor for several hours or over night, then drained,
set out, and either fat-liquored, or dried without being fat-
liquored. The sumac gives a good bottom for the subsequent
dyeing.
A gambier process different from the foregoing method is
applied in the following manner: The skins, bated and
washed, are run in an old 12° bk. liquor until they are colored;
and are then put into fresh gambier liquor, being hung therein
for 12 days, during which time the liquor is gradually
strengthened every day. The skins are then pressed and
shaved, or split as they may require. They are next run
in a 12° bk. liquor for a day or two before they are placed in
a 34° bk. fresh gambier liquor for 16 days more. Salt should
be added to the liquors to aid the tanning and keep the liquors
from getting sour. Light skins, of course, require less tan-
ning than heavy ones, the process described being suitable for
heavy kangaroo skins and calfskins.
The tanned leather is washed, set out on a machine, oiled
or fat-liquored, and dried at a moderate temperature. When
dry, the leather improves in texture by being kept in the
crust some time before it is finished. It can also be passed
through a sumac liquor after the gambier tannage is com-
pleted. Drumming in a solution of alum and salt clears the
grain.
A good method of tanning is accomplished in vats or tubs
with paddles. In the first vat the skins are colored and
handled; in the second liquor they are tanned until they are
ready to be skived or split; and in the third liquor they are
tanned out after skiving. At the start, the liquor should be
4 or 5° bk., and gradually strengthened as the tanning pro-
ceeds, until the skins are fully tanned. Into the water in the
vats should be put 6 or 7 pails of gambier liquor standing at
75° Be. in the pails or stock solution, also 4 or 5 pails of sedi-
ment gambier after the boiling. When the liquor is ready,
put the skins in and run the paddle 30 or 40 minutes to en-
sure good color on the grain. The liquor should be strength-
ened twice daily — morning and evening — with 2 or 3 pails of
236 PRACTICAL TANNING
gambier and sediment, and the paddle run 3 times daily, 10
or 15 minutes each time. At the end of 4 or 5 days the skins
should be taken out of the liquor and struck out on the flesh,
and then put into the second or stronger liquor. By running
the paddle 3 times each day, and by adding 3 pails of 75° Be.
gambier liquor each day, the skins become well struck through
in about 14 days. Then set them out on the flesh side, skive
them, and put them into the finishing liquors of 12 to 15° bk.
for 7 days. Each day the liquor should be strengthened with
2 pails of gambier, and the wheel run 15 minutes each time;
one pail of salt should be added to the liquor each week. The
final tanning can also be done in a drum.
After the leather is fully tanned it should be cleared by
drumming with alum and salt, oiled, and dried. It is then
dampened, run in warm water and shaved, after which it is
fat-liquored, set out, dried again, dampened, and colored.
Another way to treat the skins is to wash them after tan-
ning, then fat-liquor and dry, shave, and mill in sumac, and
then color. Good leather is also made by giving a light fat-
liquoring after tanning and washing, drying the skins, col-
oring, and then giving them the second application of fat-
liquor.
Dongola tannage. — Gambier, alum, and salt make what is
known as dongola leather. There are many modifications of
this process. Fine leather is made by tanning the skins first
in gambier or quebracho liquor, and then giving them an alum
and salt re-tannage. For 200 average skins, a mixture is pre-
pared of 5 lb. of alum, 9 lb. of salt, 24 lb. of flour, 10 lb. of
egg-yolks, or a corresponding quantity of sulphonated oil, and
8 to 10 gallons of water. The flour is made into paste with
cold water. The alum and salt are dissolved in part of the
water, and the flour paste is slowly stirred into the solution.
The oil or the egg-yolk mixed with warm water is next added,
and the whole mixture thoroughly stirred. -The tanned skins
are drummed with this mixture one hour, then dried, colored
and finished, thus making soft, durable leather.
This mixture may also be used on untanned skins as they
VEGETABLE-TANNED LIGHT LEATHERS 237
come from the bate or drench. They should be drummed
with it, dried, kept in crust some time, then wet-back and
tanned with chrome liquor, the result being soft, durable
leather.
The combination tannage of gambier, alum, and salt can
also be applied in the following manner: The bated and
washed skins are placed in gambier liquor in a paddle. From
3 to 5 lb. of gambier are used for one dozen skins. After they
have started to absorb the gambier, from 8 to 16 oz. of alum
and 8 oz. of salt are added to the liquor, for each dozen skins,
and the paddling is continued until the tannage is completed,
which takes from 18 to 36 hours. The leather is then washed
in warm water to remove the adhering tan, next fat-liquored
with acid fat-liquor, dried, wet-back, colored, dried again,
and finished. After the alum and salt have been added it is
customary to put the skins, together with the tanning liquor,
into a drum and run them for a few hours or until thoroughly
tanned. Some soluble oil may also be added to the liquor and
applied to the leather toward the end of the tanning process.
Excellent leather is also made by taking the skins out of the
gambier liquor when they are well struck through, striking
them out and then drumming them with a paste of water,
flour, alum, salt, and either egg-yolk or soluble oil, drying, and
then coloring them with a basic dye and titanium-potassium
oxalate.
The color of the leather can be modified by adding a solu-
tion of fustic or other dyewood to the gambier liquor, and
the entire process may be reversed. The skins may be first
drummed with alum and salt and then tanned with gambier.
Heavy skins may be tanned with gambier, split and shaved,
and then re-tanned with gambier, alum, and salt. After the
leather is dry, it can be colored with acid or basic dyes ; and,
if not fat-liquored immediately after tanning, drummed with
acid fat-liquor or with an emulsion of oil and soap, staked
and finished.
Velvet and suede leathers. — These leathers are produced
from almost all kinds of skins, and there are various ways
238 PRACTICAL TANNING
of making them. The skins intended for this purpose are
worked through the beam-house and tanned expressly for this
finish, but how to get such leather out of a skin which was
tanned in bark or some other vegetable tannage is an entirely
different matter. The skins are sorted, and those which have
poor grain and other imperfections are thrown aside. When
there is enough to make a batch of 10 or 20 dozen, they are
washed out with warm water and cleansed. The surplus
water is then struck out, and they are snuffed on the wet wheel.
After this has been done, they are re-tanned in a light solu-
tion of sumac, which also acts as a mordant for the coloring.
The skins may be colored in a tray or wheel after which they
are fat-liquored and dried. They can be washed out, re-
tanned, then snuffed, colored, and fat-liquored, dried, staked,
and ironed. Care must be taken that the iron is not too hot
or it will scorch the nap and make it shiny. If rolled in-
stead, the skins should be rolled on the unfinished side which
is simply to flatten them out.
Another way is to emery the skins dry first on regular buff-
ing wheels. Then they are treated as suggested above; but
these skins never have such a close nap as those that are wet-
wheeled.
When velvet or suede leather is to be made from sumac
or extract-tanned skins, the goods are fluffed on the flesh
side, and the grain receives a thorough grounding or buffing
on a buffing wheel. Another method is to stake them lightly
and then to buff lightly on a buffing machine. At the begin-
ning of the dyeing operations the skins are run in the paddle
or drum for 15 minutes in lukewarm water; they are next
treated in a weak acid bath — 0.25 per cent or less of sulphuric
acid — and run in this for 20 minutes to clear them. The
leather is rinsed and given a light re-tannage of 1 to 1| per
cent of sumac extract in the drum, and is then colored.
Russia calf. — As the skins come from the bate they should
be in a very open and flaccid condition. They are tacked on
sticks and suspended in the gambier liquor vats. This liquor
is made from matt gambier to which, for each 300 lb. about
VEGETABLE-TANNED LIGHT LEATHERS 239
50 lb. of liquid chestnut-oak bark extract is added. The
strength of this liquor should be about 35° bk., so that it may
be used to strengthen the liquor in the vats or diluted for new
liquor. The first liquor should stand at 18° bk., and should
gradually be strengthened so that at the end of 3 days it
should still stand at 18° bk. At the end of this time the skins
are removed from the sticks and thrown into the first handler
liquor. Each day thereafter they are passed forward through
a series of stronger liquors until tanned. Calfskins usually re-
quire 6 days in the handlers, whereas kips or heavy calf re-
quire 8 liquors. The barkometer of the first handler should be
about 20°, while each succeeding liquor should be slightly
stronger until the final handler, which should stand at 30°.
When the skins are removed from the last handler they are
given a slight washing, pressed, and shaved, and are then re-
turned to the yard for bleaching and re-tanning.
Bleaching. — Either 300 calf or 150 kips are placed in the
drum and washed for 10 minutes with running water. Twen-
ty-five gallons of water containing 5 lb. of borax is now in-
troduced, the drum run for 15 minutes and the skins again
washed in running water for 20 minutes. Add 25 gallons of
water containing 35 oz. of concentrated sulphuric acid to the
skins in the drum, and run for 30 minutes. The stock is
finally rinsed for 20 minutes in running water, and horsed-up
to dry.
Re-tanning with quebracho. — Make up a fresh quebracho
liquor standing 8° bk. and introduce the stock — 600 calf or
300 kips constituting a pack — run the wheel at half -hour in-
tervals during the day, gradually raising the strength until it
reaches 12° bk. The time of treatment should be 4 days for
skins and about 6 days for kips.
Drumming with sumac. — After the skins are pulled from
the paddle they are divided into 3 packs. Each pack is
washed with running water for 5 minutes and excess of water
allowed to drain off. Then half fill a barrel with water, add
32 lb. of sumac, boil, cool, and make up to 50 gallons with
water. Mix well, and filter 25 gallons through gunny cloth
240 PRACTICAL TANNING
into a clean barrel. Make up the filtered liquor to 50 gallons,
add this to the contents of the drum, run 30 minutes, wash,
and fat-liquor. The fat-liquor should consist of a mixture
of moellon degras, neat's foot oil and soap. They are then
hung up to dry, given a second fat-liquoring and again dried.
Vegetable-tanned kangaroo leather: Quebracho extract
tannage. — In the tanning of vegetable-tanned kangaroo
leather, quebracho extract is used, also a combination of this
substance with gambier is sometimes employed. When que-
bracho extract is used, the required quantity is diluted with
water in a barrel to form a stock solution from which the tan
liquor is made and strengthened. The first tanning liquor is
rather weak, about 8° bk. The pickled skins are suspended
in this liquor, which should contain some salt, and as the tan-
ning progresses the strength of the liquor is increased until
it is about 20°. The time required for tanning depends upon
the thickness of the skins and the strength of the liquor, and
ranges from 3 or 4 days to 2 weeks. Salt should be present
in the liquor to prevent excessive plumpness of the fibers.
A tannage with quebracho extract, salt and alum produces
full, well-tanned leather. To every 100 gallons of quebracho
liquor of 4° bk. strength add, while the liquor is warm, 2 lb.
of alum and 4 lb. of salt, and plunge the liquor well. At the
end of 36 hours the skins are ready for the second liquor.
Heavy skins may remain in the first liquor for 48 hours. The
second liquor consists of quebracho of 6° strength, gradually
strengthened until the skins are tanned throughout. When taken
from the liquor, the leather is rinsed in warm water, fat-liquored
and dried, then moistened, shaved, colored, and finished.
When quebracho and hemlock extracts are combined, the
proportions should be 66 per cent of the former and 33 per
cent of the latter. The tannage is begun in weak liquor, which
is strengthened as tanning proceeds until the goods are tanned
throughout. When the leather is taken out of the liquor it is
improved by drumming in a sumac liquor for an hour or two
before drying it out.
Gambier and sumac tannage. — Kangaroo skins may be
VEGETABLE-TANNED LIGHT LEATHERS 241
struck through by being run in a paddle in gambier and sumac
liquors of 10° bk. strength. There should be sufficient acidity
in this liquor to keep the skins plump, they being tanned after
bating and washing, without pickling. It is better to add a
quart of acetic acid for 50 skins. After running in this liquor
for a few hours, the skins are passed into a gambier liquor of
20° bk., to which acetic acid has been added. Formic acid
or butyric acid could be used with equally good results.
The skins remain about 12 hours in this second liquor. The
third liquor should be made up to a strength of 35° bk., and
the same proportion of acid added. A small quantity of oak-
wood extract added helps to make well-filled-out leather.
When well struck through the skins are ready for the sumac
bath. This is prepared in a paddle-wheel by adding water at
125° F. to 25 lb. of best sumac and cooling down the bath to
90° F. before putting in the goods.
After lying in the sumac liquor over night the skins should
be horsed-up and drained, fat-liquored, and dried ; and when
thoroughly dry, they may be dampened, shaved, and dyed
black. The leather should be soft and well tanned. Good
leather is also made by tanning the goods in a liquor made up
of 6 lb. of gambier, 2 lb. of salt, 1^ lb. of alum, 1 lb. of sodium
sulphate, and ^ oz. of picric acid for a dozen light skins. Boil
the gambier separately, as well as the other ingredients, and
then mix the two solutions. The tanning liquor can be given
to the skins in a drum, 1 gallon at a time, and drumming con-
tinued until the goods are tanned throughout. The skins need
not be pickled, but are tanned after bating and drenching.
Hanging them in the liquor is also a good way to tan them.
After being fully tanned, the leather should be drained, rinsed,
pressed, and treated with acid fat-liquor, then dried, moist-
ened, dyed, and finished.
Other tannages. — Sometimes skins which have been tanned
with gambier or with quebracho are re-tanned with alum, salt,
and soda, then fat-liquored and dried. The entire tanning
process can be carried out in a drum. This produces a soft
dongola leather.
242 PRACTICAL TANNING
Another form of dongola tannage consists of tanning the
skins first with gambier, then giving them a sort of kid tan-
nage in a drum; 100 medium skins, pressed from the tan,
being given 2 lb. of alum, 5 lb. of salt, 12 lb. of flour, 5 lb.
of egg-yolk, \ pint of olive oil, and 6 gallons of water. The
alum and salt are dissolved in 2 gallons of water and the flour
is next carefully stirred in. The other ingredients are then
mixed with warm water and thoroughly stirred in. The skins
are drummed with the mixture until they have absorbed it,
when they are rinsed off, struck out, and dried.
A combination of gambier, flour, and sulphonated oil, thor-
oughly mixed and made into a sort of paste, also makes ex-
cellent leather. No subsequent fat-liquoring is necessary.
One hundred medium skins free from acid require 50 lb. of
gambier, 6 lb. of salt, 2 lb. of alum, 12 lb. of flour, 3 or 4 lb.
of oil, and 6 gallons of water. The gambier is boiled and cooled
and the other ingredients are added. When dry, the skins
are dampened, shaved, dyed, dried again, staked, and finished.
Vegetable-tanned side leather. — In the manufacture of
leather of various kinds from hides and kips which are finished
on the grain side, various processes of tanning are em-
ployed. Hemlock bark and hemlock extract are used ; also gam-
bier, chestnut and quebracho extracts, and other extracts and
tannin-yielding materials. Quebracho extract is largely used
alone, but it is also combined with hemlock and chestnut ex-
tracts. Hides are also not infrequently started in quebracho
liquor and re-tanned with some combination of extracts. Gam-
bier is one of the staple tanning materials. It makes soft and
tough leather which is readily colored and finished in any de-
sired manner. The tanning with gambier and extracts is
usually done in vats that are provided with paddles by which
the liquor is stirred; pits or vats in which the hides are sus-
pended are also used. The less agitation and pounding hides
are subjected to during tanning the fuller and plumper the
finished leather will be, especially in the flanks and along the
sides. A common method of tanning consists of treating the
hides with hemlock bark liquor until they are struck through,
VEGETABLE-TANNED LIGHT LEATHERS 243
then splitting them and re-tanning the grains with gambier
and sumac.
Tanning with hemlock and quebracho extracts. — One of the
best combinations of extracts which a tanner can use is a mix-
ture of quebracho extract and hemlock liquors. Hemlock
is a rather harsh tannage when used alone, and quebracho is
therefore frequently used with it, the result being soft, pliable
leather of good color. Quebracho also hastens the tanning
and reduces the cost.
The hides are limed, bated and washed, and are then sub-
jected to tan liquors, consisting of about two-thirds quebracho
to one-third hemlock. This tannage can be used for tanning
almost all varieties of leather.
The color is fair and uniform, and the reduction of time
consumed by the process is about a third of that required where
bark liquors and "layaways" are used. The leather is readily
colored with little or no bleaching. When hemlock bark is
not obtainable, extract can be used in place of the bark liquor.
The sides are first suspended in a weak coloring liquor for
about 24 hours. They are then taken out and placed in a
liquor of a strength of 10° bk. As the tanning progresses,
the liquor is strengthened each day until it is about 30°. The
tanning should not be hurried by using strong liquor, as this
makes harsher and less desirable leather than a slower tannage
in weak liquor. When the sides have become well struck
through with the tan, which takes about 20 days, they are
pressed and split. The grains are then re-tanned with hem-
lock and quebracho liquor, or with gambier and sumac. A
small proportion of sulphonated oil may be added to the re-
tanning liquor with benefit to the leather.
Tanning with quebracho extract. — This extract is used at
present by tanners of sheepskins as well as by those of sole,
upper, and other heavy leathers. On sides, quebracho extract
is an admirable substitute for the higher-priced gambier, pro-
ducing fine grain, soft texture, and firm feel. On patent
leather it gives a pliability which prevents cracking after the
varnish is put on.
244 PRACTICAL TANNING
The extract made from the wood of the quebracho tree is
different from all other known tanning extracts, as it will not
turn sour. In addition to this, it is a comparatively clean ex-
tract, that is to say, it contains a higher percentage of tan to a
given density than any other of the well-known extracts. In-
asmuch as it has little or no tendency to ferment, quebracho
is extremely useful for controlling the acids in tan yards,
which tend to go sour.
Quebracho extract, therefore, is not itself a plumper, and
if it is used on leather which has not been properly plumped, is
likely to tan the outside of the hides quickly and thereby pre-
vent the penetration of the tan to the inside, the result being
cracky leather not properly filled. If, however, hides are
plumped before they are placed in quebracho liquor, this ma-
terial will penetrate, fill, and produce tough, pliable stock of
light color.
An important point to be observed in using quebracho ex-
tract is that it must be thoroughly dissolved. Solid extract
should be boiled in a tub containing a false screen bottom,
which prevents its adhering to a solid surface. The liquid
extract should be dissolved in water at 180° F. The result-
ing solutions from both grades of extract should then be
stirred well and allowed to cool down gradually before being
used. It is a great mistake to run hot quebracho liquor into
cold vat liquors, or in fact to chill any extract liquor suddenly.
The sediment that remains in the cooling tub may be worked
up with fresh water on a tail leach or elsewhere. A great
deal of the successful use of quebracho in the vats depends
upon the proper method of dissolving it, and it is much better
that such precipitation as takes place should go on in the cool-
ing tub rather than on the leather.
Tanning with gambier, sumac, and oak extract. — Where a
soft well-tanned leather is required, which can be colored any
shade or dyed black, a tannage with gambier, sumac and oak
extract may be used with satisfactory results. The hides
should preferably be split out of the lime and the grains then
bated and washed. A liquor composed of gambier and sumac
VEGETABLE-TANNED LIGHT LEATHERS 245
of about 10° bk. is prepared in a paddle. After the grains
have been in this liquor for 5 or 6 hours, they are put into a
gambier liquor of 20°, to which a quart of acetic acid for
40 small grains has been added. Tanning may be accom-
plished by suspending the goods in the liquor, by using a pad-
dle or by drumming after the grains have been well struck
with the tan.
The third liquor should be made up to a strength of 35°
bk., and the same proportion of acid added. After the grains
have been in this liquor for 3 hours, a few pails of oak-wood
extract should be dissolved and added. The tanning should
continue until the goods are tanned throughout. When this
has been accomplished, the leather is drained and then treated
with sumac in a drum or a paddle.
A sumac liquor is made up in a paddle by using 25 lb. of
best sumac in water heated to 125° F., the liquor being cooled
down to 90° F. before the skins are put in. The leather may
be turned in this liquor several times and left in over night,
or drummed with it two hours ; it is then drained, rinsed off
and dried or fat-liquored, dried, colored, dried again and
finished.
Equally good results may be obtained by using quebracho
extract in place of gambier. In the last stages of tanning,
if a drum is used, some sulphonated oil may be added to the
liquor. This helps in getting leather dried soft and pliable,
and reduces the amount of fat-liquor to be given later on.
The sumac for one dozen sides may be made from 2 pails of
sumac scalded in 20 gallons of water, and used at 90° F. The
leather may be drummed in the liquor 2 hours, piled down 24
hours, drummed again 2 hours, rinsed off, and dried.
Tanning with gambier. — The sides are started in weak
liquor, which is gradually strengthened by the addition of
fresh gambier until it becomes fairly strong towards the end
of the process. Common salt serves a useful purpose in
gambier tanning, as it assists in making soft leather, in has-
tening the tannage, and preventing contraction of the leather
fibers. Acetic acid also should be added to gambier liquor
246
PRACTICAL TANNING
to prevent thin, papery leather. It is well for the tanner to
divide his tanning liquors into three portions : In the first
the hides are colored ; in the second the tanning goes forward
until the leather is ready for splitting; and in the third the
re-tanning after splitting is accomplished. At the beginning
Figure 66. — Union splitter. Formerly much used for furniture and
automobile leather, but now replaced by band-knife machine.
the liquor may be 4 or 5° bk. It should be strengthened twice
each day, the quantity of fresh liquor added depending upon
the size of the vats and the strength of the liquor at the start.
No exact rule can be laid down, as the individual tanner must
decide this and other problems. The tanning should always
go steadily forward until the hides are tanned throughout,
when the leather should be split, re-tanned, and fat-liquored.
Combination process. — A tanning process in which hem-
lock, chestnut wood, and quebracho extracts are used for
VEGETABLE-TANNED LIGHT LEATHERS 247
tanning, and quebracho and gambier for re-tanning, is car-
ried out in the following manner: The hides are hung on
sticks in a 7° bk. hemlock liquor, and are handled each day
for 3 days, the liquor being strengthened up to 10°, and finally
up to 12°. After having been in the 12° liquor 24 hours, the
sides are passed into a 16° combination liquor, made of chest-
nut-wood extract and quebracho extract. This liquor is grad-
ually raised to 20°, the process requiring from 14 to 16 days.
The sides are then pressed, split, and tanned. The re-tanning
liquor is made of quebracho extract and gambier, 3 parts of
the former and 1 part of the latter; and the strength 26° bk.
The grains are drummed an hour in this liquor, then left in
piles 24 hours; drummed again for an hour; piled down for
24 hours; then washed and finished. This is a good tan-
nage for many varieties of leather, shoe upper, bag, case, etc.
As described, it is most suitable for large, heavy hides.
Pressing and splitting. — Before leather is split it is pressed
to rid it of surplus liquor and to put it into good condition for
splitting, which may be done on the union splitter (figure
66) or on the belt-knife machine. Considerable moisture
should, however, be left in it. When pressed too dry, the
leather must be milled with weak liquor to prepare it for the
strong re-tan liquor, and this milling pounds the grain and
makes it loose and "pip e Y-"
When there is considerable moisture in the grains they do
not need to be milled in weak liquor, but can be put at once
into the re-tan liquor. The more moisture there is in the
grains the better the results.
Re-tanning with gambier and sumac. — Leather that has
been tanned in hemlock liquors, no matter what the finish may
be, is much improved by being re-tanned with gambier and
sumac. Re-tanned in this way, the flanks are made fuller and
firmer, the fibers are slightly contracted, the harsh effect of the
hemlock is toned down, the leather is given a smooth feel, and
the color is less liable to fade. The leather is tanned with
hemlock and then split.
The re-tanning is effected in a drum, being thus accom-
248 PRACTICAL TANNING
plished in less time than in a vat. A good re-tanning liquor
for harness and other kinds of leather is prepared in the fol-
lowing manner : Boil 250 lb. of gambier in 80 gallons of water ;
and when the solution is fairly cool, skim off all foreign
matter. Ten gallons of this liquor is sufficient for 30 aver-
age sides. This quantity is put into the drum, together with
the leather, and 2 gallons of dry sumac are added and as much
water as needed to make the leather wet without dripping.
Run the leather in this liquor at least 30 minutes. The sides
should then be packed in boxes by doubling the flesh side out-
ward, and left in that condition for 10 or 12 hours.
They should next be scoured or washed, and treated in the
usual way of coloring, fat-liquoring, etc., according to the
kind of leather and the finish desired. Gambier and sumac
used as described improve the leather greatly, and the expense
of their use is repaid by the improved quality. Bark-tanned
and extract-tanned leather may be re-tanned with gambier and
sumac in the following manner : Two pails of Sicilian sumac
are boiled 15 minutes in 40 gallons of water, and the resulting
liquor is allowed to stand over night. On the next day, 12| lb.
of gambier is boiled until dissolved, and this solution, together
with 10 lb. of salt, is added to the sumac liquor. There
should be 50 gallons of the liquor, and it should be used at
80° F. The leather is run in it one hour, then left in piles
24 hours, rinsed off, and fat-liquored. Before being re-tanned,
the leather, after it has been split and shaved, should be
washed for a half -hour in warm water containing 3 lb. of po-
tassium carbonate in 50 gallons of water. It is next drained
and washed, and then re-tanned.
Re-tanning grains with sumac. — Hemlock-tanned and com-
bination-tanned leather, after it has been split into grains and
splits, is benefited by a re-tannage with sumac. The sides are
taken out of the last tan liquor and allowed to lie in a pile
48 hours. They are then pressed or put through a wringer
to force out the surplus liquor. Some tanners run their leather
through a splitting machine with a corrugated gauge • roll,
VEGETABLE-TANNED LIGHT LEATHERS 249
which makes pressing unnecessary. Leather that has been
pressed usually shows some marks, and to remove these it is
jacked on a stoning-jack (figure 67).
Splitting is the next operation, and the grains are then re-
Figure 67. — Iron frame stoning-jack.
tanned with sumac in a drum. This re-tanning is very bene-
ficial to the leather, making it of finer texture and color, also
rendering it capable of taking better and more uniform
coloring.
The sumac liquor is prepared by scalding 2 pails of sumac
with 20 gallons of water heated to 125° F., and allowing it
to steep some time before using it. When the liquor is cool
it is ready for use, this quantity being sufficient for one dozen
medium sides. The leather is drummed an hour in this liquor.
It is then placed in smooth piles for 24 hours, when it is
drummed again with sumac liquor the same as before, then
again piled down for 24 hours. The next operation is dip-
ping the leather in warm water to wash off the sumac, and
then scouring or setting it out and finishing it according to
the finish desired. It can be dried and then fat-liquored later.
250 PRACTICAL TANNING
The splits for flexibles or Goodyears are trimmed and put
into a drum, together with tan liquor of 6° bk. strength, and
drummed one hour, which opens them so that they will take
the re-tanning liquor. Re-tanning can be done in a drum in
about 6 days, the splits being drummed in a strong liquor 2
hours each day and left in piles the remainder of the time.
This operation is repeated daily for 6 days, when the splits
will be fully tanned and in better condition than when they
are drummed continuously.
Gambier, hemlock extract, and alum make a good re-tan-
nage for hemlock-tanned leather. The proportions of gam-
bier and hemlock should be equal parts of each, the strength
being 25° bk. Twenty-five sides should be given 4 pails of
the liquor and 4 lb. of alum dissolved in 2 gallons of water.
The leather is run with this liquor for an hour, then piled
down over night and hung up the next morning to dry. When
dry, it is fat-liquored, colored, and finished.
A combination of 75 per cent of quebracho and 25 per
cent of gambier is recommended for re-tanning grains for
upper leather. One pint of sodium bisulphite added to each
3 gallons of re-tanning liquor causes the liquor to penetrate
more quickly into the leather. The strength of the quebracho-
gambier liquor should be from 24 to 28° barkometer.
Any of the foregoing processes may be used in the re-
tanning of leather for colored and black upper stock, dull
or bright grains, and imitation kangaroo; also for bag and
case leathers.
Tanning sealskins. — Raw sealskins come to the tanner in'
a freshly salted condition, and are, broadly speaking, divided
into two classes : "small" or "white-coat seal" and "large" or
"cow seal."
The former seals are principally used for making levant
grain leather, and the latter for walrus grain, though a grain
similar to the latter is frequently produced on the small seal
and likewise the levant grain on cow seals. As the processes
differ somewhat in obtaining the different grains, it is neces-
sary to describe them separately.
VEGETABLE-TANNED LIGHT LEATHERS 251
Levant grain. — The skins, when received by the tanner, are
covered with salt and are very greasy. A convenient pack
of about 25 dozen is placed in the soak pits. The water in
the pits should not be too cold, and during the winter there-
fore it is necessary to warm it a little.
After remaining in soak for a day, the pack is hauled-up
and fleshed over a beam. As much of the loose blubber and
grease as possible is removed by the beamster. The skins are
then put into a fresh soak and remain in it 48 hours, when
they are again scraped over the beam, this time on both flesh
and hair sides. It will be found, owing to the greasy nature
of seals, that the beamsters have difficulty in handling their
knives, but this is readily overcome by occasionally rubbing
their hands with sawdust.
The skins are now ready for liming. White lime alone
should be used, as it has been found to produce the best re-
sults. Sodium sulphide and lime produces pipey grain, but
arsenic and lime yields a soft and silky grain.
The time required for liming varies according to the
weather, in winter 21 days being needed, while in summer
not more than 16 days are required. The extremely greasy
nature of the skins make it necessary to give them this long-
liming. To produce a' firm leather with the requisite hard
grain it is necessary to keep the limes as fresh as possible ; old
and stale limes make leather which is tender and has a soft
grain.
The skins are unhaired on the beam; care being taken to
.rid them of the young hair, which is sometimes difficult. After
unhairing, the superfluous lime is removed by washing in a
wheel. When the water running off is quite clear the skins
are ready for puering or bating.
Good results are obtained with Dennis "puerine," or with
oropon. The skins should be brought down fairly low, and
a good guide to determine when they are low enough is to
take one out occasionally and pinch it between the forefinger
and thumb. The process has gone far enough when a de-
cided impression is left on the grain. From 2 to 6 hours
252 PRACTICAL TANNING
should bring them down, though large skins require longer
treatment. The skins are next scudded over a beam, slate
knives being usually used for this, which is an important
operation as it removes any free lime or lime salts in the skins.
After scudding, the skins should be thrown into a bran
drench and left in for 5 or 6 hours. They are then rinsed
in warm water and tanned.
Quebracho extract and sumac are employed for tanning the
skins. A cube of solid quebracho extract is dissolved in a
barrel of boiling water. This constitutes a stock solution.
A 10° bk. solution of this extract is taken and drummed, to-
gether with the skins, in a closed wheel for an hour, sufficient
liquor being used to cover the goods. This sets the grain.
The skins are then put into a paddle containing about a 12°
liquor, and remain in it until they are tanned, the strength of
the liquor being gradually increased. Tanning should be com-
pleted in a week, which can be tested by cutting off a small
piece and observing whether the tan liquor has entirely pene-
trated the middle of the skin, leaving no white streak. When
tanned, the skins are drummed for 2 or 3 hours with a liquor
made of a half bag of sumac and a few pails of liquor. They
are then struck out on a machine and hung up to dry. When
quite dry, they are taken down and struck out either by hand
or by machine, using hot water to soak them in; then they
are hung up for part drying. Such edges as dry out
should be re-dampened with a sponge before re-setting the
skins on a table. After this re-setting, the skins are ready
for blacking.
Walrus grain seal. — The large sealskins generally used for
this kind of work are soaked in the manner already described.
In liming them, however, a pound or two, according to the
size of the pack, of sodium sulphide is used with lime. From
10 to 16 days is enough liming for this class of work.
When unhaired, the skins are washed in water and bated ;
then taken out and drummed in warm and fairly strong liquor,
which contracts the grain, thus forming the well-known walrus
grain. The subsequent tanning is effected in a paddle, and
VEGETABLE-TANNED LIGHT LEATHERS 253
when tanned, the skins are hung up, dried, blackened, grained,
and seasoned.
Heavy skins are split out of the lime on a belt-knife ma-
chine. The substance of the grains and splits varies accord-
ing to the requirements of the market. The grains are fin-
ished into patent or enameled leather, and also for bookbind-
ings and fancy leather goods. Two thin middle splits and
one rough split can, as a rule, be made from each skin; and
the "linings" are then usually thrown back into the limes for
about two days, with one handling, to get rid of as much
of the grease as possible. The linings are then washed in tepid
water, slightly acidified with acetic acid to neutralize any
hardness.
The split skins are bated, drenched, and slated out of warm
water, and are then ready for tanning.
In addition to the process of tanning with quebracho and
sumac, already described, sealskins may be made into good
leather by tanning with gambier and sumac, the liquor at the
beginning being about 10° bk. strength. Care must be taken
to have plenty of acid, otherwise the skins will fall, and will
be flat and papery when finished. After running in this weak
liquor for about 6 hours, the skins are passed into a 20° liquor.
It is well to add about a quart of acetic acid for every 5 dozen
grains or linings. The goods remain in this liquor about 7
hours.
The third liquor should be made up to a strength of 35°
bk., and about the same amount of acid mentioned above
should be added. It will also help to fill out and improve the
goods if a pail of oak-wood extract is added to the liquor after
the skins have been running in it half an hour. If this has
been properly carried out, the goods will be struck through,
and should be horsed-up and allowed to drain ready for
sumacking.
This is best done in a vat, although a paddle is sometimes
used. This bath is prepared by adding water at about 125°
F. to about 23 lb. of best Palermo sumac. Cool down to
86° F. ; enter the goods and haul-up once or twice, warming
254 PRACTICAL TANNING
the liquor each time. After lying in the sumac over night
the skins should be horsed-up, and, after draining, taken to
the sheds for drying. Care should be taken not to expose
them to strong or harsh winds in the early stages, and the
use of steam and artificial heat should be avoided as much
as possible.
Tanning the splits. — The splits may be tanned as follows :
Put them in a mixture of best oak-wood extract and water
at 35° bk., and for every 5 dozen splits add 2 quarts of acetic
acid, which helps to maintain the goods in a plump condition.
Keep the splits (linings) in this liquor for two days, handling
once. Horse-up to drain and dry out steadily. Cube gam-
bier costs more than block gambier, but it is richer in tannin
and does not contain dross. The best Sicilian sumac should
always be used.
Directions for finishing. — When the grains are brought
down from the shed, they are treated, where weight is a con-
sideration, as follows : For every 10 dozen take 28 lb. of
barium chloride, and with sufficient water to wet them, work
the goods in a drum, together with 6 gallons of sumac for an
hour at 104° F. From this they are plunged, a dozen at a
time, into a weak solution of sulphuric acid, which should be
moderately acid. Stir the skins for 3 or 4 minutes until they
assume a whitish appearance. The chemical action causes the
barium chloride to be changed into barium sulphate. After
each dozen skins is taken out of the bath, sufficient acid should
be added to maintain the required acidity.
The skins are now ready for hoisting up and striking up,
the latter being done on the grain side in the ordinarv way,
and the grain wiped over with best linseed oil. They are then
hung up to stififen sufficiently for setting. When ready, let
them lie in piles, after damping down all dry parts, for a day
or two, and then set out lengthwise and after that from neck
to butt. Now hang them up and allow them to dry out. When
dry, break down with the graining board (figure 68), push-
ing the goods upon the flesh side from neck to butt, and turn-
ing and doing the same on the grain side. Fluffing or buffing
VEGETABLE-TANNED LIGHT LEATHERS 255
follows. This should be effected on a fine emery wheel, and
done crossways, commencing at the butt, going about half
across, turning round and reversing; then drawing the skins
straight down on the grain.
Treatment for split linings. — The linings, after being dried
out, may be weighted by drawing them through a strong solu-
tion of barium chloride, as above described, but they must be
drawn through the acid bath one at a time, if tearing is to be
avoided. Now wash them with warm water and lightly strike
out with a suitable ridging board. The splits are then ready
Figure 68. — Cork arm-board.
for staining, and, when dry, are buffed on one side and enam-
eled on the other.
Tanning pigskins. — Pigskins usually come to the tanner
in a pickled condition, and should be de-greased by running
in lime or soda solution. They may be also very satisfactor-
ily de-greased with the gargoyle compound, described in
Chapter II.
Quebracho extract makes a satisfactory tannage for pig-
skins. Prepare a liquor by adding enough dissolved extract
to 700 gallons of water in a paddle to make a 4° bk. liquor.
To this liquor add 10 lb. of alum and 25 lb. of salt dissolved
in hot water. Plunge the liquor until it is thoroughly mixed.
Start the wheel, throw in the skins, and turn them 36 hours
or longer, which strikes them a light oak color, and they may
then be placed in the second bath, which should consist of
clear quebracho liquor. 'Add enough dissolved extract to
the water in the paddle to make a 6° liquor, omitting the alum
and salt. Turn the skins 36 hours ; then strengthen the liquor
256 PRACTICAL TANNING
to 10°, and leave the skins in the liquor for two days, which
completes the tanning. The second liquor may also be given
the skins in a drum. A mixture of quebracho and hemlock
extracts may be used; also a mixture of hemlock and oak
extracts.
When the skins are tanned, pass them into a sumac liquor
in a paddle or vat. The liquor is prepared by adding water
at 122° F. to 25 lb. of sumac. Cool down to 86° F. before
entering the goods, and haul-up once or twice, warming the
liquor each time. After being in the sumac liquor over night
the skins are struck out and oiled on the grain with neat's foot
oil or sulphonated oil, and hung up to dry or tacked on
frames. When dry, they are staked and boarded, and are
then ready for the finish. The leather can be bleached if a
lighter color is wanted, or colored any shade, or dyed black.
Quebracho makes a fine, natural grain, free from spue, and
firm, strong leather. For bag leather, hemlock extract is a
good tannage; so is hemlock and quebracho. The skins are
started in a weak liquor, which is strengthened twice a day,
until they are struck through, which takes about 8 days. After
tanning, they may be bleached and drummed in a sumac bath.
Next wash them with clean water; slick them out; give them
a little oil and hang them up to dry. After drying, dampen
and shave the skins that need it and then apply fat-liquor.
Tanning with sumac, oak bark, and alum. — A soft, light-
colored pigskin can be produced by tanning in the following
manner : Pickle the skins with sulphuric acid and sodium chlor-
ide (salt) ; next remove the acid in a drench of whiting and
salt, and then wash them in two baths of warm salt water.
To make the tan liquor, dissolve 6 lb. of alum, 4 lb. of Glaub-
er's salt, and 4 lb. of common salt in 6 gallons of water; in
another tub boil 5 lb. of ground sumac, 3 lb. of oak bark, and
1 lb. of ground nutgalls in 5 gallons of water. Mix the two
solutions ; strain the mixture while it is hot, and add 4 oz. of
sulphuric acid. The liquor should be used lukewarm, and the
skins drummed in it for several hours, then allowed to drain
24 hours. Tanning can also be effected in a paddle.
VEGETABLE-TANNED LIGHT LEATHERS 257
After draining, the skins should be struck-out on both sides
and oiled fairly heavily and dried. As they dry they should
be staked, so that when the leather is dry it is soft and pli-
able. It can be easily colored any shade. It is quite water-
proof and durable. Oak bark is an especially good tannage
for pigskins ; so is chestnut extract.
Another method of tanning with quebracho and sumac is
carried out as follows : A cube of solid quebracho extract is
dissolved in a barrel of boiling water, forming a stock solu-
tion. A 10° bk. solution of this extract is taken and drummed,
together with the skins, in a closed drum for a half-hour or
longer. This sets the grain. The skins are then put into
a paddle containing a 12° liquor, and remain in it until they
are tanned. The strength of the liquor is gradually increased.
When tanned, the skins are drummed with sumac liquor for
2 or 3 hours ; they are then struck-out on a machine and hung
up to dry. For black leather the skins may be handled and
blacked in the same manner as sealskins.
Tanning snake skins. — These skins should be soaked until
soft, then limed to remove the scales; and after bating they
may be tanned in bark or extract liquors like calfskins and
sheepskins, beginning with weak liquor, handling often, and
increasing the strength daily. While soaking, they should be
worked by hand until they are soft and flexible and the outer
scales have been removed ; they are then in condition for tan-
ning. Gambier, sumac, quebracho, chestnut extract, or a
combination liquor may be used. The tanned skin is soft and
flexible, and the natural colors are little changed.
A process of tanning with alum, salt, and gambier is car-
ried out in the following manner : The skin is soaked in the
usual way. It is then fleshed and put into lime for 4 or 5
days until the outer scales can be removed. It is then bran
drenched and depleted, washed, and pickled for 2 days with
salt and alum liquor of 1 part alum, 2 parts salt, and suf-
ficient water to cover. Tanning is then started in a 5 per
cent gambier liquor, which is strengthened daily until it
reaches 10 per cent. The skins are tanned in a few days.
258 PRACTICAL TANNING
Quebracho extract or chestnut extract may be used in the
same manner as gambier. After the tanning is completed, the
skins are fat-liquored with sulphonated oil ; dried, wet down,
shaved, sumacked, oiled again if necessary, stretched out
carefully, and dried. The flesh may be made clean and smooth
with sandpaper or on an emery wheel. A bright finish is
obtained with casein or shellac; a dull finish with flaxseed
liquor or gum tragacanth.
Fancy leather calfskins. — Only the finest calfskins are
selected for this class of leather, and they should, as far as
possible, be free from butcher cuts and other imperfections.
The weight of the skins for this line of manufacture usually
runs from 4 to 7 pounds each. They are generally green-
salted or are in a dry-salted condition, and must be soaked
in water in the usual manner, and made soft and clean.
One hundred skins make a pack of convenient size. They
are first run in a drum which permits a constant supply of
water being run into it while revolving, and which has open-
ings for the water to run out again. If the pack is green-
salted, washing for one or two hours is sufficient; but dry-
salted stock requires longer treatment. The main object is
to get the skins soft without the loss of substance, and this
can be greatly accelerated by having pegs inserted in the inner
side of the drum. The skins are next fleshed and limed.
During the liming of this class of leather, the tanner must
remember that a very soft-finished product is required, with
a tight, smooth, and clear grain ; therefore great care k and
judgment must be exercised at this stage, for, as most tanners
know, the liming makes or mars the finished product. Local
conditions must be considered, as well as the season of the
year.
Lime and arsenic are the depilatories used. The arsenic
is valuable, not only in hastening the loosening of the hair,
but also for the softening effect it has upon the skins, ren-
dering them supple and making the grain close and smooth.
After remaining in this one or two days, they are hauled up
and allowed to drain, preparatory to going into new lime.
VEGETABLE-TANNED LIGHT LEATHERS 259
After unhairing, the skins are well washed in running water
until the surface lime is removed and then bated and de-
limed. This is done in one of the several bating processes
which have been described for calfskins, the method of bat-
ing with oropon, or the process in which glucose, sulphur,
and yeast are used, being especially suitable. The skins should
be bated in such a manner that they are soft and clean, and
have the fine grain that is desired. After having been bated
they are scudded. This is done on a bolstered beam, using
a slate knife, and is an important operation, as it removes
much of the dirt and rids the skins of lime dissolved by the
bate. Furthermore, all of the fine hair which may still be
in the skins is removed. The skins are next drenched with
boracic acid, formic acid, or any other suitable drenching ma-
terial, and are then pickled.
Pickling for this class of leather is effected satisfactorily
with formic acid and salt, which cleanses the skins and gives
them a good grain. Pickling makes soft leather which has
a clear grain and good color. Quebracho extract is commonly
used for tanning skins for fancy leather. Some of this is dis-
solved by boiling in water in a barrel, thus forming a stock
solution from which the tan liquors are made up and strength-
ened. The skins are held in suspension in the vats by tack-
ing them to wooden strips, using galvanized iron or copper
nails so as not to stain them. One nail on each butt shank is
enough, two skins on each side of the strip, with the grain
side out, being thus suspended.
The first liquor in which the skins are hung is weak, from 7
to 10° bk. As the tanning progresses its strength is increased,
so that at the last it will be of 20 to 25°. The chief point
to be considered is to avoid drawing the grain by using too
strong liquors at first. Salt must always be present, especially
when sulphuric acid is used as a pickle, to prevent injury
from the acid. The time required for tanning varies accord-
ing to the handling of the skins and the strength of liquors,
but should be accomplished in 7 to 14 days.
When the tanning is completed, the skins should receive a
260 PRACTICAL TANNING
slight fat-liquoring. The grease should be entirely absorbed
by the leather; the skins are then drained, slightly struck-out
on the flesh side, or hung up at once and dried. When thor-
oughly dry they are sorted into various grades; those that
are light in color, clear of grain, and free of imperfections
being put into the lightest colors, while those with slightly
imperfect grains are most suitable for black leather.
Combined vegetable and mineral tannage. — Each of
these two methods of tanning possesses unique advantages,
and it has been the aim of tanners to incorporate them into
one method, but so far this has not met with much success.
The chrome process gives, for example, suppleness and
toughness to leather without fullness or weight, so that any
skin that has been chrome-tanned must not be inclined to
looseness of texture, as this fault would be accentuated in the
finished leather. The vegetable tanning process, on the other
hand, gives excellent weight and fullness, but lacks the char-
acteristic suppleness and strength of chrome leather. When
a combination of these two processes is tried by making one
follow the other, it is usually found that the production of
one good quality is accompanied by the presence of a corre-
sponding bad quality. For example, if empty chrome-tanned
leather is, for the sake of fullness and firmness, re-tanned in
some vegetable tanning liquor, these two qualities will be pro-
duced, but the toughness of the leather will be sacrificed.
Vegetable-tanned patent shoe tipping. — The tanner who
makes chrome leather from hides can realize greater profit
from his poor-grained hides by working them into tipping
stock than by allowing them to go through the works, and
then to be sold as No. 3 chrome or as a job lot of culls.
Good, strong tipping requires more liming than chrome
leather. If the tanner will sort his hides after they are de-
haired, he can have an extra lime pit and make up a medium
strong lime liquor, and all hides with damaged grain can be
put into this lime for 24 to 48 hours, and then be put through
the regular system of washing, working out, bating, etc.
After having been bated down well (tipping stock should be
VEGETABLE-TANNED LIGHT LEATHERS 261
bated low, to make a soft, strong leather), the hides should
be started to tan by tacking them on sticks and suspending
them in a weak sour liquor. If a non-acid tanning agent is
being used, the liquor should be turned to the acid side by
the use of lactic acid. The first liquor should stand about 7°
test with a barkometer. Allow the hides to remain in this
sour liquor for 48 hours, then handle them over into another
pit, or else draw off the sour liquor and pump on a fresh
sweet liquor of 10° strength. If handled over into the next
pit, the hides should be pulled out and laid in a pile to drain
for two hours in order that they will not carry too much of
the sour liquor into the next pit. Allow them to remain in
the 10° liquor 48 hours, then work them into a 12° liquor for
48 hours. Next work them into a 16° liquor and allow them
to remain 4 days, but they must be handled each day and their
positions changed, so that they will not have raw or "kissed"
spots on them. After having been in the 16° liquor the re-
quired period, the hides are worked out into a 20° liquor and
allowed to stay therein 6 days, when they are pulled down
from the sticks and allowed to lie in a pile 48 hours. They
are then pressed or put through a wringer so that they will be
in condition for splitting, or they can be run through a split-
ting machine with a corrugated roll without pressing or wring-
ing. If pressed or put through a wringer, they must be
jacked on a stoning-jack to remove all marks.
After having been jacked, they are split at a 2\ oz. gauge,
and the grains are then re-tanned in a mill with sumac, using
two pails of sumac to each dozen sides. Boil the sumac in
about 20 gallons of water, and allow it to stand until cool,
then put in the leather and run 1^ hours, take the leather out
and put it into a pile for 24 hours; then give it another run
in sumac liquor made in the same way. The leather is piled
down again and allowed to rest for 24 hours. It is then
dipped into a tub of warm water to wash off the sumac, and
after that is scoured on the table. While on the table, give
the leather a good coat of moellon degras, made by dissolving
4 oz. of potassium carbonate in 3 gallons of hot water and
262 PRACTICAL TANNING
then stirring in 2 gallons of the degras. The leather is given
a light coat of this slush, well rubbed in with a brush. It
is now folded together and laid in a pile for 24 hours, then
tacked out on frames. When dry, it is buffed by hand, and
either staked or soft-boarded and pin-blocked to soften, when
it is ready to japan. De-greasing is unnecessary when a first-
class moellon degras is used.
'Another re-tanning process. — A good way to fit bark-tanned
leather for patent shoe tipping is to split and shave it on the
machine, then for 50 medium sides dissolve 3 lb. of potassium
carbonate in 50 gallons of warm water and run in a mill for
a half-hour, then drain and wash for 15 minutes, when the
leather will be in good condition to be re-tanned.
The re-tanning liquor is made as follows : Boil 2 pails
of sumac in 40 gallons of water for 10 minutes, and allow to
stand over night. In the morning dissolve 13 lb. of gambier
and 10 lb. of salt and add the solution to the sumac liquor.
There should be 50 gallons of liquor. Run the sides in this
liquor one hour, using it at 80° F. ; next pile them down on
the floor for 12 to 24 hours, and then wash off the sumac in
a tub of water.
CHAPTER IX
VEGETABLE-TANNED SOLE LEATHERS
Rapid tanning processes. — In modern plants, sole leather
is tanned in hangers and layaways, and then made plump and
solid by being drummed in strong liquor made from que-
bracho or bark extract. As the drum revolves, the extract is
forced into the leather, which absorbs the condensed tanning
■ material in a few hours. Before this is done, however, the
leather, already fairly well-tanned, is run through the wring-
ing machine and the surplus liquor is forced out.
Some tanners use whole hides, and by having plenty of
liquor in the drum, get good, smooth grain on their leather.
The grain should be well set before the drumming in ex-
tract is begun. The extract is mixed with sweet liquor heated
to 80° F. ; it is also used in liquid form as taken from the
tank or barrel The leather, when the drumming is com-
pleted, is removed from the drum and placed in warm water
for a few hours, which plumps it; it is then oiled, dried,
sammied, and rolled once or twice. When the preliminary
tanning is done properly, the finished leather is well-tanned,
plump, solid, and has good weight. Quebracho extract in
concentrated form is the material usually preferred for the
drumming process. Apparently firm and solid leather is ob-
tained by using glucose, which makes plump flanks, bellies
and shoulders ; but the plumpness and solidity thus acquired
are not real, and the leather does not give satisfaction.
The only way to make durable sole leather is by using
nothing but vegetable tanning extracts. Some tanners, after
the drumming in extract is completed, hang the leather in
strong liquor made from the extracts from the drum ; then
they bleach it with acid and soda; oil it and hang it up to
dry in a well ventilated but darkened room; and then roll it
263
264. PRACTICAL TANNING
for market. A mixture of equal parts mineral oil and cod oil
is often used for oiling sole leather. Soluble or sulphonated
oil is also drummed into the leather and adds to its pliability
and strength. When the drum process of tanning is used,
it is the practice of some tanners to send the old drum liquors
to the handlers. These drum liquors are entirely sweet, and
do not contain enough free acid to plump the hides properly
while they are in the handlers; hence it is necessary to add
lactic acid to the liquor in order that there may be the requisite
proportion of acid to plump the hides. Not only is it advis-
able to add the acid to the head-handler liquor, but also .to
the handlers half-way down the series, in quantities growing
smaller from the head liquor. The green hides are given a
week in the handlers; next they go through a roller press or
a wringer, and are then ready for the drumming process.
During the latter process, the two essentials are the mainten-
ance of the strength of the liquor, and keeping the leather
comparatively cool. When the hides are found to be heating,
they should be allowed to cool off before proceeding with
the drumming, and the old liquor run to the handlers and
fresh liquor supplied to the hides.
Neutralizing the lime in the hides by hanging them over
night in cold water containing lactic acid, which also plumps
them before putting them into the handlers, considerably short-
ens the period they have to remain in the handlers. Tan
liquors at this time usually contain too little acid to neutralize
the lime and keep the hides plump, and some process of de-
liming is necessary. Lactic and acetic acids are commonly
used in tan liquors. Butyric acid also is used for de-liming,
and is an excellent plumping acid for the early tan liquors.
Some tanners drench their hides with boracic acid, which not
only removes the lime, but also gives the grain a smooth, silky
feel and appearance.
Some tanning extracts are more astringent than others, and
when several tanning materials are being employed it is best
to use the less astringent materials during the first or earlier
stages of tanning, and use rockers so that the hides can
VEGETABLE-TANNED SOLE LEATHERS 265
be kept in motion and penetration by the liquor facilitated.
The earlier liquors fix the grain and give it good color, and
they should be weak. When the grain is colored and set, the
hides are in condition to receive stronger liquors. The
strength of tanning liquors should be increased rather slowly
to prevent thickening the grain and a wrinkled or drawn ap-
pearance. When strong liquor is used during the early stages
of tanning, the exterior of the hides may be so hardened that
penetration by the liquor into the interior becomes impossible.
Smooth grain and fibers completely tanned are obtained only
when the rate of increase of tannin strength is very low.
Sole leather is sold by weight, and as the cost of the hide
is from 50 to 70 per cent of the cost of the finished leather,
the tanner's main object is to produce as many pounds of
leather as possible from a given weight of hide. Whatever
degree of success he may have is spoken of as a "gain."
Thus, for 100 lb. of green-salted hides the tanner can obtain
from 60 to 80 lb. of leather, so he has a gain of from 60
to 80 per cent; but from 100 lb. of dry hides he will make
from 150 to 185 lb. of leather, and so has a gain, of from
150 to 185 per cent.
For the manufacture of sole leather, either green-salted,
dry-salted, or flint hides may be used. In the preparatory
treatment they are soaked, washed, unhaired, and fleshed as
already described. They are then placed over sticks and sus-
pended in cold water over night. It is not customary to bate
hides for this class of leather.
Three general methods are used in the manufacture of sole
leather, namely, oak, hemlock, and a combination of both,
known as union. True oak-bark tannage is practically a thing
of the past, and what is sold as oak is in reality chestnut oak.
Hemlock leather is produced by the methods acid and non-
acid.
Oak leather. — Leather made from hides that have been
tanned with oak bark is distinguished by its light color and
firm texture. This tanning material imparts a bloom to the
leather which may or may not be removed, according to the
266 PRACTICAL TANNING
demands of the trade; if it is removed, the leather is spoken
of as "scoured."
On removal from the cold pool, the hides are ready for
the actual tanning process. They may be carried through as
whole hides, but they are generally cut into sides before enter-
ing the rocker. The rocker system consists of a series of
vats 8 ft. long, 6 ft. wide, and 5-J ft. deep arranged so that
the liquor from the bottom of one pit overflows into the top
of the next. The liquor is supplied to the head or strongest
liquor vat containing the most tanned hide, and gradually
works its way through all of the vats in succession, being
weakened or sapped in each by the presence of the hides. It
finally reaches the tail rocker-vat where it meets the fresh
hides, and then flows to waste or is pumped over the leaches.
The stock suspended on the frame of the rocker is moved
slowly up and down, which serves the double purpose of agi-
tating the liquor and producing an even color on the grain.
This rocking also hastens the tannage, and by preventing the
hides from touching removes the danger from untanned places
known as "kiss spots."
The rocker liquor, being acid in character, serves to neu-
tralize the lime present in the stock, and at the same time
produces a swelling or plumping effect on the hides. Much
care is necessary during this operation, as the quality of the
leather is determined by the attention given to the hides while
they are in the rockers.
The liquor used in the rockers should contain sufficient acid
to perform its function as mentioned, and in the tail liquor
is usually about 0.6 per cent. This acid is produced naturally
by fermentation of the glucosides, or may be obtained by add-
ing lactic acid. The strength of the tail rocker liquor should
be about 10°, and 18° in the head rocker.
The time that the hides remain in the rockers varies ac-
cording to local conditions, but 15 days is about the proper
period. The hides are in a plump condition on removal from
the rockers, and the grain is sufficiently tanned to withstand
the astringent action of the stronger liquors.
VEGETABLE-TANNED SOLE LEATHERS 267
After the rockers, the hides are treated in the layers. These
layaway vats are usually somewhat larger than the rockers,
and as a rule the hides from three rockers can be accommo-
dated in one layer. In these layers the hides are laid out flat,
one at a time, and sprinkled over with coarsely ground bark.
When the hides are set, a concentrated solution of the tanning
material is pumped in until the pit is full, and the hides are
allowed to remain undisturbed for a definite period, as given
below.
Some tanners prefer to substitute the first layer pit by a
press layer system. In this case the hides are thrown into
the pit, but no ground bark is used. Strong liquor is added
to the head press-layer pit, and gradually, by overflowing
from one pit to the next, presses the weaker liquor towards the
tail-press layer. The time of treatment in the press layer
is usually about 8 days and the strength of the liquor runs
from 20 to 28° barkometer.
Where still layers are employed, the time in the first layer
is usually about the same as for a press layer, or about 8
days. Whether the layer be still or a press layer, the sappage
is fairly high, owing to the fact that the stock is in a very
receptive condition at this stage.
From the press layer or first layer the hides are transferred
to other layers, the number and strength of which depend
largely upon the idea of the individual tanner, but commonly
three or four. These layers are sometimes spoken of as "hand-
lers" or "dusters."
The following schedule represents typical practice in an
oak-bark tannery :
Strength of liquor
Treatment Tunc, days degrees barkometer
Rockers 15 10 to 18
First or press layer 8 20 to 28
Second layer 12 34 to 38
Third layer 16 36 to 38
Fourth layer 25 40
Fifth layer 32 SO
In the above description of an oak-bark tannage it is as-
sumed that the agent is true oak bark.
268
PRACTICAL TANNING
When the tannage is complete, the sides are taken from the
last layer and thrown into warm water to clean the grain
from sediment. After rinsing, they are piled up to drain.
They are then swabbed with cod oil or a mixture of this and
mineral oil, and hung on sticks in the drying loft. This
loft is so arranged that the window may be closed and dark-
ened at the start, and heat and a good circulation of air pro-
vided later. This is an important factor in the proper dry-
Figure 69. — Sole leather rolling-jack.
ing of sole leather, as drying too quickly causes a cracky
grain, while drying too slowly results in mold.
When thoroughly dry, the sides are removed from the loft,
brushed with water, and placed in piles to sammie. The
properly tempered sides are oiled on the grain and rolled.
They are then returned to the loft, and when dry are ready
for market. The rolling is accomplished on a machine con-
sisting of a heavy beam on the side of which is a brass wheel
(figure 69). This wheel 'is about 8 inches in diameter and has
a 6-inch face. The leather is held under the roller on a brass
bed conforming to the arc described by the roller. A foot
lever raises the bed and thus produces the necessary pressure.
VEGETABLE-TANNED SOLE LEATHERS 269
Rolling serves to smooth the grain and compress the leather
at the same time imparting a desired polish. Owing to a
demand for a full cutting leather, the above procedure is
often modified. This is especially true in the case of extract-
ing and loading leather, the process for which will be given
in detail under the head of union tannage.
Non-acid hemlock tanning.— As a rule, dry hides are
used in the manufacture of non-acid hemlock leather. After
soaking, depilating, de-hairing, and fleshing, the hides, which
have been cut into sides, are run in the paddle for a few
hours with an acid color liquor consisting of spent liquor from
the tail handler of about 8° bk., and containing about 0.6
per cent of lactic acid. They are then toggled together and
placed in the tail handler pit. The handler pits are arranged
in series like the rockers described, that is, the strong liquor
enters the head pit and is then pressed toward the tail by flow-
ing from the top of one pit to the bottom of the next. During
the flow of liquor through the series there is a sappage of
about 6° bk., the liquor entering the head handler from 14
to 18°, and leaving the tail handler at about 8°. By means of
a power-driven reel the sides are changed several times each
day for the first three days, being pulled and replaced in
the pits. This changing exposes more surface to the action
of the tan, at the same time stirring up the liquor. After
the third day, and each day thereafter, the hides are reeled
forward into the stronger liquor until the head handler is
reached. The time in this handler is from 12 to 15 days,
during which time the stock has become plumped and the
grain well set. On removal of the sides from the head han-
dler they are untoggled and placed in the first lavaway. The
strength of the first layer is about 20° bk., and is usually an
old liquor that has been sapped in another layer. The hides
remain in the first layer for 7 days. They are then pulled and
transferred to the second layer, where thev remain for 11 days
starting with a 22° liquor. This solution is also a sapped liquor
from a stronger layer. The third layer liquor stands at 23°
and in it the stock remains for 12 days. This solution is usu-
270 PRACTICAL TANNING
ally made fresh from leach-house liquor strengthened with ex-
tract. In the fourth liquor the hides are allowed to remain
for 20 days, the strength being 25°. The fifth layer should
have a reading of 28°, and the stock should remain in it for
21 days. The sixth-layer liquor should stand at 30° and the
time should be 28 days. In the fourth, fifth, and sixth layers
the solutions are made from sweet liquors from the leach-
house, which have been strengthened with extract. The
sapped liquors from the first, second, and third layers
are used as handler liquors, while these layers are made
up from sapped liquors from the fourth, fifth and sixth
layers.
The reason for this particular method in handling the yard
liquors is based upon the fact that the hides require a cer-
tain amount of free acid to produce the necessary plumping
in the early stages of tanning. This acid is produced by fer-
mentation of the liquors. By the time the stock reaches the
fourth layer the plumping is complete, and so the hides should
then only be treated with acid-free liquor. The reason for
increasing the strength of the liquor is due to the fact that,
after the tanning content of the hide equals that of the liquor,
no more tanning will take place. In other words, the strength
of the liquor should always be greater than the tannin con-
tent of the hide. The stock, on coming from the last layer,
is thrown into a pool of warm water to remove the sediment
from the surface of the leather, or it may be washed in a
drum. From this point on the leather may be finished as
will be described under union tannage.
Acid hemlock leather. — By this is meant a variety of hem-
lock sole-leather which has received its plumpness by means
of sulphuric acid. The bulk of acid-hemlock leather is made
from dry hides which have been de-haired by the sweating
process. The hides, as they come from the beam-house, are
placed in color vats, where they come in contact with spent
liquor, which gives them a surficial tannage on the grain and
sets the color. After this treatment they are suspended in
a 0.1 to 0.3 per cent solution of sulphuric acid where they
VEGETABLE-TANNED SOLE LEATHERS 271
remain until the desired plumpness is secured, and are then
ready for the tanning liquor.
The hides go direct to the first layer liquor,, and on account
of the abnormal plumping it is not necessary to start with
weak solution as is the case with other tannages. There
are, therefore, no rockers or handlers in the acid-hemlock
process, but strong liquors are employed from the start. The
stock enters the first layer which is 38° bk., and remains in
this liquor for 8 days. During this time the liquor is sapped
to about 20°. The density, however, is no indication of
strength of the liquor, for the reason that the hides carry in
sulphuric acid and sulphates which materially raise the gravity.
The spent liquor, therefore, is run to waste as its sulphuric
acid content retards the absorption of tannin. Some tan-
ners have made the mistake of returning the spent liquor to
the leaches. When this is done, the whole yard eventually
becomes saturated with sulphuric acid, and no tannin can be
taken up by the hides. From the first layer, the sides are
transferred to a second layer, where they remain for 11 days.
The second layer liquor has a strength of 40° bk. The
sapped liquor from the second layer becomes the strong liquor
of the first layer. If low in barkometer, the spent second
layer liquor is sometimes built up with strong liquor from the
last layer.
In an acid-hemlock yard the leach-house liquor is usually
built up to strength with extract, either hemlock or chestnut
extract being used. Any excess of liquor from the second
layer, as well as the sapped liquor from other layers, is re-
turned to the leaches, and made up to strength by further
leaching and by the addition of extract.
From the second layer, the stock is transferred to the third
layer, where it remains for 15 days with a density of 42°
bk. at the start. In the fourth layer the hides remain for 24
days, the strength of the liquor also 42°. Treatment in the
fifth layer is for a period of 24 days, the initial gravity being
44°. The sixth layer has a gravity of 48°, and in it the hides
remain for 27 days.
272
PRACTICAL TANNING
From the sixth layer the hides are thrown into a warm pool
to remove the excess of liquor and clear the grain. They
are then extracted and finished as desired.
Union leather. — A combination of hemlock with chestnut
oak extract gives a satisfactory leather, and one having a color
closely resembling oak-tanned stock. The combinations used
Figure 70. — Mechanical transfer in the tan-yard, showing pack going
to rocker.
are as numerous as there are tanneries producing this grade
of leather. In some plants the tanner depends upon his leaches
for making the combination liquor, while others depend en-
tirely upon extracts for this purpose. Although, strictly speak-
ing, a union tannage is supposed to be a mixture of hemlock
and chestnut, it will be found that many tanners add other
extracts such as quebracho, mangrove and myrabolans. Most
of the union leather is cropped ; that is, the bellies and shanks
are cut from the sides, leaving what is known to the trade as
a "bend." These bends bring a higher price than the same
VEGETABLE-TANNED SOLE LEATHERS
273
leather sold in sides, because they can be cut to better advan-
tage in making soles. The bellies are used for inner-soling,
where less wearing quality is required.
Green-salted hides are generally used for making union
leather. They are soaked, limed, de-haired, fleshed, fine-
haired, and placed on sticks in the cold pool over night, when
Figure 71. — Mechanical hoist for moving hides.
they are ready for the rockers. The rocker-pits (figure 70)
are arranged in series, usually in two rows, connected in such a
manner that the liquor in them may be pressed forward, up
one side and down the other; in other words, a sort of an
exaggerated circle. Fresh stock from the beam-house is put
into the tail pit, which contains no liquor. Fresh liquor from
the extract-house or leach-house is pumped into the head pit,
which contains the hides that have been in the rockers the
longest time. As the strong liquor enters the head pit, the
liquor in it overflows to the bottom of the next pit, which in
turn overflows to the next, and so on until the tail pit is full.
274
PRACTICAL TANNING
To secure an empty pit for the next pack, the hides in the
most advanced pit are transferred (figure 71) to the layer,
and the liquor in that vat is pumped to the next in the series.
The overflow causes a change of liquor throughout the series.
The liquor in the tail pit may flow to waste, or it may be
pumped back to the extract or leach-house. The common prac-
Figure 72. — View in the tan-yard, showing series of layers.
tice is to pump back twice to leach-house and once to waste.
The frames on which the hides are suspended rock slowly
up and down, thus preventing the setting of insolubles, assist-
ing in the production of uniform color and penetration, and
obviating what are known as kiss spots.
The greatest care should be exercised in the rockers, as it
is here that the character of the leather is formed. Attention
must be given to the strength of the liquor, and the amount
of free acid and tannin carefully checked. Under no circum-
stances should the rocker liquors be mixed with those from
the other parts of the yard. Barkometer readings may be
VEGETABLE-TANNED SOLE LEATHERS 275
taken to assist in regulating the liquor, but they are not a
safe guide without occasional laboratory checks.
Assuming a rocker system in which the hides remain for
15 days, in the tail-pit there should be from 0.5 to 1 per
cent of tannic acid and from 0.25 to 0.33 per cent of free
acid, estimated as acetic. These should increase gradually un-
Figure 73.— Cropping.
til in the head rocker there should be 2\ per cent of tannic
acid and 0.6 to 0.7 per cent of free acid, estimated as acetic.
Assuming again that the union leather is being made with
an extract tannage, the proportion should be as follows :
Tannage extract Per cent
Chestnut wood !•?
Chestnut bark • 45
Hemlock bark 40
On removal from the rockers, the hides next enter the press
layers. These consist of a series of vats arranged in some-
what the same manner as the rockers, and the liquor is pressed
276
PRACTICAL TANNING
forward in the same way, working from head to tail pit.
The hides are taken from the rocker frame and thrown into
the empty tan pit one at a time. Over each hide is dusted some
chestnut-oak bark, before the next hide is placed in position.
This powdered bark tends to keep the hides separated, and
so allows more uniform contact with the liquor.
Figure 74.— Cropped hides and bellies ready for final layer.
Numerous methods are employed for handling the stock
in the press layers. A common method is to have two rows
of five vats, the number of the series depending upon the
size of the tannery and the quantity of stock being treated.
One pack enters and one is removed from this set of layers
every other day, thus making 20 days required to work the
hides through the press layers. The liquor in the head press
layer should stand at about 40° bk., and should contain 4
per cent of tannic acid and about 0.6 per cent of free acid as
acetic. During the passage through the press layer the liquor
should be sapped so that in the tail press layer there should
277
VEGETABLE-TANNED SOLE LEATHERS
be about 2\ per cent of tannin. A good combination for the
press layer is as follows :
Per cent
20
Tanning extract
Chestnut wood 45
Chestnut bark 35
Hemlock bark
The hides for the press layer are next transferred to the first
layer liquor. The layer-pits (figure 72) are not connected
Figure 75.— Quirin press or wringer.
with overflow as is the case with the rocker and press layers,
and the liquor in them is not changed during the 7 days that
the hides remain in them. No bark is used for dusting m the
first layer, and the strength of the liquor should stand at 42°
bk. The tannin content of the first layer should be about 4*
per cent, and should be made up as follows :
_ , . Per cent
Tanning extract
Chestnut wood ^
Chestnut bark 35
Hemlock bark
The temperature of the first layer liquor should be 95° F.
The second layer liquor is made up of the same materials
278 PRACTICAL TANNING
and proportions as the first layer, except that the density is
raised to 46° bk. and the tanning content therefore increased
to 5 per cent. The hides remain in the second layer for 12
days, during which time they are not removed or the liquor
changed. On removal from the second layer the hides are
cropped (figure 73). The cropped backs are placed in the
Figure 76. — Extract wheels.
third layer pits and the bellies thrown in on top (figure 74).
The liquor in the third layer is made up entirely of quebracho
extract at a density of 55° bk. and at a temperature of about
115° F. No bark is used to dust the backs, and they remain
in this liquor without changing for 35 days.
Extracting. — As the hides come from the third layer they
are thrown into water at 100° Fr for an hour, and then passed
through the wringer (figure 75). The well pressed and fairly
dry backs are next placed in the drum (figure 76), about 100
backs constituting a pack, and while the drum is in motion
500 lb. of 100° bk. quebracho extract at a temperature of
VEGETABLE-TANNED SOLE LEATHERS
279
150° F. is pumped in. The drum is run for 1^ hours, by
which time practically all of the extract has been absorbed.
From the extract wheel the backs go to the tempering pit,
which contains a quebracho extract of 45° bk. and at a tem-
perature of 80° F., where they remain 4 days.
Bleaching. — On removal from the tempering pit, the backs
Figure 77. — Ready for the bleach.
are suspended on sticks (figure 77), and hung for 7 minutes
in fresh water at a temperature of 125° F. The frame is
now lifted, and the hides immersed for 7 minutes in a weak
alkali solution (figure 78), the strength being 0.3 per cent
of sodium carbonate on the weight of the water, and the tem-
perature 125° F. From the alkali the backs pass to the first
acid dip, in which 1.5 per cent of sulphuric acid on the weight
of the water is used. The time and temperature are the
same as for the other treatments. The backs now go to a
second acid solution which, however, is somewhat more di-
lute. To remove the excess of acid the leather is clipped in
280 PRACTICAL TANNING "
plain running water for 7 minutes. After bleaching, the
hides are passed through the wringer, and are ready for load-
ing. Figure 79 shows a cross section of a standard bleaching
machine.
The bellies from the third layer are not extracted, but after
washing in warm water are bleached in the same manner as
Figure 78, — Hides suspended in the bleach.
described for backs. They then receive the same finishing
treatment as the backs.
The hides, as they come from the wringer, are placed in a
drum (figures 80 and 81) and about 50 lb. of crystal magne-
sium sulphate is added for each 100 hides. The door is then
closed, the mill started, and a mixture of 175 lb. of glucose,
6 gallons of sole-leather oil, and 1 gallon of cod oil, at a tem-
perature of 150° F., is added through the trunnion. The
stock is run for a half -hour. The hides are then set out on
a Quirin press and go to the loft. The dyeing of sole leather
must be carried out with great care, otherwise a dark and brit-
VEGETABLE-TANNED SOLE LEATHERS 281
tie grain is likely to result. The usual procedure is to hang
the leather over sticks, and for the first two days keep the
loft dark and as cool as possible, but with proper ventilation.
The temperature of the loft is then gradually raised and light
admitted. The time required for dyeing varies with the cli-
mate, season of the year, and conditions of the loft.
Figure 79. — Bleaching machine.
When the leather is thoroughly dry it is taken down and
dipped in warm water containing a small quantity of glucose
and then piled down to sammie, which takes from one to two
days. When properly tempered, the grain is wet uniformly
with warm water, and given a coat of cod oil. While still
in this damp and oily condition the leather is set out and
rolled for the first time (figure 83). The rolled stock is again
taken to the dry loft (figure 84), and this time suspended by
one end (figure 82), and when dry is again rolled. Some
tanners apply a seasoning after the first rolling, which adds
to the appearance of the leather on re-rolling. In place of
the second rolling the leather is sometimes seasoned (figure
85) and brushed on the machine shown in figure 86. After
the second rolling or brushing the leather is ready for sorting
and grading for market.
Rapid sole leather tannage. — On account of the immense
sum of money represented in hides tied up in the process of
making sole leather, many rapid tannages have been pro-
posed, some of which are of proved merit, while others are
282
PRACTICAL TANNING
entirely valueless. Practically all of the rapid tannages depend
on constant agitation of the hide in the presence of the tanning
agent. It is in the method of securing this agitation that the
various systems differ. Most of the quick tannage processes,
however, are still in the experimental stage, but whether they
will be able to compete with the old-style methods remains
to be seen.
One of these rapid tanning processes depends for its effi-
Figure 80. — Placing in loading wheel.
ciency upon rockers arranged as described under the regular
sole leather process. The hides, on coming from the beam-
house, are suspended in frames and treated just as given under
union tannage. On removal from the rockers they are at
once put in the drum, and wheeled with strong extract for
a period of from one to several days. They are then bleached
and finished in the usual manner.
Some processes depend upon tawing with alum and salt to
set the grain before entering the strong liquor.
VEGETABLE-TANNED SOLE LEATHERS 283
Many processes have been patented in which the use of a
revolving drum is the principal feature. The size, shape, and
arrangement of the hides in the drum are all features which
have been patented. Some drums are provided with frames
to which the hides are attached, thus causing the liquor to fall
over the stock. In other processes the hides are fastened to
hooks in the drum. In all of the methods the grain is first set
with dilute liquor, and then the concentrated extract is applied.
Figure 81. — Removing from loading wheel.
The chief objection to rapid tanning is the low gain, al-
though this may be counteracted by loading. The following
complete description of one of the rapid tanning processes may
be of interest:
Tanning zvith chestnut extract.- — This extract, prepared with
care, is practically a pure solution of chestnut wood tannin,
rich in tanning power per unit of density, and soluble to a
high degree. It will form liquors free from sediment or
liquor-filth, well balanced in tannin and non-tannin for oak
284
PRACTICAL TANNING
and hemlock yards, and suitable for tanning hide fiber quickly
and thoroughly.
For color reasons, chestnut extract should be well incorpo-
rated with the leach liquors. Its natural color is brown, but it
becomes red by treatment. Mix as much as 75 per cent with
the leach liquors, and the bark color will dominate. Tan the
Figure 82. — Setting-out after tempering.
stock in chestnut alone and the color will be "on the brown.".
This is the only color secret in the use of chestnut extract.
Put the extract on the head leach, through the sprinklers, or
a little at a time as the leach fills with bark, and take down
the liquors in the customary manner, making the draw of the
desired barkometer average. As the yard becomes saturated
with the cnestnut, several things will be observed — the packs
will feed more rapidly, they will "stand up" higher, and the
plumpness put into the stock in the sours will hold up to
the rolling room. This is because the liquors sent to the stock
are richer in tannin per unit of barkometer, without an in-
VEGETABLE-TANNED SOLE LEATHERS
285
crease of the liquor-filth which impedes entrance of the tannin
into the fiber of the stock. Leather is made in the beam-
house and the sour end of the yard; almost anything can be
done to it if proper beam-treatment and plumpness are parts
of its record. After the handler period is past, the stock
should enter the heavier liquors in a condition of plumpness
Figure 83. — Rolling-jacks.
and grain desired in the finished product, and from that point
forward it should be struck steadily and persistently, with such
frequent shifting as will keep the feeding process continuous.
The function of chestnut extract is thus made clear: It is
simply a tanning agent with souring properties midway be-
tween hemlock and oak, aiding the handlers in one and re-
straining them in the other. No other extract possesses this
unique property. The amount of combined tannin that can
be put into a hide depends almost wholly upon the degree in
which the initial plumpness is retained during the passage of.
the stock through the true tanning liquors, those beyond the
286
PRACTICAL TANNING
handlers. If these liquors are clean and grade up from 20°
bk. in the first layer to from 50 to 60° in the last, the com-
bining process will proceed uniformly and steadily, flanks
will be full and firm, the cut will show as much color from the
one side as the other, and the "white streak" will be firm and
plump. Such leather has good market qualities, and also has
Figure 84. — Drying-loft.
more room for finishing material and a larger area of hide-
fiber to take the tannin. Chestnut extract promotes exactly
these conditions, with, at the same time, a beneficial effect on
the sour end of the yard.
There are various ways of using this extract: Some tan-
ners put it directly on the leaches, and there allow it to dissolve
and percolate through the ground bark. The chief advan-
tage claimed for this is that the disagreeable bluish-gray color
on the stock is avoided. Other tanners dissolve the extract
in a separate tank and then run it on the leaches through the
sprinklers. Others prefer to dissolve the extract separately,
VEGETABLE-TANNED SOLE LEATHERS
287
then mix the solution with bark liquors as they come from
the leach-house. These methods, however, are not the latest
nor the most approved, practical experiments having shown
that chestnut extract is used most successfully along other
lines, which may be described as follows :
The hides are soaked, fleshed, limed, and de-haired in the
! KNHtti
tmf?^
Figure 85. — Applying the bright finish to sole leather.
usual way. After de-hairing, they are well worked on the
grain, then left hanging over night in the cold water pool, to
which lactic acid has been added. For ordinary packs, 40
lb. will be sufficient. As they are plumped, and the fixed
lime is also neutralized, the ordinary time in the handlers
may safely be considerably reduced. Coming from the cold
water pool, the hides should again be washed on the grain be-
fore going to the liquors. The green pack is given a week in
the handlers, which are soured to the proper degree by addi-
tion of lactic acid. The hides go from the handlers through
the first two layers until struck, after which they are run
288 PRACTICAL TANNING
through a roller press, and are then ready for the drumming
process.
The extract is poured into hot water, and the solution is
run on the stock through the gudgeon at about 16° bk. The
drum is revolved slowly at first. The two essentials at this
stage of the process are the maintenance of the liquor strength
Figure 86. — Brushing machine for sole leather.
and keeping the stock comparatively cool. When the hides
become warm, they should be withdrawn and allowed to cool.
During this interval the old drum liquors are run to the
handlers and new liquor is supplied to the drums.
After the leather is thoroughly tanned, weight is given by
putting it in a drum together with a certain amount of undis-
solved extract, and then drumming long enough to have it
absorb the extract. It is then finished as usual. One of the
advantages of the drum system is that entirely sweet liquors
can thus be given to the stock, since the natural resistance of
the fiber to the penetrating power of the tannin is overcome
by the agitation. However, it can readily be seen that the
old drum liquors sent to the handlers will not contain a
sufficient amount of free acids — other than tannin — requisite
for the holding of the plumpness of the hides; hence it is
necessary to add lactic acid to the handlers so that the proper
relations of the acids may be maintained. As there is an
absence of natural lactic acid, the best results are obtained
VEGETABLE-TANNED SOLE LEATHERS 289
by adding the commercial article to the head handler liquor
in the proportion of 1 lb. of lactic acid to every 100 lb. of
hides, green weight. Besides adding to the head-handler
liquor, it is advisable to add lactic acid to the other handlers
half way down the series, in quantities growing smaller from
the head liquor.
Chestnut extract is a valuable tanning material for manu-
facturers of heavy leather, its tannin being so easily available
it is one of the most acceptable on the market. Light skins,
prepared as for any other tannage, may be tanned by sus-
pension in chestnut liquor or drummed in liquor made direct
from the extract, or from a mixture of two extracts. Skins
intended to be colored subsequent to tanning are usually tanned
direct in the extract liquor, with occasionally a re-tan in sumac.
Stock to be run in the natural color is usually struck in the
mixture, giving the shade desired. With very thin leathers,
the main requirement of the tanning material is that it shall
be clean, bright, and quick in action.
Light hides for side leathers are first put through a series
of sour liquors, in which they are plumped. The liquors
are prepared by direct solution of the extract in water or
freshly made bark liquor; thus prepared, they are given sweet
to the nearly struck goods, usually as layaways, not infre-
quently in revolving drums. These stocks are always tanned
out in relatively weak liquors, rarely exceeding 15° bk., as
freshly prepared. Tanning is then completed in drums.
Where a particular color quality is desired, the leather is re-
tanned with suitable material, such as gambier, mimosa, que-
bracho, sumac, etc., according to the shade or color condition
desired.
Drum tanning for sole and belting leathers. — In using
quebracho, 85 per cent, and oak, 15 per cent, a flrst'-class piece
of leather can be made, by carrying out the following process :
After putting the hides through the beam-house, a 4° liquor
is made of quebracho and oak extract as mentioned above.
In preparing these liquors, make up 3,000 gallons of 4° solu-
tion in the cooler, then add 4 gallons of acetic acid and 1 gal-
290 PRACTICAL TANNING
Ion of dermi forma. After standing 5 or 6 days, run the
liquor on to the green hides. Strengthen each day with enough
liquor to fill each rocker for green hides in turn. Raise the
liquor 3° daily until the strength is 20° bk. Add each day 1
gallon of dermiforma and 6 quarts of acetic acid, then feed
from head rocker, keeping liquors at 20 to 22°. Never have
the tail liquor above 4°, as quebracho extract penetrates much
faster than oak extract. It is safe if the tail falls to 3°, but
it is best to keep it at 4°. There should be 10 rockers in a
section, and the hides should hang 20 days. Then take them,
from the rockers and crop them for the drums.
Put 50 backs in a drum, fill the drum two-thirds with 75°
liquor, and run for 48 hours without changing the liquor,
but watch the temperature and keep it below 105° F. After
the 48 hours, discharge all of the liquor and fill again with
75° liquor, filling the drum only half full this time. The
drum should be large enough to hold 25 barrels when half full.
Drum 24 hours, when the hides will be tanned throughout,
plump and of fine color.
The hides must be well toggled together — grain inside — to
prevent the grain being damaged by rubbing together. After
a 72-hour run, take the leather from the drum, and lay it
away in a 75°, liquor for 4 days. Put 300 backs into a vat
8 by 9 by 6 feet, with 50 lb. of sumac to 100 backs. On the
fourth day, raise the stock, run it through a wringer, and put
it back into the drum. Add 3^ lb. of quebracho extract to
each back, dissolved and not diluted. Put 50 backs into the
drum with 175 lb. of extract, and drum for 30 minutes. Then
take them from the drum and throw into a sour liquor. It
will be found that by running the backs through the wringer
or press the extract will penetrate much better, and little will
remain on the surface. The sour liquor should be 25 to 30°
bk. After lying in the sour liquor for 24 hours the leather
is ready for bleaching. It is advisable to scour lightly on
the grain. Have one pit holding 750 gallons of water, two
of the same size for soda, and two for acid. Put 22 lb. of
soda ash in the first pit and 3 lb. in the second ; also 30 lb. of
VEGETABLE-TANNED SOLE LEATHERS 291
sulphuric acid in each, and heat to 125° F. Hang 8 backs in
each pit; strengthen after every 40 backs, putting 4 b. of soda
into the first pit, but none in the second, as puling stock
from the first to the second will maintain the soda content
in the second pit. Also add 4 lb, of sulphuric acid into each
pit for 40 backs. From the pits the backs are put into clear
water for 2 hours; then oiled, and run through the press or
hung up to drain; preferably the latter, as the press draws
more or less extract to the surface. For oiling use | lb. of
cod-liver oil, or a mixture of this and a mineral oil Re-
garding sugar and glucose, putting them in with the oil and
then drumming is the cheaper method, but best results are
obtained by re-tanning.
When dry, dip the leather into water for rolling. It prop-
erly looked after in the rolling room, the backs will look just
like vat-tanned oak backs, only they will be firmer and of a
brighter color. From 70 to 75 per cent finished gam can be
made by this process.
CHAPTER X
BELTING LEATHER
The description of belting leather in this chapter is taken
largely from a lecture given by F. H. Small before the tanning
and applied leather chemistry students of Pratt Institute, Brook-
lyn, N. Y., for which the author desires to give him credit,
Necessary characteristics. — Leather to be used in the man-
ufacture of belting should have the following characteristics :
Good driving surface, with sufficient friction between belt
and pulley to keep slippage small and enable the belt to carry
its load when slack, whereby useless waste of power at the
bearings is avoided.
Lateral stiffness coupled with pliability: Stiffness to pre-
vent the belt from curling at the edges when shifted, and
from twisting and waving; and pliability to enable the belt
to hug the pulley, wrapping itself around to secure the larg-
est possible arc of contact, and enable it to alter its shape
with the minimum of internal resistance as it travels round
the pulley.
High tensile strength, so that it may carry a heavy load
without breaking.
Little stretch but considerable elasticity: Little stretch so
that it will need to be shortened as seldom as possible, doing
its work uninterruptedly ; and elasticity that it may easily take
up and let go its load as it travels round the pulley.
Straightness, so that it may run true on the pulleys.
Resistance to external conditions, (such as heat, moisture,
chemicals, etc. ) so that it may do its work in any place at any
time enduringly.
Low initial cost.
It is generally admitted that leather comes nearer to pre-
serving all of these qualities than any other material. Many
of the qualities specified, however, are almost opposite, and it
292
BELTING LEATHER 293
is apparent at the outset that no material and no leather can
meet all of the requirements with full satisfaction. Lateral
stiffness is not compatible with pliability ; elasticity rarely goes
hand in hand with no stretch. The best we can hope to do,
therefore, is to make a leather that will have the desired qual-
ities in the largest degree, and in which we have compromised
some of the incompatibles.
Leathers used in belting. — There are various kinds of
leather used for making belting, but the most popular belting
is that called "oak-tanned leather," the general conception of
which is belting made from leather tanned with oak bark in
the old way. While it might not be safe to say that after
diligent search it would be impossible to find a small amount
of leather that has been tanned in this way, the quantity
would be a very small proportion of the whole. The terms
oak, hemlock, and union have gradually grown to have less
and less significance when applied to leather. This is not
saying that there are no manufacturers using large quantities
of oak bark in making their oak-tanned leather, but it is
indicative of the general trend.
Bearing in mind that the term "oak-tanned" as used today
stands in general for a "type of leather" rather than for a
"true. oak-bark tanned leather," the description of the manufac-
ture of oak-tanned leather for making belting may then be
understood.
It will perhaps be as well to mention the fact that by no
means is all of a hide usable for making leather belting; in
fact, ordinarily only about a third of the hide is so used, the
part used being called a belting bend. For a cheap grade of
belting, other parts of the hide, particularly the best part of
the shoulder, are sometimes utilized.
Razv material. — The belt-maker, who is also a tanner, tans
the whole hide, and his raw material is the green hide. The
raw material of the belt-maker who is not a tanner is a
market or belting butt, as belt bends are not commonly on
. the market. A belting butt is that part of the hide left after
cutting off the bellies, head, neck, and tail. The bellies are
294 PRACTICAL TANNING
cut off at the flank on a line parallel to the backbone; the
head and neck in a line at right angles to the backbone.
This butt is divided by the belt manufacturer into a belting
bend and a trimmed shoulder by cutting the butt at right an-
gles to the backbone at a point 54 inches from the tail. The
bellies, heads, and shoulder are collectively called the offal.
The butt and offal are sometimes processed independently in
the tannery, but the hide is at least started as a whole, and so
we may begin our consideration of the leather manufacturing
process by devoting a few moments to one of the raw mate-
rials — the hide.
Hides used for tanning into belting leather are commonly
green-salted packer hides. They should be free from brands,
and as far as possible free from flesh cuts caused by poor
flaying, from scratches on the grain whether or not healed,
and from grub-holes — whether or not healed. These all will
constitute defects in the finished leather, and shorten the life
of the belting made therefrom.
The take-off of American hides is reasonably good, more
fault having to be found in this connection with foreign hides.
Fortunately the scoring is usually worst on the belly and
shoulder-parts of the hide, which are not used for belting;
but the cuts in this case lessen the value of the offal.
Barbed. wire is perhaps not as common now as some years
ago, but at that, it is difficult to secure hides free from the
scars, long and short scratches, each of which may possibly
be the nucleus of a crack which is at first surficial, but will
ultimately work into, the leather deep enough to cause the
belt made from it to give way.
It requires no argument to demonstrate the damage done
to a hide by the larvae of the warble fly. These work their
way out through the skin, leaving behind a hole, which, even
though it may heal over, will always be a weak and unsightly
spot in the finished leather. It is not an uncommon sight to
see skins so full of grub-holes that they look as though they
had been riddled by a shot-gun. Within recent years, how-
ever, the U. S. Department of Agriculture, co-operating with
BELTING LEATHER 295
the Tanners' Council, has done much to eliminate this source
of damage.
Manufacturing processes. — For belting leather, the best
hides will be none too good, so the first step in the process of
leather making will be to secure the best hides possible.
These hides will then need preparation for tanning, and are
put through the regular beam-house processes of soaking,
fleshing, liming, de-hairing, beaming, and de-liming. The
old-time tanner who said that the quality of his leather was
made in the beam-house, knew whereof he spoke, and the
beam-house work will merit and demand the most careful
attention.
The points of most importance in the beam-house practice
when belting leather is to be made are as follows :
1. Good hides, sound, green-salted, unbranded, well flayed,
and so far as possible free from grain scratches and grubs.
2. Thorough soaking.
3. Average liming, as for instance a 3 to 6-day liming in
limes of progressive sharpness and newness, the limes con-
taining 4 to 5 lb. of lime and not over 1 lb. of sodium sulphide
per 100 lb. of hide.
4. Drenching or bating the hides to remove surface lime
and bring down the grain.
In the United States the common practice is to carry the
hide through the beam-house as a whole hide, and usually
also through part of the tanning process, the bellies perhaps
being cropped off when struck through. In foreign countries
it is usual to "round" the hide, or cut the hide into a belt bend,
untrimmed shoulder and bellies, in the beam-house. The
theory is that the belting bend represents the greatest value,
so it should receive the best tanning material and the most
careful attention. The offal represents less intrinsic value, so
it can be tanned with cheaper material and by a cheaper
process. Frequently one of the various rapid-tanning proc-
esses is used on the offal, and it is not uncommon to finish
the tannage of the bellies by drumming with strong liquors.
296 PRACTICAL TANNING
As offal is not belt leather it will be given no further
consideration.
Tanning agents. — In selecting the tanning agent for pro-
ducing belting leather, the basic material should be chestnut-
oak wood extract. There is no other material that has so
many merits, or which will produce a leather having so many
of the best qualities sought. It gives a good grain, deposits
enough bloom and filling matter in the fibers of the leather
to make a solid, firm leather, which is resistant to water to
a considerable degree, although its tendency is possibly to-
ward too little pliability.
On account of the bloom and filling matter deposited, the
leather made with chestnut-oak wood is sufficiently solid to
have little stretch and yet be elastic. The tannin of chestnut-
oak wood is of the pyrogallol group, and hence gives a dur-
able leather and one calculated to be reasonably indifferent
to external conditions. The best chestnut-oak wood is one
of the cheapest tanning materials per unit of tannin on the
market at present. It is not only cheap, but it is practically
inexhaustible, in view of the fact that it requires only 20
years for a chestnut tree to grow to a size at which it may
be cut. This wood, however, is inclined to produce a rather
harsh leather. Chestnut liquors develop little acid, and un-
less artificially acidified by the addition of acid, are inclined
to make a rather thin leather. It is desirable to combine
with the chestnut-oak wood some material which will develop
natural acidity in the yard, obviating the necessity of arti-
ficial acidifying, and which will modify the harshness of the
tannage somewhat. In myrabolan is a material which well
supplements chestnut wood. It gives a mellow tannage, and
will modify the harshness of the chestnut-oak wood liquors in
the early stages. It is perhaps the best of the acid-producing
materials, and will develop enough acid in the liquors so that
with the aid of the little we get from the chestnut-oak wood
it will be unnecessary to resort to artificial acidifying. Myra-
bolan is also a pyrogallol tannin, and so makes a permanent
leather. It will brighten and lighten the color of the leather,
BELTING LEATHER 297
and the color will be little affected by sunlight. The de-
ficiencies of the myrabolan are offset by the qualities
of the chestnut-oak wood. Myrabolan, used alone, produces
a light weight, somewhat spongy leather, which tans slowly,
We have in chestnut-oak wood and myrabolan, then, a couple
in which the qualities are complementary; what one lacks the
other supplies. The chestnut-oak wood comes much nearer
itself to producing the sort of leather we desire than the myra-
bolan does, and the mixture used will certainly not be one of
50: 50; but merely enough of the myrabolan to give the acid-
ity and mellowness needed. In fact, probably the myrabolan
will not be introduced into liquors except for the early stages
of the tanning where the acid is particularly needed for plump-
ing, and for the mellowness of liquor to prevent drawing and
harshness of the grain.
Another material that might be used in place of the myra-
bolan, and with even better results, is algarobilla. The sup-
ply of this material is, however, so uncertain that it is diffi-
cult to rely upon it. If, as is best, myrabolan is used only
in the earlier stages of the tanning process, it will be desirable
to mix with the chestnut-oak wood in the latter liquors of
the tanning process some material to assist at that stage. For
this purpose a catechol tannin should be used, either hemlock
or oak bark, preferably the latter. Of foreign materials, either
mallet (from Australia) or mimosa could be used, preferably
the former. An ideal tannage would consist of chestnut-oak
wood extract as the basic material. To this should be added
oak bark in the later stages, working the liquors down through
the yard and adding some myrabolan or algarobilla to them
in the early stages of the tanning process. The chestnut-oak
wood would constitute more than 50 per cent of the tanning
material throughout the process, but the exact proportion used
would be governed by the character of the leather as it came
along; as with the combination chosen, the proportions could
be modified to remedy almost any deficiency in the leather,
and to vary its qualities within fairly wide limits. This is
one reason why a combination is so much superior to a single
298 PRACTICAL TANNING
material; it is much more elastic and yields a much higher-
grade product.
Having selected the tanning materials to be used, and hav-
ing selected them with the idea of making a leather which
shall have all the qualities mentioned as being so desirable in
belting, the next step is to see how to use the materials, and
produce the best results in the shortest time and most
economically.
Practical considerations. — Without going into the theory
of the tanning process, suffice it to say that the underlying
principles, according to which leather is successfully made,
are that the tannage shall be started in liquors weak in tan-
nin, usually liquors through which many hides have previ-
ously passed, and then be gradually transferred to stronger
and fresher liquors, so that the last liquor from which they are
taken is the strongest of all and freshly made. The tannin
acid, and non-tannin constituents of the liquors must be so
proportioned throughout that the hide acquires the proper
condition of plumpness, retains that property, and tans steadily
and thoroughly.
The tannin penetrates the hide by diffusion, and as the
rate of penetration depends on the difference in concentration
of the liquor in the hide compared with that outside, it is
apparent that the hides should be placed in liquors of succes-
sively greater concentration. If, however, the increase in
concentration is too rapid, the tanning may be rapid but in-
complete, in some cases even to the extent that the interior
will not tan at all. Another probable defect from too rapid
increase of concentration is wrinkled or pipey grain. Difficul-
ties of this sort are most likely to occur when tannins of
the astringent type, such as quebracho and mimosa, are em-
ployed. The difficulty occurs most commonly in the early
stages of the tanning process before the hide is struck through,
as, after it is once struck through, it is little susceptible to
damage from too rapid strengthening of liquors. The more
mellow the early liquors the less likelihood there is of drawing
the grain or case-hardening the leather. Inasmuch as old
BELTING LEATHER 299
liquors are more mellow than new, both from having the
more astringent tannins sapped from them and from their
lower purity due to the increased percentage of non-tannin
matters, it is almost general practice to top off with strong
new liquors and work these liquors down through the yard:
that is, the greener the hide the older the liquor it gets until
the hide from the beam-house is entered in the oldest and
weakest liquor. To increase the mellowness of the early liq-
uors still further, the use of myrabolan has been advocated
at this stage, which of itself is a very mild tanning material.
The acid and tannin content of the early liquors must be
carefully balanced, as too little acid will make a thin, soft
leather; while too much will make an over-plump leather,
with cracky grain, inclined to brittleness, also probably poor
in color. Too much acidity and too much plumpness also
result in slowing up the tanning process. A certain excess
of acid in the early liquors is necessary not merely to open
up and plump the hide, but also to remove the lime which
remains from the beam-house processes. If the hide is pre-
pared for tanning with a 3 to 6-day liming and sufficient bat-
ing to remove surface lime only, it will enter the liquor in a
fairly plump condition. The surface being free from lime,
it will take a clear, bright color and begin to tan. The acid
will diffuse into the hide more rapidly than the tannin, and
will neutralize the excess of lime. The hide, as the lime is
neutralized, loses its plumpness and gradually begins to fall
back or grow soft. This effect becomes more marked as the
hide is moved ahead into liquors stronger both in tannin and
acid, until at the end of a week or ten days it is completely
down and like a rag. In some plants the tendency is to re-
move all of the lime before entering the yard, and then use
purer and stronger liquor from the start. A hide then takes
on plumpness, but this time an acid plumpness ; and as it pro-
gresses in the tanning process it becomes more and more
plump and solid, until it has reached the particular condition
of plumpness that will yield leather of the firmness and pli-
ability sought. Ability to judge when this condition has been
300 PRACTICAL TANNING
reached and to secure more or less plumpness is what makes
the tanner. Inasmuch as the same apparent result may follow
from a variety of causes, the aid the chemist can give the
tanner is by no means inconsiderable, as it will often enable
the tanner to throw out various hypotheses from the list of
possibilities. Often, too, chemical analyses may detect a
change in the composition of the liquors before the effect on
the hide has become apparent, and so enable the tanner to
adjust his proportions to the correct balance before the leather
has gone off. Inasmuch as the lime in the hides neutralizes
the acid of the liquor, the earliest liquors will naturally be
lower in acid than the later. The normal variation of the
acidity, however, would be for the new liquors to be lowest
in acid, and the acidity to increase steadily to a maximum
from fermenting action as the liquors age. We find, there-
fore, in practice, a combination of these two results, that is,
the sapped or spent liquors are lowest in acid from lime neu-
tralization, the acidity increases as treatment progresses until
a maximum is reached where the effect of the lime is lost
and the result of the fermenting action is greatest, the acidity
from then on decreasing again. Of course the tannin has
steadily increased in the liquors, and also the purity.
As an example, the tail liquor might have an acidity of 0.3
to 0.4 per cent reckoned as acetic, a tannin content of 0.2 to
0.3 per cent, and a purity of say 10 per cent; that is, the non-
tannin constituents would make up 10 times as much of the
total solid as the tannin. With a liquor such as this at the
bottom end of the yard, the tannin strength would steadily
increase as well as the purity and acid, until a maximum acid-
ity of perhaps 0.7 to 0.8 per cent is reached in a liquor con-
taining 2 to 3 per cent tannin, and of a purity in the neighbor-
hood of 30 per cent. From this point on the acidity will
gradually decrease and the tannin increase, together with the
purity. The last liquors given the hides will be perhaps 50 to
60° bk. and contain 8 to 9 per cent tannin. The strength of
the final layer liquors will depend somewhat on how much
the hide has been plumped, and on the beam-house conditions.
BELTING LEATHER 301
If the hide was rather strongly plumped, or too long in strong
liquors it will likely produce a leather entirely too solid for
belting purposes. Both treatments make a tender leather,
lacking in tensile strength, and likely to crack on the surface
and break after comparatively short usage; also a leather
likely to tear at the lace-holes if put together with lacing.
Tanning of belting leather. — The hides, as they come
from the beam-house, should be flat and free from wrinkles,
folds, or marks of any kind. In order that they may not ac-
quire folds or wrinkles during the early stages of the tanning
process, it is essential that they be put in the liquor with a
flat surface, or at least one with no sharp bends to the action
of the tan liquor. Each hide, morever, must have sufficient
room to prevent its coming in contact with another hide.
Where two hides touch, a kiss spot is found; that is, the tan
liquor does not come in contact with the hide at this spot and
it fails to color. This is likely to result in a final uneven
coloring, for unless the hides take the color evenly at the start,
it is almost impossible to prevent the hide from showing a
somewhat mottled appearance when finished.
Rockers. — To give the hide an even color and start the tan-
nage uniformly, the best practice is to commence in rockers.
The hides from the beam-house are laid out flat and nailed
to a stick at the butt end, so that when the stick is lifted
by its two ends, the hide hangs from it head down vertically.
The sticks are then put in a frame which is so supported in a
vat that it can be rocked up and down and the hides with it.
If whole hides are being tanned, the vats must be suffi-
ciently deep to allow the hide to hang down straight; but if
only belting bends or butts, shallower vats may be used. Oc-
casionally the hides are hung over sticks, but this is not good
practice, as it often leaves a thin place in the leather, and
usually a pipey grain where it came in contact with the stick.
The rockers are best worked in a series of say 10 vats,
called a "round" because they are arranged in a group with
no head or tail, and because each vat in rotation becomes the
head of the round. One vat is emptied of the hides longest
302 PRACTICAL TANNING
in the round, and one filled with green hides from the beam-
house each day. The vat full of oldest liquor is emptied into
the sewer or returned to the leaches each day, and a vat is
filled from the handlers each day. The cycle of a round may
be made in either one of two ways : either the liquor may be
pumped down or the hides are moved ahead. In the first
method, the head pit from which the hides are taken today
becomes the tail pit; yesterday's tail pit liquor is run to the
sewer, and all the liquors are pumped to the pit next but one
below in the round, the new head pit being filled with liquor
from the handlers as mentioned above. In the second method,
one pit is always empty of hides and full of new liquor from
the handlers; but instead of moving the liquors, the hides are
moved two pits ahead each day. As will be seen, the hides
stay about 10 days in the rockers.
Handlers. — The hides then go to handlers or suspenders,
which differ mechanically from rockers only in that hides are
hung at rest. The handler round is usually larger than the
rocker, but even though it contains only the same number of
vats, the hides stay in it longer, generally about 20 days.
The principle on which it is run is the same as for the rock-
ers. Occasionally, instead of being run as a round, the han-
dlers are run on a straightaway, the hides being moved ahead
and the liquor pressed down ; that is the vats communicate
with each other so that if liquor is run into the head vat,
some of the old liquor in this vat is pressed down into the
next below, which in turn transfers some of its contents to
the one below it, and so on down the line. Enough liquor
is removed from the tail pit of the handler section to make
room for what is run in at the head.
Instead of using rockers and handlers, the hides are some-
times rocked throughout the early stages up to the time when
they are laid away. This has some advantages, and undoubt-
edly hastens the tanning process ; in fact, one of the quickest
tannages is dependent for its success on the rocking of the
hides until the tannage is complete. For making belting
leather, however, any straight suspension process is not desir-
BELTING LEATHER 303
able, as it is practically impossible to hang the hides so that
they will not bag and draw somewhat into lengthwise
wrinkles from their own weight. The quantity of wrinkled
and baggy leather obtained by a straight suspension process
is too great to warrant its use. The head liquor for the
handler section is one of the oldest liquors from the yard
proper, or the layaways to which has been added some fresh
myrabolan liquor, in order that the necessary acidity may be
developed in the handler and rocker liquors, and the liquors
so mellowed. The liquors are worked down through the
handlers, going then to the rockers, and finally to the sewer.
Layaways. — At the end of 30 days in rockers and handlers
the hides are fairly well struck, the color is set, and they are
fairly well fixed in their condition of plumpness. As they
hung on the sticks they assumed their most natural position,
bellying out here and in there, and not at all resembling the
flat piece of leather which it is desired to make. However,
had the hides been piled down in these early stages, or had
they been pressed or pounded to remove wrinkles and bag-
giness, the plumpness would have been squeezed out, probably
never to return. This would have been serious to both the
yield and quality of the leather; flatness having been a rather
minor issue to this point, attention having been fixed on se-
curing color, uniform tanning, and the right degree of plump-
ness. At the end of the handler stage, however, the hides
are sufficiently well set so that they may be piled down and
flattened out moderately without undue loss of plumpness.
If the flattening process is deferred too long, the wrinkles
become so fixed that further remedies can only modify and
not eradicate them. At this stage, therefore, the hides go to
the layaways. These are vats large enough to permit the
hide being spread out flat. They are laid down with a layer
of tan bark or some inert material between each successive
hide so that the liquor with which the vat is filled may come
in contact with all parts of the hide. In the early days of vat
tanning, when only what would be now called very weak liq-
uors were obtainable, the layer of tan bark between the hides
304. PRACTICAL TANNING
was thick, and was used as much to supply tannin as to sepa-
rate the hides. With the use of the present-day strong liquor,
bark has become unnecessary as a source of tannin, and it is
used merely to keep the hides apart and let the liquor get at
them. This is not always true in sole-leather tannage, where
valonia and similar materials are used 'for dusting. The
early layers are for a fairly short time, and gradually increase
in length and strength of liquor as the hides become more
thoroughly tanned. A 100-day layaway series, for instance,
would run 3, 5, 7, 9, 12, 16, 21, 27 days per layer, the pack
being hoisted at the end of each period and laid away in a
different and stronger liquor. Some tanners prefer to use a
fewer number of layers, allowing the pack to remain in each
layer for a longer period. At each hoisting the hides are very
carefully pulled and stretched, and piled so that all wrinkles
and bagginess, hip pockets, etc., will be flattened out, and the
hide so far as possible put in such a condition of flatness,
that when laid on a level floor it will touch at all points.
The last four or five, possibly six, liquors are fresh leach-
house liquors; the earlier ones are those from which one or
more packs have been drawn, so that they have mellowed
and gained in acidity. These liquors are gradually worked
down through the yard, through the handlers and rockers
to the sewer. All the layaway liquors are not so worked
down and out. some being returned to the leach-house to be
strengthened and freshened; and, as previously described, the
liquor run to the handlers is strengthened by fresh material,
notably myrabolan liquor, to develop acid. In some tan-
nages other materials are frequently added at this stage to
secure some special color, mellowness, or other quality. The
strength of these layer liquors depends on the tannage desired,
but in general for belt, leather the strongest liquor used would
not run over 40 to 60° bk. Not many years ago, a 45° liquor
would have been regarded as too strong, but with a better
knowledge of the tanning process, and the growth of the use
of extracts, liquors as high as 120° bk. are not at all uncom-
mon, though not suited for making belting leather. As de-
BELTING LEATHER 305
scribed, the tanning process has required 130 days, an average
time, but both longer and shorter being in use.
Bleaching. — It is generally held that tanned hide must be
allowed to dry before being curried, in order to "set" the
tannage. It is therefore common practice, whether the leather
is tanned in the same factory where it is to be curried and
made into belting, or whether it is tanned to be sold in the
rough as a market butt, to give it a preliminary crude finish
such as is seen on ordinary rough leather. This finish con-
sists of washing, bleaching, oiling, and drying. Inasmuch as
rough belting butts are sold by the pound, the usual tannery
washing is the least that will conduce to a satisfactory ap-
pearance, and enable the leather to undergo the usual physical
examination to which buyers subject it.' Of course, when the
leather is produced for local consumption, the washing at
this stage will be sufficiently thorough to obviate the need of
the further washing usually given leather before the currying
process. Bloom is left on leather to be sold in the rough, but
this must be scoured off before the currying is begun or as a
part of the currying process. Briefly, the washing consists of
soaking in water at 110 to 120° F., or warm weak liquor, and
brushing off the surface dirt with a hand brush or by machine.
Some tanners use an old weak sour liquor for soaking, claim-
ing to get less loss of weight and some improvement of color.
Color is the tanner's bugbear. , If color and quality were syn-
onymous, there would be some excuse for the stress laid on
the former, but frequently leather of good color is poorest in
quality, hence the tanner feels compelled to make his leather
present as attractive an appearance as possible. Good looks
is the only excuse for bleaching, and when' one considers the
damage — both present and future — which the leather suffers
in the bleaching process, it will be seen that this quality is
dearly bought. The bleaching of the leather is usually ac-
complished by soaking or wheeling the leather in a bath of
sal-soda or borax, and rinsing, and placing it in a bath of
some dilute acid — generally sulphuric or oxalic. After this
bath the leather is thoroughly rinsed in clear water to remove
306 PRACTICAL TANNING
the acid. Unfortunately, the total removal of the acid is
very difficult, and some remains in the leather. As sulphuric
acid acts destructively on all organic material as long" as it
is present in a free state, a gradual deterioration — rotting of
the fiber — is bound to occur in leather containing any of this
free acid. A combined washing and bleaching process, which
seems less objectionable than many of those in use, is to soak
the hides in a liquor made from one of the heavily sulphited
extracts. In fact, extracts of this type are on the market
under the name of bleaching extracts, and give fairly satis-
factory results. If, however, the hides are properly prepared
in the beam-house, and the liquors rightly proportioned, there
is no reason why leather cannot be made, which, after care-
ful washing, will give a sufficiently good color without
bleaching.
Oiling. — After washing and bleaching comes oiling, which
consists in covering the wet leather all over with a heavy coat-
ing of Newfoundland cod-liver oil. After oiling, the leather
is ordinarily 'piled-down over night to give the oil a chance to
strike in somewhat, and is then hung to dry on hooks or
clamps fastened to the butt end.
Drying. — This process • demands careful attention if best
results as regards color, flexible grain, etc., are to be secured.
It was a rather uncertain process as far as results were con-
cerned when the leather had to be dried under ordinary atmos-
pheric conditions, but in these days of steam heat and venti-
lating fans there is no real reason at all for failure to secure
as certain and regular results in the drying as in any other
part of the leather-making process. The essentials of suc-
cessful drying are to start the process in a cool, moist air, and
increase the temperature and dryness of the air with the dry-
ing of the leather. When the leather has been dried, it may
be trimmed somewhat, rough corners cut off, etc., and is then
ready for the market.
Currying. — While most belt-makers probably do not tan
the leather they use for making into belting, they nearly all
curry the leather. They buy market butts in the rough, curry
BELTING LEATHER 307
them, and make them into belting. Currying may be defined
as introducing grease into leather and giving it such a finish
as will best adapt it to the purposes for which it is to be used.
As a matter of fact, currying, if properly performed, is really
making a combination-tanned leather out of the oak leather
by giving the latter a supplementary oil or fat tannage. In
order that the fat may produce this result it must be deposited
on the minute fibrils which make up the fiber bundles consti-
tuting the leather. The fibrils, having already been separated
by the vegetable tanning process, the fat may easily be de-
posited on them ; but an essential condition for the successful
deposition of the fat is that it be introduced into the leather
while the stock is wet. As the water dries out from between
the fibrils, the fat replaces it and brings about the secondary
oil tannage, which renders the leather more pliable, more
resistant, and permanent, and of increased tensile strength.
Inasmuch as the grease is introduced into the leather when it
is wet, the first step in the currying process would seem to be
to wet-back the leather.
The wetting-back of the leather is, however, not ordinarily
done merely as a preliminary operation to putting- the grease
into the leather, but is a clearing process intended to remove
superfluous tannin, bloom, etc. As the washing which the
rough leather usually receives at the tannery is as little as is
consistent with a satisfactory appearance, the belt manufac-
turer finds that it improves the quality of his leather to remove
some of the excess tannin left in by the tanner and replace it
with grease. He therefore gives the leather a rather thorough
washing, its completeness depending on the currier's previous
experience with the leather, or his judgment of how much is
needed.
Scouring. — If the tannage be inclined to excessive solidity
and firmness, the leather will be soaked to soften it somewhat
and then drummed with warm water. This treatment will
last from 10 to 30 minutes, perhaps with no change of water,
but probably with a constant stream of warm water entering
the wheel; in extreme cases, the leather may be drummed in
308
PRACTICAL TANNING
\a weak solution of borax, then in clean warm water. The
drumming is ordinarily followed by a scouring process, needed
particularly in the case of leathers with much bloom. This
scouring is sometimes done on a Vaughn machine, a stream
of water being run on the revolving roll and the leather; but
it is perhaps done more successfully on a Fitz-Henry machine.
A stream of water is run on the part of the leather worked
on by the stones of the Fitz-Henry machine, and the move-
ment of the stones under these conditions scours the leather
satisfactorily. If the tannage is lighter, it may be sufficient
Figure 87. — Currier's knife.
merely to soak the hides and work them out on a Vaughn or
Fitz-Henry; or even — if the leather carries little bloom — after
the soaking, merely brush the leather by hand or machine.
The belt butt, usually after the washing, but sometimes
before, is cut into a belt bend and shoulder. While the best
part of the shoulder may sometimes be used for a cheap
quality of belting, our interest is in the belt bend; but the
process of currying the shoulder for belting is similar to that
for currying the belt bend, save that more and somewhat dif-
ferent treatment is required to work out wrinkles as much as
possible. The belt bend is at this stage cut into three pieces —
a center and two sides — the divisional cuts being made par-
allel to the backbone and at equal distances from it on either
side. There is a growing tendency to finish and stretch belt
leather in the whole bend rather than in center and sides.
Skiving. — This is the removal of superfluous flesh, etc.,
from the flesh side of the leather. It used to be done almost
entirely over the beam with a knife with a turned edge (fig-
BELTING LEATHER 309
ure 87), but this is now done by the belt-knife splitting
machine! Still another method of skiving, wh.eh.ts largely
used at present, is by the whitening machine (figure 88).
Whitening is done at a later stage, but at whatever stage per-
form d its object is to give a clean, smooth back to the eather
wTth no superfluous flesh. If, for instance, the leather ts
Figure 88.-Whitening machine u^d for cleaning-
up flesh side of various kinds of leatner.
to be used for a double belt, that is, one made of two thick-
1 es of leather cemented together flesh-to-flesh, it .*£ not
be possible to cement the leather so that it wou d hang to
gether under the conditions of service if any loose or super
fluous flesh remained on the leather. s „hiected
Hand stuffing.-^, next process the leather »**£•£
to is dependent upon the particular mode o . tiffing o be
employed, that is, the way in which grease ? shabby put nto
the leather. There are three methods in use for tuffing bekmg
leather namely, hand stuffing, wheel stuffing, and hot stuffing '
The first is the oldest method, and is still preferred by many
hirers. The leather, after skiving is amped ba*
and Diled down to even up and temper, that is, before apply
£ the stuffing it is desirable that the leather should be in
310 PRACTICAL TANNING
as uniform a condition of wetness all over as can be attained.
In this case, the grease will penetrate more evenly, and yields
a much more uniform and satisfactory piece of leather. The
currier therefore wets the leather where it seems dry and
then piles it down so that parts of the leather having too
much moisture will give up some to the dryer parts, and vice
versa. After tempering, the leather is set, usually either by
hand or on a Vaughn machine. If by hand, the leather is
spread out on a table and carefully worked out by a slicker
until it lies perfectly flat on the table with the edges as
straight as possible and the grain smooth. If by a Vaughn
machine, it is gone over several times with the roll until it
is as flat and smooth as possible. After setting, it is given
the grease or stuffing. This is applied usually to the flesh
side alone, the grain side getting a coat of refined Newfound-
land cod-liver oil. There is little variation in the composition
of the hand-stuffing of dubbin used in different factories.
It is generally made by melting together 2 parts of oil and 5
parts of tallow, if the tallow be soft, or 1 part of oil and 4
parts tallow if it be hard. These formulas are varied
slightly according to the season of the year, more oil and
therefore a softer dubbin being used in cold weather and the
reverse in warm. After melting, the mixture is stirred con-
stantly while cooling so as to produce a smooth salve-like,
homogeneous mass. This dubbin is applied with a swab to
the flesh of the leather so that it makes a smooth, even coat-
ing, the thickness depending on the currier's knowledge of
how much grease the leather will absorb, and not be discolored
or look greasy. Only the oily constituents of the dubbin
enter the leather, the harder components of the tallow, stear-
ine, and palmitin being left as a white coat on the surface.
After the leather has been given its coating of grease, it is
hung in a moderately warm room with a good circulation of
air, and allowed to dry. If too much heat is applied the
leather becomes black and greasy, the grease not penetrating
into the fibrils; but if too little heat, drying requires an ex-
cessively long time and the leather is likely to mildew. When
BELTING LEATHER 311
properly carried out, the oily portions of the dubbin enter the
leather as it dries, giving it a rich mellow feeling, and leaving
it a good color. When the leather is dry, nothing but a dry
white scale showing no oiliness should be left on the back,
The leather is now taken down, wet-back once more, and
piled-down, and is then ready to stretch.
Wheel stuffing. — The leather is washed and skived as in
the hand-stuffing process, but the division of the belt bend into
a center and sides is usually deferred until later. After
skiving, the bend is wet-back and piled-down to temper. For
wheel stuffing, this wetting-back is a most important opera-
tion, and the success or failure of this treatment depends
more on the preparation of the leather than on anything else.
The wetting is usually entrusted to one man who makes a
specialty of that work, and he must be an artisan of rather
more than ordinary judgment. For wheel stuffing, the leather
must not be wet uniformly, but the softer and spongier parts
of the leather must be distinctly wetter than the firmer parts,
otherwise they absorb so much more grease that they appear
very black and greasy in the finished leather. The usual test
to find out whether leather is in proper condition for stuffing-
is to bend it over and see if this forces out water in fine drops;
but evidently there will be a difference in behavior between
the softer and firmer parts of the leather, and the precise
action can be learned only by experience.
The leather which has been wet-back is usually allowed
to lie in a pile, covered with wet bags or protected in some
similar way, until it begins to heat up by fermenting action.
It is then touched up by the man at the wheel, the spots that
seem at all dry being given a little more water, and thrown
into the wheel as quickly as possible to get the benefit of the
heat in the leather. The old-time wheels were simply heated
by running in live steam before the leather was put in, and
the heat retained by the wheel depended upon to keep the
leather and grease warm. The better modern practice is to
use a wheel connected through the two hollow trunnions with
a fan and steam coil, so that hot air can be run in and out
312 PRACTICAL TANNING
of the wheel throughout the drumming process. The wheel
contains shelves or pins on the inside, so that the leather is
carried up by the wheel as it revolves until it is no longer
held, when it drops back to the bottom of the wheel to be
picked up once more. The warm leather having been put
into the wheel through a door in the side or rim, the hot
melted grease is added, the door closed, and the wheel started.
The temperature of the wheel inside is kept at about 120° F.
The stuffing grease used in the wheel is harder and less oily
than that used for hand stuffing. If of tallow and cod oil,
a much greater excess of tallow is used, and frequently oleo-
stearine is added to the mixture to produce a still harder
mixture. For instance, one formula used for belt leather
consists of 9 parts good tallow to 1 part refined cod oil; an-
other and harder, 75 parts tallow, 9 parts stearine, and 16
parts cod oil. As in hand stuffing, the formula used is varied
in accordance with the season of year and the known capac-
ity of the leather for carrying grease. An average leather
can carry 12 per cent of grease similar to the above mixtures,
calculated on the we1^ weight of the leather as prepared for
stuffing. It will usuahy require about an hour to work this
quantity of grease into the leather. The rolling, tumbling,
and pounding given the leather in the wheel gradually works
the grease in among the fibers of the leather, but it probably
is not really deposited on the fibrils themselves until the leather
dries. During the last part of the drumming in the wheel,
the door of the machine is frequently removed to cool the
leather somewhat and set the grease, and as the leather is
finally removed from the wheel it is piled down for at least
24 hours, being turned over during this time to prevent ex-
cessive heating, in order to give the grease still further oppor-
tunity to fix itself permanently in the leather.
If this were not done, far too much of the grease would
be worked out of the leather during the various setting proc-
esses which now follow. The wheel-stuffed leather, which
was carried along as a belt bend, is usually set on a Fitz-
Henry or Turner serial table machine (figure 89), though it
BELTING LEATHER 313
is sometimes still set by hand. The former, from its
construction, gives results much more nearly approaching
hand setting; in fact, it is a very interesting sight to watch
an experienced operator take a baggy bend and gradually
work out the bag until the bend lies smooth and flat on the
table, a procedure often requiring considerable skill. The
Figure 89. — Serial table setting-out machine.
Turner machine is very simple, and requires no special skill
to operate. The bends are spread over the edge of a moving
table which passes between revolving rolls. These rolls press
the leather down, spread and flatten it, and set it out fairly
well, if the leather was in reasonably good condition to start
with, that is, fairly flat and not too hard and heavy. In the case
of a really bad bend, however, hand-setting or the Fitz-Henry
machine must be resorted to. The great advantage of the
Turner machine is in the increased amount of work it can
do. After the belt bend has been set out it is cut into a
center and sides, if desired, or carried through as a whole
bend, and is worked out still further on the Vaughn machine
314 PRACTICAL TANNING
to give a smooth grain free from wrinkles and make a more
compact piece of leather; then oiled on the grain, and is ready
for the stretching process.
Hot stuffing. — There is one more method, namely, the so-
called hot stuffing. It is rather curious that if very hot grease
be put on a piece of leather which contains any appreciable
amount of moisture, it will burn it, making it brittle and of
no strength. If, however, this same hot grease be applied to
an absolutely dry piece of leather, it exerts no harmful effect.
The hot-stuffing method then consists in placing the belt bends .
in a dry room where they are heated until all moisture has
evaporated, and either laying them on a table and pour-
ing hot grease over the flesh or grain, or both ; spreading it
by a brush so long as it is absorbed by the leather, or actually
dipping the whole bend into a tank of melted grease, and
allowing it to remain until it has absorbed all the grease possi-
ble. In either case the grease may be 200° F. or over. In
the second case, the leather, after removal from the tank,, is
hung in a hot room to drip and permit surface grease to melt
off, after which it is thrown into cold water. The bends
piled on the table are thrown into cold water as soon as
filled.
The grease put into the leather in this way does not "com-
bine with the leather, coating the fibers and bringing about
a beneficial grease tannage, but merely serves as a filler. Be-
fore the leather filled with grease by this process can be said
to be really stuffed and curried, a way must be found to
make the grease come into intimate contact with the fibrils of
the leather. This is accomplished by wetting the leather and
allowing it to dry, when, just as in the hand and wheel-
stuffing processes, the grease follows the water into the in-
most fibrils of the leather and brings about the grease tannage.
The hot-stuffed leather, being saturated with the grease, is not
readily wet-back, consequently simple soaking in water will
not suffice. The leather is therefore put in a wheel and
drummed with water until it has become soft and wet through.
This is really a drum-stuffing process reversed. In the one
BELTING LEATHER 315
case, wet leather is put in and drummed in grease ; in the other,
creasy leather is put in and drummed in water. At the end
of the drumming process the leather must be put through some
sort of cleaning process to remove the grease from the sur-
face and so yield a product of good appearance. The hot-
stuffed leather, stuffed on the table by having hot grease spread
on the flesh side alone, may be brought through in a condi-
tion where the grain is clear and free from grease and so need
no bleaching; but this is doubtful policy, as it may have the
grain side lacking in grease and likely to finish harsh and
dry. There are a large number of bleaching processes in
use, some using the regular soda and acid bleach, which is
likely to be less harmful at this stage on account of the con-
siderable amount of grease in the leather. Some makers use
a little borax, soda, or soap to cut surface grease. In some
cases drumming with sumac leaves is found to work satis-
factorily, and this latter method would seem to have less ob-
jectionable features than any of the others. After the wheel-
ing and bleaching processes, the belt bend is handled the same
as the belt bend in the drum-stuffing process. It is piled-down,
set, cut into center and sides, worked on a Vaughn machine,
oiled on the grain, and stretched.
There are advantages and disadvantages connected with
each mode of stuffing. For instance, it is impossible to over-
load the leather with grease by the hand-stuffing process ; but
on the other hand, it is impossible to put into the leather any
of the harder greases which give leather a peculiarly mellow
and substantial feel, as well as making it more permanent
and resistant.
Stretching. — This process and finishing are the same for
all the leather, whether hand, wheel, or hot-stuffed. The
idea underlying the operation is that leather, being a fibrous
material, will, when subjected to stress, "give" more or less
and stretch out, becoming longer. If this stretching takes
place after the leather has been made up into belting and
put on a machine, the belt may soon become so loose that
it will fail to drive, necessitating a shut-down until the belt
316
PRACTICAL TANNING
can be shortened; so the leather is stretched to remove most
of the give, and that the trouble from the belt stretching on
the machine may be lessened. It is not desirable that this
preliminary stretching be carried to the utmost limit, as this
undoubtedly weakens the leather and reduces its term of
service.
The stretching process is simple, and consists in fastening
Figure 90. — Heavy rolling-jack.
the ends of the piece of leather in clamps, one of which is
securely fastened at the end of a rectangular frame or board,
the other of which can be moved, and by a tooth-and-dog ar-
rangement fastened at any desired point. The frame and all
is then put in a machine which grips the two clamps, and suit-
able mechanism pulls the free clamp slowly away from the
fixed one, thereby stretching the leather. When sufficiently
stretched, the dog is allowed to drop into place, and the frame
removed from the machine and hung in a room where the
leather can be left to dry out in the frame in its stretched
condition. The leather, when removed from the frame, if it is
BELTING LEATHER 317
good leather of reasonable elasticity, springs back somewhat
and loses some of the stretch given it. Moreover, on ac-
count of the unnatural condition of the fibers when dried, the
leather has a rather stiff and bony feel. It is therefore worked
on a heavy rolling- jack (figure 90) on the flesh side, which
mellows the leather, removes the stiffness from it, and gives
it pliability. If a dull finish is desired on the grain, the
leather is brushed under a rotary brush; and if a glossy finish,
the leather is passed on a glazing-jack, after which it is ready
to be made into belting.
The question whether a leather belt should be run with the
grain or flesh side next to a pulley has been much debated,
and tests of the power capacity of each side were recently
made by the Leather Belting Exchange at Cornell University,
under the direction of R. F. Jones. The test covered two
months. Five 4-inch single belts, 30 feet long, of different
makes, were used; and all were thoroughly "run-in," or had
reached a condition of constant capacity when the records were
taken. The method was to take horsepower readings from
the belts, first when running on the grain side and then on the
flesh side, the power being gradually increased until about 4
per cent slip had been reached. A summary of all the tests
was clearly in favor of the grain side from the standpoint of
transmission. Under reasonable shop tension, the flesh side
will average only 50 to 60 per cent as much power as the
grain side; but the running is more uniform than the grain
side.
CHAPTER XI
STRAP, WELTING, BAG, CASE, AUTOMOBILE, AND
HARNESS LEATHER
Strap leather. — In this chapter only a general outline is
given of the various operations, as the details involved have
been already covered in previous chapters.
Stock. — The stock should be green-salted packer steers and
cows, ranging from 50 to 70 lb. ; South American frigorificos,
or green-salted Chinas. These hides should be free from
grubs, cuts, brands, and scars.
Soaking. — The trimmed stock, either as hides or sides,
should be washed in the mill for 15 minutes with running
water, toggled together, and then placed in the soaks, fresh
water being used. After 24 hours the hides should be reeled
to a second soak for another day.
Depilating. — For this grade of leather it is very essential
to conserve as much hide substance as possible, and in order
to do this, very old lime should be avoided and the time of
treatment reduced to the minimum. A process which gives
exceptionally good results is as follows : The soaked stock
is reeled into a tail-lime liquor which has been pressed down
from the head pit and to which has been added a half-pound
of crystal sulphide for each side. Having established the
liming process, half of the tail liquor is discharged and its
place is taken with well plunged liquor from the pit above. The
sulphide is added to the tail liquor. As the tail lime is dis-
charged, fresh lime should be added to the head pit.
Unhairing. — The depilated hides as they come from the
warm pool should be spotted on the floor for white hair, and
then unhaired on either a Leidgen, Whitney, or Turner ma-
chine. They should then be fleshed on the machine, and fine-
haired on the beam if necessary. The unhaired and fleshed
stock should be washed in a slush-wheel or paddle.
Bating. — The bating should be done with oropon XX. In
318
STRAP, BAG, AND HARNESS LEATHER 319
using this bate, start the paddle with 12 oz. of oropon for each
100 lb. of stock, discharging a third of the liquor each day
and making up with 8 oz. for each additional 100 lb. At
the end of the week, completely discharge the old bate and
start fresh on Monday. The temperature of the bate should
be about 90° F. when the pack is entered, and the stock
should be bated through before removing from paddle.
Washing. — The bated stock should be thrown into the pad-
dle-wheel and washed with cold running water for half an
hour.
Rockers or stick pits. — The washed hides should be placed
on sticks, preferably using a rocker system, or some other
satisfactory method of agitating the liquor. The tail liquor
should stand at about 8° bk. and contain about 0.31 per cent
of acid. The density of the liquor should increase gradually
to 15°, and should be pressed forward each day for 20 days.
It will be understood that various combinations of tanning
material could be used, but it is suggested that a combination
of 33 per cent hemlock, 33 per cent ordinary quebracho., 31 per
cent of chestnut bark, and 2 per cent of myrabolan be em-
ployed. In order to prevent an accumulation of soluble non-
tans, it is desirable to discharge at least one out of every five
tail rocker liquors ; the other four may be returned to the leach
or extract mixer.
Splitting. — One of the most important factors in making
strap leather is in connection with the splitting. If the stock
is over-tanned before splitting, it is likely to be weak. When
in proper condition the hides should be well struck, but should
show yellowish through the center portion.
Layaivays. — From the rockers or stick pits the hides are
jacked and split to gage, and the grain placed in the layer.
The tail-layer liquor should stand at 20° bk. and the head layer
at 28°. The stock should be handled forward after 24 hours,
again after 3 days, at the end of 7 days, at the end of 11 days,
and removed at the end of 2 weeks. The same combination
of liquor may be used as in the rockers except that the myrab-
olan should be eliminated. A slightly better combination,
320 PRACTICAL TANNING
however, consists of a mixture of 50 per cent ordinary que-
bracho, 25 per cent chestnut, and 25 per cent hemlock.
Bleaching, — As it comes from the layers the stock is washed
slightly and then stripped with a small amount of borax, say
| per cent on the weight of the stock, running for 10 min-
utes ; the borax solution is removed and the alkaline condition
eliminated by running for 10 minutes with |- per cent of sul-
phuric acid. It should be understood that both the borax and
sulphuric acid must be very dilute.
Re-tanning. — To the bleached stock still in the mill, enough
water is added to float it, and then 2 per cent of dry sumac
is introduced. The stockis milled with the sumac for half an
hour, well washed, and passed through the Quirin press.
Stuffing. — The well-set stock from the press is again placed
in the mill and heated with hot air. When warmed through,
a mixture of 3 lb. of stearine and 8 lb. of tallow for each
100 lb. of stock is melted, and at a temperature of 130° F.
is added to the leather in the mill. The mill is now run for
half an hour to absorb all of the fat. From the drum the
stock is piled-down for several hours to set the grease.
Setting. — When the grease has become fixed, the stock
should be dipped in cold water, and then set out on the ma-
chine, preferably the Fitz-Henry. The stock should next be
piled-down over night, and then set by hand, using a dubbin
of 3 parts of tallow to 1 part of cod oil on the flesh. The
leather should again be piled-down over night and re-set by
hand without application of dubbin.
Tacking. — A light coat of cod oil should finally be applied
to the grain and the stock tacked.
Whitening and snuffing. — When dry, the sides are removed
from the boards and whitened on the flesh side. They are
then snuffed by hand, although some success is being ob-
tained by using a special shaving machine and emery wheels.
To the flesh side a solution of Irish moss or lissom extract
should be applied, and the stock rolled on the flesh while yet
damp.
Finishing. — To the flesh side, a solution of either dextrine,
STRAP, BAG, AND HARNESS LEATHER 321
lissom, or flaxseed liquor containing an acid yellow, should be
applied. This mixture produces the russet shade. When dry,
the stock should be smooth-plated and given a tallow finish
on the grain. This tallow finish could consist of either pressed
tallow or stearine made into an emulsion with soap. These
finishes may also be purchased on the open market. When
the stock is perfectly dry, it should be brushed on the machine
and is ready for use. Some equipment manufacturers prefer
to receive the leather before the tallow finish has been brushed,
as it protects the leather during the handling through their
shop. The tallow finish has an advantage over shellac finish
in that it is more waterproof.
Goodyear welting. — The better grades of welting are made
from plump hides weighing 50 to 60 lb. each, and tanned ex-
pressly for welting. Welting is also made from the shoulders
of belting butts, but such leather is likely to be harsh and
brittle, and not as satisfactory as that made from upper
leather. The hides are limed thoroughly and bated down low
to give a fine grain.
Tannage. — The tanning should be effected fairly slowly and
the tannage should be mild to prevent drawn and rough grain
from too strong liquor. Any good upper-leather tannage is
suitable for welting. A combination (2 to 1) of quebracho
and .hemlock extracts produces good leather. The sides are
suspended in weak coloring liquor for 24 hours and are then
transferred to stronger liquor, which is strengthened from
day to day until the sides are well struck through. Chestnut-
oak wood, as well as oak and hemlock, also makes good welt-
ing leather. Leather tanned in weak liquors finishes softer and
tougher than that rushed through strong liquor. The hides,
when well struck with the tan, are put in the press and made
ready to be split. Before being split, they are, however,
cropped and the bellies sent back to be re-tanned. The backs
are split 6 to 8 oz., according to the weight desired, and are
then put into a drum and re-tanned with strong gambier liquor.
Sumac should not be used, as it has a tendency to make the
grain coarse. The next process is bleaching to remove the
322 PRACTICAL TANNING
stains from the splitting machine. The leather is run in the
drum for 30 minutes in a solution of 6 lb. of borax in 40
gallons of water at 100° F. After this, the leather is washed
in clear water to remove the borax, it is then milled in a solu-
tion of sulphuric acid, using 1 pint of acid in 40 gallons of
water, and running the leather in it 20 minutes. The leather
is then washed in clear water and fat-liquored.
Any good fat-liquor will do, but better results seem to be
secured with the use of neat's foot oil and chip soap. The
leather is fat-liquored, dried, and- sammied, and set out thor-
oughly. A light coat of cod oil, mixed with 25 per cent of
paraffin oil, is then given the grain ; the leather is next turned
over and struck out on the flesh, a light coat of fat-liquor
being then applied to the flesh, and the leather hung up to
dry. When partly dried, it is taken down and re-set with a
heavy slicker, then dried and put into pres's. It is not rolled,
nor is any finish applied. If the work is carefully done, the
grain has a light, clear color which readily absorbs any stain
or color that may be applied.
Rough leather of soft tannage makes good welting when
finished in this manner, but it must be firm and pliable, and
not harsh and brittle.
The shoulders of the hides, the butts of which are made
into belting, cut from the hides before they are tanned, are
largely used as welting. The shoulders, after having been
tanned, are run through the splitting machine and leveled.
They are then bleached with sulphuric acid after a borax bath,
as described, washed with clear water, scoured, hung up to
dry, and when in condition, are rolled on the sole-leather roller.
A coating of oil is next given them, and they are then dried
out, receiving no other finish. This shoulder welting is never
as good as that made from the backs of upper stock treated
in the manner previously described. An oak tannage is pre-
ferred to other tannages for shoulder welting.
Bag and case leathers. — The first essential in the manu-
facture of bag and case leathers is good hides, preferably
green-salted, which are clear on the grain and free from
STRAP, BAG, AND HARNESS LEATHER 323
butcher cuts on the flesh side. When the hides have been se-
lected, trim off the heads and shanks and put the hides into
clean soft water. The best way to soak them is to suspend
them in the water for 24 hours ; then take, them out or run
off the water and fill the vat with fresh water, and soak 24
hours longer. Then split into sides, taking care to keep the
backs straight. Five pounds of borax, dissolved and added
to 1,000 gallons of water, helps to soften and cleanse the
hides. After having been split into sides, the hides are
fleshed, when they are put into clean cold water over night
and the next day into the lime, which usually requires 6 or 7
days. The hides are then washed and bated by using any
one of the several bating processes that have previously been
described. The hides require a clean bate to prevent staining,
and need to be well bated to produce a soft and clear grain.
They may then be either pickled or drenched.
Tanning. — Hemlock and quebracho extracts used in 33 : 66
proportion make an excellent tanning process for bag and case
leathers. The sides are nailed on sticks and suspended in a
weak coloring liquor for 24 hours. This produces plumper
leather than a paddle-vat. The sides are then put into a liquor
of about 10° bk. strength, and each day the liquors are bet-
tered until they are about 30°. When well struck through
with the tan the sides are pressed and split. The grains may
be re-tanned in a drum with hemlock-quebracho liquor, and
then colored and finished. Tanning with hemlock and re-
tanning with a combination liquor is effected as follows:
The sides are tacked on sticks and hung in a 7° hemlock liquor.
They are handled every day for three days, and the strength
of the liquor is gradually raised to 10° and then to 12°.
After being in a 12° liquor for 24 hours, the sides are put
into a combination liquor made of chestnut-wood extract and
quebracho extract. The strength at first is 16° ; but this is
gradually raised to 20°, taking 16 days to do it. The leather is
next pressed and split, and the grains are then re-tanned. The
re-tanning liquor should be 3 parts quebracho and 1 part gam-
bier of about 26° strength, and the leather milled in it one
324 PRACTICAL TANNING
hour, then placed in piles for 24 hours, after which it is in
condition to be bleached and colored.
Another good tanning process consists of two-thirds hem-
lock and one-third oak-bark. The hides are first colored in
a sour liquor, then put into the tan liquor of 7° and handled
each day, the liquor being strengthened until it is 10 or 12°.
When well struck with the tan, the hides are pressed and split.
Re-tanning is done with either quebracho and sumac, or with
quebracho and gambier. If the former is used, the liquor
should be 20°, two-thirds quebracho and one-third sumac.
Running the leather in this liquor for an hour accomplishes its
re-tannage, after which it is ready for coloring and finishing.
It is sometimes advisable to drum the sides in a solution
of borax, and then in an oxalic acid liquor after they are
split and before re-tanning, in order to clear and bleach them.
The leather is first run in a borax solution for 20 minutes and
then washed, after which comes a solution of 2 lb. of oxalic
acid in 15 gallons of water for 10 minutes, finally washing
free of acid and re-tanning,
The usual practice, however, is to bleach leather which re-
quires it, after it is re-tanned. It should not be pressed too
hard for splitting, since the more moisture there is in the
grain when re-tanned the better the results will be. When
leather is pressed dry for splitting, the grains should be milled
in weak liquor before they are re-tanned, and this extra mill-
ing prepares them for the re-tannage. More rapid and thor-
ough penetration results by adding 1 quart of sodium bisul-
phite to each 6 gallons of re-tan liquor. Excellent leather is
made by tanning the sides in a one-bath chrome process, then
washing and re-tanning, the latter being done with quebracho
and chestnut-oak extracts" in the proportion of 3 parts of the
former and 2 parts of the latter. The liquor should be 12°
bk. at the start, strengthened to 18° the next day, and to 24°
on the third day. Each night the hides should be taken out
of the liquor and piled down until the next morning, and then
put into the strengthened liquor. After having been re-
tanned for three days, the sides are piled down until the next
STRAP, BAG, AND HARNESS LEATHER 325
day, then pressed and split. The well-washed hides, after re-
tanning, should be stuffed with a mixture of equal parts of
degras and cod oil emulsified with a soluble oil, and hung
up to dry. The dry stock should then be sammied, set out,
oiled off with cod oil. and tacked. On stripping, the hides
should be seasoned with flaxseed liquor, rolled, and soft-
m
Figure 91. — Boarding machine.
boarded For soft-boarding, the machine shown in figure 91
is commonly used.
Vegetable-tanned splits. — The splits taken off untanned
hides, that is, from hides which are split out of the lime, or
out of acid pickle, or out of a pickle of aluminum sulphate
and salt, can be tanned in various ways — with extract of hem-
lock, quebracho, gambier, and finished into inner-soling and
other leather. Splits taken from limed hides are drenched
with lactic acid or some other suitable de-liming material,
then tacked on sticks and hung in the tan liquor and tanned
wholly by suspension. Splits taken from hides full of acid
and salt should be first drummed in a solution of 10 lb. of
salt and 6 gallons of water for 100 lb. of splits for 20 min-
utes. This puts all parts of the splits into condition to take
the tan liquor. The first solution into which the splits are
placed is a plumping liquor made of hemlock extract, and
should contain at least 0.6 per cent of lactic acid to swell the
326 PRACTICAL TANNING
fibers of the splits so that they will absorb the tannin. The
splits should then be put into a regular bark yard and worked
through stronger liquors, being handled every other day, from
two to three weeks being required to tan them, according to
their thickness.
Splits taken from hides pickled with aluminum sulphate
and salt may be put into weak liquor or drummed therein,
and then tanned in hemlock liquors of gradually increasing
strength until they are fully tanned. No salt is needed in the
liquors, and the sulphate or alum is washed out before the
tanning is finished.
The most satisfactory way to tan splits is by suspending
them in the liquor. Where this cannot be done owing to lack
of vats, a paddle-wheel may be used, this being better than
a drum. There is no violent pounding in the paddle, and the
splits therefore finish up finer than when a drum is used.
Heavy splits may be put into a 10° bk. quermos extract liquor
in a paddle until they are struck through. They should then
be tanned in strong hemlock bark or hemlock extract liquor
until they are thoroughly filled and tanned. For light, flex-
ible splits, some softer tannage may be used, such as quermos
extract, the first liquor being 10°. The splits are then passed
into stronger liquor, or the weak liquor may be strengthened.
This method of tanning makes soft splits which require very
little oil or fat-liquor.
Before splits which are full of alum, or aluminum sulphate
and salt are put into extract or bark liquors, it is advisable
to drum them in weak gambier liquor until they are softened.
They should then be tanned in strong liquors, the alum and
salt disappearing before the splits are ready to be finished.
The splits should never be washed in water before they are
tanned, or they will be flat and flabby when finished. Splits
are also improved by being drummed in gambier liquor after
they are tanned. This has no effect as a tannage, but it does
improve the texture of the leather. Scouring and cleaning
the leather is also beneficial ; or the splits after they are fully
tanned and drained can be rinsed in a vat of water, which will
STRAP, BAG, AND HARNESS LEATHER 327
remove any sediment. They should never be put into a drum
and washed as this causes them to lose their plumpness and
fall away and become thin. After they are rinsed off, they are
hung on poles to dry, and when dry, they are dampened and
stuffed. Rough splits for inner-soling are re-tanned with a
mixture of two-thirds quebracho extract and one-third hem-
lock extract, then rinsed and re-tanned with sumac in a vat.
They are then partly dried and stuffed, a good mixture con-
sisting of 1 part tallow, 2 parts soap, 6 parts Irish moss, and
30 parts water. After having been stuffed, the splits are
set out on a table, and a mixture of 6 parts Irish moss, 1
part starch and 2 parts soap is rubbed in on both sides with
a stiff brush. They are then set out with a slicker and hung
up flat to dry. A jacking completes the work. Tanners who
want to increase the weight of their splits add a little grape
sugar to the stuffing mixture.
Splits taken from hides tanned with hemlock, quebracho
and chestnut extract in combination process can be worked
into Goodyear stock by being trimmed after they are split,
and re-tanned in a paddle with a combination liquor com-
posed of quebracho and chestnut extract. They may be run
a short time in a drum with a weak liquor to break up the
crust caused by the belt-knife. They are then put into a 16°
liquor and left in it 48 hours, and next placed in piles 48
hours ; then returned to the liquor for 48 hours, the paddle be-
ing run about 2 hours in the morning and 2 hours in the after-
noon. When well filled, they are left in piles for a few hours
and then put into a drum with the following mixture : For
50 Goodyears, use 4 lb. of flour, 8 lb. of epsom salts, 1 gal-
lon of cod oil, 1 gallon of degras, and 10 lb. of talc, all mixed
together to a smooth paste; then add water at 85° F., to
make 25 gallons. Run the splits in this solution for a half-
hour and then put them into piles over night. In the morn-
ing set them out thoroughly; apply a paste made of Irish
moss or lissom extract and flour, and hang them up to dry.
When dry, give them a coat of Irish moss and talc on both
sides, and roll hard; then dry.
328 PRACTICAL TANNING
Softening and stuffing heavy splits. — The dry splits require
careful dampening and softening. A good way to do this
is to wet half of them in water; then place a dry split on the
floor, then a wet split on top of it, then another dry one,
then another wet one until all are piled-down. Leave them
there 2 or 3 days to become uniformly soft and damp, keeping
them well covered. Proper dampening is the secret of soft,
well-filled goods. The splits can also be dampened by being
sprinkled with water or sprayed with a hose and left in cov-
ered piles until they are damp and soft; 200 lb. of dry splits
should not weigh more than 260 lb. when damp.
The amount and kind of grease to be used depends upon
the tannage, and must be decided by the operator. Some
tannages take more grease than others, gambier and other
soft tannages not requiring as much as hemlock and combina-
tion tannages. The harder the grease the more can be put
in. Sometimes 100 lb. of dry splits will carry over 100 lb.
of grease, 110 lb. being the maximum. The grease should
be heated to 125° F., and the drum with live steam to the
same temperature, before the splits are put in. Some degras
may be used and a little sod oil, say 10 per cent of it, but
not more, and this only when the grease is good and hard,
or when stearine is used in making the stuffing. The splits,
as well as the grease, having been weighed exactly, should be
carefully and uniformly dampened, and the right temperature
maintained during the process. A good stuffing mixture for
gambier-tanned splits is made of 6 gallons of brown grease,
4 gallons of common wool grease, and 2 gallons of stearine.
If the brown grease is good, use less stearine. Use from 4
to 6 quarts of sod oil to every 12 gallons of the stuffing mix-
ture. If the splits are very hard, use a half gallon more of
sod oil to each 12 gallons of stuffing. After having been
stuffed, the splits are finished by being whitened, blackened
with soap and lampblack, dried, trimmed, given a paste of
flour, dried, rolled or glazed and covered with a size made of
gum tragacanth, lissom extract, dried again, sorted, and
graded.
STRAP, BAG, AND HARNESS LEATHER 329
Stuffing for waxed splits. — To make 100 lb. of stuffing
grease, take 45 lb. of tallow, 10 lb. of wool grease, 25 lb. of
stearine, and 20 lb. of paraffin wax. Dissolve the stearine
and wax, add the tallow and then the wool grease. Use from
35 to 40 lb. of the stuffing to 100 lb. of dampened splits. Heat
the drum to 125° F., and the grease to the same temperature.
Let the drum run 20 minutes with the door closed and 10
minutes with the door open. Hang the splits up until they
are well cooled off and stiff; next set them out tightly on the
back and then on the face side, and hang them up to dry.
Another formula for stuffing is : Heat hard glucose to 140°
F. in a suitable kettle. In another kettle place one-half wool
grease, one-half brown grease, and one-third best stearine,
and cook thoroughly. Use about 12 lb. of glucose with 40 lb.
of combination grease, mixing just before using. The glu-
cose gives good color and weight, but it must be used carefully
and with judgment. If the splits are too wet or too dry, or
of hard tannage, no stearine is necessary, good brown grease
and wool grease and glucose being sufficient under such con-
ditions. Dampening for stuffing should be done in such a
manner that 300 lb. of splits take an additional weight of 35
pounds.
Harness leather. — Green-salted hides are generally used in
the manufacture of harness leather. They are washed for
10 minutes in running water, cut into sides, and soaked for
48 hours in the pit. When thoroughly soaked they are fleshed
and limed for 5 days with hydrated lime and sodium sulphide.
Unhairing is most generally done on the Leidgen machine,
after which the sides are bated with oropon. When well bated,
the stock goes to the tail rocker containing an 8° bk. liquor
with an acidity of 3 per cent. The sides remain in the rockers
for 8 days, the strength being gradually increased to 15°.
The liquor in the handlers consists of the mixture of hemlock
bark, quebracho and chestnut-wood extract in about equal
proportions. On removal from the head rocker, the sides are
placed in the first layer for 5 days where they meet a 21°
liquor made up in the same proportion as the rocker liquor.
330 PRACTICAL TANNING
In the second layer the stock remains for 11 days, meeting
a liquor of 22°. In the third layer, standing 23°, the sides
remain for 15 days. The spent liquor from the first, second,
and third layers is used for strong liquor in the head rocker.
The fourth layer liquor is made up, 50 parts quebracho, 30
parts chestnut-wood extract, and 20 parts hemlock-bark ex-
tract, and stands at 20°. Here the stock remains for 25 days.
To secure more uniform treatment it is customary to use
dust in the second and third layers. From the fourth layer
the stock is washed and bleached, wrung out, shaved, and hung
up to dry. The dry sides are sammied back with water, and
when properly tempered they are ready for stuffing.
The stuffing is carried out in a drum with a hot mixture
of oleostearine, degras, paraffin wax, and tallow, using 38
per cent on the weight of the stock. The sides, on being re-
moved from the drum, are hung up to chill and set on the
grain on a Fitz-Henry machine. They are again set by hand,
using a dubbin of tallow and cod oil. The well-set sides
are then hung up and allowed to dry thoroughly. When dry,
the stock is jacked and snuffed.
A blacking of hematin and nigrosene is applied to the grain,
the color being set with an iron striker. Scar paste, which
consists of a mixture of glue, nigrosene, and potassium ferro-
cyanide, is then applied. The dry stock is now given a coat
of tallow and is whitened on the flesh. It is then jacked and
brushed.
Good color on heavily stuffed leather. — The moisture
content of leathers is perhaps the most important point to
watch in the production of a good color. A leather contain-
ing too much moisture absorbs the grease with difficulty, but
leather which is dry absorbs the grease too readily, as already
mentioned, and allows it to remain on the surface, producing
a dark color. The fineness of the division of the oil also
determines the color of the resulting leather. The more finely
divided the oil the more likelihood there is of producing a
clear color. It is for this reason that emulsions of oil have
advantages over pure oils, and since degras produces one of
STRAP, BAG, AND HARNESS LEATHER 331
the best emulsions known, it is in great favor with curriers,
when a light color is desired.
The nature of the greases which enter into the composition
of the stuffing mixture is of first importance from the point
of view of color, it being a good plan to have as large a
proportion of hard grease as possible, keeping in mind the
degree of suppleness desired. Solid greases which can only
be introduced into the leather by the aid of heat, possess the
property, during cooling, of lightening the color. The use
of stearine instead of tallow may be of advantage if the
leather is originally sufficiently soft, since it produces greater
firmness than tallow.
In recent years, many solid mineral greases, which possess
the double advantage of producing good color and of being
cheap, have been put on the market. Certain of these products
have the special advantage of being emulsifiable with water,
thus playing the part of a solid grease in the shape of a fine
emulsion. It is also possible to mix these materials with tal-
low or stearine in such a way as to produce greases having
varying melting points, according to the degree of suppleness
desired. The solid mineral greases which are emulsifiable gen-
erally have melting points somewhere about 113° F. They
may be used alone or in an admixture with tallow. If used
with the latter, the melting point may go down to 95° F.,
which is helpful for suppleness. These greases may also be
mixed with stearine, or with a mixture of tallow, stearine,
and moellon. By this means it is possible to obtain a much
brighter color than was formerly possible by the old processes
of currying, a greater quantity of grease being introduced at
the same time. This is not harmful to the quality of the
leather, rather beneficial. Goods thus stuffed have, in fact,
a greater tendency to maintain the dry appearance of well-
stuffed leather.
One of the features of the superiority of modern currying,
as viewed from the final color of the leather, rests in the
practicability of stuffing the leather in a drum. It will be read-
ily understood that this treatment possesses the advantage of
332 PRACTICAL TANNING
increasing the fineness of the division of the grease, thus al-
lowing it to penetrate the fibers of the leather and be assimi-
lated more rapidly, all of which helps in the production of a
satisfactory color. To this advantage may be added the fact
that a considerable proportion of hard grease, at least 25 to
30 per cent of the total, can be used ; and a finished leather
will be produced, which, in drying, will not make apparent
the amount of grease which has been incorporated.
For the drum stuffing of leather there are two common
methods of procedure : the first being to apply the grease to
the leather on the table, and when thus plastered, to drum it
in a heated drum; the second treatment being to warm the
drum, and after introducing the leather, turn it for a few
minutes to warm the latter. The grease, at a suitable tem-
perature, is then put in, and turning is continued from a half
to one hour, until all the grease has been absorbed. Curriers
who use the first method give it preference. A leather of
good color is very easily produced by this process, but it is
probable that a less quantity of grease is introduced than by
the second method. If it is not desired to introduce a great
quantity of grease into the leather then this first method, that
is, to apply the grease on the table and drum afterwards, may
be used ; but it is quite probable that just as good a color may
be obtained by the second method, and at the same time a
larger proportion of grease be introduced. The chief reason
why some curriers do not succeed with the second method is
that they do not sufficiently study, before stuffing the leather,
its condition as regards moisture, its proper condition in this
respect being indispensable for success. If the hollow or
loose parts of the leather are not sufficiently dampened at the
moment the goods are put into the drum they will absorb
too much grease, and too dark a color will result, while the
other portions will remain insufficiently stuffed and will be
of a much lighter color, a bad result.
The secret of success in direct drum stuffing rests in putting
the leather into proper condition of moisture before stuffing;
this work should be entrusted only to a skilled man, who can
STRAP, BAG, AND HARNESS LEATHER 333
detect at a glance the hollow part in the leather and how
much moisture should be given to it. Once the leather is
properly dampened, giving more to the hollow parts, it should
be placed in a pile for a sufficient period for the moisture to be
evenly distributed among the fibers, and then to proceed to
the stuffing. With these precautions observed, the second
method of manipulation will give a color just as good as the
first, and in addition, it will allow a much larger propor-
tion of grease to be introduced into the leather.
As a final precaution, the stuffing formula should contain
an emulsifying agent, which will ensure a perfect emulsion
of the whole ; for example, soluble oil, moellon, or one of
the mineral greases mentioned, which being themselves emulsi-
fiable, impart this property to the other greases.
Certain curriers make it a practice to open the door of the
drum after the absorption of the greases, and continue the
turning of the drum until the greases solidify. There is, how-
ever, no marked advantage in this method. It seems prefer-
able, as soon as the grease has been absorbed, to remove the
leather and to hang it up until cold. After this, it is good
practice to soak the goods in a sumac bath for one or two
days until complete penetration has taken place, and finally
set them out. In this way, other things being favorable, a
perfectly satisfactory color will be obtained.
The stuffing of belting leather can be carried out either on
the table or by immersion. There is an indispensable precau-
tion to be taken in order to produce a good color, and that is,
when stuffing is carried out by hand, to moisten the grain
lightly in order to prevent the grease from penetrating through
to it. Without this precaution the grease traverses and makes
the surface a dark color. On the other hand, moistening the
grain causes the grease to set the moment it reaches it, and
thus helps to maintain the color.
There is also another method of procedure which gives
good results, and that is, the grease must be appreciably hotter
than the leather. On a table, which should be a little larger
than the butts, are placed a certain number of pieces of felt
334. PRACTICAL TANNING
capable of absorbing moisture easily. These pieces should be
as large as the table itself, and on top of them is placed a
similar piece of felt, the whole forming a soft cushion on the
table, which is kept wet. Each butt, on coming from the hot
chamber, is placed grain downwards on the cushion, and the
grease is applied to it in this position. The cushion, by its
softness, adapts itself to the surface of the butt, and its mois-
ture prevents the grease from penetrating to the grain, because
as soon as the grease traverses the leather and reaches the
moist grain, it sets. In spite of this, it is essential that the
grease should be applied as rapidly as possible, as the butt
must be allowed sufficient time to cool down during the process.
Finally, great care must be taken that the temperature of the
grease always remains the same. Immediately after this ap-
plication of grease the butts are immersed either in cold water,
in weak liquor, or in a sumac liquor, and left there two or
three days. This obviates drumming the leather after stuffing,
an operation which always causes a loss of weight. The
longer the butts are allowed to lie in this liquor the greater
the chance of causing the dark stains, which may have been
produced on the grain, to disappear. The butts are finally
rinsed in cold water and set out carefully on a table. The
grain is moistened regularly with water, and a mixture of
tallow and cod oil in equal parts is applied to it cold, a good
natural color being thereby produced. If a lighter color is
desired, less grease is given. There are other precautions
that may be taken after stuffing, which help to produce a good
color. In the first place, the drying after stuffing must take
place very slowly.
The temperature of drying must not be too high, other-
wise the grease will melt and appear on the surface. It is,
however, necessary that the drying should be carried out in
a sufficiently high temperature for the greases to remain soft,
in order that they can be finely divided as they penetrate to
the interior of the leather. The temperature most suitable
must be determined by the melting point of the grease em-
ployed. In some works, time is saved by not drying out com-
STRAP, BAG, AND HARNESS LEATHER 335
pletely, but by setting out in the half-dry state. It is, how-
ever, much more preferable to dry completely and dampen
back again regularly in order to set out. This precaution
should especially be observed when dealing with leather stuffed
by dipping. It is good practice after currying to leave the
goods in the warehouse for a sufficient time for the grease
to be properly assimilated in the interior of the leather. After
this period the last trace of grease which remains on the
grain may be removed with care by means of a fine slicker.
The process of bleaching, which contributes to the produc-
tion of a regular and light color, can be carried out after
tanning, either before or after stuffing. In principle, bleach-
ing before stuffing is to be preferred. Weak solutions of
.oxalic acid, sulphuric acid, potassium oxalate, or sulphurous
acid are used. There are also on the market products called
"hydrosulphites," either under this name or under special trade-
marks. These materials enable one to produce an efficient
bleaching in a simple manner, the solution being prepared
at time of using. In spite of the superiority of bleaching
before stuffing, it often happens that it is more convenient to
bleach after the stuffing. A method of bleaching leather,
which has been stuffed with a large quantity of grease, is as
follows : The first precaution is to remove completely all ex-
cess of grease from the surface of the grain. The butts are
placed in a pile for 24 hours and immersed for one minute in a
bath at 77° F. containing 3 per cent of caustic soda, the leather
thereby becoming very dark. It is washed in tepid water, and
then placed in a cold 5 per cent solution of hydrochloric acid
until it becomes light again, when it is carefully rinsed with
cold water. This process must only be taken as an example.
In principle, the processes of bleaching used before stuffing
may be equally well used after stuffing, but to make their
application successful after stuffing it is essential that every
trace of grease shall be removed from the grain. This can
be accomplished by means of a good washing with a soap
solution, followed by careful rinsing. The ordinary process
of bleaching can then be applied, and may be combined with
336 PRACTICAL TANNING
treatment in sumac. For belting leather, the butts, after hav-
ing been washed and set out by machine on flesh and grain,
are placed in a pit, together with a strong lukewarm sumac
liquor, and left therein one day, being removed two or three
times. The sumac may also be given in a drum for one or
two hours. The butts are set out on a table with a stone
slicker, carefully brushed, allowed to dry gently, and placed
in a pile when half dry. Treatment in a sumac bath helps
to brighten the color of harness leather also. The quantity of
sumac depends upon the nature of the original tannage, but
about 2 lb. per butt is an average quantity. In the manufac-
ture of harness leather, and especially for leather that is to be
stained with light colors, special precautions are sometimes
taken. In the first place, only hides of particularly good
color are selected. After shaving, they are drummed in a
sumac bath, which has already been used once before, then
set out by machine. They are then given a second sumac
bath, this time one freshly prepared. The treatment with
sumac does not necessarily exclude chemical treatment with
oxalic acid. If the two processes are combined, the color
obtained is even lighter. If the suggestions given are fol-
lowed it Is possible to obtain a leather which has absorbed con-
siderable grease and is of sufficiently light color and dry ap-
pearance to satisfy the most exacting customer.
Automobile leather. — For automobile, carriage, and up-
holstering purposes, spready hides are used, so that the hide
dealer or tanner taking up the stock makes his selection on
spreadies. The hides used for this class of leather are usually
green-salted.
In the preliminary work the hides are soaked, fleshed,
limed, unhaired, and bated. They are then run in the paddle
with an acid-spent tan liquor to set the grain and impart a
uniform color. The hides, having been colored, are sus-
pended by the butt in rocker frames, in which case the pits
must be sufficiently deep to prevent sagging to the bottom.
The rocker system for this class of stock is worked on the
same principle as that described under sole leather.
STRAP, BAG, AND HARNESS LEATHER
337
Tanning. — The liquor commonly used in the rockers con-
sists of a mixture of hemlock and chestnut-oak bark. The
tail liquor should be very weak, stronger liquor being used
as the tanning progresses. Usually from 8 to 10 days is
a sufficient time for the rocker treatment, as it is only nec-
essary to bring the hides into such a condition that they may
Figure 92. — Sheridan embossing press.
be split. The rocker liquor, of course, should be sufficiently
acid to produce the necessary plumpness.
On removal from the rockers, the hides are passed through
the wringer, and are then worked on the stoning- jack to re-
move any wrinkles and smooth out the leather. A grain split
is first removed, and the remainder again split into various
weights according to market demands and the judgment of
the splitter. The grains split are usually re-tanned in a drum
with quebracho or a mixture of quebracho and gambier. The
flesh splits are, as a rule, re-tanned in the paddle, although
some tanners prefer to re-tan in the pits. For re-tanning the
338 PRACTICAL TANNING
flesh splits gambier is very largely used, but sometimes mixed
tannages are employed.
The re-tanned splits are next run in a paddle with sumac
liquor, to which degras in the form of an emulsion is added.
They are then set out carefully either by hand or machine
and given a coat of degras and cod oil. Having been oiled,
the leather is tacked closely on special frames, these being so
Figure 93. — Embossing machine.
constructed that the leather may be stretched in all directions,
clamped in the extended condition, and allowed to dry.
The dry leather is removed from the frames, broken to
make it soft, and after buffing is ready for the application of
the finish.
Finishing. — The finish of this leather is usually made by
boiling linseed oil with a drier and some pigment. The oil
is heated over a coke or oil fire to a temperature of about
600° F., and is allowed to cool to about 350°. The fire is
then extinguished, and the necessary amount of naphtha is
slowly added. This produces a jelly-like mass known as
"sweetmeats." The pigment, which has previously been
ground in oil, is now carefully incorporated and forms what
is known as the "daub."
The grains and splits, having been assorted for grades, are
stretched on frames and given a heavy coat of daub. This
material is applied evenly, and the excess is removed with a
STRAP, BAG, AND HARNESS LEATHER 339
slicker. The hide is then allowed to dry in the air. A sec-
ond coating of the same material is applied; and the frame is
placed horizontally in the drying oven in which a tempera-
ture of 120° F. is maintained. The third coat consists of
plain boiled linseed, which is dried in the oven at a tempera-
ture of about 130° F. When perfectly dry, the surface is
Figure 94. — Turner hydraulic embossing and
smooth-plate press.
rubbed down with a brick of pumice stone. The number
of daub coats and varnish coats varies, the brighter the finish
desired the more varnish applied. After the bottom or daub
coats the finishing coats are always rubbed down with pumice
before application of another coat, except in the case of the
last coat, which is not pumiced. After thorough drying in
the oven, the frames are placed in the sun to remove the
stickiness, and after sun-drying the splits are stripped and
trimmed, and are ready for market.
The greater part of this kind of leather is embossed in order
to produce an imitation grain. This grain may be of various
designs and color according to the demands of the trade.
Figures 92, 93, and 94 show three kinds of presses used for
this purpose.
340 PRACTICAL TANNING
In place of the daub coat above mentioned, many other
materials and combinations of materials are used; the most
common, however, is pyroxylin.
"Spanish leather," so called, which is much used at present,
is produced by tanning the hide in strong quebracho liquor
which draws up the grain and gives the leather its unique
appearance. In finishing this leather it is dyed to shade and
then rubbed over with a pigment in oil. The excess of pig-
ment is removed from the surface by brushing, but leaves a
color in the wrinkles. The same effect, however, is more
commonly produced by finishing with linseed oil daub, and
then embossing the product with a Spanish grain. The color
in the wrinkles is produced in the same manner as just
described.
CHAPTER XII
PATENT LEATHER
Patent leather. — Any leather that carries on the surface
a high-gloss varnish finish is called "patent leather." The terms
japanned, enameled, and patent are synonymous, except that
enameled leather is usually that in which the finish is applied to
the flesh. The following description is taken largely from a
lecture given by George W. Priest before the tanning and
applied leather chemistry students at Pratt Institute, Brook-
lyn, N. Y., for which the author desires to give him full
credit :
In a description of patent leather the subject should be
divided into three parts, namely, (1) raw materials; (2)
preparation of compositions and varnishes; and (3) applica-
tion of the above.
The raw materials used in making patent-leather composi-
tions and varnishes are : linseed oil, turpentine, naphtha, solu-
ble cotton, amyl-acetate, lampblack, Chinese blue, Prussian
blue, umber, litharge, and spirit black.
Linseed oil. — This material belongs to the class of oils
which absorb oxygen from the air and dry to an elastic,
flexible film of varnish. No other oil approaches linseed in its
drying properties.
The oil is expressed from flaxseed which comes from Rus-
sia, India, South America, and the United States and Cana-
dian Northwest. That made from the North American seed
makes the strongest and most flexible varnish. Calcutta comes
next, making a softer varnish, while the South American seed
is poorest. Consumption of linseed in America is so great
that the domestic production is too small, and supplies have to
be drawn from India and Argentina.
It was formerly believed that Calcutta oil made the best
341
342 PRACTICAL TANNING
varnishes. This idea probably arose from the fact that all
the Calcutta oil was expressed, made up, and tanked ready for
use as soon as it came in. This tanking gave the oil an age-
ing which made it better. The domestic oil was expressed
and sold at once. An oil kept for a long time at a moderate
temperature makes a more brilliant and flexible varnish, and
one which works freer.
The present great demand for linseed oil does not permit
of any long storage in refiners' hands, so that oil is put on
the market only a few weeks old, often only a few days.
Modern methods of refining have been so perfected that a
fresh refined oil is better than some of the old tanked oils.
Two classes of oil are sold to the patent leather manufac-
turer. One called an "aged" oil, which has received some
beneficial treatment in the refinery, is used for making the
"daub" or bottom coats. The treatment causes the oil to
"body" more quickly so that the cooking time is shortened.
This oil is of a softer nature than the varnish oils.
For the varnish coats a refined varnish oil is used, although
there is no reason why the "aged" oils should not be used.
Special varnishes and other patent-leather compositions are
of such a heavy and viscous nature that some solvent must be
mixed to thin them so that they will flow freely under a brush.
Turpentine. — This makes an ideal thinner as its boiling
point is high enough to permit plenty of time in brushing
before it evaporates. It was formerly used to thin down the
varnishes so that they would flow easily, but the high price
has almost prohibited its use, although some tanners still use
it mixed with naphtha.
Naphtha. — Two grades of naphtha, motor gasoline and V.
M. & P. naphtha, are used for reducing varnishes and compo-
sitions. The former dries out completely in a short time,
while the latter takes more time and probably never com-
pletely evaporates. The higher boiling portions of the heavier
naphthas have been known to cause serious trouble, and at-
tention must be given to these goods to see that they run
uniform and dry completely.
PATENT LEATHER 343
Soluble or nitrated cotton. — This is the non-explosive form
of guncotton, which, when reduced with amyl-acetate, is used
as a lacquer. Mixed with camphor it forms celluloid. Ni-
trated cotton makes a very tough, transparent film that cannot
be used alone for producing a finish on leather, but must be
mixed with some kind of oil.
For patent leather it is customary to mix the cotton with
boiled oil and amyl-acetate. Such a composition is particu-
larly adapted for small fine-grained skins like kid or coltskin.
Amyl-acetate is the only practical solvent for guncotton, and
gives the best results on leather. It may however be mixed
with a small proportion of naphtha without precipitating the
cotton from solution.
Lampblack. — In order to get a black foundation for the
bottom coats a very fine grade of lampblack is used; this
lampblack weighs about 4 lb. to the barrel.
..Chinese bine. — This comes in lumps or powder of an iri-
descent purple color. It is used as a dryer in making var-
nishes. Some makers use the lumps directly in the kettle ;
others buy the blue in powdered form ; and still others powder
the blue, grind it in oil, and then boil it with the varnish.
Any one of these methods seems to make equally good varnish.
Prussian 6/we.— This salt, which is of nearly the same chem-
ical composition as Chinese blue, is used ground in oil, with
a little black, and mixed with the bottom coats as a pigment
to give color.
Umber. — This is used as a dryer in the oil boiled for the
bottom coats.
Litharge. — A lead oxide, is sometimes used with umber
and sometimes replaces it. It makes a softer coating than
the umber.
Spirit black. — This is a coal-tar color used to give color to
the nitrated cotton coats.
Boiling the oil for the daub coat. — The bottom or daub
coat acts as a filler or sizing on the leather, whether it be
chrome or vegetable-tanned. In order to keep this coat from
penetrating too deeply and so injuring the leather, the oil
344. PRACTICAL TANNING
is boiled to a very heavy, viscous mass. This requires a
long time at a fairly high temperature. To assist and shorten
the time, the so-called "aged" oils are commonly used, which
have had some treatment that makes them cook and come
to a body much quicker than a raw oil. The treatment does
not in any way injure the strength and elasticity of the
coatings.
The oil is boiled slowly at first with \ of 1 per cent of
umber ; the temperature is then raised gradually until it reaches
575° F. or thereabouts. This temperature is maintained by
pulling the kettle on and off the fire. As soon as the tem-
perature reaches about 350°, light vapors begin to come from
the oil ; these have a rather fragrant odor, but as the boiling
continues the vapors become much denser and more pungent.
As the oil breaks up under the heat, oxidation takes place, and
large quantities of acrolein are given off, which attacks the
mucous membrane acutely. To protect the oil boiler, the chim-
ney in which the boiling is done is well ventilated so that the
obnoxious and poisonous fumes are carried away.
During boiling, the oil loses about a fifth of its bulk through
distillation and the breaking up of the glycerides of the oil.
In Germany, where the phenomena of oil boiling have been
carefully studied, it has been found that the linolein, which
is formed by oxidation at low temperatures, is more elastic
and tougher than the linoxyn formed at higher temperatures.
When the oil has reached the desired consistence, which
can only be judged by practice, the kettle is taken off the fire
and taken about 20 feet away. The outside of the kettle is
sprayed with water to put out all sparks, and the hose is
turned on the fire in the boiling-house until the fire is com-
pletely extinguished.
The daub is so heavy that naphtha or other solvents will
not mix with it in the cold, therefore the naphtha is put into
the hot daub. This sudden addition of cold naphtha to very
hot daub at once vaporizes the naphtha, which travels along
the ground like a white fog. For 50 gallons of daub, 100
gallons of naphtha are generally used, about half of which
PATENT LEATHER 345
evaporates. As the lighter parts evaporate first, the heavier
parts, which are slow drying, are left in the oil.
A machine patented by George Priest is in use in several
plants, and by it the daub is stirred mechanically during the
mixing and the naphtha is caught in a condensing dome.
No naphtha is lost in this machine, so there are no fumes and
no danger to the boilers. The daub made by this machine is
said to be much smoother than by the old method. The
machines have been in operation for over 15 years without
explosion or trouble and seem to be practical.
After the naphtha has been added, the daub is stored ready
for mixing, which is done by the addition of more naphtha
and lampblack according to the judgment of the head mixer.
The consistence of the boilings varies from a heavy body,
which will string out in silks, to one that is like heavy flour
paste in body. The more open the leather to be coated the
heavier should be the boilings. The second coat was formerly
put on with a slicker, and was the same as the daub, but with
more naphtha in it. It is now customary to make a special
boiling, which, when reduced with naphtha, is thin enough
to be applied with a brush. This color coat contains Prus-
sian blue in oil.
Varnish. — As the varnish has to stand all the wear and
tear of hard usage and weather, the greatest care is taken in
selecting the oil, and in its cooking.
The driers used are Chinese blue lumps, about 3 per cent
on the weight of oil. These are introduced when the oil is
at about 350° F. In making varnishes, the temperatures are
raised gradually and with constant stirring. Within reason,
the lower the temperatures and the longer the time of cook-
ing the stronger and more flexible is the varnish. Chemical
changes take place at low temperatures which improve the
oil, causing the varnishes to become more elastic and to dry
quicker. The consistence of the varnishes varies with the kind
and quality of the leather, and is controlled by the boiler.
The varnish is usually stored 10 days before using; longer
storage does not improve it enough to warrant extra time.
346 PRACTICAL TANNING
Application of compositions to leather. — After the leather
has come from the de-greasers, it is stretched tightly in frames
by means of metal toggles.
The consistence of the bottom coat is largely a matter
of judgment. The stock daub which contains naphtha, heavy
boiled sweetmeats, and lampblack, is reduced with the proper
amount of naphtha in a mixing machine. This is spread
evenly over the surface of the hide and well rubbed in by
hand; afterwards the excess is spread off with a steel instru-
ment called a "slicker." When properly applied, the surface
should be uniformly black, free from streaks, and should
stick slightly to the hand. The hide is then stood up to dry
in a drying room at a low temperature. This coat is not
exposed to the sunlight. If pyroxylin is used, it is reduced
with amyl-acetate to give the best results, and applied with
a sponge and dried in a way similar to the oil finish.
The second coat is applied on top of the daub on the fol-
lowing day. The hide receives a slight rubbing with pumice,
and the second coat is applied with a brush. This composi-
tion contains some pigment to give color to the leather. It
is well brushed in, and the hide is stood up in a drying room
at a moderate temperature. If the hide is very open a third
coat may be applied.
Before the varnish is put on, the hide is well stoned and
carefully brushed with a wet brush to free it from all dust
which may have been made by the rubbing down with the
pumice. Great care is taken while varnishing. The room
is well heated so that the varnish will flow freely. While
a certain amount of ventilation is necessary, this is so ar-
ranged that no direct draught blows over the leather under
treatment. The men work stripped from the waist up to
avoid flying dust and lint from clothing. The varnish is
in 15-gallon cans, this size giving the best results because it
is so deep that any dirt getting in the cans settles at once to
the bottom far away from the reach of the varnish brush. On
hides, the varnish is usually applied with a large round brush
4 inches in diameter and with bristles 8 inches long. A brush
PATENT LEATHER 347
full is applied to the hide, and is flowed on and well brushed
down to avoid streaks and ensure an even coating. The hide
is then placed in a horizontal position in the oven, the dis-
tance between the hides being about 3 inches. The tempera-
ture is gradually raised to about 160° F., and the hide is left
in over night. The next morning the varnished surface
should be brilliant, free from dirt, and a bit tacky or soft.
To overcome this, the hide is generally exposed to the sun-
light all day. The combination of the ultra-violet rays in the
sunlight, and the air, finish the oxidation of the varnish, so
that it is soft and flexible, but will not stick if two varnished
hides are laid away face to face.
A method of drying patent leather by the use of the Cooper-
Hewitt mercury-arc quartz lamp has been developed by George
Priest. This method has been used successfully in a number
of plants. The theory is as follows:
It has been known for a long time that the ultra-violet
or short wave-length rays in the sunlight produce certain
chemical results. They bleach linen, discolor dyed leather and
fabrics, and oxidize oils and varnishes.
It has also been known that the old form, of Cooper-
Hewitt lamp produced small quantities of ultra-violet light.
This lamp is a long tube of glass suspended horizontally from
the ceiling, which produces a peculiar and somewhat ghastly
green light, but which is, of all artificial lights, least trying
to the eyes, and is used wherever much night work is done
requiring constant application of the eye.
It is known that the stronger the electric current the more
ultra-violet light can be produced, but two things prevent
the common mercury lamp from giving this result ; first, ultra-
violet rays will not go through ordinary glass (the other
rays go through, but it acts as a screen for the violet rays) ;
second, in increasing the strength of the electric current the
glass tubes were melted.
Within the last few years the art of making transparent
quartz has been perfected. Quartz transmits the ultra-violet
rays, and has such a high melting point that strong electric
348 PRACTICAL TANNING
currents, which produce light rich in ultra-violet rays, can be
used. The lamp was at first found to be very fragile and
short-lived, but was eventually perfected for patent-leather
work, and made practical the indestructible quartz lamp of
today. An exposure of 2 to 4 hours under the quartz lamp
will accomplish as much as a 6-hour exposure to sunlight.
The advantage of this method of treating leather is that
no new materials are used. No change is made in manu-
facture except in the exposure. Wearing tests in shoes, and
in leather laid away in piles face to face, has demonstrated
that there is no difference between sun-treated and lamp-
treated leather.
This method eliminates factory shut-downs during pro-
longed periods of wet weather, or in extra exposures during
the hot, humid days of summer when varnishes dry poorly.
After the leather has been exposed to sunlight or ultra-
violet rays, it is stood up in a cool place over night and the
next day cut from the frames, trimmed, and piled away face
to face for a few days, when it is ready for shipment.
While at present more is understood about the manufac-
ture of patent-leather varnishes and compositions, much more
technical skill is required than formerly on account of the
varying qualities.of linseed oils, and the type of naphthas now
supplied, which are not always adapted to the requirements
of the patent-leather manufacturer. Close chemical checks
should be kept on the oils and solvents used. The oil and
naphtha agents should not be blamed, however, because they
can only sell what comes to them, but, recognizing what is
coming, proper treatment can be given the article in question.
This can only be determined by chemical test.
The real problem, however, which confronts a tanner of
upper leather, is to make a leather that stands the mechani-
cal treatment of the shoemaker. It almost seems as if the
wearing of the shoes was a secondary consideration. Prob-
ably the shoeman takes it for granted that all leather will
give good satisfaction in shoes.
Leather must stand the heavy pull of the lasting machine
PATENT LEATHER 349
and other devices for making the vamp fit the last snugly.
The leather is almost invariably wet before lasting, the tip
is not only wet but also stuck to the lining with alcoholic
shellac cement; frequently the vamp is soaked in sulphonated
oil "to help it," and is often given some secret mixture which
the foreman of the lasting room has found effective. In a
few places the leather is lasted without treatment.
Attention is called to this treatment previous to lasting,
because the patent leather tanner must always have it in
mind. All leather is more stretchy when wet or damp than
when dry, and all damped or wetted leather contracts on
drying, and if stretched too tight when wet and held firmly
in place will frequently crack on the grain.
Leather is generally carefully cut into vamps, the cuttings
being selected for the proper parts of the shoe.
The vamps are next stitched to the uppers and then damp-
ened, lightly tacked on the last, put into the pulling-over
machine, and under heavy pressure made to fit the last snugly,
and then tacked. They are left in this condition over night
and the next day the soles are stitched on, which operation
tightens the vamp still more. A pressure of probably 75 lb.
to the square inch is applied and held there. There is no
give to this pressure as long as the last stays in the shoe.
Today the shoemaker demands a piece of leather which is
more or less firm. Such leather makes a good-looking shoe
because it "stands up in the shoe," as they say; in other
words, the shoe retains its shape and looks well on the counter.
It also wears well and the shoe does not slump over and lose
its shape. But the tanning and currying methods which make
such a leather also tend to make a weak grain, and a leather,
which, when wet, is a bit rubbery, so that on drying there
is considerable contraction and a consequent parting of the
grain.
The manufacture of patent leather is then a mechanical
problem. Glazed kid, box calf, colored calf, and velour
leathers all have oil in them, and have never been subjected to
any drastic treatment or high temperatures. They are fre-
350 PRACTICAL TANNING
quently oiled off before being shipped to the shoe factory.
In cutting the vamps from such leathers the greatest care is
used to get the right selection for the vamps so as to make
a good-looking shoe. The exact reverse of this treatment is
given patent leather.
Most patent leather is tanned almost to the limit of crack-
ing in order to get the stretch out of the leather. A minimum
amount of oil is given it in the fat-liquor, and this is after-
wards washed out with a naphtha bath. The leather has 3 or
4 coats of linseed-oil compositions and 3 or 4 days tempera-
ture of 110 to 160° F. The character of linseed-oil varnishes
is that they are very flexible but only temporarily elastic;
that is, they will stretch back and forth about 20 per cent;
but if stretched 20 per cent and held, the film parts at once
in a long striation. In cutting patent leather, as it all looks
good and is all expensive, no selection is made in cutting
vamps and "everything goes," so to speak — and does go liter-
ally, for bellies, legs, and necks always give trouble.
This characteristic of linseed-varnish film complicates mat-
ters. If leather that has received too drastic a treatment in
the tannery, or for other reasons has contracted when dried
more than it should, is used for vamps, and is soaked and
pulled while wet over a last, the varnish, being temporarily
elastic, will stretch with the grain. But as the leather again
dries and tightens, the varnish, if it has been put on too heavy,
is likely to break in long striations. If, on the other hand,
the varnish has been applied lightly, the grain may break. A
linseed varnish is slightly hygroscopic and is tougher when
wet than dry. When patent leather acts as described the re-
sult is the discarding of shoes made from it.
In spite of all difficulties, tanning has reached such perfec-
tion that most leather stands all the shoe factory roughness
and makes good shoes.
The strain on the leather during lasting is greatest over
tips and across the ball of the foot. Cracks on the tip can
be buffed off, and a heavy varnish, made especially for the
purpose, put on. This is called "flowing the tips." When
PATENT LEATHER - 351
cracks appear on the ball of the shoe on the inside, the vamp
has to be torn off and another put on. /
Take at random three patent leathers made by as many
different tanners : One of these leathers is made with soft
river water, another with artesian well water, the third with
lake water. They are all standard leathers, and the success
of each one seems to show that the kind of water used has
nothing to do with the quality of the leather produced. This
means that the tanner has made the best of his local condi-
tions and adapted his methods to meet them.
It is interesting to note that each one of these tanners uses
a different beam-house method. One uses straight sulphide,
10 per cent in a paddle-wheel ; another 5 per cent lime and
5 per cent sulphide; while a third uses 6 per cent lime and 1
per cent sulphide. They all use different bates.
Two of these people de-grease their leather, and one does
not. Two tack their leather out on frames in the tannery,
and the other one has the leather stretched in the japanning
frames, but does not tack in the tannery. The point is that
adaptation of proper methods to the local tannery always pro-
duces good leather. The methods must be practical of course.
Because one man makes good leather with sulphonated oil
it does not mean that he could not do the same with soap and
oil. If the reason were traced back why his leather seemed
to be better adapted to a sulphonated oil it might lead to the
beam-house. And it might be found that it were better to
operate the beam-house as it was, rather than change the fat-
liquor. The making of a successful leather is the blending
of methods and materials which give best results for the local
plant.
In the manufacture of patent leather, many tanners take
advantage of the fact that hides and skins with poor grain
can be successfully put into such leather, which is done by
tanning in the usual manner and then snuffing off the grain.
In fact, even high-grade side leather is often snuffed in order
to make the finish adhere more closely.
CHAPTER XIII
DYEING LEATHER
Having carried out the various processes of soaking, de-
pilating, bating, and tanning for glove, fancy, shoe, and other
pliable leathers, the next step to be considered is the method
employed in coloring the product to meet the demands of the
trade. A short description of the various classes of dyes will
be given, together with a general outline of their application,
and an effort made to point out what conditions are best
suited for the different grades.
Classification of dyestuffs. — The earliest classification of
dyestuffs divided them into two classes, "substantive" and
"adjective." Substantive colors are those which are capable
of producing a fully developed color upon textile material
without the assistance of any other combining substance; ad-
jective dyes are those which require an intermediate combin-
ing substance, called a "mordant," to fix and fully develop the
color. This grouping is still in use, but during recent years
the tendency has been to use the term "direct" color in place
of substantive, and mordant color in place of adjective. In
general, this classification holds good, but there are certain
grades of color that are direct on some fibers, but require
a mordant on others.
A classification which divides the dyestuffs according to
their origin is of broader application. It recognizes three
groups as follows: (1) natural organic dyestuffs; (2) min-
eral dyestuffs; and (3) artificial organic dyestuffs.
Though the various subdivisions of this classification, par-
ticularly of the artificial organic dyestuffs, are numerous, this
classification has the advantage that one class does not overlap
another.
Natural organic dyestuffs. — A subdivision of natural or-
ganic dyestuffs is as follows : ( 1 ) indigo and related com-
352
DYEING LEATHER - 353
pounds; (2) logwood; (3) dyestuffs producing shades of a
red character; and (4) dyestuffs producing shades of a yel-
low character.
Indigo.— Indigo blue or indigotin is found in many plants,
but the natural product has been almost completely replaced
by the synthetic material. As it has practically no use in the
dyeing of leather it is of no particular interest to discuss it
in this volume. .
Logwood.— This is the product of a large tree known as
haemotoxylin campechianum. The wood is rasped or chipped
and extracted with water, and this solution is evaporated
either to a syrupy consistence or powder, and is sold as liquid
or solid extract. If evaporation be done in an atmosphere
free from oxygen, the product is known as unoxidized log-
wood extract, and contains haematoxylin as its active princi-
ple. If, however, air is blown through the solution, a change
takes place and the product is then known as oxidized log-
wood extract or hematin, and contains haematein as its
active principle.
Logwood is a mordant dyestuff requiring a metallic mor-
dant to fix it on the fiber. This mordant in the leather in-
dustry is usually spoken of as a striker. The mordants used
with logwood in dyeing leather consist of salts of iron, chro-
mium, copper, nickel, antimony, and titanium. This dyestuff
is used in producing black or other dark shades.
Brazil zvood, peach wood, and Japan wood. — Extracts from
these woods are sometimes used in dyeing leather, but require
a mordant to develop the color. The metallic mordants used
are salts of aluminum, antimony, tin, and titanium.
Fustic, or Cuba wood, contains a yellow dyestuff obtained
from the wood by leaching. It comes to the tanner as a
liquid or solid extract and may be used either with an alumi-
num, chromium, iron, titanium, or antimony mordant.
Osage orange.— The wood of the osage orange contains
a bright yellow dyestuff which has largely replaced fustic in
the dyeing of leather.
Cutch.— This material is used to some extent in producing
354- PRACTICAL TANNING
brown shades when mordanted with copper. Its application
however, is very limited in the dyeing of leather.
Mineral dyestuffs. — As a class, these substances are very
unimportant so far as their application to leather is concerned.
As a color, however, for certain classes of leather finish they
are fairly largely employed. In recent years the use of pig-
ments with some form of binder has come into fairly wide-
spread use, and they are not only being employed in finishes,
but find application in the actual coloring of the stock.
Artificial organic dyestuffs. — The dyestuffs belonging to
this group are legion and may be classified according to their
derivation, their composition, or in respect to the character-
istic, color-forming groups they may contain. As these class-
ifications are of no particular interest to the leather colorer,
and as many groups of color have no value when used on
animal fiber, we will simply consider such groups as are ap-
plied in the dying of leather, which are as follows: (1)
basic colors; (2) acid colors; (3) direct colors; (4) aliza-
rine colors; and (5) developed colors.
Basic colors. — Chemically the basic dyestuffs belong to that
class of compounds known as substituted ammonias or amines.
Like ammonia, they are basic in character, hence the name.
Basic colors have a direct affinity for vegetable-tanned leather,
while with chrome-tanned and other leathers they must be
first mordanted with tannic acid before the basic color is
applied. Basic colors are characterized by their great bril-
liancy and high coloring power. They are, however, not very
fast to light and do not penetrate the fiber.
Acid colors. — These colors are called so on account of their
acid character. From a chemical point of view they may
be divided into three classes : ( 1 ) those which are nitro
compounds; (2) those made by treating basic colors with
concentrated sulphuric acid, thereby introducing the sulphonic
acid (HSO3) group; and (3) those which contain the azo
( — N=N — ) group.
Acid dyes are applied direct to leather without any mor-
dant. It is customary, however, to give the stock a bottom
DYEING LEATHER - 355
of some vegetable coloring material in order to secure full-
ness of shade. The color is applied in an alkaline solution
and is finally fixed by the addition of a small quantity of
acetic, formic, or lactic acid. Acid colors are very fast to
light and penetrate deeply into the fiber. They are not, how-
ever, as brilliant as basic colors.
Direct colors. — These colors have a direct affinity for cot-
ton and so get the name. Their method of application to
leather is the same as for acid colors, and like them are also
fast to light and readily penetrate the fiber.
Alizarine colors. — These are derived from anthraquinone,
and are usually applied to leather in the presence of sodium
dichromate. They are made more soluble by the addition of
borax and are fixed upon the fiber by means of an acid. Aliz-
arine colors, like acid and direct colors, are very fast to light
and penetrate deeply into the leather.
Developed colors. — Such colors as are fixed on the fiber
by means of some developing agent are used only to a lim-
ited extent, but when once produced give very full shades and
are fast to the light.
Dissolving dyestuffs. — Natural dyes may be dissolved in
boiling water.
Basic dyes are best dissolved in distilled water or rain
water. Where only well or river water is available — either
of which is more or less hard — the addition of acetic acid is
recommended. The basic dyestuff is first made into a thin
paste with a little cold water and the requisite amount of
acetic acid (generally one-half the amount of acetic acid, 28
per cent, as of dyestuff used is sufficient). This paste is
then poured into the necessary amount of hot water ( 180
to 190° F.) and stirred until completely dissolved. Actual
boiling with live steam should be avoided.
Acid dyes are best dissolved by boiling with the requisite
amount of water. No acid should be added while dissolving
the color or to the stock solution.
Never mix an acid with a basic dye.
356 PRACTICAL TANNING
Preparatory treatment before dyeing vegetable-tanned
skins. — In order to obtain satisfactory results it is necessary
to prepare the skins properly before dyeing. They are thor-
oughly soaked and washed in lukewarm water to remove all
excess of tannin which might cause difficulty during the dye-
ing operation. If the tannage is dark it is advisable to give
a slight re-tannage after the washing, with light-colored tan-
nins like sumac. This is given in the drum or paddle-wheel
and usually requires half an hour. After the tannin has been
taken up by the leather it is advisable to fix it with tartar
emetic or titanium-potassium oxalate (^ to 1 oz. per dozen
skins). These salts are dissolved in water and added to the
drum or paddle-wheel after the re-tannage, running the skins
10 to 15 minutes longer. The skins are then rinsed and are
ready for dyeing.
Dyeing vegetable-tanned leather. — There are four
principal methods of dyeing, namely, brush, tray, drum, and
paddle dyeing.
Brush dyeing. -r-This is used mostly for large leather, that
is, heavy cowhides used in bags, harness, and upholstery; also
for light leather in cases where an unstained flesh side is de-
sired. A dyestuff solution of proper strength is applied to
the dry leather with a medium hard bristle brush. Accord-
ing to the desired depth of shade one or more coats of the
brushing solution are applied. The leather is then hung up
to dry.
Tray dyeing. — This method is used on light skins only
where an unstained or only slightly stained flesh side is de-
sired. The moist skins are either folded singly, (lengthwise),
or. paired together flesh-to-flesh, and dipped for 5 or 10 min-
utes in the warm dyestuff solution in the tray until the de-
sired depth of shade is obtained. Then the leather is hung
up to dry. Owing to the great amount of labor required for
so small an output, this method is not largely employed.
Drum dyeing. — This is the method most generally used.
Light side leather, kips, horsehide, calf, sheep, and goatskins
are all dyed in this manner. The drum is loaded with the
DYEING LEATHER
357
leather and sufficient warm water to allow easy moving of
the leather while the drum is running. The temperature of
the bath is 100° F. Then the drum is started, and the dye-
stuff solution is added through the gudgeon while the drum
is running. Dyeing requires from 30 to 45 minutes. Other
ingredients or chemicals such as acids, metallic salts, etc.,
Figure 95. — Coloring goatskins.
which may be required for the proper development of the
dyeing, are also added in the same manner.
Paddle dyeing. — This is mostly used for the dyeing of
very light leathers, such as skivers or light sheepskins which
might be torn by the violent pounding in the drum. The
paddle-wheel is filled with water at 100° F., the wheel is set
in motion, and the damp skins are thrown in. The dyestuff
solution is then added in portions by pouring it slowly out of a
dipper and alongside the wall of the paddle-wheel. Dyeing
requires about a half-hour. Should other chemicals (acid or
mineral salts) be needed during the dyeing process they should
be added in solution while the paddle-wheel is running. Basic
358 PRACTICAL TANNING
dyes are dyed without additional chemicals. Acid dyes re-
quire the addition of about half the amount of acetic acid as
of dyestuff used, or quarter the amount of sulphuric acid.
When the dyeing process is completed, the skins are rinsed
in water, set out, oiled off, if necessary, and dried on frames
or on hooks.
Dyeing chrome-tanned leathers. — These leathers are
dyed in the drum. The treatment preparatory to dyeing is
as follows :
After shaving, the weight of the leather is determined.
This weight serves as the basis for calculating the amount of
dyestuffs and chemicals to be used in the dyeing process. The
leather is placed in a drum (figure 95), and washed for a
half-hour in running cold water; following this it is drained
and neutralized. Borax, sodium bicarbonate, wyandotte soda
or similar mild alkalies are used for the latter process. Ac-
cording to the acidity of the .chrome tannage, 1 to 2 lb. of
such alkalies will usually ;be found sufficient for 100 lb. of
leather. Neutralizing is done in the drum at a temperature
of 90° F., and requires 30 minutes. An excess of alkali
should be avoided. The leather should be almost neutral
to litmus paper, or show only' a faint acid reaction. After
neutralizing, the leather is again washed in lukewarm water
and is then ready for bottoming. Bottoming is done with
vegetable products, and serves the double purpose of filling
the chrome leather and giving a suitable foundation for the
dyestuff to be subsequently applied, especially for basic dyes.
The products used belong either to the class of tannins, such
as osage orange, sumac, gambier, cutch, quermos, etc. : or to
the vegetable dyestuffs, such as fustic, quercitrone, hypernic,
or logwood. From 1 to 3 lb. of extracts per 100 lb. is gen-
erally sufficient. Too much vegetable matter should be
avoided, as this is liable to change the character of the chrome
tannage. Bottoming is done in the drum at from 90 to 100°
F., and requires about 30 minutes. After this period, the
vegetable extracts are fixed by the addition of a suitable
amount of mineral salts, such as tartar emetic, titanium-potas-
DYEING LEATHER 359
sium oxalate, potassium or sodium dichromate, or similar
products; the drum is then run an additional 15 minutes. Two
to four ounces of these salts is sufficient for 100 lb. of
leather. The leather is then washed in the drum with luke-
warm water for 10 to 15 minutes, when it is ready for the
dyeing proper.
Both basic and acid dyes are suitable for dyeing this class
of leather. The 'dyeing is done in the drum at a temperature
of 125° F., and requires about 30 minutes. The drum is
loaded with the leather to be dyed and with sufficient warm
water to allow an easy floating of the skins. Then it is
started, and the dissolved dyestuff is added in two or three
portions through the gudgeon while the drum is in motion.
Basic dyes are used without the addition of any acid. Acid
dyes sometimes require the addition of a little acetic or sul-
phuric acid to develop their full strength, 4 oz. of the former
or 2 oz. of the latter for 100 lb. of leather is generally suf-
ficient to ensure good exhaustion and full development of a
shade. Where acid is used, it is given at the end of the dye-
ing operation to allow the color to be taken up uniformly be-
fore being fixed.
Blacks on chrome leather. — These are usually dyed on a
logwood bottom. The leather is first bottomed in the drum
at 125° F., with from 1 to If lb. of logwood extract or crys-
tals and with a small amount of soda ash (about 2 oz.) for
100 lb. of leather. After running 30 minutes, 4 oz. of cop-
peras or equivalent amounts of other suitable strikers are
added, and the running continued for 15 minutes. The
leather is then dyed either in the same or in a new bath (the
temperature of which is 125° F.) for one-half hour with the
necessary amount of National nigrosine or National Erie
black ; then rinsed, fat-liquored, and finished in the usual way.
Dyes for chrome-tanned calfskins. — The following formulas
are included by the courtesy of the National Aniline & Chem-
ical Co., they being for dyes used to produce fashionable
shades on chrome-tanned calfskins, and are calculated for
100 lb., shaved weight:
360
PRACTICAL TANNING
Gold Brown
Bottom
3 lb. sumac extract paste
\y 2 lb. cutch
2J4 oz. titanium-potassium oxalate
Dye
12 oz. National resorcine brown R
954 oz. National wool orange A cone
\ l / 2 oz. National induline NT
1J4 oz. National wool scarlet BR
4 oz. sulphuric acid
Moccasin
Bottom
3 lb. sumac extract paste
\y 2 lb. cutch
2% oz. titanium-potassium oxalate
Dye
18 oz. National resorcine brown R
18 oz. National azo yellow A 5 W
3?4 oz. National induline NT
6 oz. National fast red S cone.
4 oz. Sulphuric acid
Cauldron
Bottom
3 lb. sumac extract paste
W2 lb. cutch
2J4 °z. titanium-potassium oxalate
Dye
12 oz. National resorcine brown R
12 oz. National fast red S. cone.
2J4 oz. National induline NT
3 oz. sulphuric acid
Chestnut
Bottom
3 lb. sumac extract paste
\y 2 lb. cutch
2% oz. titanium-potassium oxalate
Dye
12^4 oz. National resorcine brown RN
12 oz. National azo Bordeaux
354 oz. National induline NT
4 oz. sulphuric acid
Morocco
Bottom
3 lb. sumac extract paste
\y 2 lb. hypernic paste
\y 2 oz. potassium bichromate
Dye
12 oz. National resorcine brown RN
\6 z / 2 oz. National fast red S cone.
3U oz. National induline NT
2 oz. sulphuric acid
Jonquil
Bottom
3 lb sumac extract paste
3 oz. tartar emetic
Dye in fat-liquor
T l / 2 oz. National metanil yellow 19S5
3 oz. National resorcine brown R
2 oz. sulphuric acid
Aluminum
Bottom
3 lb. sumac extract paste
1 y 2 oz. logwood crystals
\y 2 oz. copperas
Dye in fat-liquor
2Vi oz. National resorcine brown R
f s oz. National metanil yellow 1955
2 oz. titanium-potassium oxalate
Smoke
Bottom
3 lb. sumac extract paste
1 y 2 oz. logwood crystals
\y 2 oz. copperas
Dye in fat-liquor
\y 2 oz. National nigrosine 27722
1 oz. National metanil yellow 1955
Black
Bottom
1 lb. logwood crystals
2 oz. bicarbonate of soda
2 oz. copperas
Dye
1 lb. National nigrosine 128
Chippendale
Bottom
3 lb. sumac extract paste
\y 2 lb. cutch
1 y 2 oz. titanium-potassium oxalate
8 oz. National resorcine brown R
2 oz. sulphuric acid.
Top with
11 oz. National Bismarck brown 53
y oz. National Victoria green WB crys.
1 oz. National safranine A
Gold Brown
Bottom
2 lb. sumac extract paste
1 lb. cutch
\y 2 oz. titanium-potassium oxalate
8. oz. National resorcine brown R
2 oz. sulphuric acid.
Top with
9 oz. National chrysoidine Y extra
y 2 oz. National auramine O
1 y 2 oz. potassium-bichromate
Morocco
Bottom
3 lb. sumac extract paste
1 y 2 lbs. hypernic paste
1 y 2 oz. Potassium bichromate
iy 2 oz. National fast red. S cone.
2y 2 oz. National buffalo black NBR
2 oz. sulphuric acid
Top with
^y 2 oz. National safranine A
7V& oz. National Bismarck brown 53
y% oz. National methyl violet 2 B
cone. crys.
DYEING LEATHER 361
Coloring alum-tanned leather. — This leather is, as a rule,
dyed with wood colors which may be shaded with acid dyes;
another way is to bottom with wood colors and then top with
basic dyes. The wood dyes are the most durable, but the
coal-tar dyes are the easiest applied. A mordant is not neces-
sary, as the alum itself acts as a mordant, and the color ad-
heres readily to the alum-tanned fibers. Wood-color extracts
in crystal form dissolve readily in boiling water and give clean
shades of color on alum-tanned skins. It is necessary to wash
the skins thoroughly before coloring them. This is done by
running in a drum, giving three changes of warm water (85°
F.) and adding a small quantity of ammonium carbonate to
the second water, say 2 per cent on the weight of the skins.
Washing consumes about an hour. Some skins require more
washing than others. A polygonal drum is useful in washing
and coloring any kind of leather. When a white flesh and
colored grain are desired, the dye is applied to the grain side
only by means of a brush or a sponge. Coloring in a drum
dyes both the flesh and grain side.
Coloring is carried out best in a drum heated by steam.
Anthracene yellows and chromate browns are used in the fol-
lowing manner : The leather is thrown into the drum, and the
solution of dyestuff at 120° F. and containing 1 per cent of
ammonia, is poured in and the drum run for 15 minutes. A
solution of formic acid, well diluted, and in which potassium
dichromate is dissolved, is then added to the liquor in the
drum. The temperature is raised by steam to 160° F., and the
goods drummed at this temperature for 15 minutes. The
liquor is allowed to cool to 120° F., when 5 per cent of gam-
bier is added, which is absorbed by the leather in another
half-hour's drumming. Finally the skins are rinsed in warm
water, set out, dried, and dressed in the customary manner.
The anthracene yellows and anthracene chromate browns
can be combined with each other to produce any desired
shade. Yellow glove and mitten leather is obtained by color-
ing with gambier, picric acid, and fustic. Boil 25 lb. of gam-
bier in a barrel three parts full of water. To this solution
362 PRACTICAL TANNING
add 1 pint of muriate of tin and 3 oz. of tin crystals, and
fill the barrel with water. To color 100 skins use from 6 to 10
gallons of this gambier liquor in 4 gallons of water at 90° F. ,
and drum the leather for a half -hour.
Prepare a solution of picric acid and fustic by dissolving
8 oz. of each in 2 gallons of boiling water, to which add
1 gallon of cold water. Pour this solution into the drum
with the gambier liquor, and drum the leather 30 minutes.
This process of coloring may be applied either before or after
fat-liquoring. Staking, drumming with powdered soapstone,
and staking again, completes the process of manufacture, and
the leather is ready for use.
Methods of coloring chrome-tanned sheepskins. — The
coloring of chrome-tanned sheepskins is accomplished in vari-
ous ways. Artificial dyes are in general use. Drum color-
ing is usually given the preference over the paddle-wheel, tray
and brush coloring, as it accomplishes uniform dyeing of a
large number of skins in a short time and with little labor.
Skins which are to be colored should be prepared with partic-
ular care. Only sound skins are suitable and they should be
well tanned, free from lime spots and discoloration, and the
grain should be as free from natural grease as possible. It
is also necessary that the process of tanning used should yield
a leather that is soft and full after it has been dried and staked,
even though it is given very little fat-liquor or none at all.
Complete neutralization of the acid in the skins is also of great
importance. Even though acid dyes are applied, it is always
best to neutralize the leather before coloring it. Where there
is acid in the leather, the fat-liquor is imperfectly absorbed,
the dyestuff is liable to be precipitated in the bath, and when
finished the leather is likely to spew. If the skins are colored
immediately after they have been neutralized and washed, the
last washing should be in warm water, thus raising the tem-
perature of the leather in anticipation of the dyeing process.
The flesh side should be shaved smooth before the skins are
colored. Where fat-liquoring is done previous to dyeing, it
is essential that the liquor should penetrate completely into
DYEING LEATHER 363
the leather so that it does not leave the grain greasy or sticky.
Before it is colored, the leather should be kept wet and pro-
tected as much as possible from light. Dyeing may be accom-
plished with acid dyestuffs direct, without mordant, or with
basic dyes after the skins have been mordanted with tannin.
Coloring with acid dyestuffs. — A practical method of color-
ing with direct or acid dyes is carried out according to the
following instructions : The skins, neutralized and shaved,
are fat-liquored lightly, and then rinsed in warm water.
Twelve gallons of water at 125° F. for each 100 lb. of skins
is put into the drum, which is then started. The dyestuff
solution is poured through the hollow axle into the drum and
the leather is milled from 15 to 25 minutes. Where good
penetration is desired, 1 or 2 oz. of ammonia should be added
to the liquor in the drum. At the end of this time the dye-
bath is acidified by the addition of formic acid. Enough acid
should be used to neutralize the ammonia added, and in addi-
tion to which, 2 parts by weight of formic acid for every 4
parts of dyestuff, should be used. The acid thus added fixes
the color on the leather by 10 minutes' longer drumming.
To increase the fullness of the leather, some sumac or gam-
bier liquor should be added to the dye-bath or run into the
drum after the bath has been acidulated. This treatment is
particularly advisable if the skins are to be glazed.
The sumac liquor referred to is a decoction of 6 to 8 lb.
of sumac leaves or sumac powder in 5 gallons of hot water.
Two gallons of such liquor are used for each 100 lb. of
leather. After 20 minutes a solution of 3 to 4 oz. of sulphuric
acid, or three times as much sodium bisulphate in one gallon
of water for each 100 lb. of stock is added gradually while
the drum is turning, and the drumming is continued 10 or
15 minutes longer. The colored leather is then rinsed and
passed on for further treatment. The temperature of the
dye-bath should be from 120 to 140° F. It is good practice
to pass the skins through water at 140° F. before throwing
them into the drum.
The richest and fullest color results are obtained when
364 PRACTICAL TANNING
acid colors are topped with basic dyestuffs. This is done by
adding a solution of 2 oz. or more of some basic color to the
dye-bath as soon as all the acid color has been exhausted from
the dye-bath. If this cannot be effected completely, the basic
color is applied by drumming the leather in a fresh bath, in
which case no further rinsing is necessary.
Acid dyestuffs are dissolved by pouring boiling water over
them and boiling to complete solution if necessary. The solu-
tion is then passed through a piece of cheese-cloth or a fine
sieve, and any particles remaining undissolved are brought
into solution by pouring more boiling water over them.
Formic acid is used in the dye-baths to get the full shade.
The leather is not harmed when an excess of formic acid is
used, as it evaporates during the drying of the leather.
Coloring with basic dyestuffs. — Basic colors are applied to
chrome-tanned sheepskins in the following manner : The neu-
tralized and shaved leather is treated in a drum with a sumac,
gambier, or fustic liquor. After this has been done, the dye-
ing is proceeded with, the process lasting 20 minutes or
longer at a temperature of 125 9 F. It is always advisable
to add the solution of dyestuff in several portions through
the hollow axle while the drum is turning.
A decoction of 7 or 8 lb. of sumac leaves or sumac pow-
der in 5 gallons of hot water is suitable for mordanting
the leather. For very light shades, 6 quarts of such liquor
is sufficient for 100 lb. of leather; for dark shades, from 8
to 10 quarts. It should be strained before using. As the
sumac bath alone does not fasten the tannin to the skin, a
solution of tartar emetic (antimony-potassium tartrate) is
generally used to overcome this uncombined condition and
fix the color on the leather. After the skins have been treated
with the sumac, the solution of tartar emetic is poured into
the drum and the process is continued 15 minutes. The
leather is then rinsed in warm water, the spent liquor run to
waste, and the leather dyed with the basic color in an acid
solution. From 8 to 12 oz. of tartar emetic is used for 100 lb.
of leather.
DYEING LEATHER 365
Gambier mordant. — Two or three pounds of gambier for
100 lb. of leather is another excellent mordant for basic dyes.
Boil the gambier in 4 gallons of water, then add cold water
to make 12 gallons of liquor. Use at 125° F., and drum the
leather with it 30 minutes. Then dissolve 4 oz. of titanium-
potassium oxalate in hot water, pour the solution into the
drum and run 10 minutes longer. Drain off the liquor and
proceed to color the leather with the basic dyestuff.
Fustic or osage orange mordant. — Fustic extract is an ex-
cellent mordant for shades of tan and yellow. Use from 2
to 3 lb. for 100 lb. of leather. Dissolve in boiling water; then
increase to 12 gallons by adding cold water and use at a tem-
perature of 125° F. Drum the leather 20 minutes. Then
dissolve and add 4 oz. of titanium salts and let the drum ro-
tate 15 minutes longer. Drain off the liquor and color the
leather with basic dyestuff.
Two pounds of gambier and one pound of extract of fustic
is also an excellent mordant for basic or acid dyes, and may
be used with titanium-potassium oxalate the same as gambier
or fustic alone.
Sumac and titanium-potassium oxalate. — Four ounces of
liquid extract of sumac may be used for each dozen small
and medium-sized skins. The sumac is mixed with hot water
and the skins drummed with the liquor for 20 minutes. Then
pour the solution of titanium-potassium exalate (| to 1 oz.
for a dozen skins) into the drum and run 10 minutes. Wash
the skins and dye with basic colors, or dye them with acid
colors without first washing. Dry powdered sumac may be
used. The particles of sumac serve the useful purpose of
taking up whatever grease there may be on the grain, as well
as acting as a mordant by giving up tannic acid.
Combined dyeing process. — Bottoming with acid dyestuffs
or with diamine and anthracene colors, and then topping with
basic dyes, is an excellent method of coloring chrome-tanned
sheepskins, especially if they have damaged grain and it is
desired to .cover up such defects as much as possible. The
366 PRACTICAL TANNING
coloring is usually done in two baths, namely, the bottoming
and the topping bath.
The leather is first drummed with the requisite quantity of
fustic extract. The solution of acid dyestuff is then poured
into the drum and drumming is continued another half-hour,
and complete absorption of the acid dyestuff s is then brought
about, if necessary, by the addition of 2 to 3 oz. of acetic
acid per 100 lb. of leather, and then a solution of the basic
dye added.
Colors of superior fastness may be obtained by adding from
4 to 8 oz. of sodium dichromate to the bath containing aliza-
rine colors, finally adding acetic acid, and working the goods
at as high a temperature as possible, say 150 to 160° F. The
color solution is then drained out of the drum and the leather
is topped with basic colors in a fresh bath.
The skins are fat-liquored either before dyeing* or after
topping. If the latter, they should be rinsed thoroughly before
fat-liquoring. Acid, diamine, alizarine, and basic colors can be
recommended for full, even, and rich shades. The quantity
of dyestuffs required to color a lot of leather depends, of
course, upon the color desired, the size and condition of the
skins, and must be decided by the dyer. It is always wise
first to try a few dyeing experiments on a small scale.
Dyeing light shades with acid dyestuff s. — When light shades
such as gray, drab, champagne, pea green, etc., are desired,
the skins should be colored in the following manner : They are
neutralized, shaved, weighed, treated in a drum with the solu-
tion of acid dye, according to the shade, and then set with
formic acid. An acid fat-liquor is poured in and the leather
drummed 20 minutes. The procedure can also be reversed
by first fat-liquoring the skins with an acid fat-liquor and
dyeing afterwards. To secure complete penetration, all that
is required is to neutralize the skins well and prolong the
drumming.
After the leather has been drummed a half-hour it is ad-
visable to add a decoction of sumac or gambier to the bath
after the fat-liquor has been exhausted by the leather, and
DYEING LEATHER 367
run the drum another half-hour. Where the color is added to
the fat-liquor, which should be alkaline, from 2 to 4 oz. are
used for 100 lb. of leather. Acid dyes are particularly suited
for coloring light and fancy shades.
Dyeing with direct colors. — These colors are of value to the
dyer of chrome leather. After the skins have been neutral-
ized and shaved, the solution of direct dye is applied, no
mordant being required. After the leather has taken up the
color, a solution of sodium dichromate or of copper sulphate
should be poured into the drum for the purpose of setting the
dye and making it faster to the action of the fat-liquor. A
little salt added to the dye-bath will result in good shades.
No acid is used and no re-tannage is necessary, and the
leather should be perfectly neutral before it is colored.
Direct blacks are used successfully with logwood, the leather
being dyed first with this and then with the direct black. A
good way to use these dyes for colors is to dye with them and
then top off with basic dye. Direct dyes are especially use-
ful for coloring leather which is finished dull or on the flesh
side. It is best to use acid fat-liquor on leather colored with
these dyes.
Acid colors and sodium bisulphate. — About 100 lb. of
leather can be nicely colored by using acid dyestuffs and so-
dium bisulphate as follows : The required dyestuff is dis-
solved in boiling water and made up to 12 gallons of liquor,
which is used at 140° F. After the leather has been drummed
20 minutes, 8 oz. of bisulphate is dissolved in hot water and
added to the contents of the drum, which is run 10 minutes
longer, when all the dyestuff will have been absorbed. The
leather is then rinsed with warm water and. is fat-liquored.
Complete penetration is obtained by adding 2\ oz. of ammonia
to the dye-bath and drumming a half hour longer before add-
ing the bisulphate. When this is done, the quantity of bisul-
phate should be increased slightly to neutralize the ammonia.
Coloring with phosphine dyestuff. — Tans and browns of
good color and penetration are obtained on chrome sheep-
skins by the use of phosphines and titanium-potassium oxa-
368 PRACTICAL TANNING
late. The procedure for 100 lb. of leather is as follows:
Drum for 10 minutes with a solution of 3 oz. of oxalate.
Then pour 1 lb. of fustic crystals in solution into the drum,
and let the leather run 10 minutes. Then add 3 oz. more of
the oxalate and drum 10 minutes. Rinse the leather, drain
it, and color with phosphine blended with Bismarck brown,
both of which are basic dyes, from 2 to 16 oz. of the phos-
phine and from 1 to 4 oz. of brown according to shade desired.
Fustic and logwood bottom. — A mixture of 2 lb. of fustic
extract and 2 to 3 oz. of logwood crystals produces excellent
results as a bottom for acid colors. After the desired shade
has been secured, the skins are drained and treated either
with acid fat-liquor or with an emulsion of "oil and egg-yolk.
Topping acid colors with basic dye is one of the most ap-
proved methods of getting tan and golden-brown shades.
Formic acid added toward the end of the process increases
the depth of color and fastens the color on the leather.
Sumac and acid color mordant. — Full, rich shades of tan
and brown can be secured by treating as follows: Drum the
skins in a solution of 2 lb. of sumac extract and 6 oz. of
acid brown aniline for 20 minutes. Then dissolve 5 oz. of
titanium-potassium oxalate in a little hot water, pour the solu-
tion into the drum and run it for 10 minutes. Wash the
skins in two changes of water and color them with basic dyes.
Practical formulas for popular shades: 1. Dark tan. —
For 100 lb. of leather, drum 30 minutes with 1| lb. of phos-
phine at 120° F. ; add 5 lb. of fustic extract in solution at
120° F. and drum 30 minutes; finally pour 2 oz. of sodium
dichromate at 120° F. into the drum, and run it 20 minutes
longer; fat-liquor, set out, and dry the leather.
2. A rich shade of chocolate brown is obtained in the fol-
lowing manner: Boil 2 lb. of gambier and 1 lb. of extract
of fustic in 4 gallons of water until dissolved, cool with cold
water to make 12 gallons of liquor. Drum 100 lb. of skins
for 30 minutes with this liquor; then pour 4 oz. of titanium-
potassium oxalate dissolved in hot water into the drum, and
run the skins 15 minutes longer. If the mordant has been
DYEING LEATHER 369
taken up by the leather, run off the liquor and pour the dye
solution into the drum; if it has not been taken up, it is best
to wash the skins before giving them the dye. For 6 dozen
skins use 8 oz. of basic yellow and drum the skins 10 minutes ;
then add 1 lb. of chocolate brown and 8 oz. of Bismarck
brown, dissolved together and poured into the drum. Run
the drum 20 minutes after the color has been put in; then
wash and fat-liquor the skins, and hang them up to dry. Ex-
tract of sumac may be used for the mordant if preferred.
3. Golden-rod yellow, Bismarck brown, and champagne
colors are efficient in dyeing chrome-tanned skins. A com-
bination of golden-rod yellow and blue and brown produces
a fine shade of tan. Mordant the skins with gambier and
fustic, apply titanium salt, wash and dye with 20 oz. of auro-
min, 8 oz. of Bismarck brown, and 8 oz. of methylene blue
or malachite green. Drum 20 minutes, and the result is a
fine, fast, and uniform shade of tan.
4. An ox-blood color can be secured as follows : For each
dozen skins use from 4 to 6 oz. of extract of fustic. Drum
the leather 15 minutes with this. Then add to the liquor in
the drum 2 oz. of tartar emetic for each dozen skins, and
run 15 minutes longer. Wash the skins and prepare a color-
bath at 120° F. Use from 2 to 3 oz. of amaranth 3R for
each dozen skins and drum 20 minutes, then wash and fat-
liquor the skins. The shade can be darkened by using 2 oz.
of the amaranth and 1 oz. of chocolate brown for each dozen
skins. A liquor made of fustic and peachwood extract is
an excellent mordant for wine color. The skins are drummed
in this for 20 minutes, when a solution of titanium salts is
run in. Then they are drummed 10 minutes, washed, and col-
ored with amaranth, to which a small quantity of malachite
green has been added.
5. Alizarine brown and fustic produce a fine shade of color
for gloves, linings, etc. For each 100 lb. of leather, dissolve
2 oz. of alizarine brown by boiling in 6 gallons of water.
Add 6 gallons of cold water and use at 145° F. Drum 30
minutes. While the skins are being drummed in the alizarine
370 PRACTICAL TANNING
dye, dissolve 1 quart of fustic extract in 1 gallon of hot
water, and at the end of 30 minutes pour the solution into
the drum and run 15 minutes longer. Drain off the spent
liquor; wash, and fat-liquor.
6. To color chrome sheepskins an attractive shade of green,
drum a dozen skins with 4 oz. of sumac extract at 110° F.
Then to the bath add 4 oz. of titanium salt dissolved in hot
water for 100 lb. of leather. Drum 10 minutes. Drain off
the liquor and color, using 3 oz. of either leather green special
or dark green M and lJr oz. of amaranth 1R for each dozen.
Drum the skins 20 minutes, wash, and fat-liquor.
7. If a dark olive-green color is required, take the skins
from the shavers and for each 100 lb. use 19 gallons of hot
water and wash in this for 15 minutes; then drain the drum.
Pour in 3 lb. of extract of fustic dissolved in 12 gallons of
hot water and run 30 minutes. Make up a solution of 12 oz.
of copperas and pour half of this liquor into the drum, and
inspect the skins after 15 minutes. If they are dark enough,
wash, and fat-liquor; if not dark enough, add more copperas
liquor and drum 15 minutes longer; then wash the skins thor-
oughly and fat-liquor them.
Coloring after fat-liquoring. — Uniform results are obtained
by coloring chrome sheepskins after they have been fat-
liquored. Having been washed and shaved, mordant with
gambier or with gambier and fustic, fat-liquor with acid fat-
liquor, then color with aniline dyes, and dry them for finishing.
This method of coloring is preferred by some dyers. The
process can also be varied by fat-liquoring the skins first, then
applying the vegetable tanning material and coloring with
basic dyestuffs. Titanium-potassium oxalate may be used in
the usual manner, and assists in obtaining uniform colors.
The shades most in demand at present may be obtained
with the following basic dyestuffs, which can be mixed as
desired : paraphosphines, Bismarck browns, leather browns,
Russian red, and ox-blood A and B ; for darkening the shade,
or for saddening basic colors, use neutral blue and solid green
crystals.
DYEING LEATHER 371
Acid colors for shades of tan and brown are Indian yel-
lows, acid phosphine, and Havana brown; and for ox-blood,
new red B, roccelline mixed with Havana brown or acid
phosphine J I. For saddening the shade or as a sad-
dening agent for acid colors, use naphthol black B and fast
acid green B.
Flesh-finished chrome sheepskins. — For some purposes,
sheepskins finished on the flesh side with a soft, velvety finish
are required. Skins that have defective grain are used for
this class of leather, since the value of the leather does not
depend upon the quality of the grain. The leather is made
by the usual methods of chrome tanning, but instead of being
finished on the grain, the skins are dressed smooth and vel-
vety on the flesh side.
After the skins have been neutralized and washed they
are put into a drum with 4 gallons of water and 5 lb. of
pipeclay for 100 lb. of leather, and are milled for 20 minutes.
They are then run on a wet wheel which gives a good face
to the leather. After this has been done they are run in warm
water and then colored. Coloring is done in the same manner
as on grain-finished skins. Fustic, gambier, and sumac are
used as mordants for basic dyes. Wood dyes are also used
in conjunction with titanium salt. A satisfactory method of
coloring is to apply acid dyestuffs in a drum. Good penetra-
tion is essential on this leather, and it is helpful to add 1 to 2
oz. of ammonia to the dye liquor. At the end of 20 or 25
minutes, 2 parts by weight of formic acid for every 4 parts
by weight of dyestuff are added to the drum to acidify the
bath. A little more than this quantity of acid may be neces-
sary to neutralize the ammonia previously added. The leather
is drummed 10 minutes longer. Some sumac or gambier
liquor added after the bath has been acidulated imparts a
feeling of fullness to the skins. As a fat-liquor, an emulsion
of egg-yolk, olive oil, castile soap, and flour is especially suit-
able; but a less expensive liquor can be used. The skins, after
coloring, are washed and fat-liquored.
Drying and staking are carried out in the usual manner.
372 PRACTICAL TANNING
Staking on a machine should be followed by knee-staking to
eliminate all stretch. The skins should then be given a light
buffing on a very fine emery wheel, and are then ready to be
trimmed and sorted. If the work has been properly done,
the skins finish soft, are evenly colored, and have a smooth,
velvet-like face.
If white skins are required, the tanning process is followed
by treatment with flour ; fat-liquoring and finishing being done
as already described.
Coloring chrome-tanned sheepskins after fat-liquoring and
drying out. — Chrome sheepskins take color well before they
have been fat-liquored and dried, but it is generally considered
impracticable to dye such skins after they have been dried
out. However, this has been proved to be incorrect, as good
results may be secured in the following manner :
After the skins have been fat-liquored and dried out they
are soaked and are ready for dyeing. This is best effected
in a drum fitted with steam pipes ; neither the paddle nor the
tray are suitable without some arrangement for keeping the
dye hot. Dyeing is best carried out at a temperature of
140° F.
The method is as follows, for a dozen skins: 8 to 10 oz. of
the dye is carefully weighed out into a wooden tub and dis-
solved by pouring on it about 200 times its weight of boiling
water, stirring briskly. Then 8 to 10 oz. of sodium bisulphate
is dissolved in hot water in a separate vessel. Half of the
concentrated dye solution is now added, with the bisulphate
solution, to enough water at 140° F. in the drum to cover
the skin. The leather is placed on the shelf, and the drum
is started. After running 'the goods in this dye-bath for 15
minutes, the remainder of the dye solution is added and mill-
ing is continued for 30 minutes longer, or until the goods have
attained the depth of shade required. After dyeing, the skins
are washed in warm water, set out, lightly rubbed over the
grain with glycerine, and dried out while strained on boards.
Blacking with hematin and direct chrome black. — A fine rich
black is obtained on chrome sheepskins by the following
DYEING LEATHER - 373
method : Dissolve 1 lb. of hematin crystals for 100 lb. of
leather in 4 gallons of boiling water, add 6 or 8 gallons of
cold water and a little ammonia to make it slightly alkaline,
and use at a temperature of 125° F. After the leather has
been run in this dye for 15 minutes, add 1| lb. of chrome
leather black dissolved in 5 gallons of boiling water to the
liquor in the drum, and run the leather 15 minutes longer.
Drain the drum and pour in the fat-liquor ; then run the drum
for a half -hour; wash the skins in warm water, set out, oil the
grain lightly with neat's foot or mineral seal oil, and hang
up to dry.
Sheepskins which are to be given a glazed finish, are bene-
fited by a light re-tannage with gambier before they are dyed.
This assists in getting a fine color and finish, and makes the
leather less stretchy. The skins may be paddled or drummed
in the gambier liquor.
Blacking zvith logwood and titanium-potassium oxalate. —
In this process of dyeing, logwood extract or crystals, titan-
ium salt, and direct chrome black are used, the quantities given
below being for 100 lb. of shaved leather. Drum the leather
in a Solution of 3 oz. of titanium-potassium oxalate for 10
minutes, then pour in a solution of 2 lb. of logwood, -J lb. of
chrome leather black, and 4 oz. of ammonia in 12 gallons of
water. Drum the skins in this liquor for 20 minutes; then
pour in a solution of 3 oz. of titanium-potassium oxalate and
allow the drum to run 10 minutes longer. Then either drain
the drum and run in the fat-liquor, or wash the skins and
then fat-liquor.
Blacking with direct chrome black. — Put the leather, neu-
tralized and shaved, into the drum with 10 gallons of water
at 125° F. for each 100 lb. Run for a few minutes, then pour
the solution of dyestuffs through the hollow axle of the
drum. Dyeing will be completed after about a half-hour's
drumming. For blue-black with a blue flesh side, use from
1 to 1 1 lb. of chrome leather black. It is advisable to add a
small quantity of logwood liquor to the dye-bath after a short
drumming to fill the leather somewhat.
374. PRACTICAL TANNING
Fat-liquoring may be done either before, during, or after
dyeing. If the fat-liquor is added to the dye-bath it is ad-
visable to drum the leather in the dye liquor for 15 minutes
before adding the former. Another method of blacking with
direct chrome leather dyes is as follows : Use 4 or 5 oz. of
nigrosine G and 4 oz. of chrome leather black C for 100 lb.
of leather. This produces the desired fine grain black and
the blue-black flesh. Chrome leather black C used alone also
produces blue-black flesh and black grain. The leather, thor-
oughly neutralized and treated with alkaline fat-liquor, is dyed
for 30 minutes in a drum with 2 lb. of dye for 100 lb. of
leather, at a temperature of 120 to 140° F.
By dyeing first with 8 to 10 oz. of chrome leather black
C for 20 minutes, then adding 1 oz. of acetic acid and 10 min-
utes later a solution of 8 oz. of leather black T B, drumming
the leather 10 minutes more, and then fat-liquoring, a fine
color is secured on both flesh and grain sides. A' lit-
tle logwood extract liquor added to the dye is beneficial, in-
creasing the fullness of the leather.
Methods of dyeing vegetable-tanned skins: Blacking
vegetable-tanned skins. — There are many methods of dyeing
black on gambier, quebracho, sumac, or combination-tanned
leather. One of the newer and better processes is by the use
of logwood and titanium-potassium oxalate. Drum the skins
in a solution of 4 oz. of the titanium salt for 100 lb. of dry
leather; next pour slightly alkaline logwood or hematin liquor
— made by dissolving 4 lb. of liquid extract in 5 gallons of
water — into the drum, and after the leather has been treated
with this for 15 minutes, pour in 4 oz. more of the titanium
salt; drum 10 minutes longer, then wash and fat-liquor. No
copperas, iron liquor, or other striker is required. The titan-
ium-potassium oxalate after logwood produces a soft, deep,
and permanent black.
When soft black leather is wanted, the following procedure
may be adopted : Take the skins out of the tan liquor, wash,
and press them. Then treat with acid fat-liquor, or with an
emulsion of soap and oil, and dry out in the usual manner.
DYEING LEATHER 375
When dry, soften the skins with warm water and dye as al-
ready described; then wash and dry for finishing A few
ounces of fustic paste or crystals boiled with the logwood
makes the black deeper and richer. For some purposes the
skms work out sufficiently soft without being fat-liquored,
but if soft leather is desired, they should be fat-liquored im-
mediately after tanning, or after they have been colored
there are several direct blacks obtainable which dye the
leather a deep black without the use of logwood. When the
flesh side has to be colored, the skins are drummed with the
solution of dyestuffs; and when it is to be left uncolored the
black is applied by hand to the grain side only. If the flesh
side is to remain undyed, the staining process is to use a solu-
tion of direct black heated to 125° F. and applied directly
suffidenf am mCanS ° f " brUSh - UsUElly tW ° COats are
If the flesh side is to be colored blue, purple, or blue-black,
the skins are drummed with the solution of black and then
stained on the grain with the same dye, washed, and dried
For leather that is to be given a glazed or other bright finish
a black with a greenish cast is preferred
Dyeing zvith acid and basic ^^.-Fancy-colored skins
must have clear and uniform colors to give satisfaction, but
it is not an easy matter to get such colors unless the grain is
sound and free from excess of tannin. Tanning should be
done in clean liquors, and all excess of tannin should be elim-
inated before coloring is started. The dye, especially a basic
dye, quickly strikes defective spots in the grain, and on ac-
count of the precipitation of the dye on such spots, and the
darker coloring resulting therefrom, the finished leather shows
an unevenly colored grain which detracts from its value Tar-
tar emetic is useful in removing surplus tannin from the grain
fixing the dye on the leather, and getting uniform shades'
Basic dyestuffs are also deposited on the skins rapidly which
often causes uneven coloring. Acid dyes color more' slowly
than basic dyes, and more time is therefore required for the
production of well developed shades; but the colors are gener-
376 PRACTICAL TANNING
ally more uniform and more permanent, and the defective
spots do not show as plainly as when basic dyes are used.
The skins are usually dried after they are tanned, and are
softened and washed and cleared before they are colored.
They are shaved to secure uniform thickness. When the wash-
ing is properly done, the colors are clear, full, and deep. The
dry skins are moistened in a tub, and left in piles for some
hours to become soft and wet; or they may be moistened in
a drum. The water used for this work should be soft and
warm, as such water has greater softening and cleansing
power than cold water. A safe temperature is from 85 to
95° F. The skins are washed until soft and clean.
Sorting for black and colors is best done before the skins
are washed. The light shades require leather free from de-
fects, while the dark shades allow of a certain amount of
covering from the dye-bath.
Coloring with artificial dyestuffs. — Sumac freshens up the
skins so that they readily take the dye liquor, therefore, 4 oz.
of sumac extract for each dozen skins is placed in the mill and
the skins are drummed in this solution for 20 minutes. To
clear the grain and set the dye, a solution containing 2 oz.
of tartar emetic for each dozen skins is poured into the drum,
and the skins are run 15 minutes longer. After this it is
best to rinse the skins in warm water, drain the drum, and
return the skins to color them. From 2 to 4 oz. of dyestuff is
required by each dozen skins. The temperature of the dye-
bath should be about 100° F. Fustic may be used instead of
sumac. Either basic or acid dyes may be used on the skins
prepared in this manner. Dyeing is usually commenced by
entering the skins in a weak dye-bath, which is gradually
brought to full strength. A fairly even temperature of 120°
F. should be maintained, and on this account it is advisable to
heat the skins in hot water before passing them into the dye-
bath. Some dyers color with acid colors and then top off with
basic colors. When this is done, it is best to apply the basic
dye in a fresh bath so that there may be no precipitation of
the dyestuff in the liquor.
DYEING LEATHER 377
Another method of preparing the skins for dyeing is as
follows : The dry leather is moistened and softened, then run
in a solution of 8 oz. of titanium-potassium oxalate for every
100 lb. of dry skins. Drumming with this solution for 10
minutes gives a yellow base on which any shade of tan,
brown, ox-blood, etc., can be easily obtained.
If acid dyes are to be used, the skins may be colored at the
end of 10 minutes without being washed; if basic dyes are to
be applied after the drumming in the titanium solution, the
liquor should be run off, and the skins washed and then put in
the dye liquor.
Where extract of fustic is used as a mordant, 1| pints dis-
solved in a pail of boiling water should be used for 100 lb. of
leather. The skins, together with enough water to float them,
are put into the drum which is set in motion. The fustic solu-
tion is next slowly poured in, and drumming is continued 20
minutes. A solution of 4 oz. of titanium-potassium oxalate
is then added to the liquor, and the leather is run 15 minutes
longer. The skins can then be either fat-liquored and dyed,
or dyed first, and then fat-liquored.
After the leather has been running in the solution of acid
dyestuff for 20 minutes, 4 oz. of formic acid for each 100
lb. of leather is poured into the dye-bath to exhaust it on
the leather ; the drum is run 10 minutes longer, and the skins
are then rinsed and fat-liquored.
Ox-blood shade. — 1. For 100 lb. of dry leather previously
treated with sumac, use 8 oz. of titanium-potassium oxalate.
Soften the skins with warm water and drum them in the solu-
tion of titanium salt at 95° F. for 10 minutes. Drain the drum
and rinse the skins; then dye them. One dozen skins of aver-
age size require about 6 oz. of amaranth 3R and -§ oz. of mala-
chite green. Dissolve these dyes in 1 gallon of hot water,
add 7 gallons of cold water, apply to the skins at 100° F., and
drum 15 minutes; then wash and fat-liquor.
2. Directions for coloring 10 dozen skins : Moisten with
warm water, and run in the drum with water at 90° F. Dis-
solve 3 lb. of tartar emetic in hot water. Pour the solution
378 PRACTICAL TANNING
into the drum, and run the drum 15 minutes; then drain off
the liquor. To color, use 4 lb. of amaranth 3R, adding to
the skins in four portions at intervals of 10 minutes. Then
add 1^ lb. of amaranth 1R with 8 oz. of chocolate brown, and
run the drum a half-hour. Drain off the liquor, run in the fat-
liquor, add 10 oz. of potassium bichromate, and let the drum
revolve 10 minutes longer; then wash the skins and dry for,
finishing.
3. A good shade of ox-blood can be obtained on vegetable-
tanned skins in the following manner: Boil 10 lb. of hyper-
nic chips and strain the liquor. Put the skins in drum with
water at 90° F. Add the hypernic solution while the drum
is running, and mill the skins for a half-hour. Dissolve 7
oz. of amaranth 3R in 1 gallon of water. Strain the solu-
tion through cheese-cloth and cool to 110° F. by adding cold
water. Apply this to the leather in three portions at intervals
of 5 minutes, running the drum 15 minutes after the last of
the dye is added. Drain out the spent dye liquor, rinse the
skins in clean, warm water, and then drum with a solution
of 3 oz. of ootassium bichromate for 15 minutes and finally
fat-liquor.
Brown shades. — 1. Mordant the skins with sumac and
titanium-potassium oxalate, then dye with 1 oz. of leather
brown F for each large skin, and less for smaller ones. Drum
the leather for a half -hour, wash, and fat-liquor.
2. Another excellent shade of brown can be obtained by
drumming the skins in a solution of titanium-potassium oxa-
late for 10 minutes; drain the drum and add the color solu-
tion made of 4 oz. of phosphine, \ oz. malachite green, and
^ oz. methyl-violet 2 B; and run the leather in the dye for 15
minutes, finally washing and finishing it.
Tans and browns, all shades, are produced by the following
method: For each 100 lb. of dry leather, sumacked, washed,
and cleaned, use 1 to 3 lb. of phosphine and 1 to 8 oz. of
Bismarck brown, according to the depth of shade required.
Drum the leather in the color-bath for a half-hour, or until
DYEING LEATHER 379
it is exhausted. Add 4 to 10 oz. of titanium-potassium oxa-
late dissolved in hot water, and drum 10 minutes more and
rinse well. If not previously fat-liquored, apply such liquor
and dry the skins for finishing.
Tartar emetic may also be used on the skins after they
have been run in the sumac liquor, the goods then being
washed and colored. Leather which is dark, greasy, and dirty
can be much improved by using borax and sulphuric acid.
Put the skins into the drum with warm water containing con-
siderable borax, and wash them 20 minutes. Drain off the
borax bath and put warm water acidified with sulphuric acid
into the drum, and wash the skins 10 minutes, rinse in clean
water, make a sumac bath strong and hot, add a little salt
to it, and drum the leather in this for 30 minutes; rinse in
warm water, and strike out the leather for coloring. Run
it in warm titanium solution, then in the dye, rinse, and finish.
Dyeing with fancy effects. — By a special preparation or by
manipulation of the leather, or by suitable application of the
dyestuff, a great variety of effects may be produced, of which
those described in the following notes meet 'the present de-
mands of fashion.
Marbled effects. — These are obtained by folding the moist
leather prepared for the dyeing into a great number of irreg-
ular pleats, and pressing the pleats so formed as firmly and
as closely together as possible, whereupon the leather is dyed
either by spraying on the dye, or by placing it on a metal
plate and dipping it quickly into the liquor. This must be
done rapidly. The leather is then rinsed in pure water kept
ready. The greatest variety of effects may be obtained by re-
peating the operation several times with different color solu-
tions, and the effect may still further be varied by treating in
like manner leather previously dyed a uniform shade. The
method of dressing which follows is the same as usual.
Spray dyeing. — This is carried out with various dyestuff
solutions by means of a blowpipe provided with a fine noz-
zle, the leather being spread out flat on a table or hung on
380 PRACTICAL TANNING
hooks. There is of course plenty of scope for a great variety
of effects, according to the dyestuff solutions applied, the
leather, if desired, being previously dyed to some uniform
shade, or stencil plates are used, which again varies the effects
obtained by this process. To ensure good fastness to rubbing
and water, solutions of color soluble in alcohol, with the ad-
dition of some shellac, are frequently used for spraying.
"Changeant" dyeings are produced by spraying the color solu-
tion sideways onto the previously pressed leather, the side
opposite to the pressed parts thus remains either undyed, or
is sprayed over with a different color solution.
Antique leather. — This method is also frequently applied
for producing so-called antique leather. The rough, irreg-
ular, and wrinkled effects in favor for leather of this descrip-
tion are produced by pleating the skins and crushing them up
tightly in sacks, or nets, treating them in strong tanning solu-
tions, and only opening the bundles to complete the tanning,
when there is no longer any fear of the wrinkles disappearing.
The antique grain may also be imparted to the leather by em-
bossing. In dressing leather of this kind, the wrinkles should
be well preserved and superfluous setting-out avoided.
Various methods are applied for producing antique effects,
for instance: The raised portions of the grain of the pre-
viously dyed and dried leather are buffed by means of fine
emery paper or pumice. The raised portions of the surface
of the previously dyed and dried leather are given a coating
with a "fatty resist" consisting of wax and vaseline, where-
upon the deeper portions are dyed by means of a soft sponge
or a brush, or by spray dyeing. All parts protected by the
"wax resist" remain undyed. Any excess of dyestuff which
may be present is then removed with a moist sponge and the
leather is dried. The dyestuff intended to stain the deeper
portions of the grain has to be applied in a rather highly con-
centrated form, owing to its rapid absorption, and it is advis-
able for such purpose to use acid dyestuffs or basic colors
which have no tendency to bronze. The wax resist may, if
necessary, be replaced by collodion varnish.
DYEING LEATHER 381
If collodion varnish colored with cerasine and mineral col-
ors are used for dyeing the deeper portions of the grain of
the previously dyed and dried leather, the leather is first given
a coating of thin Irish-moss decoction. When dry, suitably
stained collodion varnish is applied, which, after being allowed
to dry for a short time, is removed from the raised portions
of the grain by means of a linen pad dipped into amyl-acetate
and pressed out well, the bottom shade then reappearing.
Antique effects may likewise be obtained in the reverse man-
ner by dyeing the raised portions of the grain with colored
gelatine, shellac dissolved in spirits, or collodion varnish, the
deeper parts of the grain thus retaining the original shade.
By clever manipulation, exceedingly handsome and entirely
original effects may be produced. When using collodion
varnish it is better to add some castor oil, in which the dye-
stuff may be dissolved, to enhance the pliability of the leather.
Shellac dissolved in spirits may be colored with basic col-
ors or with dyestuffs soluble in spirits, and collodion varnish
with cerasine colors and the addition of mineral colors, to
any desired shade.
To remove from the leather the smell peculiar to collodion
varnish with which it has been treated it is hung up for some
time in a well-ventilated room at a temperature of 110° F.
The subsequent dressing is the same as for colored leather.
Bronze dyeings (dyeings with metallic luster). — The leather
is first dyed in the tray with a solution containing 1 to \\
oz. of some suitable basic color to \\ gallons of water (dis-
solved with the addition of alcohol), then rinsed, and topped
with a solution containing up to 2 oz. of a suitable acid color
per 1^ gallons. It is better to treat such leather before dye-
ing with a solution of tartar emetic. After this dyeing in
the tray, the leather is struck out on the flesh side, the grain
being oiled lightly with linseed oil, and dried. The subse-
quent glazing may be facilitated by lightly rubbing the grain
side, immediately before the glazing, with a cloth containing
a little linseed oil.
382 PRACTICAL TANNING
The following is another method of producing bronze dye-
ing of particularly good resistance to water: The leather is
first dyed as desired with a strong solution of basic color.
After drying, it is glazed by machine, and then coated with
a stained collodion varnish diluted with about half its weight
of amyl-acetate, and then dried. This treatment is repeated
if necessary, and yields an intense bronze luster, which may
be still further enhanced by severe glazing. For so-called
velvet or antelope shades a very deep penetration is required
as a rule. This effect is produced on buffed, bark-tanned and
sumac-tanned cowhides and calfskins, or are imitated by dye-
ing the flesh side of bark-tanned sheepskins. This is ensured
to best advantage by working according to the following
method : The leather is first prepared like other colored
leather, buffed in a dry state, and soaked. It is then dyed
warm in the drum with acid colors, some ammonia being
added at the beginning of the operation. The material is
dyed for about an hour, the requisite quantity of formic acid,
up to ^ per cent, being added towards the end of the dyeing
operation. The leather is then rinsed thoroughly, set out,
oiled, and dried. Some shades, especially black, may be pro-
duced to good advantage by topping the acid colors with basic
colors. Black, for instance, is produced by dyeing with 2 per
cent of nigrosine, shaded if necessary with other dyestuffs,
the acid being added after about an hour's dyeing, and the
leather topped with 1 per cent of leather black T B or velvet
black B, and some alum or acetic acid. The leather is then
dyed for about another 20 minutes, rinsed, set out, oiled, and
dried in the usual manner.
When dyeing these leathers by the staining process, the
solutions of acid colors are brushed on without the addition
of acid ; the leather is then dried, and the second coloring ap-
plied, this time with the addition of formic acid in order to
fix the acid color. A dense shade of black is produced with
about 1 lb. of nigrosine, shaded if necessary with orange, etc.,
and the addition of 8 oz. of formic acid for 10 gallons of
DYEING LEATHER 383
dye liquor, the leather being then dried. This treatment is
followed by the application of another solution of 1 lb. of
leather black T B in 10 gallons of staining liquor. A pre-
paratory treatment with titanium-potassium oxalate, and an
after-treatment if necessary with a tanning solution, enhances
the fastness to rubbing.
Coloring and finishing India-tanned skins. — India-tanned
sheepskins and goatskins in various colors and finishes are used
for the manufacture of shopping-bags, traveling-bags, belts,
collar-boxes, bookbindings, carriage trimmings, linings, etc.,
and in making leather novelties and specialties. They can be
finished with any kind of grain, in any color, glazed or dull,
smooth-grained or embossed; they can likewise be made soft
or firm as may be desired. Large, heavy skins are used for
suitcases and bags ; the smaller ones for purposes where light,
soft leather is suitable. Bookbinders use India skins in a
variety of colors, the staples being pebbled grain, dark green,
dark blue, wines, and blacks. As bookbinders' leather must
be fairly thin to cover the backs and corners of books, the
skins are split to the thickness required.
Washing. — The water used should be at a temperature of
90° F., and its efficacy is enhanced by adding some borax
or washing soda, from 2 to 3 lb. for 100 gallons of water.
The skins are washed in this solution for 15 or 20 minutes,
then in clear water and made ready for further treatment.
It is necessary to re-tan the skins with some tannage that
makes soft and light-colored leather; and if for light shades,
it is necessary to bleach the skins with acetic acid after the
borax bath. The borax cleanses the skins perfectly, but
darkens the color; the acid-bath serves to brighten up the
color. The skins are drummed in the acid solution (from 2
to 3 oz. of acid per gallon of water may be used), then washed
thoroughly to remove every trace of it, when they are ready
for the sumac treatment.
Re-tanning zvith sumac. — The sumac liquor should be
strong and at a temperature of 105° F., and the leather should
384 PRACTICAL TANNING
be treated in a drum or in a paddle. One to two pounds of
sumac should be used for each dozen skins. The leather is
run in this sumac liquor for 30 minutes to an hour, after
which it is washed in warm water, struck out with a slicker,
and hung up to dry. When dry, it can be dyed any shade
of color.
Instead of sumac, quermos extract may be used, as it pro-
duces a light color and is stainless. After the washing from
the re-tan, the skins have a good color and for some purposes
they can be finished without dyeing. The borax removes some
of the tanning material and much of the natural grease. The
acid bath brightens the leather and the sumac replaces the tan
washed out, thus making the skins softer and the grain better
prepared for subsequent dyeing. Some tanners use sodium
hyposulphite in the wash-bath in place of borax, 10 lb. being
dissolved in a barrel of hot water; the solution is used at
110° F., and washing for a few minutes, only. The use of
normal sodium sulphite, or the tri-calcium phosphate, with
acetic acid, to clear the skins before going into the sumac, is
somewhat milder and gives satisfactory results.
Coloring the skins. — To prepare the dry leather for color-
ing it is moistened with warm water. For single pairs of
skins the tray is used, while for larger quantities the drum
is necessary.
The dyeing process is usually begun by entering the skins
in a weak dye-bath, which is gradually brought to its full
strength. For single pairs, 8 or 10 minutes is sufficient; for
larger numbers, from 15 to 30 minutes should be allowed.
A fairly even temperature of about 115 to 120° F. should be
maintained, and on this account the skins are sometimes heated
before they are placed in the warm liquor. The weights of
dyestuffs are calculated on the number of skins, the average
size being generally taken. Light shades require 1 to 14 oz.,
medium shades If to 2\ oz., and full shades up to 5 oz. per
dozen.
L One method of coloring the skins is as follows: They
DYEING LEATHER 385
are run in a drum with warm water until they are soft and
open. For each dozen skins from 2 to 5 oz. of tartar emetic in
solution is added, and the drum is run 15 minutes. This clears
the grain and sets the tannic acid. The water is then drained
out of the drum and the skins are colored with basic dyestuffs.
2. Another process is to drum the skins for 10 or 15 min-
utes in a warm solution of 6 to 8 oz. of titanium-potassium
oxalate for each 100 lb. of dry leather, then rinse and apply
the dye. This process is recommended, since it mordants
with titanium tannate, itself a yellowish shade, on which bot-
tom all shades of tan, brown, green, blue, and maroon can
be easily obtained. After running off the liquor, a slight rins-
ing with warm water is advisable but not always necessary.
If acid dye is to be applied, the rinsing may be omitted; if
basic dye is to be used, it is necessary to wash the skins only
when the mordant bath has not been fully exhausted. After
the desired shade is obtained, the leather is washed and
finished.
The dyed skins which are to be glazed subsequently should,
on leaving the liquor, correspond approximately in shade with
the dry pattern; if they are to remain dull or are to be glazed
but lightly, a wet portion of the pattern should be used for
matching. After dyeing, the leather is rinsed, set out, and
tacked on boards.
Dyeing the skins black. — 1. India-tanned skins can be
blacked through flesh and grain by using logwood and titan-
ium-potassium oxalate. A fairly strong logwood liquor,
slightly alkaline, should be used, and 10 oz. of titanium salt
for 100 lb. of dry leather. Dissolve the latter and drum the
leather in the solution for 10 minutes, then drum with the
logwood liquor for 15 minutes. No copperas or iron liquor
is used, as the logwood and titanium-potassium oxalate dye a
deep, permanent black. It is advantageous to use logwood
crystals and add a little fustic paste to the liquor to intensify
the black.
2. To dye flesh and grain of the re-tanned leather, the skins
386 PRACTICAL TANNING
should be first drummed in a solution of methyl-violet and
then in a basic black solution. For 250 lb. of dry leather,
8 oz. of methyl-violet and 5 or 6 oz. of basic black are re-
quired. Drum in the violet solution for 20 minutes, then
for 15 minutes in the basic black liquor to which 4 oz. of
titanium salt in solution has been added, wash and finish.
3. Where the flesh side of the skins is to be left uncolored,
Figure 96. — Top pan blacking machine used for seasoning and coloring.
or to be dyed black or dark blue, tHe use of the direct leather
black can be recommended.
If the flesh side of the skins is to be left undyed, the black
is applied to the grain side by the staining or brushing proc-
ess. The dye solution consists of 1 lb. of dyestuff and 8
oz. of acetic acid in 10 gallons of water. The dye liquor
should, during its application, be kept at 130° F., and be
thoroughly brushed into the grain. Usually two applications
are sufficient for dry leather.
4. If the flesh side of the leather is also to be dyed, direct
leather black is applied in a paddle or drum, preferably the
latter. Usually 1| lb. of the dyestuff per 100 lb. of leather
DYEING LEATHER * 387
is required, to which 3 to 5 oz. of acetic acid is added with
the necessary volume of water.
5. Where the flesh side of the skins is to be dyed dark
blue and the grain black, the leather is first dyed with the
direct black in a drum for half an hour at 115° F. It is
then strongly set out, and after having been dried, is dyed
on the grain by the staining or brushing method with the
same material.
6. The skins can also be flesh-colored by the use of blue
nigrosine. For each dozen skins, 2 to 3 oz. of nigrosine is
dissolved in hot water and applied at 110° F. The skins are
drummed in the solution for 20 minutes, and then blacked
on the grain by hand or on a machine with logwood and iron
liquor.
7. The leather can also be dyed by being first drummed in
logwood liquor and then the color developed in the drum by
the addition of iron liquor, or by passing the leather through
the grain-blacking machine shown in figure 96.
Drumming the leather in a warm solution of sulphonated
oil or adding the oil to the logwood liquor increases its soft-
ness and improves its texture.
Ooze leather. — This is prepared by snuffing the grain until
it has a soft, velvety appearance. Dyes for ooze leather should
be selected for their penetrating power. Excellent results in
coloring sheepskins may be obtained by dyeing first with acid
colors, as, for example, dyeing coffee shades, first with In-
dian yellow G; tan shades, first with orange extra; and red-
brown shades, first with fast brown B N, and then topping
with the proper mixture of diamine phosphine J. Bismarck
brown E E, methylene blue B B, or new blue R.
The acid dyes produce an excellent level bottom for the
basic colors. Light pearl, gray, champagne, blue, and helio-
trope are most successfully obtained with easily leveling dyes,
such" as cyanole fast green, cyanole F F, lanafuchsine S
G and S B, orange extra, and acid yellow A T. These dyes
give also good fastness to light.
388 PRACTICAL TANNING
Coloring chamois leather. — Dyeing this class of leather is
not as simple a process as dyeing vegetable-tanned skins. The
oil-tanned fibers do not take up the dye readily unless the
skins have been previously mordanted. The most common
mordants used for this class of goods are chrome-alum and
potassium dichromate, especially when alizarine dyes are used.
The leather must be wet back with warm water, and the ex-
cess of oil removed. For this purpose the goods are drummed
in a solution of washing soda at 95° F. ; an excess of soda
is not very harmful unless the temperature is too high, a suit-
able strength being about 2 per cent. When the grease has
been removed in this way, the goods may be fat-liquored
lightly and dried out. If the skins are for light shades, they
can. be bleached with sodium peroxide and sulphuric acid, or
with potassium permanganate and sulphurous acid. When
the goods have been dried, they are fluffed on one side and
again wet-down. Mordanting with chrome-alum follows,
which is best done in the drum. The chrome-alum is dis-
solved to make a 1^ to 2 per cent solution, and this liquor
placed in the drum with the goods, about 25 gallons being
sufficient for 6 dozen skins. Drumming is continued until
the chrome-alum has entirely penetrated the thickest parts,
which usually takes from 30 to 40 minutes. When the mor-
dant has penetrated the goods they are ready to be dyed.
For this purpose it is customary for the dye to be added to
the mordant bath without running it away, but it is better to
remove the goods from the mordant bath and treat in a fresh
dye-bath.
As already stated, alizarine colors are used for this class
of goods. The dyestuff should be dissolved in boiling water,
and the color developed by the addition of sodium bisulphate
at a temperature of 115° F. Half of the dye to be used is
added to the drum and the goods are milled for 20 minutes.
The quantity of bisulphate then added is about twice the weight
of the dye-stuff used, and the remainder of the dye is intro-
duced. Drumming is continued for 20 minutes, when the
goods should be thoroughly dyed, the color having penetrated
DYEING LEATHER 389
completely through the fibers. After fat-liquoring and drying,
the goods are ready for finishing.
Dyeing chrome-tanned calfskins black: 1. Dyeing with
logwood and direct leather black. — The use of a direct chrome
leather black, combined with logwood or some product of
logwood, is the most approved method of dyeing chrome
calfskins black. A typical formula is : hematin crystals, 1 lb. ;
ammonia, 1 oz. ; and chrome leather black C, 1| lb. for each
100 lb., shaved weight.
The skins are thrown into the drum together with 8 or
10 gallons of warm water. The logwood or hematin liquor,
made by dissolving the dye in 2 or 3 gallons of boiling water,
and made alkaline by the addition of the ammonia, is then
poured into the mill and the leather is drummed for 15 min-
utes. The chrome leather black dissolved in 4 gallons of
boiling water is next added to the liquor in the drum through
the trunnion, and the leather is drummed 15 minutes longer.
2. Dyeing with logwood, leather black and titanium salt.
— A rich black is 1 obtained by carrying out the following in-
structions, the quantities of dyestuffs mentioned being suf-
ficient for 100 lb. of leather: Drum the leather in a solution
of 3 oz. of titanium-potassium oxalate for 10 minutes. Dis-
solve, by boiling in 8 gallons of water, H lb. of logwood
crystals, 4 lb. of chrome leather black, and 4 oz. of sal-soda,
and drum the leather in this liquor for 15 minutes. Then
pour in another solution of 3 oz. of the titanium salt and con-
tinue drumming 10 minutes longer. The leather is then fat-
liquored.
3. Dyeing with acid-blacks. — This method of blacking the
leather is preferable if the skins have not been entirely neu-
tralized or if special value is placed on good penetration.
From 1| to 2 lb. of nerazine G or of neutral black B are
required for 100 lb. of leather. The leather is run for a few
minutes with 10 gallons of water at 130° F. The dissolved
dyestuff is then poured into the drum, and the drumming is
continued for 20 minutes. About 1 lb. of formic acid is then
390 PRACTICAL TANNING
added and the drum is run for 10 minutes longer. For filling
the leather, a fairly large quantity of logwood extract or gam-
bier may be added to the dye-bath. When this method of
dyeing is used, it is best to fat-liquor before dyeing, since the
black is likely to bleed when an alkaline fat-liquor is used
subsequent to the dyeing.
Acid blacks are also combined with direct blacks to get
good penetration; in this case, the addition of acid is omitted,
the leather being entirely neutralized before it is blacked.
Coloring chrome-tanned calfskins. — When these skins
are to be colored, they should be selected with care. Only perr
fectly sound skins free from lime spots, scars, and other
defects, should be used. It is essential that the chrome tan-
nage yields a full leather which is soft after it is dried, even
if but lightly fat-liquored. Before any attempt at coloring is
made, the leather should be thoroughly neutralized and washed
free of acid and salts acquired during the tannage ; and after
the skins have been washed it is necessary that they be shaved
and made smooth and clean on the flesh side.
Dyeing may be done in several different ways. The same
procedure as given under dyeing sheepskins may be applied.
The amount of color used will, of course, depend upon the
depth of shade desired.
In dyeing with basic colors, the stock is mordanted with
sumac, gambier or fustic, and fixed with titanium-potassium
oxalate. A solution of the basic dyestuff is then applied.
Acid colors are used on chrome-tanned calfskins in the same
manner as given under chrome-tanned sheepskins. For bright
shades possessing good penetration a combination of acid and
basic color is sometimes employed.
Usually a drum is used so that a large number of the skins
may be colored at one time, thus saving a great deal of time
and labor.
Dyeing vegetable-tanned calfskins black: Logwood
liquor. — For blacking leather, logwood extract in paste, solid,
and liquid forms are employed.
DYEING LEATHER 391
When the paste is used, from 6 to 8 lb. for each 100 lb.
shaved weight is dissolved in 40 gallons of water together
with | lb. of borax or sal-soda, and brought to boiling point.
This liquor is very strong, and is usually diluted with water.
Hematin and other similar products are used in the pro-
portion of about 3 lb. for each 100 lb. shaved weight to a
barrel of water. The dye is first boiled a few minutes in a
half barrel of water, which is then filled with water. From
1 to 2 lb. of borax may be added to the dye liquor. A few
ounces of fustic paste or crystals boiled with the logwood
serves to intensify the color.
The leather is first given the logwood liquor by running
in the drum for 20 minutes, and then the striker, consisting
of a solution of 1 per cent of iron sulphate and \ per cent of
copper sulphate, is introduced and the stock run for 15 min-
utes longer.
To color vegetable-tanned calfskins a deep black, the use
of titanium-potassium oxalate as a striker is recommended,
100 lb. of dry leather requiring from 8 to 10 oz. of the titan-
ium salt. If the leather is not fat-liquored before dyeing,
it should be washed, fat-liquored, dried, and finished.
Dyeing with direct leather blacks. — Methods of dyeing
leather black by the application of special blacks, without the
use of logwood, are of fairly recent origin. Leather black
T B and T G are useful in blacking any kind of vegetable-
tanned leather, either on the grain side only, or upon both
the flesh side and grain. The color is a rich, permanent black.
The dyestufls are dissolved by mixing 2 parts by weight with
1 part by weight of acetic acid (30 per cent), and then pouring
boiling water over it while stirring constantly, so that a solu-
tion of about 1 per cent results, which is diluted if necessary.
The dyestuffs are applied in the customary manner, either by
the staining process, or in a paddle or a drum.
Coloring vegetable-tanned calfskins. — For this treatment,
basic and acid dyestuffs are used. The latter are applied with
the addition of some acid, 4 parts of an acid color usually
392 PRACTICAL TANNING
requiring 2 parts by weight of formic acid, or 3 parts by
weight of lactic acid. The acid, before it is given to the
leather, should be diluted with 100 times its weight of water.
The leather is first run in a drum with the solution of dye-
stuff, and when it has taken up most of the color, say in about
15 minutes, the acid is poured into the drum and the leather
is run for 10 minutes longer.
The leather is frequently freshened up with sumac before
it is colored. When this is done, it is likely to contain uncom-
bined tannin, which causes uneven or cloudy coloring, so
tartar emetic is used to prevent this. The leather is first
drummed with sumac liquor. This may consist of a decoc-
tion of sumac leaves or powder, or of a solution of 1 lb. of
extract of sumac in sufficient water at 100° F. for 4 dozen
skins. The leather is drummed with the sumac for 20 min-
utes, after which, 8 oz. of tartar emetic, dissolved in water,
is poured in, and the leather is run 20 minutes longer. The
grain is thus cleared and prepared for the basic dye. No
potassium dichromate or other setting agent is required, as
the color will be fixed on the leather.
In the treatment of leather which has acquired a dark color
from the tannage it is advantageous to bleach it before
coloring.
In dyeing vegetable-tanned calfskins the same methods are
employed as under vegetable-tanned sheepskins. The quantity
of dyestuff used depends upon the depth of shade desired.
As vegetable-tanned calfskins should be dried out before color-
ing it is customary to run them in an emulsion of turkey red
oil prior to dyeing. They may then be shaved, dampened
back, and colored with basic, acid, direct, or alizarine dyes.
Coloring velvet or suede leathers. — Coloring is done most
satisfactorily with acid dyestuffs. The dye-bath is prepared
in the usual manner, and \ lb. of potato starch is added for
100 lb. of leather to ensure evenness of color and cover im-
perfections. At the end of 20 minutes in the dye-bath, acid-
ulate with £ per cent of sulphuric acid, rinse the dyed leather,
set it out, and dry in the usual manner.
DYEING LEATHER 393
Finishing is done as follows : Dampen the skins with clear
damp sawdust and stake; then buff them on the buffing ma-
chine and fluff lightly on the flesh. In place of buffing on
the wheel, the skins may be lightly worked over with the
knife by hand, finishing off by working over the grain with
a very fine emery made up into a suitable pad. The latter
method gives an even, velvety feel and appearance to the
leather. The finishing touch is a brushing with a stiff brush.
For vegetable-tanned goods, which are to be stained on the
flesh only, the buffing in the first stage applies, and when
buffed, they can be treated as follows: First give the skins
a coat of "clearing," made by dissolving 2 oz. of oxalic acid
in 3 or 4 gallons of water. Allow them to level well by
lightly airing, and then work over with a light coat of stain,
using in the dyestuff solution 4 oz. of dextrine and 4 oz. of
gum dragon in 8 to 10 gallons of solution. In staining this
class of goods it is the rule to give first a weak coat to ensure
a more even absorption of coloring matter, finally working
up the shade required in the second coat. For producing
good shades in light browns, the use of titanium-potassium
oxalate will serve a useful purpose in obtaining a bottom
which is really rich, using about 3 oz. of the salt to 100 lb.
of leather, drumming the skins with the solution for 20 min-
utes, and then adding the color solution to the drum.
A light crutching and rubbing up the velvet on the colored
side with a fine emery pad, or a light buffing on the wheel,
finishes the leather. Coloring the skins according to the fol-
lowing method produces deep penetration of color: The
leather is buffed dry and soaked. It is then dyed warm in
the drum with acid colors, some ammonia being added at the
beginning of this operation. According to the thickness of
the leather, up to 5 per cent of dyestuff, calculated on the
weight of the moist leather, is used. The skins are dyed for
one hour, the sulphuric or formic acid, up to £ per cent, being
added towards the end of the operation. The leather is then
rinsed thoroughly, set out, oiled, dried, and finished in the
394 PRACTICAL TANNING
usual manner by moistening in damp sawdust, drumming in
a dry drum and glazing or ironing on the grain side.
Black is produced by dyeing with 2 per cent of nerazine
G, shaded if necessary with other dyestuffs, the acid being
added after about an hour's dyeing, and the leather topped
with 1 per cent of velvet black and some alum or acetic acid.
It is then dyed 20 minutes, rinsed, set out, oiled, dried, and
finished.
Notes on ooze calf and Russia chrome leathers. —
Chrome-tanned calfskins are finished into several fancy
leathers. The most important of these are the boarded-tan
calf, chrome Russias, and ooze in black and colors. The
skins for boarded-tan calf and chrome Russia are selected in
the wet tanned condition and colored before they are dried
out.
The skins for ooze leather are fat-liquored after tanning
with an emulsion of egg-yolk and flour, and then dried; after
which process they are sorted and colored. The fancy ooze
colors according to the "Leather Manufacturer," can be made
by bottoming with sumac or fustic extract and some mordant
like sulphate of iron, tartar emetic, or titanium-potassium
oxalate, then coloring with basic dyes; or by coloring with
acid or diamine dyes, and sometimes topping with basic dyes.
Some light shades are also made with pigments.
Black ooze is made with a combination of logwood, nera-
zine, or oxydiamine black and leather black, or with a com-
bination of developed black and leather black. One process
of making black ooze calf is as follows : The skins are sorted
after washing out of the chrome tannage. They are next
shaved and fat-liquored 30 minutes with 5 per cent egg-yolk
and 10 per cent flour. The skins are then drained off, hung
up, and dried. When dry, they are dampened in sawdust,
staked, and buffed. They are then ready for dyeing. The
skins must be buffed very clean so that after coloring they
will not need a second burring. The next operation is a
thorough wetting in a drum with water at 140° F. The
DYEING LEATHER 395
skins are next dyed 30 minutes at 130° F. with 12^ per cent
diamine ooze black C R, then fixed 15 minutes with 5 per
cent muriatic acid. The skins are next drained off and rinsed
in cold water. They are then diazotized, running the first
5 minutes in 10 per cent muriatic acid; then add 5 per cent
sodium nitrite, and run them 15 minutes, drain them off, and
wash thoroughly.
The muriatic acid is given before the sodium nitrite be-
cause the latter has an alkaline reaction, which has a tendency
to wash the black from the leather before it can be diazotized.
The diazotizing must be done cold so that the nitrous gas
will not escape easily from the solution.
The skins are now developed 15 minutes with 0.8 per cent
phenylene-diamine dissolved with 1.6 per cent soda ash and
0.2 per cent betanaphthol dissolved with 0.2 per cent caustic
soda. The two solutions are made separately, but are mixed
before they are applied. The skins are then drained off and
washed, and next topped with 2 per cent leather black and 4
per cent acetic acid. The skins are then thoroughly rinsed
off and fat-liquored 45 minutes with 2 per cent of soluble oil.
They are then dried on hooks, dampened in sawdust, staked,
dry-milled, and tacked out.
Chrome Russia leather and tan chrome boarded calf are
colored in about the same manner. As the latter leather is
glazed it is necessary to keep the colors lighter and yellower
because the glazing makes them sadder and redder. These
colors are usually made with basic dyes on top of a vegetable
bottom, because they give very full, even shades. Acid and
diamine colors which would be much faster to light can be
selected.
Dyeing chrome-tanned goat-skins: Dyeing with acid
colors. — The neutralized and shaved leather is fat-liquored
and then rinsed in water at 120° F. Twelve gallons of water
heated to 125° F. is used in preparing the dye-bath for 100
lb. of leather. The leather and the hot water are put into
the drum. The solution of dyestuff without any addition
396 PRACTICAL TANNING
of acid is then poured into the drum while it is rotating and
the leather is run for 20 minutes. If particular value is
attached to a good penetration, 1 oz. or more of ammonia
should be added to the dyestuff, but this is effective only where
the skins have been completely neutralized.
At the end of the 20 minutes, the dye-bath is acidified by
adding formic or sulphuric acid, preferably the former.
Enough acid should be used to neutralize the ammonia, and
in addition, 2 parts by weight of formic acid or 1 part by
weight of sulphuric acid for every 4 parts by weight of dye-
stuff are necessary. After the color-bath has been thus acidi-
fied, the leather should be drummed 10 minutes to allow the
dyestuff to become fixed.
The addition of some sumac or gambier liquor to the dye-
bath after it has been acidulated improves the feel and full-
ness of the leather, and makes it easier later on to obtain a
good glazed finish.
To remove any excess of acid which may be present in the
leather after it has been colored, a solution of 4 oz. of sodium
acetate crystals for each 100 lb. of leather should be added to
the water in which the skins are rinsed.
Very full shades are obtained by first coloring with acid
dyes and then topping with basic color. This is done by add-
ing a solution of some basic color — -2 oz. or more of dyestuff
for 100 lb. of leather — as soon as by the addition of acid all
of the acid color has been exhausted from the dye-bath. If
this cannot he effected completely, the topping may be carried
out in a fresh bath, in which case no further rinsing is needed.
The temperature of the dye-bath should be kept as high as
possible during the process, not lower than 120° F. It is
advisable to pass the skins through hot water before throwing
them into the drum, or treat them in it to warm them thor-
oughly. The sumac liquor used with the solution of dye-
stuff is made by steeping from 12 to 16 lb. of sumac leaves,
sumac powder, or sumac extract, in 10 gallons of hot water;
2 gallons of the decoction is used for 100 lb. of skins. Sumac
DYEING LEATHER 397
may, however, be partly or wholly substituted by gambier;
that is to say, the liquor may be made of equal parts of sumac
and gambier, or gambier may be used alone.
Dyeing with basic colors. — The method of coloring chrome
leather with basic dyes generally used consists of mordanting
it with tanning extract such as sumac, gambier, or combina-
tions of these two; or gambier and fustic, the latter or osage
orange also being often used alone. Dyeing may be done
either before or after the skins have been fat-liquored. For
the mordant, sumac is chiefly used for light shades, fustic
or osage orange for tan and yellow shades, and gambier for
the darker ones. A decoction of 4 to 5 lb. of sumac is suffi-
cient for 100 lb. of leather. After having been treated with
sumac, gambier, fustic or osage orange, the skins are dyed
with basic colors. The dyeing period should last 15 or 20
minutes, and the temperature of the bath should be 125°. It
is advisable to add the dyestuff to the leather in several por-
tions through the hollow axle while the drum is rotating. The
drum should not be stopped until the solution of color has
been in at least 10 minutes, otherwise the leather may be
spotted.
Sumac mordant for basic and acid dyes. — Chrome-tanned
goatskins are nicely colored by carrying out the following
instructions : Prepare a sumac liquor by using a decoction of
4 to 6 lb. of sumac leaves for 100 lb. of skins, or a solu-
tion of 20 oz. of extract of sumac; use at a temperature of
125° F., and drum the leather in it for 20 minutes. Then
pour in 4 oz. of titanium-potassium oxalate dissolved in a
little hot water for 100 lb. of leather, and let the drum rotate
10 minutes longer. Then drain the liquor out of the drum
and run the skins in a solution of dyestuff, either basic or
acid dyes being used, preferably the latter. The result of
this method of coloring gives full and uniform shades of
color. It is also good practice to apply the dyes first to the
sumac-treated skins and the titanium salt afterwards. This
gives clear, bright colors.
398 PRACTICAL TANNING
Gambler mordant for tan shades. — For 100 lb. of stock,
use 2 lb. of gambier dissolved in 12 gallons of water at a
temperature of 125° F. Drum the skins in this solution for
20 minutes. Then pour in 3 or 4 oz. of titanium-potassium
oxalate dissolved in hot water, and let the drum turn 10 min-
utes longer. Drain out the liquor and color the leather with
acid dye, or rinse it in warm water and color with basic
dyestuff.
A liquor composed of equal parts of gambier and fustic is
also an excellent mordant for shades of tan and brown.
Process for tan and brown shades. — Drum the leather for
10 minutes in a solution of 3 oz. of titanium-potassium oxa-
late; add 1 lb. of fustic crystals dissolved in boiling water
and drum 10 minutes; pour in another solution of 3 oz. of
titanium salt and drum the leather 10 minutes longer; wash
the skins, drain, and dye them with phosphines shaded with
Bismarck brown to the exact color desired ; drum 20 minutes,
then fat-liquor the leather — if not fat-liquored before dye-
ing — with a slightly alkaline fat-liquor, and finish as usual.
Five ounces of liquid extract of fustic may be used for each
dozen skins, or 1 to 2 lb. for 100 pounds.
Clearing the grain of grease. — Skins which have greasy
grain may be cleared by being drummed 15 minutes in a solu-
tion of 1 to 2 gallons of lactic acid in 50 gallons of hot water;
they are then rinsed and treated with sumac, gambier or fustic,
and colored. The acid removes the surface grease and opens
up the pores of the grain so that the mordant and dye may
go in more deeply and more uniformly.
Dyeing with fustic extract and direct or anthracene colors.
— Wood dyes, such as fustic extract, may be used with direct,
or anthracene colors in the production of fast colors on chrome
leather. The process is as follows : The leather is drummed
for 30 minutes with the requisite quantity of fustic extract.
The solution of dyestuff is then poured in and the drumming
is continued for a half-hour longer. Complete absorption of
the dyestuff is finally brought about by the addition of 2 or 3
oz. of acetic acid per 100 lb. of leather.
DYEING LEATHER 399
Color of superior fastness may be obtained by adding from
4 to 8 oz. of sodium dichromate to the color-bath before the
acetic acid is added, and by working the goods at as high a
temperature as possible, or from 150 to 160° F. The liquor
is then drained out of the drum and the leather is topped in
a fresh bath with basic dyestuff. The leather is fat-liquored
either before the dyeing is begun or after topping with basic
color. In the latter case it should be rinsed thoroughly be-
fore it is fat-liquored.
Light shades, such as gray, drab, champagne, beige, bis-
cuit, etc., are obtained by using acid dyestuffs in the follow-
ing manner: The neutralized leather is drummed with the
diluted solution of dye (3 to 4 oz. for 100 lb. of leather)
at a temperature of 130° F., for 10-minutes. The fat-liquor
is then poured in and the leather is drummed for a half-hour.
This method of working may be reversed by commencing with
the fat-liquor and adding the dyestuff after some time, also
by using both dyestuff and fat-liquor simultaneously. All
that is needed to obtain complete penetration is to neutralize
the leather completely and prolong the drumming correspond-
ingly. If necessary, -J to 1 per cent soap may be added to the
ordinary fat-liquor. It is usually advisable to add a decoc-
tion of from 6 to 8 lb. of sumac or a solution of 3 to 4 lb. of
gambier to the bath after the fat-liquor has been exhausted
by the leather, and allow the drum to rotate a half -hour
longer. The leather is then rinsed and set out.
Use of tartar emetic. — Chrome-tanned leather, previous to
the application of artificial dye, is usually prepared with some
tanning extract, as already stated. When uncombined tannin
remains on the grain of the leather imperfect coloring results,
and to prevent such defect and fix the color on the leather
some dyers use tartar emetic, which is a tartrate of antimony
and potassium. The leather is run in the sumac, gambier,
or fustic liquor, as the case may be, the required period, when
tartar emetic dissolved in hot water is added to the drum and
the leather is drummed 15 minutes longer. At the end of this
400 PRACTICAL TANNING
time it is rinsed in warm water and colored with basic dye,
then rinsed again and fat-liquored. Two ounces of tartar
emetic is generally sufficient for one dozen skins.
Notes and suggestions. — While fustic extract is used in
coloring, it may be combined with the fat-liquor, and the two
processes of mordanting and fat-liquoring performed at one
operation, coloring being done afterwards.
When chrome-tanned skins are colored after they have been
fat-liquored, more dye is required than when coloring is done
previous to fat-liquoring. This is due to the fact that the
fat-liquor prevents penetration of the dyes into the pores of
the leather. On the other hand, when the leather is colored
before it is fat-liquored, the hot fat-liquor removes much of
the color and makes it difficult to get the exact shade wanted.
Basic dyes have the advantage over acid dyes in that no acid
is required to set the color. When acid dyes are used, the
leather should be washed and freed from every trace of acid
before it is fat-liquored. It .is the custom to color and fat-
liquor chrome leather before drying it out, as it is not prac-
ticable to color the leather by the usual methods after it has
been dried. It is said, however, that the leather can be fat-
liquored and dried, and then wet-back and colored with acid
dyestuffs in a bath to which a quantity of sodium bisulphate
has been added. The process is as follows : The acid dye
is dissolved in boiling water. Bisulphate, equal to the amount
of dye, is dissolved in hot water in a separate vessel. Half
of the dye solution and all of the soda solution are added to
enough hot water to drum the leather — 12 gallons for 100 lb.
of leather — the skins being drummed in the liquor for 15
minutes. The remainder of the dye is then added, the leather
is drummed 30 minutes longer, then washed in warm water,
set out, and dried. From 8 to 10 oz. of dyestuff is usually
required for a dozen skins. This method of dyeing is said
to color leather satisfactorily which has been dried after fat-
liquoring.
It has been found that a better finish can be secured on
DYEING LEATHER 401
skins that have been given a light re-tannage with some vege-
table tanning extract, either before or during the coloring
process. Acid dyes are used successfully on such a bottom.
A mixture of 2 per cent of fustic extract and £ per cent log-
wood crystals produces excellent results as a mordant. After
having been colored with coal-tar dye on this bottom, the
skins are drained, and treated with an acid fat-liquor or an
emulsion of oil and egg-yolk. Some dyers use basic color on
top of an acid color, which makes the color faster to the fat-
liquor. Applying fustic and logwood first, then acid dyestuff,
and topping with basic dye, is a good method of obtaining
tan and golden-brown shades. Sulphuric or formic acid added
towards the end of the process increases the depth of color.
Formic acid is preferable to sulphuric acid, as the latter is
liable to cause greasy spots by curdling the fat-liquor.
Coloring with natural dyestuffs. — A few practical instruc-
tions will now be given by means of which chrome-tanned
goatskins can be colored desirable shades without the use of
artificial dyes. Fast colors are obtained by using dyewood
extracts, and the cost of the materials is less than that of
coal-tar dyes.
Light tan shade. — Take the shaved skins and put them in
the drum with 12 gallons of water heated to 125° F. In a
clean pail, dissolve 2 lb. of fustic extract (lemon shade) in
hot water. Start the drum, and then add the solution of fustic
and run the skins in it for a half -hour. Then add 4 oz. of ti-
tanium-potassium oxalate dissolved in a little hot water, and
let the drum run 15 minutes longer. The skins will then be
found well colored, and should be washed and fat-liquored.
The color, if not quite satisfactory, can be modified by the
use of coal-tar dye.
Dark tan shade. — Run the skins in a solution of 4 lb. of
fustic extract (red shade), at a temperature of 125° F., for
30 minutes, using 12 gallons of water for 100 lb. of leather.
After that period, add without stopping the drum, 6 oz. of ti-
tanium-potassium oxalate dissolved in a little hot water. Allow
the drum to turn 15 minutes longer, then wash and fat-liquor.
402 PRACTICAL TANNING
Ox-blood shade. — A desirable shade of ox-blood is produced
in the following manner: For 100 lb. of leather, dissolve
2\ lb. of hypernic extract, 2 oz. of logwood extract, and \
oz. of leather red by boiling in a few gallons of water; then
add sufficient water to make 12 gallons of liquor, and use it
at 125° F. Drum the skins in this liquor for 30 minutes.
Then dissolve and add 4^ oz. of titanium-potassium oxalate
and allow the drum to rotate 15 minutes longer. The skins
are then in condition to be washed and fat-liquored.
Chocolate shade. — For this color use 2\ lb. of fustic ex-
tract (lemon shade), 10 oz. of hypernic extract, and 3 oz. of
logwood crystals in 12 gallons of water for 100 lb. of skins.
After the drum has been running 30 minutes, pour in 5 oz. of
titanium-potassium oxalate dissolved in hot water. Run the
drum 15 minutes longer, then wash and fat-liquor the skins.
Dyeing chrome-tanned goatskins black. — These skins
may be dyed black in a variety of ways. The customary
method is to dye them in a drum, using logwood extract and
direct leather blacks, thus obtaining a full black in one opera-
tion, and fat-liquor them after they have been blacked. The
skins should be thoroughly neutralized and shaved before they
are dyed.
Dyeing with hematin crystals or logwood and direct leather
black. — This is one of the most approved methods of blacking
chrome leather. The pack of skins (100 lb.), is weighed and
thrown into the drum with 12 gallons of water heated to 125°
F. Dissolve 1 lb. of hematin or logwood crystals in boiling
water and add a little ammonia. The liquor is poured into
the drum through the hollow axle and the leather is drummed
15 minutes. Dissolve 1^ lb. of direct chrome leather black
C in boiling water and add the solution to the drum, and run
the leather 15 minutes longer. The exhausted dye liquor is
then drained out and the hot fat-liquor is poured in. After
is has been fat-liquored, the leather is washed 5 minutes in
warm water, set out, oiled, and hung up to dry.
Dyeing zvith logwood, leather black, and titanium-potas-
DYEING LEATHER 403
siimi oxalate. — For 100 lb. of leather a solution of 3 oz. of
oxalate is used, and the leather drummed in it for 10 min-
utes. A solution of 1^ lb. of logwood crystals, | lb. of
chrome leather black, and 4 oz. of sal-soda in boiling water, is
next added and the leather is drummed for 15 minutes. Then
a solution of 3 oz. of oxalate is added to the drum, and the
treatment is continued 10 minutes longer. The leather is then
either washed, struck out and fat-liquored, or fat-liquored
immediately after it is blacked, and washed afterwards.
Dyeing with chrome leather black. — The skins, neutralized
and shaved, are fat-liquored and then thrown into the drum
for blacking. A solution of 1| or 2 lb. of chrome leather
black C in 10 gallons of water is poured into the drum, and
the leather is treated with it for 30 minutes. The tempera-
ture at the beginning of the process should be 125° F. To
fix the dyestuff, 1 oz. of acetic acid may be added towards the
end, but in most cases this is unnecessary. A black grain
and a blue-black flesh are obtained when this method is em-
ployed. Logwood extract or crystals may be used with the
direct black to increase the fullness of the leather. The log-
wood solution may be added along with the dyestuff or im-
mediately afterwards. No striker or other medium is
required, the logwood becoming fixed on the leather during
the dyeing.
'Another method of direct blacking. — The following proc-
ess can be used if the flesh side is to be dark blue or blackish-
blue. The leather is first dyed for 20 minutes at 125° F. in
the drum with 6 to 12 oz. of chrome leather black C in 10
gallons of water; then f oz. of acetic acid is added for fix-
ing the color, and 10 minutes later 6 to 9 oz. of leather black
T B or T G. The leather is drummed 10 minutes longer and
then rinsed. Fat-liquoring may be done either before or
after blacking.
Blacking with logwood and iron liquor. — For 100 lb. of
leather, boil 3 lb. of logwood extract and 4 oz. of fustic ex-
tract, in 12 gallons of water, and add 1 oz. of ammonia. Drum
404 PRACTICAL TANNING
the skins 30 minutes, then drain off three-fourths of the dye
liquor and pour in, after the drum is turning again, 4 or 5
oz. of iron liquor in 10 gallons of water. After a further
drumming for 10 minutes, the liquor is drained off and the
skins washed thoroughly in running water.
Dyeing with logwood, potassium permanganate, and iron
liquor. — This process is used in the following manner : In
the drum are placed 450 lb. of skins as they come from the
shaving machine, and 30 gallons of water heated to 120° F.,
after which the drum is closed and started. Dissolve 2\
lb. of permanganate in 55 gallons of water at 120 F., and add
2\ lb. of muriatic acid of 21° Be., this solution being run into
the drum through the hollow gudgeon. After 10 minutes,
stop the drum, open it, and allow the liquor, which is now
spent, to run out. Close the drum again, and after re-start-
ing, pour 2 gallons of iron liquor mixed with 45 gallons of
warm water in through the hollow axle. After 10 minutes,
stop the drum, and allow the liquor to drain out. Next dis-
solve 3 lb. of extract of logwood and 3 lb. of sal-soda in 45
gallons of warm water, and after the drum has been started
again, add this liquor through the gudgeon. Allow the drum
to run 10 minutes, then stop it, and remove the skins. The
next step is washing the leather, which is now black; this is
done in a drum or twister supplied with running water. After
being washed 15 minutes, the leather is ready to be fat-liq-
uored and dried for finishing.
The iron-liquor referred to can be purchased as black iron,
or may be prepared by dissolving scrap iron in dilute com-
mercial acetic acid. The liquor ready for use should stand
at 10° Be. ; but any suitable ferrous salt of iron may be
substituted.
The muriatic acid should always be added to the perman-
ganate solution when all of the water required is present,
and never to a hot concentrated solution of permanganate.
It is claimed that a deep, rich, and more permanent black, be-
sides other advantages, is economically obtained by using this
DYEING LEATHER 405
process, which was patented by William M. Norris, Princeton,
New Jersey.
Dyeing chrome kangaroo black. — The same methods as
given under goatskins may be applied to this class of leather.
Yellow flesh and black grain. — Where leather with a yel-
low back and black grain is required, the skins are treated
with acid fat-liquor after they are tanned, and are then dried.
Preparatory to flesh coloring, the leather is wetted in a tub
of warm water and placed in a pile to soften. For 100 small
and medium skins, | pail of sumac is scalded with hot water
for 2 hours. The sumac, with 4 pails of water, made slightly
acid with lactic acid, is put into a drum and milled 25 min-
utes, the temperature of the liquor being 110° F. After the
skins have been drummed in the sumac liquor, the yellow
dye is added, and the leather run in it for 10 minutes. For
the dye, dissolve 1 lb. of yellow S or other basic yellow in ^
barrel of water, and use 3 or 4 pails of the solution for 100
lb. (dry weight) of leather.
After the leather has been colored yellow, dye the grain
on a table or a machine with logwood and striker, or with a
solution of direct leather black. Rinse the leather, set out the
grain, oil it lightly, then hang up the skins to dry.
Chrome-tanned ooze calfskins. — The skins that are
worked into ooze leather must be free from butcher cuts
and have full flanks, but good grain is not essential. In
almost every pack of skins there are some that have defective
grain which are unsuitable for grain finish, and can be fin-
ished only upon the flesh side. Such skins can be sorted out
after the pack has been tanned, or they can be selected after
they have been de-haired, and tanned separately from the
others.
One method of finishing the skins into ooze leather is as
follows : The skins are treated with a suitable fat-liquor, and
some substance is added to the same, which, during the sub-
sequent drying, isolates the fibers of the leather in such a
manner as to allow them to be soaked and softened without
difficulty. For this purpose, dextrine, grape sugar, syrup,
406 PRACTICAL TANNING
etc., are used. The stuffed leather is dried and then buffed.
Buffing is done either by running the flesh-side on an emery
wheel or by slightly snuffing the grain. The snuffed leather
is then drummed with warm water until it has regained its
original softness, and is then colored with acid dyestuffs.
During or after dyeing a somewhat larger quantity of gambier
or sumac is added than is otherwise customary with chrome
leather, in order to impart the necessary firmness to the
leather. The nap of the skins is then raised by working the
leather in a dry drum after it has absorbed some moisture
by a treatment with wet sawdust. The coloring is done in
the same manner as described for grain leather.
Another way to produce ooze leather is as follows : After
shaving, 100 lb. of skins are run with 1 quart of pumice in a
clean drum for 30 minutes ; then the flesh side is cut on a wet
wheel so that the fibers are uniformly fine over the entire
skin. After this has been done, wash the leather thoroughly
to remove all of the pumice. The skins are then in condi-
tion to be colored and fat-liquored, these processes being the
same as for grain-finished leather.
If black leather is desired, drum the skins in a solution of
Bismarck yellow-brown or some other direct yellow-brown,
then drum with a logwood liquor which is slightly alkaline,
and strike with acetate of iron or copperas (iron sulphate),
and fat-liquor them, following this with direct leather black,
fat-liquoring again, and then hanging the skins up to dry.
There are special ooze blacks on the market which produce
good results. They dye direct without the use of a mordant
or logwood.
For light skins, a fat-liquor of egg-yolk and sperm oil is
suitable; and for both light and heavy skins, one made of
olive-oil soap, neat's foot oil, and moellon degras is recom-
mended. It is made as follows : 1 lb. of the soap is dissolved
in 6 gallons of boiling water. To the solution is added 4
lb. of the oil and 2 lb. of degras, and the whole is boiled for
30 minutes. Next add water to make 20 gallons of liquor.
DYEING LEATHER 407
In a separate vessel dissolve 6 oz. of potassium carbonate, add
this to the fat-liquor, and stir thoroughly. This quantity of
fat-liquor is sufficient for 200 lb. of leather. Use it at 140°
F. Drum the leather 40 minutes, and then let it drain until
the next day. Strike out each skin ; oil the grain lightly, and
hang up to dry.
When dry, dampen and stake the skins, and before they
are dry, put them into a dry wheel and run them 3 hours;
then tack them out. When dry, stake them lightly and run the
flesh side on a plush wheel, which is the finishing touch.
Softness, freedom from spots, and smooth, uniform colors
and fibers are the essential qualities of this leather.
Velvet or suede leather is finished from chrome calfskins in
the following manner: The skins are taken in a dry or crust
condition and are dampened with clean, wet sawdust in the
customary manner. They are next fluffed on the flesh side,'
care being taken to avoid scratches with new or coarse car-
borundum or emery. The grain then receives a thorough
grinding on the buffing-wheel, after the leather is perched or
staked lightly. After buffing, the skins are given a coat of a
solution of dextrine, potato starch, or Irish moss (kelp ex-
tract), and are then allowed to remain until the moisture
has almost evaporated from them. Sufficient moisture should
be left in the goods to keep them cool for the wheeling or
fluffing on the grain, which follows immediately.
The next process is coloring ; and for this a good drumming
in warm water is necessary to soften the leather. Add 8 oz.
of borax to 12 gallons of water, and drum the skins 20 min-
utes ; then rinse them for a few minutes.
A. treatment with sumac is necessary to impart firmness
to the leather, 3 or 4 lb. of sumac extract in water at 125°
F. being used for 100 lb. of leather, which is drummed 30
minutes. A solution of gambier is also suitable for the pur-
pose. Drain the liquor out of the drum and proceed to color
the leather with acid dyes. Prepare the dye-bath by dis-
solving the amount of color necessary in 15 gallons of hot
408 PRACTICAL TANNING
water, pour this solution into the drum while it is rotating,
and run the skins 10 minutes. Then add 4 or 5 oz. of fustic
extract (a tannin from a West Indian wood) in solution to
the bath and let the drum run 20 minutes longer. Then acid-
ulate the dye-bath by adding 3 or 4 oz. of sulphuric acid, or
three times as much sodium bisulphate in 1 gallon of water,
and let the drum run 15 minutes longer. The dyed leather is
next rinsed well in lukewarm water, and then given a drum-
ming with a solution of egg-yolk for 10 minutes; it is then
rinsed, struck out, and dried.
Complete penetration of the dye is secured by adding 2
oz. of strong ammonia to the dye-bath, and prolonging the
drumming to 40 minutes or even longer ; the ammonia is then
neutralized by using slightly more acid or soda than the quan-
tity mentioned.
The finishing operations consist of dampening the dry skins
and staking them, then buffing on the machine and fluffing
lightly on the flesh side. In place of buffing, they can be
worked over with a warm knife, and finished off by working
over the grain with very fine emery made up into a suitable
pad. This last method gives a beautiful, even, velvety feel,
and fine appearance to the leather. The last touch is brush-
ing with a stiff brush.
Chrome bag and belt leathers. — Black chrome leather
with a printed or boarded grain is used to some extent in
the manufacture of hand bags and traveling bags, and belts
for personal use. The leather, when it is suitably fat-liquored
and finished, is well suited for these purposes, as it is soft,
durable, and waterproof. It must, however, be firm, clean,
and free from grease. The sides are tanned in the same man-
ner as for shoe leather, preferably in the one-bath process,
but the leather is given less fat-liquor. It is desirable that
the color penetrate through the flesh so that the edges will
be black and not blue. Direct blacks are preferable to log-
wood for dyeing. The leather is fat-liquored and then dyed,
or it may be run first in a solution of the dye to stain the
DYEING LEATHER 409
flesh, then fat-liquored and dyed on the grain by hand. The
use of a direct chrome black with logwood produces a rich
color, and gives a fuller feel to the leather than the direct
black alone. It is also practicable to fat-liquor the leather
while it is being dyed, drumming it first in the dye liquor and
then with hot fat-liquor. The fat-liquor may be a solution of
sulphonated oil or a mixture of such oil and neat's foot oil.
Getting the leather too soft and greasy must be carefully
watched as when it is greasy, the grease strikes through the
linings and is easily perceptible, so the leather must be fat-
liquored just enough to make it supple without being soft
and stretchy.
The grain is boarded two ways, or printed with a box grain
arid then boarded. Belts made of this material are almost
indestructible, and bags give great satisfaction as regards ap-
pearance and wear. The more novel the leather is made to
appear the more it is liked, there being an unceasing demand
for new things in these lines of leather goods.
Dyeing chrome side leather.— This is done quickest and
most uniformly in a drum, the general practice. For
the production of the shades of tan and brown usually in
demand, acid and basic dye-stuffs are used. The acid colors
may be applied direct to the chrome leather without a mor-
dant, although most tanners prefer to bottom with fustic and
titanium-potassium oxalate. The basic colors are always ap-
plied upon a tannin mordant or base.
Direct dyeing with acid colors. — The same method as given
under goatskins may be applied to this grade of leather.
Tannin mordant for basic dyestuffs. — Coloring with basic
dyes is effected by first applying a mordant of gambier, fustic
or sumac, fixing with titanium-potassium oxalate or tartar
emetic, and then dyeing to the shade desired with the proper
dye.
Red-brozvn shade. — A popular shade of red-brown is ob-
tained by applying 4 oz. of alizarine brown G, 4 oz. of alizar-
ine yellow R extra, and 1 oz. of alizarine new yellow extra
410 PRACTICAL TANNING
for 100 lb. of leather. Dissolve the alizarine brown G by
boiling in 8 gallons of water, then acid 4 gallons of cold water,
and use the solution at 160° F. Drum the leather in this
solution for 15 minutes.
Meanwhile, dissolve the other dyes in 3 gallons of boiling
water and pour into the drum. Let the drum run 15 minutes;
then drain off the liquor and fat-liquor the leather. It is
also beneficial to the color to add 1 lb. of extract of fustic dis-
solved in hot water to the drum after the second 15 minutes,
and let the drum run another similar period. Then dissolve
and add 2 oz. of sodium dichromate, running the drum 10
minutes longer. Wash and fat-liquor the leather.
Dyeing chrome side leather black. — One of the most
approved methods of dyeing chrome side leather black con-
sists of the application of logwood and direct chrome leather
black. The wet shaved leather is weighed and thrown into
a drum with 12 gallons of water at 125° F. for 100 lb. of
stock. Dissolve 1 lb. of hematin in water at 125° F. ; add 1
oz. of ammonia to the solution, pour the latter into the ro-
tating drum and run the leather for 15 minutes. Dissolve 1^
lb. of chrome leather black in water at 140° F., and pour
the solution into the drum. The leather is treated 15 min-
utes, and may then be drained and fat-liquored, or the fat-
liquor can be added to the dye-bath at the end of the dyeing
process, the drum being run a half-hour longer. The leather
is then washed in warm water, set out, oiled with suitable
oil, and hung up to dry. Other methods already described
may be used equally well on side leather.
Yellow leather. — If yellow leather is required, the stock may
be colored with gambier in the following manner : Boil 125
lb. of gambier in 20 gallons of water, add 1 pint of mu-
riate of tin and 3 oz. of tin crystals, stir thoroughly, and fill
the barrel with water. For 50 sides use 4 pails of this gam-
bier liquor, and add 2 gallons of water, also ^ lb. of picric
acid and -J lb. of fustic dissolved in 3 gallons of hot water.
Mix the color solution in a tub and use it at 90° F. Drum
the leather in it for an hour.
DYEING LEATHER 411
Coloring vegetable-tanned upper leather. — Hides that
have been tanned by a gambier, quebracho, or combination
process can be finished in various ways. For black upper
leather — glazed or dull — the following process may be carried
out: The grains of sides split out of lime, bated, pickled, and
tanned, or the grains of sides split after tanning and then
re-tanned, are washed and pressed. They are then fat-liquored
and dried. The dry leather is then wet-down and colored blue
or blue-black as a foundation for the subsequent black. The
grain is next dyed black with logwood and striker, or with a
direct leather black applied by brushing on. The skin is then
set-out smooth and hung up to dry; next dampened, staked,
and trimmed.
Where colored leather is wanted, the leather is fat-liquored
and dried; then treated with sumac and colored; or it may
be fat-liquored after coloring, and then dried and finished.
For both black and colored leather, the author would
recommend the use of sulphonated oil fat-liquor.
Where it is desired to dye only the grain black, leaving the
flesh undyed, the use of direct blacks such as leather black
T B and T G is preferred. For bright finish the bluish leather
black T B is especially well suited ; for leather which is to be
finished dull, the deeper and Somewhat more greenish leather
black T G is preferable. Leather which is given a moderate
polish by being rolled or brushed may be dyed equally well
with either brand. No preparatory or after-treatment is
required.
Blacking the grain side only is done by brushing the solu-
tion of dye into the grain, two coats being generally sufficient
for the dry leather. The color solution consists of 1 lb. of
the leather black and 8 oz. of acetic acid in 10 gallons of
water, the temperature being maintained at 120 to 140° F.,
during the operation. The dye is mixed with the acid and
enough boiling water is poured over the pulp to make a solu-
tion of the proper strength.
Dyeing sealskins. — The well set-out skins are placed in
piles, one dozen in each, with the necks and butts running
412 PRACTICAL TANNING
one way, and are then dyed with the following materials :
Blacking. — A pail of good strong logwood liquor, to which
a half cup of ammonia has been added, is heated to boiling
point and applied to the skins with a brush. This is imme-
diately followed by a solution of iron liquor and glue, pre-
pared by pouring 1 gallon of iron liquor over ^ lb. of best
glue; this is allowed to stand a few hours and is heated be-
fore use. This "floss," as it is commonly called, is put on
the skins evenly and thinly, and rubbed in thoroughly. After
blacking, the skins are laid face to face, covered up, and al-
lowed to remain over night for the black to set.
They are then grained from angle-to-angle with a board
covered with a piece of thin tin, perforated similar to a nut-
meg grater. After these two "cuts" they receive another cut
on the belly with a cork-board, followed by a cut straight up
the skin; they are dried in a hot room, "emeried," and
seasoned.
The goods may also be utilized for colors by soaking in
warm water, running them through a weak acid-bath and
dyeing in a paddle at 115° F. If acid dye is used, the goods
can be dyed out of tan; if dyeing is effected with basic dye,
the tannin should be fixed with tartar emetic. After dyeing
to shade, wash in cold water and tack out, taking care that
the goods are not dried too rapidly, a moderate heat being
preferable. When dry, they are taken off the frames or boards,
and the side that is to be faced is filled with a potato-flour
paste, made by adding sufficient farina to water to form a
stiff paste. When the paste is cold, add a little color and
apply a good coat, after which tack on the frames.
Dyeing pigskins. — Dry the leather and store it away for
a while to mellow. Then, if it is to be colored, dampen and
clean the grain with borax followed by sulphuric acid. To
do this, wash the leather for 15 minutes in a warm solution
of borax. Drain off the solution and run the skins in a solu-
tion of sulphuric acid. Drum them in this solution, then wash
and run them in sumac again. After having been rinsed they
are in condition to be colored. When colored, give them a
DYEING LEATHER 413
light coat of cod oil and dry. Staking, boarding, and glazing
complete the process.
If black leather with undyed flesh is required, the skins
should be dyed on the grain side only by the staining method.
A solution of 1 lb. of leather black in 10 gallons of water
is recommended for this purpose. It is brushed on the grain,
two applications being usually sufficient.
Pigskins are much used in plain russet finish. For this
they need to be bleached according to the instructions given
above. For inner-soling, the skins are oiled with a mixture
of fish and mineral oils, and finished by rolling.
Process for producing marbled suede leather. — The fol-
lowing description covers a process of finishing the flesh side
of leather so that it will have a mottled appearance and a
velvety feel. Leather made in accordance with the directions
given is soft and pliable and has a velvety surface, which is
ornamental and adapted for use in making ladies' bags, for
table covers, and for a great variety of articles for which a
soft ornamented leather is desirable.
The skins are tanned as usual, and the flesh side is then
subjected to the customary preliminary steps taken in the
ordinary manufacture of suede or velvet leather, that is, shav-
ing and then wet-wheeling, or subjecting it to the action of an
emery wheel while it is wet. While still wet, the skin is laid
on a table with the flesh side up, and is puckered or gathered
into folds, this being preferably done by hand, and some dye
is poured onto the flesh side.
The exposed portions of the skin will, of course, be ex-
posed to the full action of the dye, while the portions within
the folds or puckers will be more or less affected, depending
upon the character of the fold. If the fold is a deep one,
and the sides happen to be pressed closely together, the dye
will not penetrate to any extent into the fold, and the surface
of the leather within the fold will remain practically in its
natural condition. Other portions of the skin, where the two
sides of the fold are not pressed closely together, will be
affected somewhat by the dye and will be partly covered, al-
414 PRACTICAL TANNING
though the color will not be so deep as at the parts entirely
exposed. The skin is then buffed on fine emery, dried, and
the flesh washed, which results in giving it the velvety sur-
face desired.
Pigment finish.* — Owing to the shortage of dyestuffs dur-
ing the early part of the world war, tanners were forced to
try other means for coloring leather, and somebody sug-
gested the use of mineral pigments. The results were so
satisfactory that the application of pigments at once became
general. Even now that coal-tar colors are again available,
many tanners prefer to continue using pigments.
In the coloring and finishing of leather by means of pig-
ments there are two general methods of application. The
first is employed for coloring splits and ooze leather, and
consists of adding the pigment in the mill ; while in the other
method the pigment is applied by hand or machine after the
leather has been mill-colored with artificial or natural dyestuffs.
Mill coloring. — This method is mostly applied to splits. The
neutralized, washed, and fat-liquored leather is pressed or
whizzed to remove excess of water, and is then placed in
the drying wheel and run in the presence of hot air until dry,
and then sorted for coloring. The splits are placed in the
color wheel, and enough hot water is added to wet them
thoroughly and uniformly. The dry pigment may be thrown
into the drum and sufficient water to float the stock added,
or the pigment may be mixed with water and added through
the trunnion ; but in either case the mill is run until all of the
pigment has been absorbed. When this has taken place, the
splits are removed from the drum and again dried in the
drying wheel. After drying they are staked, trimmed, and
sorted. The stock may be colored and fat-liquored at the
same time without the intermediate drying, but better results
are obtained by the method given. This method also permits
a better selection for colors.
Any of the mineral pigments may be employed in the above
* This description was largely supplied by C. B. Kinney, a former student of the
author, to whom he desires to give full credit.
DYEING LEATHER 415
process provided they are properly ground. Such colors as
yellow ocher, chrome-yellow, chrome-green, iron oxides, zinc
oxide, lithopone, burnt umber, and the like.
The finish. — Pigment finish has to meet a number of re-
quirements — it must go on evenly without giving a painted ap-
pearance; it must withstand rubbing, boarding, and wetting;
it must penetrate and have a fine appearance as regards bright-
ness, luster, and evenness ; and it must not injure the leather
or natural break.
The first problem in making a finish is to get the pigment
into suspension. There are a number of mediums in which the
pigment may be ground, but the most commonly used is some
form of soluble oil. The pigment is mixed to a thick paste
with the oil and then ground in an iron or burrstone mill.
Under ordinary circumstances 24 fluid ounces of oil will carry
15 ounces of pigment to form a satisfactory paste. After
the pigment has been ground it must then be added to the fin-
ish. The nature of the finish varies with the results to be
secured, and finishes are as numerous as the varieties of
leather. They are made in the same manner as ordinary fin-
ishes, and consist of solutions containing one or more of the
following: shellac, casein, glue, blood albumen, egg albumen,
gum, beeswax, Japan wax, soap, Irish moss, flaxseed, and all
of the other finishing materials.
When the finish is ready, the pigment is stirred in slowly.
A solution of some coal-tar color is next introduced, either
to shade or give fullness and brilliancy. A clear, brilliant
and full color with pigment alone is impossible, as straight
pigment shades are flat and dead. It is best not to use too
much water, but use solutions of dye and then season the
body by adding the pigment. When incorporating the pigment
it is best to add a little of the finish to the pigment paste.
This throws the pigment into a fine emulsion, which mixes
readily with the main body of the finish. After mixing thor-
oughly and diluting to the proper consistence, the whole solu-
tion should be strained through a fine cheese-cloth, and it is
then ready for application. A stirring machine should be used
416 PRACTICAL TANNING
at the table, so that the solution may be constantly agitated
and thus prevent deposition of pigment.
Hand seasoning. — The stock is passed through a seasoning
machine, dried out, and again run through the machine. For
these two coats a solution of coal-tar color, as near as possi-
ble to the shade desired should be used. The leather is then
thoroughly dried and glazed. It is then given two coats of the
pigment finish, using a flat swab covered with fine plush.
After each coat the leather is dried, and glazed after the second
coat. In these two bottom coats the amount of pigment should
be greater than in the subsequent coats. After glazing, the
leather is smooth-plated and given three top coats, each top
coat containing less pigment than the preceding one until the
last coat, which should contain no pigment. The top coat
should contain some albumen to give the required brilliancy.
After the last top coat the leather is thoroughly dried, lightly
staked, and smooth-plated.
Machine seasoning. — The leather is dyed on the machine,
as given under hand-seasoning, but the stock is not glazed.
Three coats of pigment finish are now applied on the machine
and when the last coat is dry the sides are glazed. Three more
coats are then applied, and when dry, the leather is again
glazed. The same procedure as given under hand seasoning
should be carried out in machine-seasoning.
Full grain finish. — If the finish is to be applied to full grain
leather it must be of such consistence that it will be easily
taken up by the stock and will not crack. The application is
much simpler in this case than in the preceding ones, in that
the dye coats are unnecessary. The only results required are
an evenness of finish and a clear color. From 2 to 4 coats
only are required, the leather being glazed after each applica-
tion. For full grain leather hand seasoning is the most
satisfactory.
Blacking and stuffing chrome harness leather. — The
leather, re-tanned, and shaved, is in condition to be blacked
and stuffed. There are two methods : either the leather may
DYEING LEATHER 417
be blacked and then stuffed, or it may be first stuffed, then
dried, buffed, and bleached.
When the leather is blacked first and then stuffed, it is
taken, a side at a time, set-out smooth on a table and blacked
with logwood liquor and striker ; then it is washed, run through
a wringer, and put into condition for stuffing.
The logwood liquor is made of 6 lb. of logwood crystals
and 2 lb. of borax in 50 gallons of water. The striker is
made of 7 lb. of iron sulphate and 5 lb. of copper sulphate in
50 gallons of water, although any good striker may be
used. The leather, after it has been wrung, is ready to be
stuffed, 100 lb. of it requiring 10 lb. of mineral wax, 10 lb.
of best stearine and 5 lb. of good hard grease. These mate-
rials should be boiled and thoroughly mixed, and applied
hot to the leather in a warm drum. The leather is drummed
40 minutes, then placed in piles, covered up and left until
the next day. It is then struck out on the flesh side, hung up
until partly dry, and next stoned out on the grain. The grain
then gets a light coat of cod-liver oil, and is again gone over
with the stone and slicker. The leather is then hung up to
dry.
The stuffing described above may be used, or a mixture of
60 per cent stearine, 20 per cent tallow, and 20 per cent min-
eral wax, heated to 190° F., 24 lb. being used for 100 lb.
of leather. The leather is weighed and run a few minutes
in the hot drum. The stuffing is then thrown in and the drum
run 45 minutes. After lying in a covered pile over night,
the leather is struck out on flesh and grain and hung up to
dry. When it is partly dry, the grain is re-set, and the leather
is then thoroughly dried. When dry, the scratches and im-
perfections can be buffed from the grain, and it is then ready
to be blacked with logwood and striker. A sig (a seasoning
of adhesive compounds) is necessary to prepare the leather
for the logwood. When blacked, the leather is washed off,
set-out, and hung up to dry.
Finishing. — This is done with mutton tallow and cod oil,
3 lb. of the former and 2 lb. of the latter being melted
418 PRACTICAL TANNING
together, and the grain given a good coat with it, which is
thoroughly glassed in. The leather is then left in a pile for
24 hours, when it is re-glassed, this being the finishing touch.
In case a dry feel is desired, the sides are seasoned with a
solution of blood albumen, isinglass, and nigrosine in log-
wood liquor, then dried and oiled off with hot paraffin oil, or
with a mixture of paraffin and neat's foot oils. Sometimes
a coat of starch decoction is applied to the flesh side.
By using 7 lb. of quebracho liquor, 70° bk., for each side,
weight and solidarity are given the leather. Chrome-tanned
harness leather made by the methods that have been described
has greater tensile strength and is more waterproof than
ordinary bark-tanned leather.
CHAPTER XIV
FAT-LIQUORING
In the production of leather of any kind, the use of oils,
fats, waxes, or soaps, or a combination of these is absolutely
necessary during some part of the manufacturing process.
These materials are used either as part of the tanning process
or are introduced to give strength and pliability to the product.
The oils selected are chosen with a view of producing special
results or of imparting certain characteristics to the leather.
A discussion of oils is not within the scope of this book,
but for those who desire more information on the general
topic, reference may be made to the "Manual of Industrial
Chemistry," written by the author of this treatise on tanning.
It may not be out of place, however, to mention a few of the
salient points which may be of value to the reader.
Oils, fats, and waxes constitute a large class of substances
which are of animal, vegetable, or mineral origin. True oils
and fats are derived from animals, both terrestrial and ma-
rine, and from vegetable sources, and consist chemically of
a combination of fatty acids with glycerine. The nature and
proportions of the fatty acids present determine whether a
substance is an oil or a fat, but there is no distinct line of
demarcation. What is a solid fat in cool climates may be
liquid oil in a warm climate, so that some authorities prefer
to make no distinction between fats and oils, simply calling
one class liquid and the other solid. Solid fats usually con-
tain a larger proportion of stearine. Most natural oils, how-
ever, are mixtures of several fatty acids with glycerine. The
chemical constituents of a fat may perhaps be better under-
stood from the following formula:
(CnH^COCOsCsHs (stearine)
(C 17 H 33 COO) 3 C3H5 (olein)
(C 16 H3iCOO)3C 3 H5 (palmitin)
In other words, the above combinations constitute the prin-
419
420 PRACTICAL TANNING
cipal ingredients of most oils, and the proportions of each
determine whether it is liquid, pasty, or solid. In addition
to these typical compounds, most fats or oils carry some other
bodies which give them special characteristics. Depending
upon whether the oils contain larger or smaller quantities of
unsaturated fatty acids we have drying, semi-drying, and non-
drying oils.
Any oil, when treated with caustic alkali, undergoes a
change which is called saponification, meaning the formation
of soap. For example, if we treat tallow, which contains a
large amount of stearine, with caustic soda, we have the fol-
lowing reaction:
(Ci 7 H 35 COO) 3 C 3 H 5 + 3NaOH = 3Ci 7 H 3B COONa + C 3 H 5 (OH) 3
stearine caustic soda sodium stearate glycerine
or soap
This sodium stearate is what we are familiar with as soap.
The character of the soap is influenced by the quantity of
sodium stearate which it contains; the more stearate present
the harder the soap.
Waxes differ from oils and fats in that they are a combina-
tion of fatty acids with higher alcohols. They do not lend
themselves so readily to saponification as oils, but when they
do so saponify the resulting product is a soap and a higher
alcohol. Certain oils have the property of combining with
sulphuric acid, forming what is known as sulphonated oils, or
soluble oils, a more complete description of which will be
given later in the text.
Mineral oils are entirely distinct from true oils in their
chemical composition, being a mixture of hydro-carbons which
are incapable of saponification. These oils are derived mostly
from petroleum, and are usually spoken of as petroleum or
paraffin oils. These mineral oils range in fluidity from light
mobile liquids to heavy wax-like substances.
Oils of the above-mentioned classes are used in the produc-
tion of leathers either for fat-liquoring, oiling, or stuffing.
FAT-LIQUORING 421
Their uses for various purposes will be seen in the following
pages.
Fat-liquoring process. — This is a process of much impor-
tance in the finishing of leather. No matter how well tanned
the hides or skins may be, if they are not properly fat-
liquored they dry out stiff and lack that full, well-nourished
feel that is so essential; the fat-liquor imparts to the leather
the necessary fullness and softness. The process consists in
treating the leather in a drum with a hot emulsion of soap,
oil, and other ingredients, which is entirely absorbed by the
leather. If given too much grease they work out too soft
and cannot be finished satisfactorily. The fat-liquor should
be a perfect emulsion; if it is not, the grain is likely to have
a greasy feel and the colors a patchy appearance. Neat's foot,
olive, castor, and sulphonated oils are generally considered the
most suitable oils for fat-liquoring light leather ; egg-yolk and
soap being sometimes combined with them. There are also
several prepared fat-liquors and oils obtainable which are of
much value. Commercial fat-liquors are carefully prepared,
blended and aged, and containing no excess of alkali they pro-
duce excellent results on both chrome and vegetable-tanned
leather. Sulphonated oils require merely to be dissolved in
hot water to be ready for use. The best way to use such
oils, however, is to combine them with oil or grease, such as
neat's foot or moellon degras. The sulphonated oil so used
acts as the carrier and emulsifier of the other oils and greases.
Before being fat-liquored, the leather is sometimes pressed
or struck out to rid it of the surplus water, which would re-
tard the penetration of the fat-liquor; but as a rule the fat-
liquor is applied to the wet stock immediately after coloring.
A suitable drum is heated with live steam to a temperature
of about 140° F. for chrome-tanned leather and 120° F. for
vegetable-tanned stock. Whatever water there may be in it
is drained out, and the skins are thrown in and drummed for
5 minutes to warm them. The hot fat-liquor is then poured
into the drum through the hollow axle and the skins are
drummed in it for 30 minutes, being then dipped into hot
422 PRACTICAL TANNING
water, placed smoothly over horses and covered up for several
hours so that the grease may combine with the fibers. '
Fat-liquors for chrome-tanned sheepskins. — After these
skins have been neutralized, washed, and shaved, they are either
dyed and then fat-liquored, or fat-liquored and dyed after-
wards. Some tanners combine the two processes, first dye-
ing the leather in a drum and then running the spent dye liquor
out and applying the fat-liquor. It is also practicable to add
the fat-liquor to the dye liquor in the drum after the skins
have assumed the desired color. The fat-liquor feeds and
nourishes the leather. Sheepskins are naturally soft and do
not require much fat-liquor; nevertheless, some grease and
oil are required to impart to the leather the desired fullness
and soft feel. When the fat-liquoring is a separate process, a
suitable drum is heated with live steam, the leather is thrown
in and drummed 10 minutes to warm it and make it more
receptive to the fat-liquor. The fat-liquor is now poured into
the drum through the funnel attached to the hollow axle and
the leather is drummed with it for 30 minutes or longer, or
until it has absorbed the oil and grease and left the water
behind. After the process is finished, the leather is taken out
of the drum, and if it was not previously colored, it should be
rinsed in hot water, drained, and dyed; if it was colored be-
fore it was fat-liquored, the custom is to strike it out, oil
the grain, and hang it up to dry. Any one of the following
formulas may be used with the assurance that the leather will
be fat-liquored in a satisfactory manner:
1. For 100 lb. of leather: 1 lb. of castile soap, 1 pint of
neat's foot oil, and ^ lb. of egg-yolk. Boil the soap in 2 gal-
lons of hot water; add the oil, and mix thoroughly. Then
add cold water to make 12 gallons of liquor. When the tem-
perature has been reduced to 120° F. by the cold water, add
the egg-yolk and mix thoroughly.
2. For each dozen skins to be fat-liquored, use 1 pint of
egg-yolk, -| pint of olive oil, 4 oz. of castile soap, and 6 gal-
lons of water. Chip the soap into the water and boil until it
is dissolved ; then stir in the oil. Boil the mixture of soap and
FAT-LIQUORING 423
oil; cool down to 100° F., and add the egg-yolk. For glove
leather, make a paste of 1 pint of flour and cold water and
stir it into the soap, oil, and egg solution. Mix thoroughly,
run it into the drum at 110° F., and mill the skins with it
for 30 minutes.
3. A fat-liquor considerably richer than the foregoing is
made of 2\ lb. of neat's foot oil, | oz. of potassium carbonate,
| lb. of potash soap, and f lb. of sulphonated oil. Mix and
use the same as No. 2. This fat-liquor gives a well-nourished,
springy feel to the leather, and there is no danger of spew.
4. Chrome-tanned skins can be fat-liquored with egg-yolk
and neat's foot oil. Such a fat-liquor is especially suitable for
colored leather. For each dozen skins use 1 pint of egg-
yolk and \ pint of neat's foot or olive oil. Beat the two
thoroughly together and add warm water. Use at a tempera-
ture of 125° F., and drum the skins with it for 30 minutes.
5. For chrome-tanned glove leather: 1 lb. of olive oil soap,
2 oz. of borax, \ lb. of neat's foot oil, and 2 lb. of egg-yolk
for 100 lb. of leather. Apply before dyeing at a temperature
of 125° F.
6. For 200 lb. of skins, use soap, 8 oz. ; olive oil, 2 lb.;
treated cod-liver oil, 2 lb. ; birch oil, 2 oz. ; and potassium car-
bonate, 3 oz. Boil the soap, olive and cod oil in a few gallons
of water, then add the birch oil. Stir the emulsion thor-
oughly, then add the potassium carbonate dissolved in a little
hot water. Add enough water to make 15 gallons of liquor,
and use at a temperature of 160° F.
7. A good fat-liquor for 200 lb. of heavy dull-finished
leather is made of soap, 1 lb. ; neat's foot oil, 3 lb. ; moellon
degras, 3 lb. ; and salts of tartar, 4 oz. Boil the soap and
oil in a few gallons of water, then put in the moellon degras
and stir thoroughly. Dissolve the salts of tartar in a little
water; add the mixture and stir again. Run in enough water
to make 24 gallons of liquor and apply to the skins at 150° F.
8. The sulphonated oils now on the market are of value
in fat-liquoring. The oil is dissolved in hot water and the
leather is drummed with the solution either before or after
424 PRACTICAL TANNING
it has been colored. The oil can also be added to the dye
liquor and applied to the leather in that form. It is generally
best to pour it into the drum after the color has been taken
up by the skins. •
Neat's foot oil should not contain any solid fatty substance
which is likely to separate at a low temperature and thus
cause exudation, nor should there be any solid fatty acids in
the soap. A small quantity of borax or sal-soda is often
added to obtain a finer emulsion ; and the use of castor oil,
Turkey red oil, or castor-oil soap is advisable when very pli-
able leather is required. Fat-liquor should penetrate the
leather easily and should not contain any ingredient likely to
cause exudation or spewing. A greasy or sticky feel of the
leather after fat-liquoring indicates insufficient neutralization
or the presence of lime. Where leather is to be colored after
it is fat-liquored it should, immediately after completion of
that process, be dipped in clean, hot water, to remove surface
oil. This rinsing in hot water clears the grain, so that the
mordant and dye "take hold" more readily.
Fat-liquoring chrome-tanned calfskins. — After calfskins
have been tanned into leather by a process of chrome tan-
ning it is necessary to treat them with oil or grease in some
form so that they may be finished into soft, well-nourished
leather. The quality of the finished product depends largely
upon how this process is applied, and what materials are used.
Nothing that seriously affects the color or makes the leather
greasy or spotted can be used. The skins can be fat-liquored
either before they are colored or afterwards, the usual cus-
tom being to do the work before coloring in order that the
fat-liquor shall not injure the color. Black leather, however,
is usually fat-liquored after it has been blacked. Some tanners,
in order to save labor, do not wash their leather after dyeing
it; they simply drain off the spent dye liquor and run in the
fat-liquor, and in some cases the dye liquor is not even
drained off, the fat-liquor being added after the leather is
colored. The oil and grease are employed in the form of an
emulsion, which is readily taken up by the leather.
FAT-LIQUORING 425
The skins are generally shaved before being fat-liquored;
but some prefer to shave after blacking. When this is done,
only half of the dye required for shaved leather is used, nigro-
sine or other color must be added to the fat-liquor to cover up
the unevenness produced by shaving.
Sulphonated oils are of great value to the tanner of chrome
calfskins. Combined with neat's foot oil and moellon degras,
the sulphonated oil acts as an emulsifier and carrier of the
others. The following fat-liquors can be used on black or
colored leather with perfect safety:
1. Take 6| lb. of neat's foot oil and heat to about 160°
F. Dissolve 2\ lb. of potash soap in hot water, stir it into
the oil, and mix thoroughly. When the mixture has cooled
slightly, add d\ lb. of sulphonated oil and mix well. Three
pounds of this mixture dissolved in 12 gallons of hot or boil-
ing water will fat-liquor 100 lb. of leather.
2. A richer fat-liquor, which gives a better-nourished feel
to the leather, is made of 12| lb. of neat's foot oil, 2\ oz. of
potassium carbonate, 3f lb. of potash soap, and 4 lb. of sul-
phonated oil. Heat the neat's foot and the potash to 160°
F. ; add the dissolved soap, and stir well; cool slightly and
add the sulphonated oil, stirring the mixture thoroughly. Use
3 lb. of this mixture dissolved in 12 gallons of hot water for
each 100 lb. of leather.
3. An excellent fat-liquor is made of soap, oil, and degras.
For 100 lb. of leather use, fig or olive oil soap, 1 lb.; neat's
foot oil, 2 lb. ; moellon degras, 2 lb. ; and caustic soda, 1 oz.
Boil the soap in a few gallons of water until it is d' solved ;
then add the oil and boil the mixture for 15 minutes. Then
stir in the moellon degras, adding the caustic soda dissolved
in water. Add water to make 12 gallons of fat-liquor; use
at 125° F., and run the leather in it for a half-hour
4. The following is a good fat-liquor for colored leather :
Soap, 1 lb. ; olive oil, 2 lb. ; treated cod oil, 2 lb. ; birch oil,
2 oz. ; and salts of tartar, 3 oz. Boil the soap until it is dis-
solved; add the olive and cod oils, and boil several minutes;
then stir in the birch oil and the salts of tartar dissolved in a
426 PRACTICAL TANNING
little water. Add enough water to make 12 gallons of liquor,
and use it at 125° F.
5. Castor-oil soap and castor oil make an excellent fat-
liquor for colored skins. A half pound of the soap and f
lb. of the oil may be used in 10 to 12 gallons of water for
each 100 lb. of leather.
6. Neat's foot oil and cod oil are used in another liquor,
1 pint of each being stirred together with 1 pint of a 10 per
cent solution of soda, and the mixture added to a hot solu-
tion of 3 lb. of soap chips in 6 pints of boiling water; 5 or
6 lb. of the mixture is used for 100 lb. of the shaved skins.
7. For light-weight colored skins, a satisfactory fat-liquor
is made of Castile soap, 1^ lb.; neat's foot oil, 1| pint; egg-
yolk, |- lb., for 100 lb. of leather. Dissolve the soap in a
pail of hot water, then add the oil, and when cool the egg-
yolk, and mix well. Make up to 12 gallons and use at 125° F.
8. One pound of fig or other good soap, 4 lb. of treated cod
oil, 2 lb. of moellon degras, and 1 oz. of caustic soda is par-
ticularly suitable for dull-finished leather. Boil the soap; add
the oil and boil again ; then add the degras and soda and stir
for 5 minutes. There should be 12 gallons of the liquor, used
at 125° F., and the leather drummed with it for a half-hour.
9. A fat-liquor made according to the following formula
is suitable for either black or colored leather, and is quite
satisfactory : Olive-oil soap, 1 lb. ; borax, 1| oz. ; neat's foot
oil, ^ lb. ; egg-yolk, 1^ lb., for 100 lb. of leather. Boil the soap
in 2 gallons of water; dissolve the borax in a little hot water,
and stir it into the neat's foot oil; add water to reduce the
temperature to 90° F., and stir in the egg-yolk. Make up to
12 gallons, and apply at a temperature of 125° F. The fat-
liquor is usually absorbed by the leather in 30 minutes.
10. Sulphonated oil alone, or mixed with neat's foot, cod,
or moellon, gives satisfactory results on chrome-tanned calf.
Oiling the leather. — When the fat-liquoring is finished, the
skins should be placed smoothly over horses to drain several
hours. They are next struck out on the grain side and oiled.
The water should be pressed out of the leather before the
FAT-LIQUORING 427
oil is put on so that the latter can quickly penetrate into the
body of the skins where it will add strength to the fibers. For
the oiling there is none better than neat's foot, which is used
alone and also in combination with paraffin oil. For a bright
finish, a mixture of 1 part neat's foot and 3 parts paraffin oil
is sometimes used; for dull leather, equal parts of the two
oils.
It is advisable to apply the oil hot to the leather, and avoid
oiling the flanks, after which they are hung up to dry. It
is best to dry them rather slowly in a moderately warm room
with a good circulation of air.
Fat-liquoring chrome-tanned kangaroo. — 1. An acid
fat-liquor recommended for kangaroo leather is made of sul-
phonated oil and neat's foot oil. Mix 6| lb. of the latter oil
with 6| lb. of sulphonated castor oil, and make a rich emulsion
with water. Three pounds or less of this fat-liquor, diluted
with 10 gallons of water at 140° F., is enough for 100 lb.
of leather. The addition of | lb. of ammonia is recommended
where there is a slight trace of acid in the stock.
2. A fat-liquor somewhat richer than the foregoing, which
gives a well-nourished leather, is made of 12| lb. of neat's
foot oil, 2\ oz. of potassium carbonate, 3f lb. of potash
soap, and 4 lb. of sulphonated oil. Dissolve the carbonate in
a little hot water, and stir it into the neat's foot, and heat
the oils to 160° F. Then add the potash soap and stir it
thoroughly. Shut off the steam and add the sulphonated oil,
stirring thoroughly until a perfect emulsion results. This
fat-liquor gives a good feel, and the leather can later on be
finished in dull or glazed.
3. This is also recommended: fig or olive oil soap, 1 lb.;
neat's foot or cod oil, 2 lb. ; moellon degras, 2 lb. ; and caustic
soda, 1 oz. Boil the soap in 6 gallons of water until it is
dissolved; add the oil and boil 15 minutes; then add the moel-
lon degras, and stir 5 minutes. The caustic soda, dissolved
in 2 quarts of water, is added last. Enough cold water should
then be introduced to make 12 gallons of fat-liquor for 125
lb. of leather.
428 PRACTICAL TANNING
4. The following fat-liquor and No. 3 are recommended for
dull-finished leather: moellon degras, 3 lb.; and salts of tar-
tar, 4 oz. Dissolve the latter in 3 gallons of hot water; then
stir in the degras, and stir thoroughly for several minutes ;
finally adding enough water to make 12 gallons of liquor.
Use at 140° F.
Applying the fat-liquor. — An approved method of fat-
liquoring chrome-tanned kangaroo leather is first to dye the
skins black and then wash them, pressing or striking out the
surplus water. The clean drum is heated with live steam ;
the water is drained out, then the leather is thrown in and
drummed a few minutes to warm it. The hot fat-liquor is
finally poured in and the leather is drummed for 40 minutes.
All of the grease should be taken up by the leather, leav-
ing nothing but clear water behind. Some tanners use the
following method : The leather and a quantity of hot water
are put into the drum and run 10 minutes. The drum is
then stopped and the fat-liquor in a slightly concentrated
form is poured in, and, mixing with the hot water, accom-
plishes its purpose. It is also customary to add the hot fat-
liquor to the dye liquor after the color has been exhausted.
Finally the leather is placed over horses to drain at least 12
hours; it is then set out, oiled on the grain with neat's foot
and glycerine, and hung up to dry.
Fat-liquors for chrome side leather. — The fat-liquoring
of chrome-tanned grain leather may be done before coloring
or blacking, or immediately afterwards. The preferred method
is to fat-liquor leather before it is colored, and black
leather after it has been dyed. The methods given under
chrome calf and kangaroo leather will work equally well on
this class of stock.
Fat-liquoring vegetable-tanned side leathers. — In the
finishing of sides into dull and glazed boarded grain leather,
imitation kangaroo as well as black and colored Russia leather,
a not uncommon practice is to give the goods two applica-
tions of fat-liquor, one before and one after coloring. Both
fat-liquors may be sulphonated oil, or the first may be a solu-
FAT-LIQUORING 429
tion of the sulphonated oil, and the second an emulsion of
oil, soap, and degras. The procedure is as follows: After
the leather has been split, re-tanned, pressed, and shaved, it is
sammied and then weighed for the first application of fat-
liquor. The drum is heated with live steam to 125° F., and
the leather put in with a small quantity of hot water, and
drummed until it is filled and the moisture evenly distributed,
the fat-liquor being thus rapidly absorbed. Another way to
moisten the leather is to dip it into warm water and place it
in piles until it is softened throughout, this being less likely
to "pipe" the grain than dampening in the drum. An excess
of water in the drum or in the leather must be guarded against,
as it prevents absorption of the fat-liquor. After having re-
ceived the first application of fat-liquor, the leather is rinsed
off in clean water to free it from particles of leather fiber and
fleshings, which, containing oil, are liable to spot the leather
while it is drying. Previous to being hung up to dry, the
leather should be placed on a horse for a few hours to allow
the fatty matter to penetrate.
When leather is given two applications of fat-liquor, the
first treatment should be at least half of the whole quantity
used. Colored leather can be given no better fat-liquor than
sulphonated oil, used alone or combined with neat's foot or
degras, such fat-liquor being also good for black leather. A
thoroughly emulsified fat-liquor of soap, oil, and degras is
also suitable, while some tanners prefer to buy a commercial
^at-liquor rather than make it themselves.
Glazed and boarded grain leather is colored blue on the
flesh side before the second application of fat-liquor, and
blacked upon the grain afterwards ; flesh and grain may also
be dyed at one operation if desired.
Colored Russia leather is usually bleached, mordanted, and
colored previous to the second application of fat-liquor.
When dry from the first application of fat-liquor, the
leather is dampened and colored, then dried and dampened
again for the second fat-liquoring. Imitation kangaroo and
dull grains are usually yellow-backed before the second ap-
430 PRACTICAL TANNING
plication of fat-liquor. After it is fat-liquored, the leather
is again dried for finishing. Kangaroo calf and sides are
sometimes fat-liquored and dried, then yellow-backed, grain-
blacked, dried, and finished. The leather may be washed after
re-tanning; pressed and fat-liquored; dried, and then colored
and finished.
Quebracho, gambier, and combination-tanned leather can
be handled satisfactorily in the following manner : When the
re-tanning is completed, the sides are washed and pressed to
remove surplus liquor. After pressing, the leather is shaved
and fat-liquored. In some cases it is drummed with sulphon-
ated oil and dried before it is fat-liquored, this being a good
method to follow in finishing colored leather. A drum is
heated with steam to 100° F., and 1 gallon of sulphonated
oil is used for 150 lb. of leather, weighed after pressing and
shaving. The leather is drummed with the oil for a half-hour,
then hung up and dried. After drying, the leather is weighed,
dampened with warm water, and placed in piles to soften.
It is then put into the drum and run with just enough water
to soften it uniformly, when it is in condition to receive the
fat-liquor. This method is entirely practicable and satisfac-
tory, but some tanners omit the oil and fat-liquor the leather
after it has been drained and pressed.
To fat-liquor the leather, the drum should be heated to 125°
F. with live steam, and the leather drummed in warm water
until it is soft and full. The fat-liquor should be given to
the leather in portions of. 1 to 2 gallons at a time through the
hollow gudgeon, and after all of it is in the mill, the leather
should be drummed 40 minutes. After being taken out of the
mill, the leather should be rinsed in clean Warm water, drained,
and dried. When dry, it may be colored blue on the flesh and
black on the grain, or yellow upon the flesh and black on the
grain ; or it may be colored any shade desired, dried, and fin-
ished with smooth, boarded or printed grain, or into imita-
tion kangaroo leather.
The following fat-liquors have been used in tannery prac-
tice, with good results :
FAT-LIQUORING 431
Fat-liquor formulas. — 1. Boil 25 lb. of potash soap in 25
gallons of water until it is dissolved. Add 50 lb. of English
sod oil and 6 quarts of neat's foot oil to the solution, and stir
for several minutes. A few pounds of moellon degras may
also be added. Enough cold water is next introduced to make
50 gallons of liquor, and 20 gallons of this liquor suffices for
100 lb. of dry leather which has been run in sulphonated oil
previous to being dried. The exact quantity to use, how-
ever, varies with the tannages, the quantity stated being the
maximum ; but a smaller quantity will in most cases produce
the desired result.
2. Five pounds of soap and one gallon of moellon degras
boiled and made into a fat-liquor with a half barrel of water
is sufficient for 400 lb. of leather. It may be applied to the
leather immediately after tanning, or the leather may be
drummed with a little sulphonated oil and dried before it
is fat-liquored.
3. A good stuffing for imitation kangaroo and dull-printed
sides is made of 12 lb. of cod oil to each 100 lb. of leather,
dried after re-tanning, and weighed after it is dampened.
Use at 130° F. Pack the leather down over night to harden;
then set it out by hand and hang it up to dry. When dry,
buff off the grain, trim, and stake the leather; then color the
flesh yellow, and black the grain and finish the leather.
4. For hemlock, quebracho, gambier, and combination-
tanned leather, the following fat-liquor is recommended: 10
lb. of soap, 4 gallons of neat's foot oil, and 10 lb. of degras
to a barrel of liquor. Use at 125° F., preferably after color-
ing; then set the leather out, oil the grain, and hang up to
dry. The leather, dried after re-tanning, is dampened, col-
ored, and then fat-liquored, when the grain is struck out and
oiled with neat's foot, and the sides are then tacked on frames
to dry. Ten gallons of this fat-liquor is sufficient for 25
sides of 20-foot 4-ounce leather. It is best to use the liquor
after the leather has been dyed black, or colored.
5. For bright printed or boarded grains, another suitable
fat-liquor is 12 lb. of pure cod oil, 2 lb. of French degras, and
432 PRACTICAL TANNING
2 gallons of thin soft soap for 100 lb. of damp leather.
Apply at 125° F. The leather, after being re-tanned, should
be drummed for an hour in warm, strong sumac liquor; then
rinsed, scoured on both sides, and hung up to dry. When
dry, it is dampened and fat-liquored, set out, and a light coat
of oil applied to the solid parts of the flesh side. The leather
should be set out very hard on both sides, since the tighter
it is set the finer and more even the grain will be when the
leather is finished. When dry, the leather is dyed black,
dried, staked, and finished.
Fat-liquoring vegetable-tanned calfskins. — The fat-liq-
uors described under side leather are suitable for quebracho,
gambier, hemlock, and combination-tanned calfskins; and can
be applied to the leather immediately after it is tanned, or
later, after it has been dried and colored.
Fat-liquoring is one of the most important processes in the
manufacture of calf leather. Only the best grades of ma-
terials should be used, so that the leather will not be greasy,
gummy, or liable to spew after it is finished. Sulphonated
oil unites with the fibers of the leather and does not decom-
pose in the leather; it also prevents greasiness and darkening
of the grain.
From the scientific point of view there is yet a great deal
unknown regarding the action on leather of those emulsions
of oil and soap which are technically termed fat-liquors. As
now used on many varieties of bark and combination-tanned
leathers, fat-liquor is a development of chrome leather manu-
facture. Indeed, it is no exaggeration to say that the suc-
cess of the chrome leather industry was dependent upon the
discovery and application of fat-liquors; and even today the
use of a proper fat-liquor is necessary for the production of
a marketable product.
To a considerable degree, the formulas for various fat-
liquors are among the most carefully guarded secrets of a
leather manufacturer; yet in the main the composition and
method of preparation of a good quality of fat-liquor has
become well known. Practically, a fat-liquor can be defined
FAT-LIQUORING 433
as an emulsion of oil and water, usually containing soap
and frequently other emulsifying agents. Its purpose is to fill
or nourish the leather and keep it from drying hard or brittle.
Although the claim has never been put forward, Robert
Foerderer, the inventor of "vici kid," the first merchantable
chrome leather, is accredited as being the real inventor of the
emulsified fat-liquor; yet according to all evidence, it was
the use of the fat-liquor which made vici leather far superior
to the products of other leather manufacturers. When the
knowledge concerning the use of emulsion of oil began to leak
out, other manufacturers then started to make good chrome
leather.
Having described the methods for producing fat-liquors, it
will perhaps be well to consider their general constitution and
the properties of their ingredients. An emulsion is a mixture
of liquors that are mutually insoluble, but which are so mixed
that fine particles of one are suspended in the other. The
term is usually, although not necessarily, applied to mixtures
of oil and water. Milk is often cited as the most perfect of
emulsions. In order that an emulsion may be at all perma-
nent, it is generally necessary that a third substance, called
an emulsifying agent, be present. Such agents act by increas-
ing the viscosity of the one liquid in which the fine particles
of the other liquid are suspended to such a degree that the
tendency to separate into different layers is largely overcome.
In the case of milk, the casein, or milk albumen, acts as an
emulsifier. In the familiar example of cod-liver oil emulsions
of the pharmacy, the agent used is gum acacia or gum arabic.
For leather manufacture it has been found that neither the
casein of milk, nor gum arabic, nor indeed any other gum acts
suitably as an emulsifying agent in fat-liquors. Primarily,
they make trouble by perceptibly stiffening and harshening the
leather, and then their power to increase viscosity diminishes
rapidly with a slight increase in temperature. Soap has there-
fore become largely used as the emulsifier in the preparation
of fat-liquors. Regarded simply as such, soap is not es-
pecially effective, but it has the extremely important advan-
434 PRACTICAL TANNING
tage, that is, provided the right kind of soap is used, that it is
absorbed by the leather and does not injure it. To increase
the efficiency of soap, or to replace it, two other emulsifying
agents are used, namely, egg-yolk and sulphonated oils. The
former is itself an emulsion, and the emulsifying agent in it
is known as vitellin, an albumen considerably resembling
casein. Presumably, because the proportion of oil and albu-
men in the egg-yolk to the water contained in it is greater
than in milk, it can be used in relatively greater proportion;
egg-yolk is therefore much more efficient in a fat-liquor than
milk.
Sulphonated oils. — The subject of sulphonated oils is a
large one and can be only briefly considered here. The best
known of these is Turkey red oil which is largely used in the
textile industry, especially in the dyeing of Turkey reds, hence
the name. It is made by the action of sulphuric acid on cas-
tor oil. Its manufacture requires considerable care, and it is
best made on a large scale in factories specializing in its
production. Inasmuch as leather manufacturers using it have
generally desired to keep that fact secret, they have endeav-
ored to manufacture it for their own use rather than purchase
it from an experienced maker, but such manufacture is usu-
ally attempted with imperfect apparatus, as well as inadequate
knowledge. In the first place, castor oil is practically the only
oil that can be sulphonated in the true sense, because the prin-
cipal fatty acid in castor oil is ricinoleic acid, an unsaturated
acid. This does not mean that other oils than castor cannot
be treated with sulphuric acid, and some sort of a product
obtained ; nor should it be understood that it is impossible to
sulphonate fatty acids other than ricinoleic acid. For exam-
ple, the fatty acids of linseed oil are largely unsaturated, but
unless extraordinary precautions are taken to cool the mixture
of acid and oil, the reaction is so violent that what is known
as secondary reactions take place and the fatty acids are
largely destroyed.
The tendency of linseed oil to become resinous does not
recommend it as a good leather lubricant. The more com-
FAT-LIQUORING " 435
mon practice is to treat oils, for example, neat's foot and
tallow, whose fatty acids are principally acids of the oleic acid
class. Oleic acid sulphonates only at a high temperature, and
when an attempt is made to sulphonate one of the oils con-
sisting largely of this substance, no sulphonation results; but
the oil is simply broken up by hydrolysis and separates into its
constituent parts, namely, fatty acid and glycerine.
Casein. — This has been employed as an emulsifying agent,
but the fact that it is soluble only in alkaline solutions, makes
its use objectionable. Also the liability of casein solutions to pu-
trefy is a disadvantage, especially as the usual antiseptics pre-
cipitate it. Probably the most satisfactory preservative for
casein solutions is white arsenic, only a very small quantity
being needed, and so little arsenic remains in the leather that
no objection can be raised to its use. One part of arsenic to
two thousand parts of fat-liquor is a proportion that has
been used with success.
Egg-yolk. — This, as has been stated, is a valuable constit-
uent of fat-liquors. It is itself an emulsion in which an al-
bumen similar to casein is the emulsifying agent. Probably
one reason for the superiority of egg-yolk to casein is that,
in the case of the latter, the natural emulsion is broken up,
while the former is used in an unchanged state. There is a
sufficient excess of albumen in egg-yolk over that required to
emulsify the natural oil it contains to make it suitable for
holding large proportions of other oils in a state of emulsion.
It is for this purpose that it is valuable in fat-liquors. Unfor-
tunately, some dealers in the material add other oils to the
egg-yolk, which while not necessarily deleterious to the fat-
liquor, they reduce the emulsifying power of the egg-yolk,
and so are rightly considered an adulteration. Still
more reprehensible is the practice of adulterating egg-yolk
with emulsions of oils and casein, which are colored by aniline
dyes. An easy test is the addition of a small quantity of
ammonia to one portion of a suspected sample, and a little
acetic or muriatic acid to another. If either the ammonia
or the acid produces a decided color-change in the egg-yolk,
436 PRACTICAL TANNING
it Indicates the presence of an aniline yellow, and is presum-
ably an adulterated product.
Potash soaps. — These are preferably used as the soap con-
stituent of fat-liquors. The reason for this is that they are
soft soaps, that is, have a lower melting point than the hard
or soda soaps. The objection to the high melting point — or
to express it another way, the low solidifying point — of the
soda soaps is that it causes white specks or soap crystals to
form in the leather, which is one variety of the familiar spew-
ing, an especially annoying defect in finished leather.
While all of the potash soaps are softer than the corre-
sponding soda soaps, that is, those made from the same oils or
fatty acids, one prepared from a hard, solid fatty acid will
be nearly as hard as a soda soap made from a liquid fatty
acid such as oleic acid. Also, if a soda soap is made from a
liquid fatty acid, and a large percentage of water is allowed
to remain in it, it will closely approximate the appearance of a
potash or genuine soft soap. A simple drying test will, how-
ever, serve to distinguish the true from the false. In order
to appear soft, a soda-soap must contain a high percentage
of water, which will evaporate and the soap remain behind
hard and dry if a small sample is exposed a few hours to
gentle heat in a shallow dish. Potash soaps, on the other
hand, will not dry out hard unless made from hard fat.
Fig soap. — A soap which has had much vogue for fat-liq-
uor purposes is the so-called fig soap. It was originally a
potash soap made from olive-oil foots. Much of the fig soap
on the market is made from a mixture of olive-oil foots,
cotton-seed oil, and tallow, and in appearance is much supe-
rior \o that made exclusively from olive-oil foots.
For practical use, a soap is probably better made in the old
way, as the hard stearic acid soaps (from the tallow) will
crystallize in the leather and cause spewing.
The use of rosin oils must be especially avoided. These
oils are obtained by the distillation of rosin, and while they
are saponified, the products so formed have but few of the
properties of ordinary soaps, and are unsuitable in fat-liquors.
FAT-LIQUORING 437
The free fatty acids of rosin oils are objectionable as they
oxidize and become resinous or gummy. Some sulphonated
rosin oils have been offered for fat-liquoring purposes, but
from theoretical considerations there is no reason to suppose
that they will have sufficient efficiency to replace castor-oil
compounds. A final word in regard to fat-liquors is the ques-
tion of alkalinity or acidity. The first fat-liquors were essen-
tially alkaline, on account of their large soap content; while
the sulphonated oil compounds have an acid nature. If alka-
line and acid fat-liquors are mixed, as frequently has been the
case, the possible good effects of either when used separately
are nullified.
The effects on colors should also be considered, and it
should be especially remembered that an acid fat-liquor has
much less effect on colors than one which is alkaline or con-
tains a considerable quantity of soap.
How to make and use sulphonated oils. — A sulphonated
oil is one that has been subjected to the action of sulphuric
acid. The oils that can be sulphonated are castor, neat's
foot, olive, cod, corn, and a few other saponifiable oils. Those
that have been treated by the process of sulphonation have
come more and more into use in the manufacture of heavy
and light leathers. They are especially useful in fat-liquoring
vegetable and chrome-tanned leather.
During the process of manufacturing sulphonated oil, the
acid must be added to the oil very slowly; the oil should be
thoroughly stirred while the acid is being added to it and also
while it is being washed out. To obtain the best result, the
oil must be chilled while it is being acidified. The following
instructions will enable anyone to prepare a usable sulphon-
ated oil : Take a barrel and saw it in two parts just below
the two hoops near the top. This makes a tub of convenient
size. Then put a 15-gallon crock into the tub and surround
it with cold water. If the water is not below 60° F., add
ice to lower its temperature, as it must be cold enough to chill
the oil. Put 6 gallons of castor oil into the crock and stand
over night to become thoroughly cool.
438 PRACTICAL TANNING
The next morning carefully pour 6 oz. of 66° Be. sulphuric
acid into the oil, and stir for at least 5 minutes after the
acid has been added. Three hours later introduce 6 oz. more
of acid, taking care to add it slowly and to stir thoroughly.
Four hours later stir in another 6 oz., and two hours later
6 oz. more should be added with careful and thorough stirring.
The next morning add 6 oz. of acid to the oil, and every
3 hours thereafter add 6 oz. until 24 oz. have been added on
the second day.
On the morning of the third day take a clean barrel, and
put a wooden spigot into it as near the bottom as possible.
Place the barrel on a box or a block so that it will be 6 or 8
inches off the floor. Pour the acid-treated oil into the barrel
and fill the latter two-thirds full of luke-warm water. Add
30 lb. of salt to the water and oil, and stir for 15 minutes.
Repeat the stirring every half-hour for 5 hours ; then allow the
oil to rise to the top, open the spigot, and let the salt water
run off until oil begins to show. Close the spigot and fill the
barrel with warm water as before; then add 24 lb. of salt and
stir for 15 minutes. Allow the oil and salt water to stand
again over night, then draw off the water as before, and fill
the barrel again with water, adding 18 lb. of salt, stirring as
before. Draw the water off again and fill the barrel with
warm water and put in 15 lb. of salt. Stir thoroughly for 10
or 15 minutes, and allow the oil to stand over night. The next
morning draw the water off, and the oil that remains in the
barrel is ready for use. In order to get a satisfactory prod-
uct, the oil must be well stirred when washing out the acid ;
and the acid must never be put in fast enough to burn the oil.
To keep the oil, add a little water to it — about twice its
own weight. Before adding the water, stir in enough concen-
trated ammonia to neutralize whatever acid there may be in
the oil, also to carry it to the alkaline side.
Neat's foot oil and cod-liver oil mav be combined and sul-
phonated in the following manner : Mix 30 lb. of neat's foot
and 20 lb. of cod in a 20-gallon crock standing in a tub con-
taining: cold water. Add ice to the water to lower the tern-
FAT-LIQUORING 439
perature below 65° F. Put the oil in the crock before closing
down for the night, and in the morning it will be chilled.
For the 50.1b. of oil, use 88 oz. of sulphuric acid, dividing
it into four equal portions. At about 8 a. m. pour one por-
tion of 22 oz. of the acid very slowly into the oil, stirring
while it is being added and continue for 5 minutes afterward.
This should take about 15 minutes. Allow the oil to stand
until 5 p. m. Then add another portion of the acid, stirring
thoroughly as in the morning. Let the oil stand until the
next morning; then add another portion of acid as before.
At about 5 p. m. on the second day add the last portion of
acid, stirring thoroughly as before, taking 15 minutes. On
the morning of the third day, the acid-treated oil is in con-
dition to be washed. Use a large barrel or tub holding 100
gallons, provided with a spigot, as mentioned above. Put
the oil into the tub or barrel, and add enough water at 100°
F. to fill the tub nearly half full. To the water add a pail of
Glauber's salt and stir thoroughly, then add more water until
the tub is nearly full. Allow this to stand until towards eve-
ning of the third day, then open the spigot and let the water
run off. Close the spigot and fill the tub as before with warm
water, and add a little less than a pail of Glauber's salt. Al-
low the mixture to stand until the next day, and then draw
off the water the same as before. Fill up the tub again with
warm water and I5 pails of common salt. Stir the oil and
the water thoroughly, and allow the mixture to stand 12 hours.
Then draw off the water and fill the tub again nearly full
with warm water, and add 1-J pails of salt. Stir the oil well,
and let the mixture stand until the next day. The water
should then be drawn off, when the oil is ready for use.
A method which is used extensively and saves considerable
time in washing consists in treating the sulphonated oil with
a volume of water as indicated under washing, and to the
water add sodium carbonate in place of the salt. The sodium
carbonate at once combines with the sulphuric acid, forming
sodium sulphate or Glauber's salt. The oil is thus neutralized,
separated, and washed in one operation. Care, of course,
440 PRACTICAL TANNING
should be taken not to add too great a quantity of the alkali,
otherwise there would be danger of saponification.
Sulphonated oil on chrome leather. — When the oil has
been properly treated with acid and washed, it dissolves read-
ily in hot water. When using, it is dissolved in water and the
leather is drummed with the solution ; 100 lb. of chrome leather
may be fat-liquored with 4 to 6 lb. of the oil dissolved in 12
gallons of water at 125° F. The drum used for the. purpose
should be perfectly clean, and the leather warmed in a hot
drum before it is given the fat-liquor. The exact quantity of
oil to be used must be determined by the operator, and depends
upon the degree of softness desired. Drum the leather in the
fat-liquor for 30 minutes ; then take it out and rinse it off in
hot water to remove the oil from the surface. This washing
is necessary when the leather is colored after fat-liquoring.
If colored before fat-liquoring, rinse the leather, let it drain
a few hours, strike it out, and hang it up to dry.
The best results, however, are secured when the sulpho-
nated oil is combined with neat's foot oil or some other fat-
liquoring material. Used in this way, it emulsifies the other
oils and greases and carries them into the leather. When neat's
foot or moellon degras is used with the sulphonated oil, the
leather becomes lubricated internally, and has, when finished,
a full, well-nourished feel.
Sulphonated oil on vegetable-tanned leather. — Vegetable-
tanned skins may be fat-liquored with a solution of the sul-
phonated oil, with a mixture of such oil and mineral oil, with
a mixture of sulphonated oil and neat's foot oil, or with a mix-
ture of either sulphonated cod oil or sulphonated neat's foot
oil and mineral oil. Of these combinations, the best is un-
doubtedly the mixture of sulphonated castor oil and neat's
foot oil. The emulsion can be given to the leather imme-
diately after tanning and before the skins are dried ; it can
also be brushed on or mixed with the tanning liquors toward
the end of the drum tannage. Bark and extract-tanned leather,
after it has been split and re-tanned, may be fat-liquored with
a mixture of fish oil emulsified with sulphonated castor or
FAT-LIQUORING 441
neat's foot oil. The mixture of oils can also be added to the
re-tanning liquor in the drum, thus giving fullness and a soft
feel to the leather.
Sulphonated oil on sole leather. — Another important use
for sulphonated oils is in the extracting of sole leather. When
sole leather is re-tanned in the drum it is of great advantage
to add to the liquor mineral oil to which sulphonated oil has
been previously added. This sulphonated oil is soluble in
water, with which it forms a more or less thick paste, and
mixes with mineral oil. The presence of the sulphonated oil
enables the mineral oil to penetrate the leather in small quan-
tities, and, without destroying its firmness allows it to retain
a certain interior humidity. The presence of the mineral oil
and of the sulphonated castor oil has also another object,
namely it facilitates the penetration of the tannin into the
leather, and by lubricating the inner portion, prevents
damage by rubbing of the grain against the sides of the
drum.
Castor-oil soap. — This is an excellent material for fat-
liquor. It can be made in the tannery in the following man-
ner : Dissolve 2 lb. of caustic soda in 1 gallon of water. Heat
2\ gallons of castor oil to 90° F., then pour the soda solution
into the warm oil, and stir the mixture until it becomes thick.
Cover the tub containing the soap, and let it stand over night
in a warm place. The soap is ready for use the next day.
It is advisable, but not absolutely necessary, to melt the soap
again in a jacketed pan fitted with a stirring apparatus, by
means of which a more thorough mixing of the soap is
obtained.
Potash soap. — For any purpose for which a potash soap is
required it is essential to use a pure article, but this is not
always obtainable, so to be sure of having a pure product the
safest course is to make it. This is easily done, as pure caus-
tic potash can be readily obtained. A good soap can be made,
even with crude appliances, according to the following form-
ula: Put 224 lb. of red oil in a kettle and heat it to 100° F. ;
then run in slowly, with constant stirring, 10| gallons of solu-
442 PRACTICAL TANNING
tion of caustic potash of 60° Twaddell. Allow to stand 24
hours and the soap is ready for use.
Oiling chrome leather. — The finishing of chrome leather
cannot be called currying, as no heavy stuffing or hard grease
is used, the only grease the leather receives being an emulsion
of oil, soap, and degras, or some other suitable material, and
a coat of oil applied to the grain before it is dried. The oils
used for oiling the grain of chrome leather are neat's foot,
olive, sperm, sulphonated, and paraffin. Neat's foot is often
used alone as well as mixed with paraffin oil. A good mix-
ture for chrome glazed leather is 1 part neat's foot and 3
parts paraffin oils ; and for dull-finished leather equal parts.
They should be warmed, mixed, and applied warm, the leather
being well struck out with a slicker before it is oiled.
Another good combination is 1 part olive oil and 3 parts
paraffin oil. The mixture should be applied evenly over the
grain, more being put on for a dull finish than for a glazed
finish. It is best not to oil the flanks. Sperm and olive oils
are good for colored leather.
A pure petroleum oil, such as 34° gravity neutral, is suit-
able for any glazed leather. Good results are obtained by
mixing it with what is known as fleshing oil, using equal
parts of the two oils. Heat the oils to 200° F., mix well, and
let the mixture cool before it is used.
To preserve the finish and prevent spewing, a coat of the
petroleum oil heated to 100° F. should be applied to the leather
after it is finished. The so-called finishing and kid oils are
nothing but 34° neutral petroleum oils, although they are
generally sold under fancy names at fancy prices. Fleshing
oil is much cheaper than neat's foot, and produces equally
good results.
The paraffin oils, when used together with pure cod oil in
proper proportions, are satisfactory for sole and rough leathers.
The proportions of the two oils should be 25 to 60 per cent
paraffin and 40 to 75 per cent cod; a good mixture is 60 and
40, respectively. The regular 28° paraffin oil is the most suit-
able for rough and sole leathers.
FAT-LIQUORING 443
Sulphonated castor oil is also used after glazing and be-
fore drying to prevent the leather from cracking and oxidiz-
ing in the air. In this case it is sufficient to apply a light coat
of sulphonated oil (50 per cent water) to the grain before
drying. Some tanners prefer to use for this purpose a mix-
ture of equal parts of sulphonated castor oil and a light-
colored mineral oil.
Specially treated oils, which have great softening proper-
ties, preventing spew and gum, and do not discolor the most
delicately colored leather, are also procurable.
Low grade and impure oil should not be put on chrome
leather, as such oil undergoes a process of decomposition in
the leather, imparts a bad odor to it, and spews Out on the
surface in the form of white scum, which is removed with
difficulty. The quantity of oil applied to the grain is small,
and it is advisable to use only the best grade for the purpose,
the increased cost being not worth considering in view of the
better quality of the finish.
Waterproof filling for sole leather. — The following
method of waterproofing and otherwise improving chrome-
tanned and bark-tanned sole leather, was patented by William
R. Smith and assigned to the Buffalo Leather Co., of Buffalo,
N. Y.
A bituminous composition is introduced into the leather by
bringing the latter into contact therewith at a temperature high
enough to render the composition thin and fluid, but not high
enough to injure the leather. The maximum temperature var-
ies with the kind of tannage, vegetable-tanned leather resisting
a temperature of 150° F. and chrome-tanned up to about 200°
F. To ensure proper impregnation, the leather should be free
from oils, glucose, etc. It is best to treat the leather in a
rotary tumbling drum. The fluid mixture and the heated soles
are put into the drum, which is steam-jacketed and heated,
so that the temperature of the air within it is somewhat above
the melting point of the mixture. The drum is preferably pro-
vided with radial inwardly projecting shelves adapted to raise
and release the composition and the pieces of leather as the
444 PRACTICAL TANNING
machine rotates. The operation is continued until the com-
position has thoroughly permeated the leather. Whole sides
may be treated, but the inventor prefers, for economy of
the mixture, to tumble the leather with the composition after
it has been cut into forms or soles of the final size. The
process is ordinarily completed within one-half hour.
The bituminous composition used contains as its essential
components a solid bitumen possessing a considerable degree
of elasticity, combined with some other bitumen having
marked penetrative powers. The variety of elastic bitumen
preferred is elaterite or "mineral rubber," and the variety of
penetrative bitumen is ozokerite, a "mineral wax." While the
elaterite is greatly desired in such a composition, its use has
been prevented by its infusible and insoluble character, also
by its viscosity when brought into a state of fusion by ad-
mixture with other bitumens. This difficulty is overcome by
altering the character of the elaterite so as to render it easily
soluble in melted ozokerite or equivalent paraffin. When elat-
erite is gradually added to a melted bitumen, such as gilsonite,
which is capable of withstanding a high degree of heat with-
out decomposition, it is softened and gradually dissolved, and
thus an infinitely large quantity can be melted in the presence
of a small amount of gilsonite. The elaterite, fusible at high
temperature without decomposition and soluble in hot paraf-
fins and forming therewith a thin, penetrating liquid, is herein
termed "modified elaterite."
An example of modified elaterite is the so-called "kapak,"
a bitumen well-known in the trade and produced from elat-
erite. The elaterite found in Utah (ozokerite also comes from
that State) has all the desired qualities for this process. It is
non-friable, tenacious, only moderately brittle at low tempera-
tures, elastic at normal temperatures, resilient, and resistent
to chemical alteration. When slightly warmed it becomes
more flexible and more elastic so that if drawn out or bent —
like rubber — it tends to return to its former shape upon re-
lease. It may, by fusion with a solid paraffin body, be brought
partly into solution, but it is preferable to render it substan-
FAT-LIQUORING 4-45
tially soluble in melted solid paraffin by previous modification.
Ozokerite, having a higher melting point than ordinary solid
paraffin, is found to be a superior ingredient in this special
composition. The proportion of paraffin to modified elaterite
naturally varies somewhat according to the specific qualities
given the latter, 3 parts of ozokerite to 1 of modified elaterite
being generally suitable.
The flexibility and resiliency of elaterite are found to be
measurably retained by the composition, and in addition, it
possesses a surface frictional resistance such as is possessed
by beeswax. The value of this latter quality is clearly ob-
served when chrome-tanned sole leather is worked through
this process. Notwithstanding the durable character of chrome
leather, its use for the soles of shoes has been greatly limited
by its slippery nature in wet weather. When chrome leather
is impregnated with the composition by this process, this un-
desirable quality is effectually overcome. The wearing qual-
ity of heavy leather of all kinds for use as soles and heels
is greatly increased by this treatment. When finished leather
filled with ordinary paraffin wax is placed in hot sunshine or
near a stove there is a strong tendency for the wax to melt
and exude, thus defacing the shoe or other article. On ac-
count of the viscosity and high melting point of the composi-
tion used in this process the leather is not injured by any
similar rise in temperature.
Another combination, which is not patented, consists of a
mixture of 50 parts paraffin wax, 25 parts of rosin, and 25
parts of carnauba wax.
Stuffing chrome lace leather. — After the stock has been
tanned, neutralized, and washed in the usual way, it should
be placed in a hydraulic press, or run through a Quirin
wringer to take out the excess moisture. It should be run
in a dry mill to take out all the wrinkles, and then allowed to
sammie to contain approximately 40 per cent of moisture, tak-
ing great care to prevent any portions of the hide from be-
coming dry and eventually dark when stuffed with grease.
When the leather has been properly sammied, it should
446 PRACTICAL TANNING
be weighed, placed in the stuffing drum which has been pre-
viously heated to 180° F., and allowed to run for about 5
minutes so as to open up and become heated through. Then
add to the drum for each 100 lb. of stock 10 lb. of oleo-stear-
ine substitute and 3 lb. of No. 3 "setine," melted together at
a temperature of 150° F. Run for about 30 minutes, or until
all of the grease is well taken up. The leather is then removed
from the drum and hung on hooks until the grease has set
and the stock is perfectly cold. This permits the leather to
absorb the grease so that no excess is left on the flesh and
grain.
The stock should then be placed in clean water at not over
90° F., and should remain in this water for about 10 minutes,
or until the fiber has taken sufficient water to set out easily.
It should then be taken from the water, placed on the table
and struck out on the flesh with a slicker ; then turned over,
set out perfectly on the grain, and oiled off with No. 3 setine,
giving a fairly liberal coat along the back and over the hips,
and a light coat over the balance of the hide. The stock
should then be hung up from head to tail until the oil has sunk
in from the surface. It should then be tacked out and dried in
the usual way, after which it should be sammied with water,
or preferably in sawdust, staked, and finished.
Shaving the flesh lightly on the machine decidedly improves
its appearance, after which the grain should be glassed by
hand and then a light coat of talc put on with a brush and
well rubbed in and the excess wiped off with a woolen cloth.
Each of the above products is pure white and assimilates
perfectly with the moisture in the leather. They will not
oxidize, nor will they react with the chromium salts.
The proportions recommended must necessarily be varied to
meet requirements. If the leather is inclined to be soft, oleo-
stearine substitute alone may be used to advantage, using only
the No. 3 setine to oil off after setting, so as to mellow the
stock along the back and over the hips.
CHAPTER XV
FINISHING LEATHER
In the previous chapters have been described the various
processes employed for treating hides and skins. Rather than
carry each kind of leather through the final finishing process
Figure 97. — Exterior view of Proctor dryer.
it has been thought best to bring them to a point where the
final operations of producing a marketable product become
necessary. Thus we have studied beam-house methods, tan-
ning processes, coloring and fat-liquoring, and now we will
consider the application of various seasonings and the me-
chanical operations necessary to produce the desired results.
Setting-out. — For practically all classes of leather the stock
is set-out after fat-liquoring. This is done on machines or
may be set by hand on a smooth-top table. In any case, the
447
448 PRACTICAL TANNING
idea is to smooth out the leather and free it from excess of
liquor.
Drying. — The skins or hides having been set-out are next
dried. This is usually done by hanging the stock in a dry
loft. Skins are, as a rule, suspended by the butt, while sides
are suspended by the butt and neck. The conditions of the
dry loft vary greatly with the kinds of stock, but, as a rule,
1
" ■&■■■ —**m ' * ' "*■""
m ' " 1 -— - f ■ Pk9v
- ', ■ i, '■ . .... • ; ; '; . ...' >
Figure 98. — Skins entering at the "wet end" of Proctor dryer.
it may be said that vegetable-tanned stock should dry slowly,
while chrome-tanned stock will stand a higher degree of heat
in the loft. For chrome-tanned stock several forms of rapid
mechanical dryers are employed, the most common being
known as the Proctor dryer, shown in figures 97, 98, and 99.
In the ordinary dry loft the skins are suspended from hooks
or over sticks (figure 100), and the temperature regulated by
means of steam coils passing under a grating on the floor.
To ensure a proper circulation of air, most dry lofts are pro-
vided with fans of the blower type, which may be used either
FINISHING LEATHER
449
to blow the air into the loft, or may be placed so as to draw
off the moisture-laden air. This method is best shown in
figures 101, 102, 103, 104, and 105.
The drying tunnel has been found to give exceptionally
good results on chrome leather. This consists of a long nar-
row tunnel on each side of which is an endless conveyor, both
the Proctor and Sturtevant being types of such equipment.
The damp stock enters the cool end and gradually approaches
Figure 99.— Skins leaving the "dry end" of Proctor dryer.
the hot end of the dryer from which it is removed when in
the proper condition.
Dampening. — After the leather has been dried out, in order
to set the fiber it must again be dampened back or sammied
before carrying out the finishing processes. Two methods
of dampening leather are employed, the first consisting of
dipping the stock in warm water, and then packing down in
pits over night; and the second in placing the leather in piles
with damp sawdust between each skin, and then covering the
pile completely with more damp sawdust. By either of these
methods the stock becomes uniformly damp without contain-
ing an excess of moisture in any part.
450
PRACTICAL TANNING
Staking. — When the leather is in a properly sammied condi-
tion it is ready for stretching or softening, which is done in
several ways. The most common method of stretching is
accomplished by working the skin or sides on a staking ma-
chine, illustrations of which are shown in figures 106, 107, and
108. The leather is placed on the bed of the machine, and is
then held in position while the jaws close in, and on retreat-
Figure 100. — Interior of a typical dry-room in a goatskin tannery.
The room is heated by steam pipes on the floor and ventilated
by means of fans.
ing impart a pulling and breaking effect. In place of ma-
chine staking, an older method consists in working the skins
over a blunt knife, pressure being applied by placing the knee
in the fold of the leather and drawing downward. This is
known as knee-staking, and is illustrated in the chapter on
Alum Tanning. Leather is also softened and stretched by
means of the moon knife, which gets its name from its pecu-
liar shape. This method of staking is spoken of as "perching."
Buffing. — When it is desirable to produce a velvety appear-
ance on the flesh side of the leather, the dry skins are passed
FINISHING LEATHER
451
over a carborundum or emery wheel, as shown in figure 109.
This is sometimes done while the stock is still wet, in which
case a carborundum stone is used, known as a "wet wheel."
Tacking. — To conserve as much measurement as possible
and produce a smooth piece of leather the stock is usually
tacked. This is done by placing the sammied and staked
leather on a frame and tacking around the edge. In carrying
out the operation the skin is placed flat on the board and
Figure 101. — Side view of Sturtevant dryer showing supply pipe,
heater and open tube.
several tacks are placed in the butt. The neck is then pulled
tight and tacked in position. Tacks are then driven along
the sides, two men usually working on one skin on opposite
sides. The care taken in this operation has a great influence
on the finished product. When tacked, the stock is allowed
to dry.
Stripping. — When thoroughly dry on the boards the tacks
are withdrawn, or what is known in the trade as "stripped."
Seasoning. — On removal of the skins or sides from the
boards they are ready for the application of the seasoning
solutions. These vary, and may be applied by hand, with a
452 PRACTICAL TANNING
brush, or on the seasoning machine. Some finishes require
only one application, while others may require a number.
Rolling. — For semi-bright leather the stock is usually
worked on a rolling-jack. This machine consists of an arm to
which a steel roll is attached. This roll, in playing on the bed
of the machine, imparts a smooth surface to the leather with
Figure 102.— Rear end of heaters, Sturtevant dryer, showing steam
and drip connections.
which it comes in contact. Patterns are also sometimes em-
bossed on the roller.
Glazing. — For leather which is to be finished with a high
gloss the glazing-jack is used. This machine somewhat re-
sembles the rolling-jack, except that the arm is provided with
a glass cylinder which remains stationary, and in passing over
the bed causes a certain amount of friction. The heat pro-
duced thus imparts a bright polish to the leather. Two types
of such machines are shown in figures 110 and 111, while a
"line" in operation is shown in figure 112.
Ironing. — When a dull finish is desired, the stock, in the
case of chrome-tanned leather, is oiled and then ironed with
FINISHING LEATHER " 453
a hot flat iron. The same result may also be obtained on a
smooth plate machine as described under embossing.
Embossing. — When it is desired to impart an artificial grain
to a leather it is placed between the plates of an embossing
machine. These machines are capable of great pressure, and
may be used for smooth-plating or embossing as desired.
Such machines are shown in a previous chapter.
Figure 103.— Sturtevant leather dryer, double tube, showing drying
trucks.
Boarding.— For some finishes, and when a soft leather is
required, it is customary to work the rolled, glazed, or em-
bossed stock on the table with an arm board. By the fold-
ing action thus produced the grain is raised and various ef-
fects are obtained.
Measuring.— As all light leather is sold by the square foot,
it becomes necessary to take measurements. Several ma-
chines are on the market for this purpose, but they all work
on the same principle. Figure 113 illustrates a Turner meas-
uring machine.
Sorting.— The skins are sorted and made ready for market
as shown in figure 114.
Having briefly outlined the steps employed in finishing light
454 PRACTICAL TANNING
leather we will now notice their application to the various
kinds and grades of leather.
Finishing chrome-tanned sheepskins. — After chrome-
tanned sheepskins have been dyed and fat-liquored, they are
struck out and the grain is oiled lightly with a mixture of
1 part of neat's foot oil and 3 parts of paraffin oil for glazed
finish, and equal parts of neat's foot and paraffin oils for dull
Figure 104. — End of two tubes of Sturtevant dryer, showing skins
hanging from chain belt-conveyor.
finish. Care must be taken not to give the skins too much fat-
liquor as this makes them too soft and spongy. After the
grain has been oiled the skins are hung up to dry. The best
results are obtained from rather slow drying in a room with
a temperature of about 80° F., and having a good circula-
tion of air.
When dry, the skins are dampened Imd staked. A satis-
factory way to dampen them is to put about a dozen skins
into a tub two-thirds full of water, leaving them two or
three minutes therein, then placing them in a well-covered
pile on the floor or in a box. When they have become pli-
able they are staked and re-staked, and then tacked on boards
FINISHING LEATHER
455
to dry. When thoroughly dry, they are taken off the boards,
trimmed, and prepared for the work of finishing.
Black glased finish. — Where the. grain of the leather is
greasy, it is advisable to apply a dilute solution of acid to
clear it. Either lactic or formic acid may be used. The
acid, diluted with water, is rubbed into the grain and the
leather is dried. Then the grain should be rubbed with a
Figure 105.— Looking into the end of Sturtevant leather dryer, show-
ing skins on conveyor.
soft cloth and given the first coat of seasoning. The acid as-
sists in getting a clear, bright finish.
An excellent seasoning for black-glazed finish is made of
the following ingredients : ivory soap, 1 lb. ; glue, 1 lb. ; log-
wood crystals, 3 oz. ; nigrosine, 4 oz. ; potassium dichromate,
| oz. ; fresh beef blood, 2 quarts.
Dissolve the soap and glue each in 8 gallons of boiling
water; dissolve the logwood and nigrosine in 2 gallons of
hot water, and add the dichromate ; when cold, add the blood.
Take 1 quart of the glue solution and 1 quart of soap solu-
tion, and mix into the logwood and blood solution; stir well
and strain. Rub a light coat of this seasoning into the grain
456
PRACTICAL TANNING
of the leather. Dry in a warm room and glaze. Apply a
second coat of seasoning, dry, and glaze again. Finally, after
the finish has aged a little, oil it very lightly with warm fin-
ishing oil or with a mixture of equal parts of neat's foot and
paraffin oils.
The following formula also produces an excellent season-
ing for glazed finish : whole flaxseed, 2 oz. ; logwood crystals,
Figure 106. — Standard staking machine.
2 oz. ; nigrosine, 2 oz. ; potassium dichromate, ^ oz. ; blood,
1 quart; glycerine, \ pint; and carbolic acid crystals, 1 oz.
Boil the flaxseed 30 minutes in 1 gallon of water; then
strain the solution and add the logwood, nigrosine, and di-
chromate and boil again; then cool the solution to 90° F., and
stir in the blood, glycerine, and carbolic acid. There should
be 2 gallons of seasoning. If there is less, add enough cold
water to make the quantity specified. Apply the dressing to
the skins, dry, and glaze in the usual manner.
Another formula for glazed finish is : blood albumen, 1 lb. ;
black nigrosine, 5 oz. ; logwood crystals, 1 oz. ; and denatured
alcohol, | pint.
FINISHING LEATHER
457
Dissolve the blood albumen by standing over night in 1
quart of water. Boil the nigrosine and logwood in 3 gallons
of water. When the solution is cold, add the albumen and
alcohol. Give the skins two coats of this seasoning, and glaze
them twice.
When the grain of the leather is greasy, it is best to rub
Figure 107.— Staking, or softening and stretching the damp stock.
in a solution of alcohol and black nigrosine. Dissolve 1 oz.
of nigrosine in 1 gallon of water and add a little alcohol.
Rub this into the grain of the skins, and apply the seasoning
when dry. The black is deepened by this treatment and the
grain is cleared.
A solution of oil-soluble nigrosine in benzine is beneficial
in touching up spots which are not a good black.
A kid finish on black sheepskins can be secured by the use
of the following seasoning: logwood liquor, 6 quarts; beef
blood, 2 quarts; orchil, \ pint; water, 1 quart; ammonia, \
pint; and milk, \ pint.
There are excellent seasonings on the market, so the tanner
•158
PRACTICAL TANNING
can buy them and dispense with the labor of making his own
finishes. This is done by many, who find it convenient and
advantageous.
Seasoning for dull finish. — The following is a good prescrip-
tion : ivory soap, 1 lb. ; flaxseed, -| lb. ; beeswax. 4 oz. ; black
nigrosine, 4 oz. ; gelatine, 4 oz. ; aloes, 2 oz. ; and denatured
alcohol, | pint. Put the soap, flaxseed, and beeswax into 2
Figure 108. — Perching goatskins, sometimes termed re-staking.
gallons of water and boil 30 minutes, then add the nigrosine.
Dissolve the gelatine in 1 quart of water and add to the solu-
tion. Then dissolve the aloes in the alcohol, add to the other
solution, and strain the mixture. Apply a coat of this dressing
to the grain of the leather, rubbing it in well. When it is
dry, iron the leather, and then give it a second dressing, but
do not iron it again. As a finishing touch, oil the grain with
paraffin oil.
Seasoning for colored sheepskins. — 1. A clear, bright fin-
ish is obtained on colored sheepskins by using a seasoning
made of 4 gallons of egg-albumen solution, 1 oz. of potassium
FINISHING LEATHER
459
dichromate, 2 quarts of acetic acid, and 20 gallons of water.
The ingredients should be mixed thoroughly. The seasoning
should be applied sparingly so that the grain and wool pits
will show when the leather is glazed.
A glazed finish is obtained on russet and colored leather
by using the following dressing: Dissolve 4 oz. of blood albu-
Figure 109. — Buffing room in a goatskin tannery.
men by standing over night in 1 gallon of water; cook 4 oz.
of granulated gelatin in 1 gallon of water and let it cool ; mix
I pint of white shellac varnish with \ pint of ammonia; mix
the three solutions thoroughly, add enough water to make
three gallons, apply to the skins with a sponge, and glaze
when dry. For colored skins, use a little less ammonia and
make the finish a week before it is to be used, so that the
ammonia will evaporate. For a plain natural finish, give the
leather two coats of finish and roll it while it is wet, hang
it up to dry, and then give it another coat of dressing. Boil
1 lb. of flaxseed for some time with 3^ gallons of water.
Strain the solution before using it, and beat it up the same
460
PRACTICAL TANNING
as the white of an egg. To a pail of water add 1^ pints of
milk, the whites of two eggs well beaten, and |- pint of flax-
seed liquor also well beaten up. This finish should be put on
evenly and without streaks by means of a soft sponge or a
sheepskin pad. When it has been put on, the skins are hung-
up to dry and then rolled.
If embossed leather is required, the skins should be sea-
Figure 110. — Bower glazing machine.
soned and then embossed by an embossing machine. Imita-
tions of seal, monkey, alligator, and other skins are made in
this way. Beautiful effects are produced when the leather
has been properly tanned and colored.
Finish for embossed sheepskins. — These skins, tanned by a
vegetable process, and to be grained or embossed, can be sea-
soned with the following finish: 2 oz. of casein; 2 oz. of
orange shellac ; f oz. ammonia ; and 1 gallon of water. Let
stand over night, or until solution is complete. Add 1 gallon
of water and \ oz. of glycerine, mixing all together. Apply
FINISHING LEATHER
461
with a sponge, and dry. The skins are then ready for glassing
on the machine. After glassing, they may be grained by arm
board and embossed, which is the final operation.
Finish for black embossed sheepskins. — A lasting finish is
obtained by using this dressing on skins that are to be printed,
grained, pebbled, or embossed. Put 8 oz. of extract of log-
Wood, 1 oz. of potassium dichromate and 2 oz. of prussiate
of potash in 2 gallons of water, and boil until dissolved; cool,
Figure 111. — Flat bed glazing machine.
and strain. To each gallon of the solution add either 2 quarts
of beef blood or blood albumen. Give the skins an even coat
of this dressing and let them dry. When the leather is ready
to be printed or embossed, dampen the grain evenly so that
it will take the impression without the grain being cut. Then
print, grain, emboss or pebble according to the grain desired.
Skins may be embossed in a dry state on a modern embossing
machine, although a certain amount of heat is used to make
the impression easier and more permanent.
On some kinds of embossed leather it is desirable to have
462
PRACTICAL TANNING
the crevices of the grain a lighter shade than the upper sur-
face, which gives the leather a shaded appearance. To obtain
this effect, the skins should be embossed first, and then col-
ored by hand on the table. This not only produces the desired
appearance as regards color, but also leaves the flesh clean
and uncolored. East India skins are nicely colored this way.
Figure 112. — A line of glazing-jacks for producing a bright finish on
glazed kid.
When skins are colored first and then dried and embossed,
the plate of the machine should be large enough to cover an
entire skin, so that there .will be no plate marks on either the
flesh or grain side. To keep the flesh smooth and free from
plate marks a thick piece of cowhide split should be spread
over the bottom bed of the machine. The skins to be em-
bossed are placed grain side up on this split. The plate then
comes down on the grain and embosses it, while the flesh side
remains smooth. Before embossing, the grain must be sea-
soned and glazed with considerable pressure, so that it will be
flattened out and smooth. Two or three glazings are gener-
FINISHING LEATHER 463
ally needed to get the right finish. When a sort of crushed
or wrinkled grain is desired, strong tan liquor is used, which
contracts the grain. Embossing is generally more satisfac-
tory, as it produces a more uniform result.
Very thin fancy leather is obtained by boarding or emboss-
ing plump skins and then splitting them. The grain should
Figure 113. — Segment measuring machine.
be diced by rolling with a diced roller and then hand-boarded.
The flesh splits are finished into ooze leather.
De-greasing sheepskins. — As already stated, much of the
natural grease in sheepskins can be removed by pressing in
a hydraulic press previous to tanning, or while the goods are
in the limed or the pickled condition, preferably the latter.
Pressing before tanning is always advisable, yet this method
is not always as effectual as might be desired, especially when
colored leather is to be produced. Treatment with naphtha in
liquid or gaseous form is therefore often resorted to. This
method of de-greasing usually removes every particle of grease
and oil from the leather. It is used after the tanned skins
464 PRACTICAL TANNING
have been dried and before they are finished. The work of
de-greasing with naphtha should be done in a building apart
from the main factory, and no fire or open light should be
allowed near the naphtha vats.
The skins are immersed in the naphtha in a tank or closed
vessel or drum, which either revolves or in which they can
Figure 114. — Sorting finished skins.
be stirred or otherwise agitated to ensure rapid and thorough
permeation of the naphtha. By processing the greasy leather
in this manner the liquid becomes so thoroughly saturated
with the oily matter extracted that it will take up no more.
If one bath is not sufficient to extract all of the grease, the
skins are removed to a fresh bath. They may be repeatedly
subjected to a fresh supply of naphtha, until the liquid in
which they are last placed remains pure and shows no trace of
oil or grease. The action of the naphtha is harmless, and no
strength of the leather is lost by this treatment. The leather
can be de-greased by soaking it in the fluid for several hours
and then pressing out the naphtha with a slicker. On a
FINISHING LEATHER 465
small scale, the work can be done by throwing the skins in
loosely and separately, and stirring them about for an hour
or two. Light skins show a difference after they have been
in the liquid a half -hour. When they seem sufficiently de-
greased they should be taken from the naphtha, pressed out
with a slicker, and then hung up until the naphtha is entirely
evaporated.
Finish for India-tanned leather. — India-tanned skins are
finished in various ways. Large quantities are finished in
smooth glaze and dull; some are grained with a roller or em-
bossed and then boarded up by hand ; and others are glazed
and grained. For some purposes, such as bags, belts, etc.,
they are hand-grained three ways, which gives a round and
half-round grain. To get a diced grain, the skins are rolled
with a straight grain roller and then grained crosswise; after
this they are boarded up, which softens them and produces a
uniform grain similar to the box grain. Some skins are peb-
bled and then boarded. The finish depends upon the purpose
for which the leather is to be used.
Black glased finish. — The skins, after they have been staked,
are in condition to be finished. Seasoning for glazed finish
is applied and rubbed into the grain. The skins are then
dried in a warm room and glazed. A second coat of season-
ing is then applied, dried and glazed. Sometimes it is advis-
able to stake the skins again after the first staking and be-
fore the second application of seasoning.
Smooth dull finish. — A fine dull finish and soft, full skins
are obtained by giving them after staking a coat of dull dress-
ing, drying and ironing, after which they are staked lightly.
Finish for colored skins. — An egg-albumen solution pro-
duces a fine glazed finish. Apply with a sponge and glaze
when it is dry. Egg-albumen is used for light shades, and
blood albumen for dark shades.
Re-tanning with chrome liquor. — Soft, durable leather is
made by re-tanning India-tanned skins with one-bath chrome
liquor. The skins are first sorted and all superfluous parts
trimmed off; they are then soaked and shaved. After shav-
466 PRACTICAL TANNING
ing, they are washed thoroughly, drained a few hours, and
then re-tanned with chrome liquor. Any good one-bath liquor
may be used. A stain can be added to the liquor, and re-
tanning and staining performed in one operation. When the
re-tanning is completed the leather is washed, pressed or
struck out, dyed, dried, and finished.
Morocco finish. — There are three different ways of giving
the leather a grain or the "morocco finish," as it is called. The
best way is by graining it up naturally without giving it any
false grain. This is done by a cork board when the skin is
wet. The grain of the skin is turned to the grain and
pushed backward and forward in eight ways, turning the
skin each time. This method throws up a beautiful grain
and makes a regular morocco figure. Heavy skins throw up
a large grain, while the grain of light skins is fine and small.
To hold this grain the skins are hung in a hot room to dry.
This, of course, makes them hard and stiff, and it is neces-
sary to go through the same work again, only with the skin
dry instead of wet. This method keeps the former grain and
makes the leather soft and pliable.
Another good way, where prices enter into the question,
is to take the skins from the dry room, wet them and put
them under a jig roll. This is a small steel roll about 6 inches
long, cut with indentations, so that the roll under great pres-
sure on wet leather gives a pebbled or morocco figure. This
also must be dried in, then wet down, and hand-grained just
as the natural grain skin. This gives a beautiful regular
morocco grain which will not pull out or flatten; and it is
done without deterioration to the leather itself.
The least desirable way, though much used, and really the
best known among bookbinders, is embossing. The objec-
tionable feature to this process is that, to keep the figure in,
it is necessary to use heat. This injures the fibers and the
grain, leaving the leather with an unnatural grain. No good
work should be embossed. The process is most suitable for
sheepskins or other skins when no other method will do, or
else for any poor stock which cannot be finished in any other
FINISHING LEATHER * 467
way. The grain can be made bright by glazing at any time
during these processes.
The leather is next split. The grains are used for book-
binding and other purposes, while the splits are made into ooze
stock, which is used for pillows, linings, covering handles of
golf sticks, etc.
Crushed Levant grain. — This is obtained by embossing, then
seasoning and glazing to flatten out the grain. Two or three
glazings are needed to get the desired finish. The colors are
generally blue, red, green, brown, tan, and wine. To get the
best results in coloring it is advisable to emboss the skins and
color them on the table, this giving the crevices of the grain a
lighter hue than the upper surface, besides leaving the flesh
clean and white.
Plump leather always takes a good grain in boarding. For
boarded grains it is best to roll them with a diced or straight
grain roller. Should the latter be used, the skin should be
rolled diagonally to form a small diamond, and afterwards
hand boarded. The leather, if sufficiently plump, can be split
so that the grain will be of the desired weight. The grains
finished as described are used for collar and cuff-boxes, belts,
hand-bags, pocketbooks, music rolls, etc.
Ooze or suede leather. — India-tanned skins having defective
grain can be made into ooze or flesh-finished leather more
profitably than into other grades. Softness and good color
are the essential qualities, as well as a short, smooth nap.
The following describes the methods used in finishing India-
tanned ooze leather : The skins are sorted, and those having
good grain are colored and finished on the grain; while those
having poor grain are thrown aside for ooze finish. The im-
perfect skins are thoroughly washed and cleansed of dirt and
surplus tanning material, struck out to rid them of surplus
water and snuffed on the wet wheel.
The next process is re-tanning with sumac, which not only
re-tans the skins, but also prepares them for coloring. The
sumac is applied in a warm solution in a drum, and the skins
are then colored. Coloring is usually done in a drum, the
468 PRACTICAL TANNING
tumbling and pounding being necessary to carry the color into
the leather. After the skins are colored they are fat-liquored,
dried, staked, and rolled.
Finishing skivers. — The work under this heading covers
a large assortment of grains, rolled or embossed, as well as
glazed. After the skins have been fluffed lightly, if required,
they should be given a coat of Irish moss solution on the
flesh, this having the effect of making them feel firm and
stout. A practical way of making up the moss mucilage is
by boiling gently equal parts by volume of Irish moss and
water for about two hours, after which the solution is care-
fully strained. When it is cold, it is ready for use.
A coat of moss is applied to the flesh side, and the skivers
are slowly dried out. The flaming, or filling of the grain,
follows, the solution for this purpose being made from 10 oz.
of liquid blood albumen, 1 oz. of milk, and 1 quart of water.
Apply liberally with a brush, as this class of skivers requires
considerable nourishing. A suitable seasoning is then applied
with a pad.
At this stage the skivers are laid under damp blankets for
not less than 12 hours, when they are ready for the machine
work. If the goods are for long grains they should be first
well rolled with a dull roller — either a No. 4 or 5 — from belly
to belly, two or three times if necessary, taking care to bring up
a good color. Next break the skins down on the flesh side,
with a hand board covered with rubber, air off and then glaze
carefully. This has the effect of giving them a good level
face and also flattens the roller work.
The skivers are now embossed on the plate machine with
whatever grain is desired. If, however, the goods are for
straight grains, they should be first rolled with a No. 7 size
roller, lightly boarded on the flesh, and then cut through with
a No. 4 to separate the "oat" which has been made by the
No. 7 roller, and finally lightly finished off on the glazing ma-
chine. Goods for cross-grains should be rolled on the cross
with a No. 5, boarded on the flesh, well glazed, and then
boarded again on the grain. For plain glazed skivers great
FINISHING LEATHER - 469
care should be taken in glazing, no matter what class of ma-
chine they are to be glazed on; it should be in perfect condi-
tion and should have a good level stroke. Too much pressure
must not be used, otherwise the goods will be very brittle, and
it will be difficult to finish without tearing. Such goods should
be well glazed, aired off with a little heat if possible, and then
lightly drummed.
For glace embossed skiver grains, only the stoutest skivers
should be selected; those showing ribby marks should be re-
jected. Skins showing rough flesh should be cleaned up by
a light fluffing on the wheel, care being taken that the carbo-
rundum or emery wheel is not rough enough to leave marks.
Then give the skivers a good coat of Irish moss solution of
about the same strength as that for flat finishing. Next fill
in with a solution composed of 8 oz. of liquid blood albumen,
1 oz. of milk, and 1 quart of water, adding a little color solu-
tion if desired.
The goods are now dried slowly; if dried too rapidly they
will be harsh and liable to crack. When dry, they can be
broken down on the flesh side with the rubber-faced hand
board, and placed between damp sacks for about an hour,
when they are ready for embossing to the grain required. In
the embossing, the impression of the print is, of course, left
on the flesh side; or, to be exact, the impression on the grain
side is, of course, raised up on the flesh side, and vice versa.
By running the fluffing wheel lightly over the flesh side it only
touches the skin where the raised parts are ; consequently this
part of the skin is left a little thinner, and the glazing tool
cannot get to the .bottom of these parts, being held by the
raised parts of the print. The friction caused by glazing
darkens the goods or brings out the color, the result being
a lighter shade between the scales and what appears a much
more natural grain. The skivers are now ready for season-
ing and the final work of finishing. There are great possi-
bilities in this class of work, as frequently there is a fresh
design on the market, while there is a constant and increasing
demand for both' glazed and plain embossed skivers. The
4.70 PRACTICAL TANNING
above notes on the finishing of skivers is taken from 77: j
Leather World.
Seasoning for chrome calfskins. — After the skins have
been trimmed, apply a coat of finishing seasoning, dry, and
finish. Make the seasoning of 1| lb. of ivory soap, 3 oz. of
French gelatin©, and 3 oz. of blood albumen.
Shave the soap into 6 quarts of water and boil until dis-.
solved. Dissolve the gelatine in 1 quart of hot water. When
both solutions have cooled, mix, and stir them together. Soak
the blood albumen over night in 2 quarts of water at 90° F.
In the morning stir the soap into it. Strain a quart of the
finish into 6 quarts of warm water. Apply a coat of the dress-
ing to the leather, allow it to dry, then stake lightly and give
a second application, and dry again. When the leather is
still somewhat moist, roll it; then dry and jack it lightly, using
a piece of hard felt instead of the glass. The pressure must
be light, or the leather will show shaded spots.
Bright finish, smooth or boarded. — This is obtained in the
following manner : Apply to the staked and trimmed leather a
coat of seasoning for glazed finish, and when it is dry, glaze
under moderate pressure. Then put on a coat of finishing oil
and iron the leather. A second coat of glaze seasoning is then
applied, and after it is dry, the leather is glazed again. This
gives a popular and smooth finish. If a box grain is desired,
board the skins after the second glazing.
Glazed finish. — When the leather has a clean, dry grain it
is not difficult to get a good bright finish, and only a little
seasoning or finishing solution is required. Such a finish can-
not be secured where the grain is greasy, when too much sea-
soning is applied, or when the pressure of the glazing machine
is too high.
A small quantity of ammonia or alcohol may be added to
the seasoning to overcome oily grain, but either must be used
sparingly or it will give a dry feel to the leather, and the fin-
ish will fly off during glazing. Blood seasoning is satisfac-
tory for ordinary glazed finish. Sponging the grain with a
dilute solution of formic or lactic acid cuts surface grease.
FINISHING LEATHER 471
and when the grain has dried, the leather is in condition to be
seasoned and finished.
Give the grain an application of the seasoning, rubbing it in
well. Hang the leather up to dry, and then glaze it. Next
give a second coat of seasoning, dry, and stake the skins; then
glaze them a second time.
Seasoning for black glased finish. — Whole flaxseed, 2 oz. ;
logwood crystals, 2 oz. ; nigrosine, 2 oz. ; potassium dichrom-
ate, \ oz. ; vinette, \ pint; beef blood, 1 quart; glycerine, \
pint; and crystal carbolic acid, 1 ounce.
Boil the flaxseed for a half-hour in a gallon of water, and
then strain. Add the logwood, nigrosine, and dichromate.
When the mixture has cooled to 90° F., add vinette, blood,
glycerine and carbolic acid. Stir the mixture thoroughly, and
if there is less than 2 gallons, add enough cold water to make
it up to that amount.
Boarded or box finish.— -The leather for boarded grain
should be glazed and then grain-pressed. To obtain a sharp
and regular grain it is best to press the leather before board-
ing or graining it. A powerful press and sharp-cut rolls are
required. The skins are boarded first from head to tail, then
from side to side. The grain is then oiled the same as for
smooth finish.
Smooth dull finish. — Take the skins from the tacking
frames and trim them. Apply a coat of dull dressing to the
grain and let it dry; then give another coat and dry again.
Finally, iron the leather with, a hot iron, then stake it. Fin-
ished in this way the leather has a fine break and feel, and
is soft and full.
Where the grain is bad, a light snuffing is required to im-
prove its appearance. Some finishers simply apply a coat of
the dressing and allow it to dry. A coat of finishing oil is
then applied and the leather is ironed.
Seasoning for black dull finish. The same finish may be
applied here as given under sheepskins.
Gun-metal finish.— -To get this finish, after trimming, the
472 PRACTICAL TANNING
skins are glazed and staked. Next apply a coat of gum trag-
acanth, 1 oz. ; yellow dyestuff, \ oz. ; and seasoning for glazed
finish, 1 gallon ; after which dry and iron the leather, then oil
the grain with hot oil.
Soak the gum tragacanth for 24 hours in 2 quarts of water ;
then stir it until it is dissolved. Dissolve the yellow dye in
1 quart of water. Take 1 gallon of the seasoning for glazed
finish and stir in 1 quart of the gum solution. Then add the
solution of yellow dye, a little at a time, stirring thoroughly,
until the color of the mixture has changed from black to
greenish-black. Too much yellow dye must be avoided, other-
wise the finish will be too green. For oiling off, after finish-
ing, use a mixture of equal parts of paraffin and neat's foot,
or any other good finishing oil.
Finishing chrome goat leather. — The skins having been
colored and fat-liquored, the next operation is setting out the
grain of the leather by hand or on a machine, and applying
a solution of glycerine in water — equal parts of each. The
leather is then placed grain-to-grain over a horse and left for
an hour or two. It is then set out again, somewhat harder
than before, and given an application of oil on the grain. .The
leather should be thoroughly set out, all wrinkles and marks
of the tool removed, and the grain laid down flat and smooth.
Any one of the following oils may then be used : Neat's
foot, olive, sperm, or any other leather oil; mixtures of neat's
foot and olive, or neat's foot and paraffin oils are good also.
For instance, equal parts of- neat's foot and paraffin oils make
a good oil for either dull or glazed finish. It is good prac-
tice to apply the oil warm. The skins are next hung up to
dry. Colored leather should be dried in a darkened room,
while the drying of the black leather is effected most satis-
factorily in a warm room provided with fans to keep the air
in circulation.
The dry leather should be kept in a clean, dry room until
it is desired to finish it; it is then sammied and staked.
Staking and drying should be continued until the skins are
worked out dry and soft. It is well to stake the skins both
FINISHING LEATHER 473
ways on the machine. The necks and shanks are often staked
by hand.
To remove roughness from the flesh, the leather may be
run on an emery wheel or on a buffing machine. It is then
seasoned and finished.
Clearing the grain from grease. — Dissolve 1 oz. of black
nigrosine in 1 gallon of boiling water, and when the solu-
tion is cold, add a small quantity of wood alcohol. Apply
this to the grain of the leather, rubbing it in well, then ap-
ply the seasoning for glazed finish.
Blacking defective spots. — Oil-soluble black aniline, dis-
solved in benzine, and applied with a sponge to spots which
are not well blacked, dyes them at once and improves the color
of the leather.
Black glaze finish. — A brilliant black glazed finish can be
obtained by using one of the seasonings prepared in accord-
ance with the formulas given under sheepskins. The season-
ing or finishing solution should be rubbed well into the grain,
a light and uniform coat being applied. Two applications of
seasoning are always required to get a good finish, and fre-
quently it is advisable to apply a third coat. After the sea-
soning has been applied, the skins are dried and glazed ; then
the second coat is put on, the skins dried again and glazed,
the operation sometimes being repeated four or five times.
The finishing of glazed leather requires skill and care. The
luster must be clear and bright and the grain well worked
down. After glazing is completed, the leather receives a light
application of finishing oil; it is then sorted into grades and
tied up in bundles.
Seasoning for colored leather. — The same methods as given
under sheepskin and calfskin apply equally well to this class
of stock.
Dull finish. — When dull-finished leather is required, the
skins are staked and trimmed, then given a coat of finish,
dried, given another application of finish, dried again, and
ironed with a hot iron. Heavy skins should be staked lightly
474 PRACTICAL TANNING
after ironing, which makes them softer and fuller than when
this is not done.
Finish for kangaroo leather. — The glazed and dull fin-
ishes may be obtained by following the same procedure as
given under goatskins.
If colored kangaroo is desired, the instructions given for
calfskins should be followed.
Finishing chrome side leather. — After having been fat-
liquored, the leather should be placed over horses to press
and drain until the next day, and then thoroughly set out and
oiled on the grain side. For glazed leather, use 1 part neat's
foot oil and 3 parts paraffin oil, or equal parts of olive and
paraffin oils, or treated cod oil, giving the grain a light appli-
cation, and then hanging the leather up to dry.
Dull-finished leather may be oiled with treated neat's foot
or cod oil, with dull morocco dressing oil, or with a mixture
of neat's foot and paraffin oils. The oil should be applied
evenly over each piece of leather, and it is best to warm it be-
fore using it. No oil should be put onto the flanks. After
having been oiled, the leather should be hung up to dry in a
room having a temperature of about 80° F., and there should
be a good circulation of air so that it will not dry too rap-
idly or have a parched appearance. When dry, it is sam-
mied and staked, and after having been staked, it is tacked
out smoothly and allowed to dry. It is then trimmed and sea-
soned for finishing.
Dull finish. — A coat of dull dressing is applied to the grain
of the leather, and another coat is given when it is dry. The
leather is next dried and ironed with a hot iron, then staked
lightly. When well tanned and fat-liquored, the leather, fin-
ished in this manner, is soft and full, and has a fine, tough
grain.
Glazed finish. — The leather is trimmed and staked, and
given a coat of finish and dried. The next operation is glaz-
ing. Then the leather is given another coat of finish, dried
and staked, and glazed again. If the finish is satisfactory, a
light coat of finishing oil, or a mixture of neat's foot and
FINISHING LEATHER 475
paraffin oil, is applied to preserve the finish. The leather
not infrequently requires a third coat of finish and a third
glazing to make it satisfactory.
Boarded finish. — The leather is treated as for smooth glazed
finish, and after the second glazing it is boarded from head
to tail, then across from side to side, and oiled lightly.
Dull English grain leather is given a coat of seasoning,
dried, rolled on a heavy jack with heavy pressure, then
grained and oiled heavily with a mixture of neat's foot and
paraffin oils. To obtain a sharp and regular box grain, the
leather is pressed with a powerful press and sharp-cut rolls
before it is boarded. Boarding and oiling are the finishing-
touches.
Gun-metal finish. — This finish is secured by giving the
leather a coat of bright seasoning, drying, glazing, and staking.
A coat of the following finish is next applied, and when it is
dry, the grain is ironed and oiled off with hot oil : gum
tragacanth, 1 oz. ; yellow dye, 2 oz. ; and seasoning for glazed
finish, 1 gallon.
Storm-grain leather. — For chrome-tanned oil-grain or
storm-grain leather the following formula makes a good
finish : gelatine, | lb. ; nigrosine, 2 oz. ; olive oil, 1 pint ; and
ammonia, \ pint.
Dissolve the gelatine in 2 gallons of water; add the nigro-
sine, and heat until gelatine and nigrosine are dissolved. Cool
the mixture, and just before it begins to thicken, add the oil
and ammonia, and stir thoroughly. After the leather has
been seasoned and grained, oil the grain with a mixture of
neat's foot and finishing oils, applied hot. Another finish
suitable for heavy grain leather is made of \ lb. of green-olive
soap, 1 quart of moellon degras, 4 oz. of Irish moss, 2 oz. of
logwood crystals, and 2 oz. of nigrosine.
Boil all together in 1 gallon of water for 20 minutes; cool,
strain, and add water to make 2 gallons of finish. Apply this
dressing liberally, and when the leather is half dry, roll it
on a heavy jack, applying heavy pressure. Then grain the
leather and oil off with hot oil. The leather should be rolled
476 PRACTICAL TANNING
while it is damp as this treatment produces a smoother grain
and a more uniform break when graining.
Finish for colored leather. — The same procedure should be
followed as given under sheepskins and calfskins.
Heavy chrome grain leather. — Heavy chrome leather made
from the grains of split hides and from heavy calfskins is
used in the manufacture of boots and shoes for sportsmen,
etc. This leather is soft and waterproof, due to the chrome
tannage and oils used in finishing it. The colors are black,
tan, and chocolate. The leather is very durable and is well
suited to such purposes. Hides to be made into this leather
are split out of the limes, and the grains 'are then bated,
pickled, and tanned in a one-bath chrome process.
Fat-liquoring is done in the usual manner after the leather
has been washed, neutralized, and shaved.' A good fat-liquor
for 100 lb. of leather consists of 2 lb. of neat's foot oil, 2 lb.
of soap and 1^ lb. of degras, thoroughly emulsified. The
leather is drummed with this liquor for 40 minutes, and is
then blacked by hand with logwood and striker, or with a
direct chrome black. When a direct black is used, it is ad-
visable to add a small quantity of gambier to the fat-liquor,
or drum the leather in the gambier liquor before grain black-
ing. Where it is desired to color both flesh and grain, the
leather is drummed in the dye in the usual manner, but where
the grain only is to be blacked, dyeing is done by hand or on
a machine. After having been dyed, the leather is washed,
set out, hung up, and partly dried. A heavy coat of oil is next
applied to the grain to make it soft and waterproof. A thick
fat-liquor emulsion may be used for this purpose, also sul-
phonated oil in concentrated form. The grains are horsed-up,
grain-to-grain, for 24 hours, and then hung on hooks by the
hind shanks to dry. Little staking is necessary, particularly
if the leather is staked while it is drying.
If a boarded finish is desired, the leather is grained in two
or three directions, and a finish consisting of soap, oil, bees-
wax, and water — or a dull, oily dressing — is applied to the
grain which is later on brushed, oiled again, and the stock is
FINISHING LEATHER 477
then sorted into grades. Printing or embossing with the box
grain and then boarding the leather makes a fine grain which
does not readily become smooth. For the shades of dark
tan and brown, a mordant of gambier and fustic is used,
coloring being effected with basic dyes. This is done best
before the leather is fat-liquored, as grease applied before col-
oring is likely to prevent penetration of the color into the
goods. Smooth finish is obtained by ironing or rolling the
leather before the seasoning is quite dry. Excellent colors
are also obtained by using acid dyes and sodium bisulphate
after the leather has been fat-liquored.
Black chrome oil grain leather. — This leather is usually
made from good plump hides weighing not over 50 lb. each
green-salted weight. Splitting is done after liming, or after
the sides have been tanned and pressed. In the latter case,
re-tanning with chrome liquor is necessary. Neutralizing,
washing, and shaving is done in the usual manner, and the
leather is then blacked with hematin (logwood) crystals and
direct chrome black; and after it has been washed and pressed
it is ready to be fat-liquored. It is best to press the leather
hard and then to put it into a dry mill and run for a half-hour.
Before the fat-liquor is applied, the leather should be spread
on a table, grain side up, and the flanks and bellies dampened
so that they will not take as much grease as the remainder
of the leather.
The following quantities of grease in fat-liquoring are re-
quired for 100 lb. of pressed leather: 8 lb. of stearine, 6 lb.
of tallow, 2 lb. of degras, and 2 lb. of sod oil. These stuffing
greases are put into a kettle and heated to 190 F. The
leather is first run for 10 minutes in a hot drum, then given
the hot grease and drummed 45 minutes, and 10 minutes with
the door off. It is next piled in a box, covered up, and al-
lowed to lie over night. The next morning it is struck out
on the flesh side, then on the grain side, and hung up 5 or
6 hours. It is then re-set on the grain side and tacked on
frames to dry. In re-setting it is necessary to use a setting
slush so that the leather will stick to the table. This is made
478 PRACTICAL TANNING
of 3 lb. of degras and 3 quarts of finishing oil, melted to-
gether; then dissolve 1 lb. of soap in 1 gallon of water, and
stir in the degras and finishing oil. Add enough cold water
to make 6 gallons of the mixture.
When dry on the frames, the leather is shaved lightly on
the flesh side in the shaving machine, which gives a clean
back. A clean, dry, and greaseless back is essential on this
leather, as shoes made from it are frequently unlined. The
leather is trimmed and staked, then boarded from back shank
to neck and from front shank to tail, this making what is
known as English grain. After it has been thus grained, the
leather is given two coats of finish and hung up until the finish
is dry. It is then measured and grained lightly, just enough
pressure being applied to bring up the grain. The leather is
now ready to be sorted and tied into bundles.
Leather for sporting goods. — Chrome leather is used in the
manufacture of sporting goods, such as punching-bags, foot-
balls and baseball gloves. Light hides and kips work into
this class of stock more profitably than larger or smaller
skins. The flesh splits taken from the hides can be finished
into cheap glove and mitten leather.
After having been tanned, washed, and shaved, the leather
is colored and fat-liquored. The use of sulphonated oil as a
fat-liquor, or a mixture of it and neat's foot oil, is especially
suitable for this leather. For the shades of color most in
demand it is advisable to fat-liquor first and color afterwards.
When dry, the leather is dampened, staked, and tacked out
to dry. It is then trimmed, re-staked lightly, and put into
a dry drum together with 5 lb. of talc for one dozen skins
and drummed two hours. The grain is then brushed with a
soft brush and the skins are measured and sorted.
Finishing vegetable-tanned grains into black leather. —
The goods after being fully tanned, are washed, struck out,
shaved, and re-tanned with sumac at 90° F. The leather is
put first into a sumac liquor which has been used for a pre-
vious pack, and after 24 hours is placed in a new bath. It
is then horsed-up, set-out, oiled on the grain with cod oil or
FINISHING LEATHER 479
other leather oil, hung in the air, struck out on the flesh, and
fat-liquored on the flesh with a mixture of degras and cod
oil, applied sparingly in order to avoid greasy grain. In place
of this fat-liquor, the following may be used for 100 lb. of
leather: 5 pints of cod oil, 5 pints of moellon degras, 5 lb.
of soap, 5 oz. of borax, and 15 gallons of water. After fat-
liquoring, the grains are struck out on the flesh and grain
and dried, stored a week or two, and then dyed black. If
the grain only is to be blacked, it is brushed with a direct
leather black. The grain is then oiled, and the leather is
partly dried, boarded in several directions, laid in a pile over
night, cleaned on the grain with a little barberry juice, dried,
and rubbed with a soft flannel rag. To obtain a bright finish,
a glaze seasoning is applied ; and when dry, the grain is glazed,
boarded again, given another coat of finish, dried, glazed,
and finally boarded again. Where smooth grain is desired,
boarding is, of course, omitted. The flesh side may be stained
by the addition of a suitable dye to the fat-liquor, and the
grain blacked afterwards.
Finish for bright boarded grain leather. — Dissolve 4 oz. of
logwood extract and 4 oz. of gelatine in 3 gallons of soft
water. When cold, add 2 oz. of ammonia, 1 gallon of beef
blood, 1 pint of milk, 2 oz. of ferric chloride, and 2 oz. of
spirits of camphor. Mix 1 oz. of gelatine in milk before
putting into the finish ; then stir together, putting in the iron
and camphor after the other ingredients have been worked
together.
The dry leather should be dampened, staked, and tacked;
and the grain should then be dampened with warm, weak log-
wood liquor before it is finished. As soon as the grain is
dry, apply the first coat of seasoning; dry again, and polish
on the jack. After polishing, dampen the leather and let
it lie awhile to allow the dampness to penetrate evenly; then
grain from tail to foreshank and from hindshank to top of
shoulder, and soft-board crosswise on the flesh side. Dry
the leather, and then finish graining by boarding on the grain
side crosswise and lengthwise. Next apply two light coats
480 PRACTICAL TANNING
of seasoning, the first being allowed to dry before the second
is added. When the last coat is dry, the leather is ready for
the last polishing. Sufficient pressure should be used to cause
the grain to disappear and bring the brightness from the bot-
tom of the impression of the print. After polishing, the
leather is staked and given the last graining. Grain four
ways on the grain side — very lightly — and the result will be
a fine, even grain, very black and glossy. The finishing touch
is a light coat of hot oil, made of equal parts of raw linseed,
paraffin, and sweet oils. After being oiled, allow the leather
to lie in a pile for a few days before it is sorted and rolled
into bundles. Dull-boarded leather is made in the same man-
ner, except that dull dressing is used. Printed grains are
made by printing and graining the leather with the grain
figure desired.
Finishing rough leather. — Stock selected for bags and
suitcases should be of a good light color, of soft tannage, and
free from scratches, grubs, salt and bark stains. The best
results are secured from sides that measure, when finished,
about 24 sq. ft. each, and 14 lb. weight to the side should be
the limit. The rough leather is weighed and trimmed, 25
sides making a pack of convenient size. Wet the sides down
over night, and stone them on the jack in the morning. Skive
them on the belt-knife machine and split them from 2 to 4-J
oz. per foot. The lighter leather will be the more suitable
for suitcases and the heavier for bags.
The next process is washing with borax preparatory to
bleaching. If the leather is dark, dirty, and greasy, more
borax is required than for light, clean stock. Use 25 gal-
lons of warm water, and from 2 to 6 lb. of borax for the
25 sides. Run the leather in this borax solution for 15 min-
utes, then drain off the water and wash the leather in warm
water to remove the surplus tannin and borax. The leather
is now ready for the acid bath. Mix 1 gallon of sulphuric
acid with 40 gallons of water and run the hides in the solu-
tion for 10 minutes; drain the liquor out of the drum, and
wash the leather with 3 to 4 changes of water, using 25 gal-
FINISHING LEATHER 481
Ions at each change. The leather should be washed until no
trace of acid can be detected in the water coming from the
drum. More or less acid may be used, according to the re-
quirements of the leather.
Next put the leather into the clean drum, with a strong, hot
sumac liquor, and drum for a half -hour. Some tanners add
^ pint of tin crystals and a pint of hydrochloric acid to the
sumac liquor; others add only salt. Take the leather out,
and place it in piles for 24 hours ; then rinse it in clear warm
water to wash off the sumac, and strike the flesh out hard.
If the sides are to be colored in a drum they are now in good
condition for that process. If they are to be dried first, give
them a coat of cod oil on the grain, and tack them on frames
to dry. The leather should be run in the color bath for 30
minutes, then rinsed and horsed-up. One way is to hang it
up to dry after rinsing, without setting out as this works the
dye into the flanks and sides. When dry, the leather may be
dampened, set out on the grain, given a light coat of oil, and
tacked on frames to dry. Another way consists of fat-liq-
oring rather lightly after coloring, using fig soap and egg-
yolk in equal proportions ; next horsing-up the leather for 24
hours, slicking hard on flesh and lightly on the grain, then
tacking out to dry. When dry, the leather is seasoned and
finished. If russet leather is required, the stock, after rins-
ing from the sumac bath, is finished without coloring.
After the sides are dry, stake them and give the grain
a coat of cornmeal filling. This is made by boiling slowly
for a half-hour 1 quart of cornmeal in 1 gallon of water.
Allow the paste to cool, then strain, and give the leather a
good coat, rubbing it in hard. When it is struck in well,
roll the leather and hang it up to dry. It is then ready for
the seasoning.
For colored and russet leathers, the following finish may
also be recommended : Dissolve 4 oz. of blood albumen by
standing in 1 gallon water over night; boil 4 oz. of granu-
lated gelatine in 1 gallon of water and let it cool ; and mix |
pint of white varnish shellac with \ pint of ammonia. Mix
482 PRACTICAL TANNING
these three materials together, add enough water to make 3
gallons, and let this finish stand a week before using it. Apply
with a sponge. For a bright finish, dry and glaze ; and for a
dull finish, give two coats and roll while wet; then hang up
to dry, and when dry, apply another coat. Finish by grain-
ing, printing, or embossing. For a black finish, use any of
the formulas given under calfskins.
Finishing imperfect grains into patent tipping. — Among
the stock tanned for bag and case leathers, on which a perfect
grain is essential, after the hides are split grains are found
which are imperfect and therefore not suitable for finishing
with the more perfect ones. Such grains can be made into
patent tipping, on which, the grain being buffed off, such im-
perfections are not noticeable. The grains are taken from
the splitting machine and washed in 50 gallons of warm water
to which 1 or 2 lb. of borax or washing soda has been added
for each 50 sides. The leather is washed in this water for
30 minutes, then in cold water for 15 minutes.
Re-tanning is done with a one-bath chrome liquor, the
grains being run in a drum with the liquor for 2 hours, then
piled down over night. The next morning they are washed
in running water for 20 minutes. Three quarts of extract
of fustic are next dissolved in a half-barrel of water, and the
leather is drummed in the solution a half-hour, after which
it is fat-liquored.
Fifty sides may be fat-liquored with 2 lb. of neutral chip
soap and 9 lb. of the best moellon degras in 50 gallons of
water. The leather is run in this fat-liquor a half-hour, then
piled down over night. To prepare it for finishing it is set
out and tacked on frames to dry. When dry, it is buffed
and staked, and is then in condition to be japanned and
finished.
Dressing for leather goods and furniture. — A dressing
for goods made of leather and for leather furniture is made
as follows: Put \ pint of hot water, -} oz. of annetto, and
} oz. of white soap shaved fine, into a bowl, and place the
bowl in a pan of boiling water. Into another bowl put | oz.
FINISHING LEATHER - 483
of beeswax, shaved fine, and put it in the pan of boiling water.
Stir the contents of both bowls until they are melted, then
remove them from the fire. Into the melted wax stir | pint
of turpentine, \ pint of paraffin oil, and then the mixture of
annetto, soap, and water. Beat the mixture until it is cold,
then put it in a fruit jar for future use. This preparation
may be used on brown or red leather. First wash the leather
with hot milk, using a soft cloth or sponge. If the leather
is faded, the dressing may be made darker by using two or
three times the quantity of annetto. For dark green or black
leather, a little logwood should be added to the dressing.
Removing spots and stains from leather. — Colored
leather, which is simply soiled or dirty and not stained, may
be washed off with warm castile or ivory soap suds, then
dried and rubbed. A dirty water stain is sometimes taken
out with the juice of a lemon, which is the mildest acid that
can be used. Vinegar also is employed for water and other
stains.
An oil spot may be removed by dipping a piece of rub-
ber in naphtha and rubbing over the spot. Another way is to
cover the spot with cement such as is used in shoe factories,
and after the cement has dried for an hour or a little longer,
rub or roll it off with the finger. If a little remains, go over
it with the rubber dipped in naphtha. For dirt from the
hands, a little oxalic acid well diluted may be used. Wash
the dirt off and then wash with soap and water, and perhaps
apply a little of the finish. An aniline stain cannot very well
be taken out, but it may be helped somewhat with a rubber.
Some of the aniline can be washed off with a regular wash,
as with soap and water. However, the stained part of the
leather cannot be made to look like the rest, because it has
soaked through more or less. It depends much upon the
leather as to how far aniline will penetrate. There are var-
ious preparations available which shoe manufacturers use for
stains, and some of these are employed to clean and polish
vamps in one or more operations. Leather which becomes
stained or discolored should be re-dyed into black stock.
484 PRACTICAL TANNING
Grease spots sometimes get onto the leather from oil from
pulleys or shafting, and may be taken out with shoemaker's
cement and chalk. Put the cement on first, then lay the
chalk on, and work both into the leather with the flat of a
knife or by other means. The cement will eat into the grease,
and it should stay on until the grease comes out, even if it
takes 24 hours or more. Use pure rubber cement for this
purpose, as a cheap article is likely to stain the leather. The
cement will dry after a little while so that it can be rolled off.
Another method is to place a piece of cloth or some cotton
waste saturated with naphtha over the spot. This is covered
with another cloth to prevent too rapid evaporation. More
than one application may be necessary as the grease or stain
must dry out gradually. It is the naphtha in the cement that
removes the grease; and it might be applied in any other form,
provided not enough is used to bleach the leather. Slight
spots may be rubbed out dry with a cloth saturated with
naphtha. Ether is sometimes used.
White ooze leather, and possibly also white grain leather,
that has become soiled, may be cleansed with salts of sorrel
(potassium acid oxalate, which can be procured at any drug
store). Cold water is applied to the leather, washing it all
over. A mixture of salt and lemon juice or salts of sorrel,
is then rubbed over the soiled portion, with the result that all
the spots, stains, and dirt marks disappear, and the leather
is once more white. The leather should always be washed
with water, which must be rubbed over the entire skin ; but
the mixture of salt and lemon juice is applied only to the
soiled portion.
Bright blacking varnish for shoe leather. — This varnish
is useful in producing a bright polish on grain shoe leather
of any tannage. Dissolve in a bottle, tightly corked, 1 oz.
of caoutchouc in 1 oz. of carbon bisulphide, and let the solu-
tion stand for a few days. Next dissolve 3 oz. of orange
shellac, | oz. of gum sandarac, 1| oz. of gum mastic, and
5 oz. of pure Venetian turpentine in 2 quarts of alcohol. Add
the turpentine after the other gums are dissolved. When all
FINISHING LEATHER 485
three materials are well mixed, add the caoutchouc solution.
Put the vessel containing the complete mixture in another
vessel of hot water, and heat to about 120° F. Then add 1
oz. of spirit soluble black. Keep the whole for about an hour
in water at 120° F. Then put it in a jar, cork tightly, and
let it stand at least two weeks before using, as it improves
with age.
Two thin coats should be evenly spread on the grain with
a sponge, and well rubbed in with a fine sponge or with a
soft hair brush in a warm room. Let the first coat dry be-
fore applying the second. After the last coat is absorbed,
glaze the leather slightly by hand to produce the soft feel the
stock had before the varnish was applied.
A waterproof leather dressing.— Petrolatum, 4 lb. ; Bur-
gundy pitch, 4 oz. ; rosin, 2 oz. ; ivory black (dry), 6 oz. ; and
beeswax, 4 oz. Melt the rosin, pitch, and beeswax together,
then add the petrolatum, and when it is melted, stir in the
ivory black and continue stirring until the mixture is cold.
Apply the dressing. to the leather with a soft cloth and rub
in well. If the leather is dirty, wash it with a sponge and
a little soap before applying the dressing. This gives a good
black but not a polish, and if used properly, it will make
leather soft and pliable, no matter how hard or water-soaked
it has become. A strap treated in this way may be immersed
in water for a week without absorbing any. Used as shoe
dressing, it renders the wearing of rubbers unnecessary.
A harness blacking.— Mutton suet, 2 oz. ; yellow wax, 6
oz. ; powdered sugar, 4 oz. ; yellow soap, 2 oz. ; lampblack,
1 oz. ; indigo, 4 oz. ; and oil of turpentine, 4 oz. Dissolve the
soap in the water; add the other ingredients, except the tur-
pentine ; melt and mix thoroughly together ; then add the tur-
pentine. This mixture is applied with a sponge and polished
with a brush.
Blacking for vegetable-tanned leather.— The following
is a good blacking for heavy shoe and harness leather : cop-
peras", 9 lb. ; epsom salts, 4 oz. ; acetic acid, 6 oz. ; and nutgalls,
1 oz. Put these ingredients into 2 gallons of soft water and
486 PRACTICAL TANNING
boil until dissolved; then put the solution into a barrel and
add 40 gallons of water; stir thoroughly, and the blacking is
ready for use.
If the leather has a loose and open grain it is advisable to
use 4 or 5 gallons of strong gambier liquor in place of the
same amount of water. This will tighten up the grain and
prevent it from piping when finished.
Sigs for greasy leather. — To make one barrel of sig to
clear the grain of greasy leather before applying logwood,
use the following: salts of tartar, 12 lb.; sodium dichrom-
ate, 5 lb.; ammonia (26°), 1 quart; and water, 40 gallons.
Boil the tartar and dichromate in 12 gallons of water, and
when dissolved, make up to 40 gallons, and then add the am-
monia, stirring thoroughly. If kept for any length of time
it may be necessary to add more ammonia.
An excellent sig is also made as follows : Use a 50-gallon
barrel, and boil 12 oz. of caustic soda and 12 oz. of salts of
tartar in 12 gallons of water, and when dissolved, fill the
barrel with cold water.
Finishing splits: Chrome-tanned splits. — The splits taken
off chrome-tanned hides may be finished into gusset splits or
glove and mitten leather in much the same manner as the
grains. First they should be leveled on the split side and
then shaved to a uniform thickness. It is generally neces-
sary to re-tan by drumming first in hot water and then in a
one-bath chrome liquor for 3 or 4 hours, leaving them in the
liquor over night. They should then be drummed for 30
minutes, taken out, and placed in smooth piles for 48 hours.
Washing is the next process, which is done in the same manner
as grains are washed and neutralized ; after which the splits
are colored. For black leather, a direct color is preferred.
There are special black ooze dyes which are satisfactory for
chrome splits, dyeing being effected in one operation, this
rendering the use of logwood unnecessary. Some dyers pre-
fer to use logwood first and top with the direct black. The
general procedure when both dyes are employed is to use H
lb. of logwood crystals and 4 oz. of fustic extract in 12 gal-
FINISHING LEATHER 487
Ions of water for 100 lb. of leather. This liquor is used at
125° F., and the splits are drummed in it for 30 minutes.
Then 12 oz. of direct black is dissolved in 2 gallons of boil-
ing water, the solution is poured into the drum, and the splits
run 15 minutes longer. Any suitable striker is next added to
the drum, and after 10 minutes the dyeing is completed. The
use of titanium-potassium oxalate is recommended for this
purpose. The splits should be washed thoroughly after they
have been dyed, pressed, and fat-liquored. If the leather is
for mitten stock and some shade of yellow is desired, a yel-
low dye suitable for chrome leather should be employed. Spe-
cial glove dyes are procurable with instructions for their use.
For mitten leather, the splits are fat-liquored once ; for gusset
splits, twice. After applying the first fat-liquor, hang the
splits up to dry; when dry, put them into the drum with hot
water, and run it 40 minutes; then drain off the water and
give the leather the second fat-liquor. Let the splits drain
over night; then hang them up to dry. To finish the stock,
put it in the drum with warm water, and run until soft and
moist, or dip into hot water and place in piles over night.
The next day tack the leather on boards, and when dry, run
in a dry drum until soft.
Another way to handle splits is to mill them after the
second drying until they are soft, then stake them as smooth
as possible and measure them. Tacking secures the greatest
measurement and eliminates the "bag." Splits for mitten
leather are treated in the same manner. Softness is, of
course, the most essential quality of glove leather, and is se-
cured by thoroughly tanning and re-tanning, and by applying
plenty of fat-liquor.
Gusset splits are produced not only in black but also in
colors. There are dyes for this which can be used either
before or after the splits have been fat-liquored and dried.
Some dyers fat-liquor and color their leather at one opera-
tion; but the usual practice is to dye first with basic colors
and fat-liquor afterwards. Dyes that are not stripped from
the leather by the fat-liquor are, of course, required. Good
488 PRACTICAL TANNING
penetration of the color is secured by using acid dyes in an
ammonia bath, and after 20 minutes of drumming add formic
acid to the drum, which ensures uniform color throughout
the goods.
Finish for the black. — When splits are dry after stuffing
and setting out, pack them down in a pile for a few days;
then whiten lightly on the back and to a fine face on the
flesh side to be finished. Now' trim the edges and place the
stock flesh side up on a table for the back finish. Make a
paste for the back finish by mixing 2 lb. each of red lead
and yellow ocher and pour in slowly and stir 1 gallon of
cold water. Dissolve 1 lb. of corn starch in 1 gallon of cold
water. Boil the red lead and ocher, pour in the starch, stir
well and boil thoroughly. Let the finish cool, which is then
ready for use. Spread an even coat on the flesh with a soft
brush. Hang the stock up to dry and then glass with a jack.
If the paste is too thick, add more water; and if it is not the
color desired, change the proportions of lead and ocher to
suit.
Soap black. — To make a soap black, dissolve 12 lb. of com-
mon soap in a half-barrel of water, with 2 lb. of potassium
carbonate. Add from 12 to 15 lb. of lampblack according
to quality. Boil slowly after the lampblack has been mixed in.
Next add 2 pails of strong logwood liquor and 1 lb. of in-
digo, and boil and stir thoroughly; then fill the barrel with
cold water and add 1 pint of chloride of iron. Spread this
black with one brush and rub it in with another. Sweep any
smut off with a duster. If the glassing is to be done by hand,
glass immediately after blacking. If the stock is glassed with
a jack, hang the splits up after blacking before glassing. When
the black is dry, they are ready to be jack-glassed.
Flour paste. — For pasting, make a stiff flour paste by mix-
ing 4 quarts of flour in 2 gallons of cold water. Add a little
water at a time and stir to prevent lumps forming. When
thoroughly mixed, boil for 10 minutes with live steam; then
add -J lb. of tallow and | lb. of common soap, and boil until
thoroughly cooked. Let the paste cool, and spread evenly a
FINISHING LEATHER 489
fairly heavy coat with a fine sponge. Hang up the splits,, and
after the paste is dry, glass either with jack or by hand. If
the splits will stand it, they can be oiled over the most solid
parts on the black side. Good judgment must be used in oil-
ing so as not to have the stock show the oil after it is finished.
For finishing, give an even coat of gum-tragacanth dissolved
to a thin substance. When dry, the splits are ready to be
sorted.
Finishing splits into Goodyears, chair splits, etc. — The splits
are taken from the splitting machine and trimmed, then put
into a mill with a weak tanning liquor of 6 to 8° bk., and
milled one hour. This process breaks up the crust made by
the belt-knife, and opens up the splits so they will take the
re-tan liquor. When milled, they can be re-tanned in a mill
or put back into the tan-yard for 3 weeks, using a strong
liquor. The splits should be pulled out of the liquor every
other day and allowed to drain for 4 to 6 hours, the liquor
strengthened, and the splits put back one at a time. If the
tanning is done in a mill, it will take about 6 days to make a
good split. The splits should be milled in strong liquor about
2 hours each day, and then left in piles the remainder of the
day. This operation is repeated daily for 6 days, when the
splits will be fully tanned.
When tanned, the splits are sorted, and the heavy ones
may be worked into flexibles or Goodyears, and the light ones
into chair seats.
If flexibles are to be made, the splits are put into the mill
( after lying 48 hours after the last tanning) and given a treat-
ment in a strong solution of epsom salts. This gives a light
color without removing any of the tan. This solution is made
by dissolving 75 lb. of the salts in 50 gallons of water. Use
about 12 gallons of the solution to 8 splits. Drum them 30
minutes, then pile them down over night. The next day set
out and hang up to dry. When dry, dip the splits in warm
water and lay them in piles for 24 hours; then apply a coat
of Irish moss and soap, roll hard, and hang up to dry. When
dry, trim and measure.
490 PRACTICAL TANNING
If Goodyear splits are to be made, the stock must be
trimmed to have the proper bend for this product. The trim-
mings are finished in the same manner as the flexibles and
sold for cheap insoles, the bend being leveled on the splitting
machine. Bends for Goodyears must be of uniform substance.
After they are leveled, they are fat-liquored with soap and
cod oil, using J lb. of soap and 3 lb. of oil to each 100 lb.
of leather. Run them in this fat-liquor and pile them down
over night. Then make up a clearing liquor of 2 lb. of lactic
acid in 16 gallons of water, and run the bends in this for 10
minutes; then dry them out, being careful to have them dry
flat.
When they are dry, make up a paste of 3 lb. of glue, 1
lb. of white soap, 1 lb. of Irish moss, and 1 quart of finish-
ing oil. Soak the glue over night in 3 gallons of water. In
the morning add the soap, moss, and oil, and boil for an
hour, then add enough water to make 10 gallons, and strain.
When cold, give the splits a good heavy coat of this paste and
hang them up until it has struck in; then roll it hard and
treat the other side the same way. When dry, they are
finished.
If the light splits are to be put into chair leather, they are
leveled on the machine, then put in a drum and given a mill-
ing in sumac liquor, using 1 pail of sumac in 12 gallons of
water for a dozen splits. Mill for one hour; then pile them
down for 24 hours, and set-out on both sides and hang up to
dry. Do not hang over sticks. Trim off all the shanks and
thin edges. When they are dry, make up a filling paste of
^ lb. of corn starch, ■£ lb. of dextrine, and 1 lb. of casein
which has been soaked over night in 3 gallons of water, and
boil this mixture slowly for an hour. While boiling, add £
lb. of ivory soap cut into fine shavings. This will make 10
gallons of paste. An acid dye of any color desired can be
added to the paste and the splits made into any color. They
should be given a good coat of this paste, which should be
put on smooth, and when about half-dry, the splits are rolled
hard and dried, when they are in condition to be embossed.
FINISHING LEATHER 491
After embossing they are given a coat of waterproof finish
made by cutting shellac in alcohol, and adding aniline soluble
in spirits to the finish ; using an aniline of the same color as
the splits, the finished goods will have a rich color. These
splits are also often worked into cheap suitcases and bags.
Grain leather from splits. — Imitation grain leather may be
made according to the following instructions : The splits
should be run through a borax bath in a drum, 5 lb. of
borax being sufficient for 25 splits, medium size and weight.
Heat 8 gallons of water to 75° F., and drum 20 minutes.
Then make a bath consisting of 8 gallons with \ lb. of sul-
phuric acid. Drum the splits in this for 15 minutes, then rinse
in clean cold water, washing until the acid is all removed
from the goods, then fat-liquor with 5 lb. of chip soap and
24 lb. of neat's foot oil. Boil the soap in 3 gallons of water
and add the oil, together with 1 oz. of sal soda. Cool to
80° F. and run the goods 30 minutes ; then horse-up to drain.
Next slick hard on both sides and glass on split side. Oil
with linseed oil; then hang up or tack out to dry.
When dry, the splits are ready to receive the color — black,
brown, or any other color. When colored and dry they are
ready for the moss or linseed solution. A good dressing is
made from equal parts of glue and gelatine. Apply when
warm, taking care not to have it too thick, and spread it on
evenly. After the dressing has dried, the goods are em-
bossed either in imitation of some grain or finished plain.
This is a very necessary operation, after which the embossed
side is given a coat of waterproof filling made of wax and
rosin dissolved in turpentine. This is the final finish, and the
leather is now ready for use.
Materials used in finishing leather. — In the finishing of
leather, materials are used that are neither oils, dyes, nor
mordants, and are classified as finishing materials, their func-
tion being to fill the pores and surface of the leather. They
may be divided (1) into products of animal origin, such as
blood and egg albumen, casein, gelatine, isinglass, etc. ; and
(2) products of vegetable origin, such as gums (arabic, traga-
492 PRACTICAL TANNING
canth, and shellac), starches, dextrines, moss, etc. Some of
the materials in common use will be briefly considered :
Blood. — Large quantities of bullock's blood are used in fin-
ishing leather, indeed, many seasoning liquors are nothing but
logwood extract dissolved in warm water and then thickened
with 5 to 10 per cent of blood. The best material to use is
what is commonly known as de-fibrinated blood, which is
blood that has been allowed to clot spontaneously by standing
for several hours in a warm place, and from which the clot
is then filtered. This de-fibrinated blood is practically a solu-
tion of blood albumen. The clot is albuminous but consists
of the organized or cellular structure of the blood, that is,
the blood corpuscles. The coloring matter of the blood is in
the red corpuscles (hemoglobin) and is carried down with
them in the clot, while the filtered blood, if care is taken in
its preparation, is a straw-colored fluid. To prevent putrefac-
tion a preservative should be added to the blood as soon as it
is filtered, carbolic acid or phenol being commonly used.
Nitrobenzol or oil of myrbane is also used and is quite as
effective, and although it costs a little more it is recom-
mended as it is much less poisonous than the phenol and has
a pleasant instead of a disagreeable odor.
Blood albumen. — This is made from the de-fibrinated blood
by simple evaporation in vacuum pans. The evaporation must,
however, be conducted with extreme care so that the tempera-
ture does not rise above 130° F., as above this the albumen
will begin to coagulate, and when once coagulated, is valueless
as a seasoning agent. When evaporated to a paste, the blood
is removed from the pans and placed on screens in a warm air-
drier. In this drier the temperature is even more important
than in the pan, and much albumen is destroyed by overheating.
In the United States, however, where animal by-products like
blood albumen are controlled by large packers, these prepara-
tions are made under scientific supervision, and there is much
less damaged albumen on the market here than in England
and Europe.
FINISHING LEATHER 493
Egg albumen. — This is prepared from the white of the egg,
by far the largest proportion of the world's supply being manu-
factured in China from duck eggs, and some in Russia. The
great advantage that egg albumen has over blood albumen is
its absolute freedom from coloring matter or iron, which
amounts to the same thing, as the red color of blood is due
to iron. For this reason egg albumen is used in the season-
ing of the best qualities of glazed colored leathers. Its cost
is always high — 5 to 8 times that of casein and 2 to 3 times
that of blood albumen — hence it can only be used sparingly
and on the highest-priced goods.
Gelatine and glue. — These are both used to a considerable
extent in finishing leather, and are also interesting to the tan-
ner, as they are, especially the latter, by-products of the tan-
ning industry. While there has been more or less published
on the manufacture of these products, the industry has not
reached a high state of scientific development. This condition
is not the result of lack of chemical investigation, but on ac-
count of the technical character of the subject. The present
varieties of glue are classified as hide or skin glue, the purest
forrn of which is gelatine, bone glue, and fish glue, and to the
last named, isinglass stands in the same relation that gelatine
does to hide glue. All of these varieties have a close chemical
relation to each other, and are unquestionably complex com-
pounds. Two principal constituents of glue have been sepa-
rated, and are known as glutin and chondrin, the one being-
distinguished from the other by different behavior towards
chemical reagents. While, for example, both are precipitated
from their aqueous solution by alcohol, only chondrin is pre-
cipitated by acid, alum, lead acetate, etc. It also contains less
nitrogen than gelatine and more sulphur, and, in general, bears
a closer resemblance to albumen. The glutin imparts the ad-
hesive property to glue, while chondrin is perhaps more essen-
tially the jelly-forming constituent. By treatment with caus-
tic alkalies, by a sort of hydrolysis as it were, chondrin seems
to be converted to a considerable extent into glutin.
494- PRACTICAL TANNING
Chondrin is found in greater proportion in the bones, skins,
and cartilages of young animals, and glutin in the hides of
older animals.
Gelatine. — As already stated, gelatine is the purest form of
skin glue, and is prepared almost wholly from the trimmings
of calfskins, particularly the heads and feet, which are regular
articles of commerce for this purpose. Curiously enough, these
have to be dried first before they will make good gelatine,
showing that a certain degree of dehydration is necessary to
produce the glue-forming products. The first step in the manu-
facturing process is. the washing of the glue stock. This is
accomplished in the ordinary cylindrical washing machine,
not greatly different from that used in laundries. The stock
is then limed for 10 or 12 days, with frequent changes of the
liming liquor. After liming, a treatment with sulphurous
acid is given to remove the lime and also bleach the stock.
Then the stock is thoroughly washed, and given, according
to the most approved processes, a bath of hydrogen peroxide
to complete the bleaching and also oxidize any residual sul-
phurous acid, the presence of even a mere trace of which is
now forbidden by most pure food laws. Sometimes phos-
phoric acid is used in place of the peroxide, its action being
simply that of replacing any sulphurous acid which may be
chemically combined with the stock. The latter is then given
a boiling with live steam, preferably at low pressure, which
effects the conversion into gelatine, which is then drawn off
and allowed to gelatinize. The jelly is cut into slabs, placed
on wire screens and dried by a dry, slightly warmed, air
blast. When thoroughly dried, it is ground in a disintegrator
mill and packed ready for market.
Glue. — The preparation of glue from hides and skins does
not differ materially from that of gelatine, except in the selec-
tion of the stock; the treatment, however, being more rig-
orous, and less care is necessary. When bone glue is made,
the fat is first extracted, preferably with a volatile solvent, and
then the bones are treated with hydrochloric acid to dissolve
FINISHING LEATHER 495
the phosphate of lime which constitutes their mineral matter.
The stock thus obtained is, after washing thoroughly, boiled
to glue in the usual manner.
Isinglass. — This is the purest form of fish glue and is ob-
tained from the "sounds" or air-bladders of fish. The best
quality is made from the sounds of Russian sturgeon, which
are air-dried, thoroughly washed, and boiled to the glue stage.
Ordinary fish glue is made from the scales, skins, and other
offal from fish. It is particularly adhesive glue, but its odor
renders it objectionable for many purposes. In the prepara-
tion of all glues, the essentials are the selection of the stock,
and care in the manufacturing processes, particularly the avoid-
ance of putrefaction and overheating.
Casein, also known as "milk albumen" and "lacterine," pre-
pared in a crude way has been used for centuries as a finish-
ing material on various kinds of upper leather. Without ques-
tion, much of the early Morocco and Oriental leather was fin-
ished with a curd obtained from milk. With cow's milk,
the separation of the curd from the whey and its utilization
as an albuminous material was, in Scotland a hundred or more
years ago, a considerable, if primitive industry. In the anal-
ysis of cow's milk a distinction is made between casein and
milk albumen, and this distinction is recognized chemically,
although commercially, casein is frequently known as milk
albumen. The distinction is due to the fact that milk con-
tains two kinds of albumen, the casein or insoluble albumen,
which separates from the whey when it becomes sour, or
when diluted acid is added to it, and the milk albumen proper,
which closely resembles blood albumen, but is only rendered
insoluble by acidification and heat.
In commerce, the casein is the only product which is util-
ized. This is obtained as a by-product of the butter indus-
try. The whole milk as it comes to the creamery is put
through a centrifugal separator, in which the lighter cream
containing the butter fats is perfectly separated from the
heavier skim milk. When casein is to be produced, the skim
milk must be acidified to separate it. There are three methods
496 PRACTICAL TANNING
of doing this : The milk may be allowed to sour spontaneously,
in which case lactic acid is developed by the fermentation of
the milk sugar, and this lactic acid precipitates the casein; or
sulphuric acid or hydrochloric acid may be added to the milk.
For many purposes the casein precipitated by the lactic acid
is the best product, but its odor is a serious disadvantage.
When milk ferments, not only a lactic fermentation develops
but also putrefactive bacteria, especially of the butyric acid
class, are present, which attack the casein itself, the result
being, even though in slight degree, very bad-smelling com-
pounds, so that for many purposes casein made by this process
is almost impossible to use.
Casein precipitated by sulphuric acid is, on the whole, prob-
ably the best commercial product. It is troublesome to make,
however, as the acid swells up the casein so that it is extremely
bulky, difficult to wash, and must be squeezed in powerful
presses to reduce its bulk and remove the excess of water be-
fore drying. On the other hand, if hydrochloric acid is em-
ployed as a precipitant, the casein comes down granular and
more compact, can be readily washed, and requires no press-
ing. The resulting casein is, however, not so satisfactory, it
being much less soluble in the alkaline mediums, and the yield
is low. The difference in behavior of sulphuric and hydro-
chloric acids is interesting to the leather chemist because it
is analogous to the action observed with these acids in connec-
tion with the swelling of hides, wherein sulphuric acid has
a pronounced plumping effect, while hydrochloric acid in cer-
tain dilutions has just the opposite effect and depletes the
hide. When the casein is precipitated and washed it is dried
in a warm air blast, great care being taken that the tempera-
ture does not rise much over 100° F., otherwise the casein will
become insoluble by overheating. The casein is marketed
either in the form of coarse scales as it comes from the drier,
or is ground to a coarse powder, this product being often
mixed with borax or a mixture of borax and bicarbonate of
soda, and sold as soluble casein. Since borax is much less
expensive than casein, it is more economical to buy the casein
FINISHING LEATHER 497
and dissolve it with the aid of borax, the average proportion
used being 1 lb. of borax to 9 lb. of casein. For most pur-
poses, equally good results may be obtained with 1 lb. of
borax, 2 lb. of soda, and 27 lb. of casein. In the commercial
soluble caseins, the proportion of casein is often, for obvious
reasons, considerably reduced. If, however, a casein requires
more borax than stated to make it dissolve, it is because it has
been overheated in drying.
Irish moss. — The most widely used glutinous substance of
vegetable origin in the finishing of leather is Irish moss, some-
times erroneously called Iceland moss. The true Iceland moss
is a lichen which is found on exposed highlands, notably in
Norway and Sweden, also in the Alps, and is used to a lim-
ited extent in pharmacy. Irish moss or carrageen is found on
all the rocky shores of northern Europe, and is particularly
abundant on the west and northwest coasts of Ireland. In
America, large quantities are gathered off the shores of
Scituate, Massachusetts.
When fresh, the plant varies in color from light yellowish-
green to bright purple and purplish-brown, but after it is
washed and dried in the sun it becomes lighter colored, of a
yellowish or brownish-white shade. Viscous and fleshy when
fresh, it dries to a semi-transparent, horny substance, the
branching form of the plant, though somewhat shrunken, be-
ing preserved. The preparation of Irish moss for the mar-
ket is extremely crude, and it usually contains considerable
quantities of sand and small shells. It is generally possible
to purchase moss which has been prepared with more care
and is reasonably free from these impurities at a little above
the lowest market price, and on account of the quantities used
this course is often the most economical. Large quantities
are also sold in the ground form as a coarse powder, but the
objection to this is the probability that the product is adul-
terated with corn starch.
'Algin. — In England, algin on a large scale is extracted from
seaweed and sold in its purified state for purposes of leather
498 PRACTICAL TANNING
dressing. The method of preparation is described by Lamb
(Leather Dressing, p. 277) as follows:
The dried weeds are first washed thoroughly to remove as much
inorganic matter as possible, and are then dissolved to form a thick
jelly in a boiling solution of caustic soda. It is assumed by this treat-
ment that an alkaline salt — sodium alginate — is produced; from this
salt, by the addition of acid, the algin, or alginic acid, is precipitated.
The precipitated algin is then mixed with a fresh portion of alkaline
salt to form a more nearly neutral alginate and in this form is offered
to the trade.
British reports have been, as a rule, favorable to the product,
but it never has been offered or used extensively in the United
States until recently, when the Hercules Powder Co. under-
took its manufacture at one of its Calif ornian plants. It is
now also being sold in fairly large quantities by another firm
under the trade name of "lissom."
Algin is specially recommended for finishing skivers for
hat leather; also for bookbinding and furniture leathers. Its
action is much more uniform than that of the raw moss, and
its solution keeps better, and it is more adaptable for various
purposes. The addition of a small quantity to dye solutions
as a thickener in table coloring is advocated as giving results
superior to those obtained from flaxseed and gelatine which
are usually employed. It can, however, be used only with
acid dyes, since it precipitates the basic colors.
Shellac. — This is obtained from gum-lac or simply lac,
which is an exudation occurring on the small twigs or branches
of several varieties of East Indian trees. It is produced by
the puncture in the egg-laying operation of the female insect
known as the coccus lacca, an insect similar to that from which
cochineal is obtained. The gummy exudation following the
puncture has the function of furnishing a protective covering
for the eggs and providing food for the maggots. The female
insect expires after laying eggs and is also enclosed by the gum.
The best grades of lac are obtained by breaking off the twigs
before the eggs are hatched. These twigs come into commerce
as "stick-lac." By immersion in boiling water, the gum-lac
is melted from the twigs, and the bodies of the dead insects;
eggs, etc., are removed by straining. The melted lac is then
FINISHING LEATHER - 499
spread out into sheets by pouring it on a slowly revolving sur-
face, the sheets broken into small pieces constituting shellac.
Button lac. — This is obtained by simply pouring the melted
gum on a flat surface so that it solidifies in small disks. Shel-
lac is soluble, as is well known, in alcohol, the solution being
known as shellac varnish. As the solubility of shellac in al-
cohol, however, decreases rapidly with decrease in strength of
the latter, care should be taken, if a tanner or leather finisher
desires to "cut" his own shellac, that he use at least a full 95
per cent alcohol ; also that he keep his alcohol and varnish
well sealed, as high-strength alcohol rapidly dilutes by the ab-
sorption of moisture from the atmosphere. In case the alco-
hol has become diluted, it may be freed from water by shak-
ing it up with fresh quicklime, and then decanting the clear
liquid. Shellac is soluble in aqueous solutions of the alkalies,
and also in a solution of borax, and for many purposes these
solutions, especially that in borax, can economically replace
the alcoholic varnishes ; that is, for those purposes where shel-
lac is used for its adhesive or filling properties.
Pyroxylin. — Collodion, soluble cotton, banana liquid, etc.,
are names given to the solution of nitrated cellulose in various
solvents. Nitrated, or nitro, cellulose was first known in its
highest state of nitration as guncotton, a high explosive, which
is chemically a combination of the cellulose molecule with three
nitric acid radicals. This product is obtained by immersing
thoroughly dried and purified cotton fiber in a mixture of high-
strength nitric and sulphuric acids. It was discovered later
that by immersing cotton in a mixture of somewhat less con-
centrated acids and at a higher temperature a much less explo-
sive compound was obtained. This compound, which is com-
posed of about equal quantities of tetra-nitrocellulose and tri-
nitrocellulose, has the added advantage of being soluble in
mixtures of ether and alcohol, acetone and amyl-acetate, gun-
cotton itself being insoluble or soluble in them with difficulty.
On evaporation of the solvent, a very elastic coating or var-
nish is left behind, the nature of this varnish, however, de-
pending largely upon the solvent employed. The amyl-acetate
500 PRACTICAL TANNING
leaves the toughest and most elastic varnish, and as such is
largely used in the finishing of enameled and patent leathers.
On account of its characteristic odor, the amyl-acetate solu-
tion is frequently called banana liquid, but owing to the high
cost of the amyl-acetate, the solutions are often diluted with
considerable quantities of acetone. Amyl-acetate is obtained
by the action of glacial acetic acid on amyl-alcohol in the
presence of sulphuric acid or potassium bisulphate.
The amyl-alcohol is the chief constituent of fusel oil, a
by-product in the manufacture of ethyl or grain alcohol, the
largest quantities being obtained by the fermentation of a mash
made from potatoes. Besides the use of these cellulose solu-
tions for patent-leather manufacture, their employment in mak-
ing a cement for joining the laps of chrome-tanned belt leather
is of importance to tanners. For this purpose a highly con-
centrated solution in acetone is generally used, and the best
cements contain also ^ to 1 per cent of red oil or castor oil,
which seems to have the effect of making the joint less brittle.
Indeed, it is this small quantity of oil which has been the
secret component of many of the commercial cements, and the
ignorance of its presence prevented belt manufacturers from
successfully making their own cement.
CHAPTER XVI
WOOLSKINS AND FURS
In the preservation of pelts where the natural hair is to
be retained, the processes of manufacture, of course, differ
from those already described. There are many operations,
however, which are similar to those given in the chapter de-
voted to leather manufacture, and as the preparation of furs is
a branch of the leather industry, some mention of the subject
should be made in this volume.
Considerable skill is required in the preparation of furs,
and in many cases extreme care must be exercised.
Tanning woolskins: Soaking, zvashing and scouring. —
Sheepskins that are to be tanned with the wool on, should be
good fresh skins. Old, stale skins should be avoided, as the
wool is likely to slip, for which there is no remedy. The skins
should be trimmed to remove the valueless parts, then fleshed
and washed. After washing, which is best done in a wash
wheel supplied with running water, the pelts should be run
through a burring machine, which removes all the burrs, twigs,
etc. Copper sulphate is of assistance in soaking dry pelts,
1 oz. to 15 gallons of water being sufficient, it acting as a
germicide. Some skins merely require to be washed with
borax and soft soap; others need thorough scouring, which
is done to make the wool as clean and white as possible before
the skins are tanned. It is much easier to wash the wool clean
before than after tanning, as the -alum, salt, and other tanning
materials set the dirt and grease, and make their removal more
difficult.
Scouring is done by laying the skins on a sloping table, ap-
plying the scouring solution first to the flesh and then to the
wool. The liquor may be made of a strong solution of soft
soap, to which a little ammonium carbonate is added; or it
may be a solution of soap, soda ash, and salt made in the fol-
501
502 PRACTICAL TANNING
lowing manner: Add two buckets (14 quarts per bucket) of
soft soap to 50 gallons of water in a vat or tub, then put in a
half-pail of soda ash; turn on steam and boil the soap and
alkali until they are dissolved; add one pail of salt and
enough water to make 200 gallons of liquor. The salt helps
to bleach the wool and also counteracts the caustic action of
the soda ash.
The scouring liquor is first well worked into the skin with
a brush, after which it is poured into and worked thoroughly
among the wool. The skins are next placed in waste scouring
liquor, rinsed in warm water, and then scoured again as much
as they seem to require. They are then rinsed in water until
free from soap, next wrung out or drained thoroughly, after
which they are tanned.
Liming. — The following process of liming is satisfactory :
A solution of 1| per cent of caustic soda is made into a thin
paste by the addition of talc, china clay, or some similar inert
material. This paste is applied to the flesh side, the skins
folded up — flesh in — and allowed to stand 4 or 5 hours. They
are then thrown into a 4 per cent solution of calcium chloride
(4 lb. of calcium chloride in 10 gallons of water) and left
several hours, usually over night. The pelts should then be
washed in water in the drum and de-limed with lactic acid.
About 4 oz. of lactic acid per dozen skins is usually sufficient.
The skins are now ready for tanning (from the Leather
Trades Year Book).
Tanning. — The tanning may be done with a paste of alum,
salt, and flour. Heat 2 gallons of water. to near boiling point,
and stir in powdered alum until the solution is very bitter to
the taste. Add half as much salt as alum, and allow the solu-
tion to cool. Mix some flour with water and add the paste
to the alum and salt liquor. This tanning paste makes the
flesh nice and white. If yellow color is desired, add 1 lb.
of gambier to the paste, this having been dissolved separately.
The skins are spread on a table, flesh side up, and the paste
is spread on evenly and liberally. The skins are then laid
flesh-to-flesh, or folded half over the other half, and left until
WOOLSKINS AND FURS " 503
the next day. The paste should be applied every day for a few
days. The skins should then be hung up to dry, and as they
dry, worked and staked until soft and dry. One pound of
rolled oats may be used in place of the flour, the solution of
alum, salt, and oatmeal being boiled several minutes. The
wet skins may also be tanned by using a mixture of powdered
aluminum sulphate and salt — 2 parts of the former and 2
parts of the latter — or a mixture of powdered alum and salt.
This can be used dry, and rubbed into the flesh side of the
skins every day for several days, when the skins will be fully
tanned.
Another way to tan the skins is to dissolve 8 oz. of alu-
minum sulphate and 6 oz. of salt in a gallon of warm water,
and apply several coats of the solution.
A convenient way to tan the skins is to stretch them on
frames and apply the paste or dry powder to the flesh side.
Alum-tanned skins, before drying, should be given a solu-
tion of soap or stearine which serves to fix the tannage so
that it cannot be so easily removed by washing. Egg-yolk
is also used for the same purpose. Tanning can also be done
by immersing the skins in a solution of alum and salt, then
drying them. Flour added to the tanning paste makes the
skins softer and whiter.
After the skins are dry and soft it is advisable to re-scour
them. This should be done on a table in about the same man-
ner as before tanning.
Bleaching. — A permanent white can be obtained by bleach-
ing the skins with hydrogen peroxide. The bleaching bath is
prepared as follows : Make a 1 per cent solution of sulphuric
acid by mixing 10 lb. of acid in 100 gallons of water. To
this solution add 7 lb. of sodium peroxide, stirring constantly.
The liquor is then tested with litmus paper, and peroxide or
acid is added as required until the solution is neutral; 4 lb.
of sodium silicate, previously dissolved, is then introduced.
The skins are stirred in this liquor for an hour ; then taken
out, passed through a weak solution of sulphuric acid, washed,
drained, re-tanned if necessary, de-greased, and dried. When
504 PRACTICAL TANNING
dry, they are softened and run on an emery wheel to clean the
flesh. Re-tanning is done by applying a solution of alum and
salt to the flesh sides.
Bleaching may also be done with potassium permanganate
and sulphurous acid. The skins are washed and placed in a
solution of permanganate made by dissolving 18 oz. in 120
gallons of water warmed to 95° F. The skins are stirred in
this solution until the wool is a good, rich brown. They are
then removed and drained, and next placed in a bath of so-
dium bisulphite made of 120 gallons of warm water, 7.3
quarts of liquid 33 per cent bisulphite and 6.6 lb. of hydro-
chloric acid. In this liquor they are. worked until they are
sufficiently bleached. They are then rinsed, dried and finished.
De-greasing. — Most of the grease in the skins may be re-
moved by plastering the flesh side with a paste made of whit-
ing and water. The skins are tacked out wet and the paste
of whiting is applied. The skins are then placed in a warm
room and dried. The grease is absorbed by the whiting. The
plaster should be scraped off and another coat applied. This
should be done until the paste dries clean and white. The flesh
is then washed clean, and a mixture of alum and salt is ap-
plied to replace the tanning material removed by de-greasing
and washing.
Some grease may be removed by brushing the skins with
benzine, then rinsing off with hot sumac liquor.
De-greasing may be done with benzine in the following
manner : Make a wooden tray about 1 foot deep, 3 feet wide,
and 4 feet long, with a rack about 1 inch thick to keep the
skins off the bottom of the tray. Only the leather should be
in the benzine. The lid of the tray should be made to fit in
a slot, and be filled with water to prevent evaporation of the
benzine. The skins are then dried and finished.
Tanning with formaldehyde. — The skins limed, and then
de-limed with lactic acid, may be tanned with formaldehyde.
For each 100 parts of pelt, use 1 part of formaldehyde, that
is, about 2\ parts of commercial formaldehyde in a convenient
quantity of water, so that the skins can be immersed in the
WOOLSKrNS AND FURS - 505
solution. The skins are left in from 24 to 48 hours, then neu-
tralized by washing in a bath containing sodium carbonate or
borax, or a mixture of ammonium sulphate and sodium car-
bonate; washed in clean water, drained, and fat-liquored with
a solution of 3 parts of soft soap in 60 parts of water, then
dried and finished.
Tanning with a mineral and vegetable tannage. — The for-
mula for this process of tanning is : aluminum sulphate, 5 lb. ;
common salt, 5 lb.; gambier, 2 lb.; rye flour, 13 oz. ; and
water, 10 gallons.
Dissolve the sulphate and salt in a little water; also dis-
solve the gambier by boiling in a little water. Mix the two
solutions. The rye flour is made into a smooth paste with a
little warm water, and the alum, salt, and gambier solution
are added to the paste, the whole being thoroughly stirred to
a thin paste-like mixture. This is applied to the flesh side of
the skin with a brush, applying a coating about ^ inch thick,
afterwards folding the skins into cushions. The goods, after
lying some time in the wet condition, are hung up and dried.
It is said of this method of tanning that it gives soft and
flexible skins, and the tannage is more durable than the alum
tannage.
Sheep pelts can also be tanned by a chrome process by the
methods described for furs and hair skins.
Tanning zvith gambier. — To tan woolskins with gambier,
first tan them with alum and salt, and then put them into weak
gambier liquor. The dry powdered alum and salt should be
rubbed into the wet skins, two applications being required.
The skins are then tanned with the gambier. For 50 skins
the addition of 1 lb. of picric acid to the gambier liquor colors
the wool a light yellow. The liquor should be rather weak
at the start, and strengthened until the skins are tanned
through. Alum-tanned skins can be colored a light yellow
by immersing them in a solution of picric acid previous to
tanning. After they have been scoured and rinsed, put the
skins into a bath of 15 pails of warm water, to which has
been added 4 oz. of picric acid dissolved in a little water and
506 PRACTICAL TANNING
6 oz. of sulphuric acid. The skins should be moved back-
ward and forward for 15 minutes, then rinsed in water and
tanned with alum and salt.
Tanning with alum, salt and hemlock extract.— Skins tanned
by this process, and then scoured and passed through a weak
bath of sulphuric acid, are made a golden-brown color. The
pelts are soaked and scoured before tanning, special care be
ing taken to get the wool clean. The tanning liquor is made
of alum, salt and extract of hemlock bark which is weak at
the start and strengthened as the tanning proceeds. Some
potash soap should be added to the stronger liquor to help
turn the wool and give the skins a velvety feel. After the
pelts are well tanned they should be drained off and oiled on
the flesh with a good quality of mineral oil, applied warm,
and then hung up to dry. When dry, they are scoured with
a strong solution of potash soap and soda ash. Both wool
and flesh are scoured. The scouring suds are thoroughly
rubbed into the wool and washed out again, the operation be-
ing repeated two or three times. This scouring darkens the
wool. A weak solution of sulphuric acid, made from \ lb.
of acid in 10 gallons of water, is thrown onto the wool
after it has been rinsed free from suds, and should be rubbed
thoroughly into all parts of the wool. It changes the color
of the wool to a light golden brown. The wool is next given
a good blowing out with water from a hose and made as
clean as possible, and the skins are then hung up to dry.
Finishing consists of dampening, arm-crutching, buffing on the
flesh side, and beating the wool soft and clean.
Coloring. — Woolskins and shearlings may be colored any
shade of color by the application of basic or acid dyes. Basic
colors, however, are used chiefly on the cheaper grades of
skins and where no particular demands are made for fast-
ness to rubbing and washing. Where fastness is essential,
acid dyestuffs should be used ; and in order that the skins may
withstand the high temperature required for dyeing, they
should be first subjected to a chrome tannage.
When acid dyestuffs are used, the process of coloring is as
WOOLSKINS AND FURS * 507
follows : The skins are either tanned or re-tanned with one-
bath chrome liquor. 'The temperature of the solution should
be 70° F., and the whole of the flesh side should be exposed to
the liquor. After 2 or 3 hours the skins are lifted out and
a solution of sodium carbonate is added to the chrome liquor;
the skins are put back and left in from 12 to 24 hours, even
longer if thick and heavy. They are then rinsed. Any chrome
liquor may be used, but in any case it is advantageous to add
-|- lb. of formaldehyde to 10 gallons of liquor, which increases
the resistance of the leather to heat.
To increase the affinity of the wool for the dye, the skins
are subjected to a chlorinating process. To do this, the skins
are immersed for 15 minutes in a cold bath containing 1 lb.
of hydrochloric acid in 10 gallons of water. Then, without
rinsing, they are put into a bath of cold water to which is grad-
ually added, in four portions, a clear solution of 8 to 14 oz.
of chloride of lime for each 10 gallons of liquor. After one
hour in this bath, the skins are re-entered into the first bath,
in which they are worked another 15 minutes. They are
then rinsed in lukewarm water containing 3 to 5 oz. of sodium
thiosulphate or bisulphite in 10 gallons of liquor, to remove
the last trace of chlorine. After pressing or hydro-extracting',
the skins are ready for dyeing.
Dyeing. — Black is dyed with naphthylamine black S, ESN,
SS2B, naphthylamine blue black B, BD, naphthol black, also
azo merino black B. Of these dyestuffs, 4 to 6 oz., calculated
on the dry weight of the skins, are required to produce a
deep black. Where basic colors are used, it is advantageous
to treat the skins with acid and chloride of lime as described
for acid dyes, then rinse and pass through a solution of tan-
ning material — say, 2 oz. of sumac, hemlock, cutch, or que-
bracho extract, dissolved in water — immersing for half an
hour, then wash and color. One ounce of basic dye is gener-
ally sufficient for two skins. To the solution of dye, | oz.
of acetic acid and 4 oz. of Glauber's salt should be added. The
temperature of the dye-bath should be from 100 to 110° F.
Good, fast shades of color are also produced by immersing the
508 PRACTICAL TANNING
skins in a bath of sumac, hemlock, or quebracho for a half-
hour, next immersing in a solution of titanium-potassium
oxalate, then coloring with basic dye, 2 oz. of the tanning ex-
tract and 1 oz. of the titanium salt being sufficient for two skins.
To get a slight gloss on the wool, the skins should be
passed through a weak solution of soap and oil, then dried
and finished. Six gallons of stock soap and oil mixture are
made by boiling 6 lb. of soap and 18 lb. of oil and making
up to 6 gallons, ^ pint of this mixture for two skins being
added to 10 gallons of hot water, and the skins, flesh-to-flesh,
are passed through the bath, then dried, softened, and finished.
In addition to the method described for dyeing woolskins
black with acid dyestuffs, a good black can be secured by dye-
ing with logwood, fustic, and potassium dichromate. The
skins should be scoured and rinsed well before they are col-
ored. The first bath consists of \ lb. of the dichromate dis-
solved and added to 10 gallons of water at 100° F. The
skins are doubled, flesh side in, and immersed in the solu-
tion; then they are removed and drained.
The second bath consists of strong logwood liquor to which
some fustic extract and some ammonia have been added; 1^
lb. of logwood crystals, 4 oz. of fustic, and 1 pint of liquid
ammonia being used for 10 gallons of liquor. The tempera-
ture of this bath should be 120° F., and the skins should re-
main in it until every part has been colored; they should then
be drained and immersed in a bath of 1 lb. of dichromate in
10 gallons of water. After the skins have been passed through
the liquor they should be drained, and the wool should re-
ceive an application of seal oil, well rubbed in, drained, washed,
dried, and finished.
Another process of dyeing woolskins black is as follows :
For a dozen skins, a bath is prepared of 80 gallons of water,
20 lb. of logwood extract, 3^ lb. of fustic extract, and 2 lb.
of verdigris or copper acetate. This bath is heated to 110°
F., and the skins allowed to remain in it for 3 or 4 hours,
the same temperature being maintained during the process ;
2\ quarts of acetate of iron is then added to the bath, and
WOOLSKINS AND FURS ■' 509
the skins left in the liquor until they are dyed black. This
usually requires an immersion of 30 or 40 hours, during which
time the skins are occasionally stirred.
The skins are then drained and allowed to oxidize for at
least 12 hours; they are then washed in warm water and
scoured with a solution of soft soap and ammonium carbonate,
washed and drained. They are finally re-tanned with alum
and salt, and stretched in frames to dry.
A good shade of tan is obtained by putting the skins, after
washing from the tannage, into a sumac bath for a half-
hour, 2 oz. of sumac being used for each pair of skins; next
allow the skins to drain, and then immerse them in a bath of
titanium salt, 1 oz. for two skins. This produces a yellowish-
brown color. Any shade of color can be obtained on skins
treated as described by using 1 oz. of basic dye, ^ oz. of acetic
acid, and 4 oz. of Glauber's salt for every two skins. Colors
produced by acid dyes are faster to rubbing and washing
than colors obtained by using basic dyestuffs.
Tanning furs and hair skins.— M. C. Lamb (previously
mentioned) has described a method of tanning fur skins, which
has advantages over the common alum tannage; the process
is partly mineral and partly vegetable, and skins tanned with
it are soft and durable: The process consists of applying to
the flesh side of the skins a mixture made of alum, salt, gam-
bier, and glycerine. The formula is: aluminum sulphate, 5
lb.; common salt, 5 lb.; gambier, 2 lb.; rye flour, 13 oz. ; and
water, 10 gallons. Dissolve the sulphate and salt in a small
quantity of water, and boil the gambier until it is dissolved,
then mix the two solutions. The rye flour is made into a
thin paste with lukewarm water ; the oil or glycerine is added
to the flour paste ; and finally the alum, salt, and gambier solu-
tion is added, and the whole is thoroughly mixed to a thin
paste-like mixture. To this, | to 1 lb. of glycerine or the
same quantity of olive oil is added to make the skins softer.
This addition is particularly essential when the skins are nat-
urally of hard texture and do not possess much natural grease.
The paste is then applied about i inch thick with a brush to
510 PRACTICAL TANNING
the flesh side of the skin. The skins are then folded or
placed flesh-to-flesh, and after lying for some time, and per-
haps receiving another application of the paste, are hung up
to dry.
Another excellent alum process is described in the Shoe and
Leather Reporter: For the tanning liquor, dissolve 5 lb. of
alum and 6 lb. of salt in 12 gallons of hot water. If the
skins are greasy, the addition of \ lb. of borax to the liquor
is recommended. The liquor should be warmed to 95° F., and
the, skins occasionally moved to make the tanning uniform.
After 24 hours the skins should be removed and coated on the
flesn side with a paste made of alum, salt, and flour. The
following formula makes sufficient paste for 100 lb. of skins :
alum, 4 lb. ; salt, 3 lb. ; flour, 4 lb. ; egg-yolk, 1 lb. ; and olive
oil, 1 lb.
The flour is made into a paste with water; the alum and
salt are dissolved separately in boiling water. When the so-
lution is cool, the flour paste is stirred into it, and after the
mixture has been thoroughly stirred, the egg-yolk and olive
oil are added. The primary object of the flour is to obtain
a mixture in a semi-pasty form so that it will adhere to the
skins. If the above quantity is not sufficient to make the
mixture sufficiently pasty, either less water should be used in
dissolving the alum and salt, or more flour should be used in
making the paste. The flour also helps to give fuller leather.
The egg-yolk and olive oil give softness to the skins. For
the finer furs, a small quantity of egg-yolk is quite essential.
Where economy is desired, olive oil may be substituted for
the egg-yolk, with similar results. Instead of giving a pre-
liminary treatment in alum liquors, the tannage may consist
of the application of the paste only. The skins should be
allowed to lie for some time with alum paste adhering to
them, which makes the tannage more complete and permanent.
If it is desired to dye the furs with acid colors, it is neces-
sary to wash them after they have been dried and worked
soft, and re-tan them with chrome liquor.
Soft, white, and well-tanned skins are obtained by tanning
WOOLSKINS AND FURS " 511
with a paste of alum, salt, and oatmeal. Heat 1 gallon of
water and stir into it 1 lb. of pulverized alum, then add half
as much salt as alum and boil until these are dissolved. While
the solution is boiling, add -J lb. of rolled oats, boil 15 min-
utes, and then set the paste aside to cool. By adding a few
ounces of gambier to the liquor and boiling again, the skins
treated with it will be given a light yellow color.
The cleaned and softened skins are spread out on a table,
flesh side up, and a heavy coat of the prepared paste is ap-
plied with a brush. This painting is repeated every day un-
til the skins are tanned, which takes from 2 to 6 days, ac-
cording to their thickness. When tanned, the skins are hung
up to dry, then stretched and worked out soft and white. The
fur is cleaned with dry, hot sawdust, and the flesh made per-
fectly clean and smooth by buffing on an emery wheel.
When a large number of skins are to be cleaned a drum
or cage is used; on a small scale they may be tramped on or
pounded in a barrel or tub, or cleaned by brushing the hot
sawdust into the fur with the hands, and then beating it out
.with a supple stick. Hardwood sawdust is better than that
from pine.
Washing greasy skins. — Skins containing a good deal of
natural grease should be washed in a warm solution of sal
soda and then scraped over the beam, and the grease forced
out of them. Dogskins should be fleshed dry, that is, before
they are soaked, as in this condition they flesh more easily
than after soaking.
To wash greasy skins, prepare a warm solution of sal soda
by dissolving the salt in water heated to 90° F. Dip the
skins into this solution long enough to get them wet and hot,
then put them upon the beam and go over them with a flesher
or dull knife, bearing down hard and forcing the grease out.
The dipping and scraping should be repeated until the skins
are free from grease. They are then rinsed, drained and
tanned.
Oil process. — Furs can be tanned satisfactorily with seal
oil. The goods are first freed from superfluous moisture by
512 PRACTICAL TANNING
draining or hydro-extracting, and are then rubbed over on
the flesh with a good quality of seal oil. The skins are folded
into cushions, flesh side innermost, and placed in a large
wooden tub. Impregnation of the skins with the oil is facil-
itated by a workman treading the goods with his bare feet,
thoroughly trampling the skins down and thereby working
the oil into them. The goods, after being worked in this way,
are left for several hours, and then another application is
made, and the process repeated. When the goods have be-
come thoroughly impregnated with the oil, they are laid in a
pile. Care must be taken that they do not reach a tempera-
ture higher than 100 to 104° F. A tannage effected in this
way is somewhat similar to that used in the dressing of chamois
leather, and depends on the decomposition of the oil and the
production of aldehydes. When thoroughly tanned, the goods
are rinsed through a weak alkaline solution for the purpose of
removing undecomposed oil and grease, and then are subse-
quently dried. This is the so-called "furriers' dress process."
To aid in this method of oil tannage the skins are sometimes
tumbled in small drums until the heat of reaction is produced.
Oiling alum-tanned skins. — Skins that have been tanned
with an alum paste containing oil or egg-yolk do not require
further oiling to make them soft, but where no oil is used in
the tanning paste it is advisable to apply a coat of oil after
the skins have been tanned and dressed down, or partly dried.
Sulphonated neat's foot oil is satisfactory; so is a good min-
eral oil. Mop the oil over the flesh of the skins, let them lie
on a pile for a day or two, then hang up to dry. Working
out and cleaning in sawdust completes the work.
A solution of soap, also one of stearine, is recommended
for alum-tanned skins. The use of either of these fixes the
tannage and makes it more permanent.
Deodorizing furs and rugs. — The following solution is
useful for removing objectionable odor from furs, rugs, etc.
Put 8 lb. of tanner's soap, or any other good bar soap,
chipped fine, into 4 gallons of water. Add 7 lb. of sal soda.
Boil until the soap and soda are dissolved, and while the solu-
WOOLSKINS AND FURS 513
tion is hot, add 1| oz. of borax and 1 oz. of oil of sassafras.
Put the solution aside to cool, and it is then ready for use.
This liquor can be used on skunk skins, but they should not
be rinsed out before tanning. After the skins have been dried
and cleaned it will be found that the bad odor has disappeared.
Cleaning furs. — Dark furs may be cleaned with bran or
with warm cedar, mahogany, or other hardwood sawdust.
Beat the skin gently with a stick and brush it until it is free
from dust, then lay it on a table with the hair side up and
rub the hot sawdust or bran through the fur. Use plenty
of sawdust and rub vigorously. After this, beat and brush
the fur until it is free from sawdust or bran and is clean and
fluffy. White furs can be cleaned in the same manner except
that white cornmeal is used instead of sawdust. The corn-
meal should be used warm. Soiled places may be cleaned by
rubbing with cube magnesia. Allow the powder to remain in
the fur for a day, then brush it out thoroughly.
Professionals clean fur garments, muffs, etc., by dipping
into gasoline until they are clean. They are then dried and
the gloss is produced by passing bread crust lightly with the
grain of the fur.
Liming. — Where the skins are subjected to a liming - process
before they are tanned, they work out very soft and elastic.
In this case, however, liming is a process different from liming
for leather. In the latter process the hair is loosened, but
in liming fur skins and sheep pelts the hair or wool is not
affected. The process is the same as that described under
woolskins.
Chrome-tanned furs and woolskins. — In order that the
tannage of furs and woolskins may be permanent, that is,
not affected by moisture, and the leather made as durable as
possible, it is advisable to tan with one-bath chrome liquor.
A commercial liquor may be used or any good one-bath chrome
liquor employed. Where furs are to be dyed in hot dye-
liquors, \ lb. of formaldehyde should be added to 10 gallons
of chrome liquor to increase the resistance of the skins to
heat. The skins are placed in this liquor and paddled for two
514 PRACTICAL TANNING
hours or drummed one hour. At the end of that time, 3 lb.
of washing soda in solution is added to the liquor and the
process is continued an hour or two longer if in the drum; or
the skins are left in the liquor from 12 to 24 hours if in a
paddle. They are then drained several hours, and if not to be
dyed, they are neutralized by being washed in water contain-
ing 2 or 3 per cent of borax, reckoned on the wet weight of
the skins, using sufficient water to work the furs nicely. After
this has 'been done, the skins are well washed with clean water.
After the furs have been washed and drained, a fat-liquor
is applied to the flesh side. Any light chrome leather fat-
liquor may be used, and applied in the drum or brushed on the
skins. Instead of applying the liquor in a drum, a hot solu-
tion of sulphonated oil and flour, or of the oil alone, or a
mixture of egg-yolk and flour, may be applied to the flesh
side, the skins folded and left until the next day and then
hung up to dry. An excellent method of chrome-tanning
furs, hair skins, and sheep pelts is carried out in the follow-
ing manner : The skins are soaked, fleshed, and washed clean ;
they are next plumped with caustic soda and calcium chloride
in the manner previously described, then neutralized with lac-
tic or formic acid and tanned.
The first step of the process consists of a solution of 2\
lb. of alum and 1 or 2 lb. of salt in 5 gallons of boiling water.
When the solution has cooled to 75° F. the skins are im-
mersed in it and stirred about for an hour, then allowed to
remain in the solution from 12 to 24 hours. A few pounds
of salt and 3 or 4 gallons of chrome liquor are added to each
100 gallons of water. A smaller bath may be used by keeping
the same proportions. As the skins absorb the tanning mate-
rial, more concentrated chrome liquor should be added, and the
goods are left in the solution until they are tanned through.
When the green color has penetrated throughout the thickest
skins, a few ounces of bicarbonate of soda should be added
to the liquor, and the skins left in a day longer. They are
next washed in borax water, then in clean water, drained, fat-
liquored, and dried, or dyed immediately after the tannage
WOOLSKINS AND FURS - 515
is completed. A paste made of sod oil and flour forms a
suitable fat-liquor for this tannage.
Tanning hair skins with alum and gambier. — For the
tanning of hair skins for rugs, robes, and mittens, a tannage
of alum and salt, and either gambier or quebracho is satis-
factory. The skins are soaked, fleshed, washed, and spread
on a table and a mixture of pulverized alum and fine salt
is rubbed into the flesh side with a brush until all spots are
covered. Each skin is then folded down the center, or rolled
up and left in that condition for 24 hours. A second applica-
tion of alum and salt is again brushed in and the skins are
left in piles a day or two longer. This treatment sets the hair
so that it will not slip during the, subsequent treatments. The
skins may be dried and finished without further tanning, but
a treatment with gambier or quebracho liquor makes a more
permanent tannage and a more durable leather.
A fairly strong liquor is made by boiling either gambier or
quebracho extract, and when it is cold, the skins are im-
mersed in it and left for several days, according to their thick-
ness. The liquor should be rather weak at first and strength-
ened as the skins absorb the tan.
The goods are then washed, drained, and either hung up or
stretched in frames to dry. When the excess of moisture has
evaporated, warm oil should be applied to the flesh and brushed
in. Any good leather oil may be used, sulphonated oil being
preferable. When thoroughly dry, the skins are beaten and
brushed until the leather is soft and the hair clean.
Cleaning white fur rugs. — These and wool rugs may be
cleaned by the application of a paste of powdered chalk and
water, prepared by mixing the two into a thin paste and then
rubbing the latter thoroughly into the fur or wool and allowing
it to dry. When dry, the paste is thoroughly brushed out
with a stiff brush, and, to finish, a finer brush is used to remove
every particle of chalk. This treatment takes away all dirt
and grease and causes the goods to be clean, soft, and fluffy.
Bleaching skins with the hair on. — Goatskins, sheepskins,
and lambskins intended for rugs, robes, etc., can be bleached
516 PRACTICAL TANNING
by using a solution prepared in the following manner : 4| lb.
of chloride of lime is added to 21 quarts of water, the
solution being stirred for some time. It is then allowed to
stand until it has settled, when the clear liquor is drawn off
into a solution of 5^ lb. of Glauber's salt in 10| quarts of
water. A precipitation results which leaves sodium hypo-
chlorite in solution. The clear liquor, which should be quite
free from lime, is next drawn off, and the skins are immersed
therein until they are bleached, which takes about two days.
They should next be rinsed in water and then washed in weak
suds of white soap to give the necessary soft feel. Prior to
bleaching, the skins should be washed with warm suds and
rinsed. Alum-tanned skins may require a re-tannage after
bleaching. This is done by rubbing powdered alum and salt,
or a paste of the same, on the flesh side before hanging the
skins up to dry.
Dyeing China goatskins black. — These skins, tanned and
made up into rugs, may be dyed black in the following man-
ner, the quantities being for 60 rugs, which is equivalent to
120 skins: In a vat of about 360 gallons capacity, make up
a bath of 24 lb. of concentrated ammonia and 36 lb. of sal
soda, previously dissolved. When these have been added to
the water, heat to 95° F., and immerse the rugs for 2 hours,
stirring them occasionally, then pull and let them drain
thoroughly.
Dissolve 50 lb. of dark turmeric, and 45 lb. of logwood
extract, and add all to the bath. Enter the rugs and let them
remain in the liquor until they rise to the surface. Then
haul and add 25 lb. more of logwood extract, 10 lb. of sumac,
10 lb. of bluestone (copper sulphate), 5 lb. of fustic extract,
and 60 lb. of acetate of iron. Immerse the rugs for 18 hours ;
then draw and expose them to the air for 12 hours. Heat the
liquor again to 95° F. and put the skins back for 12 hours
longer. Draw them out of the liquor; hang in the air for a
time, and then wash. The washing should be done thor-
oughly with plenty of clean running water until all dirt and
superfluous dyestuff has been removed; the rugs should then
WOOLSKINS AND FURS - 517
be wrung and tacked out to dry. When almost dry, put them
into a drum, with .a mixture of sea sand and mahogany dust,
and run 4 hours, after which they should be put into an open
slat wheel or cage and run for 2 hours to clean out the sand
and dust. The latter process, if carried out properly, will be
found to give an added brilliancy to the fur, which cannot be
obtained in any other way.
Dyeing furs with acid colors: Re-tannage. — The use of
acid dyestuffs is preferable to basic colors in the dyeing of furs,
hair skins, rugs, etc., on account of their greater fastness to
washing and rubbing. The skins can be dyed black or fancy
colors with acid dyes, but in order that they may stand the high
temperature of the dye-bath without injury, it is necessary to
re-tan them with a chrome tannage. Such a tannage not only
increases the resistance of the furs to the hot dye-bath, but
also makes them more waterproof and more durable. Alum-
tanned skins in particular require such tannage.
The skins should be placed in the chrome liquor in such a
manner that the flesh side is fully exposed. If thrown in
loosely, they should be stirred frequently and kept opened
out. It is well to suspend large skins in the bath so that the
flesh will get the full benefit of the re-tannage.
Chlorinating the furs. — To impart greater affinity for the
dyestuff to the skins, it is necessary to treat them with chlor-
ide of lime in the same manner as described under woolskins.
Dyeing.— For 100 lb. of furs, 10 to 20 lb. of Glauber's
salt, 2 to 5 lb. of acetic acid, and the dyestuff in solution are
added to water heated to 120° F., and the furs are placed in
this bath. The temperature of the bath is gradually raised
by steam to 165° F. ; and after a half-hour from 6 to 8 lb.
of sodium bisulphate is added in 2 or 3 portions, and the skins
worked at the same temperature for 30 minutes; they are
then rinsed thoroughly and drained or hydro-extracted.
After the furs have been rinsed, it is advisable to pass them
through a solution of soap and oil, which imparts a soft feel
to the hair. The solution is made of 1 lb. of olive oil soap,
2 or 3 oz. of olive oil, and 1 or 2 oz. of ammonia in 10 gal-
518 PRACTICAL TANNING
Ions of water. The furs are worked in this solution for 15
minutes or longer, and are then drained or hydro-extracted
and dried without rinsing. When dry, they are worked out
soft and cleaned.
A rich black is obtained by dyeing the furs in the manner
that has been described with from 4 to 6 per cent, calculated
on the dry weight of the skins, of the following dyes : naph-
thylamine black S, ESN, SS2B ; napthylamine blue black B,
BD; naphthol black B, SG; and azo merino black B. As
shading dyestuffs for black, the following are used: Indian
yellow FF ; tropaeoline OO ; acid yellow AT ; fast yellow S ;
and orange 11, extra.
For blue shades : cyanole FF extra ; tetra cyanole V ; indigo
blue N; azo wood blue SE; naphthol blue R; solid blue R;
and formyl blue B.
For shades of yellow and orange: fast yellow S; acid yel-
low AT ; fast acid yellow 3 G, TL ; Indian yellow G, R ;
naphthol yellow S; tropaeoline GO, OO; and orange GG,
extra II, IV, R.
For red, claret, etc. : lanaf uchsine SG ; SB ; 6 B ; azo orsei-
ble BB; Bordeaux BL; and brilliant orseible C.
For violet : azo wood violet, 7 R ; 4 B ; acid violet 4R S;
and 6 B S.
For green : naphthol green B ; fast acid green B N ; and
cyanole green B.
For brown: Combinations of various yellows, orange, green,
blue, etc., are used.
For light shades, about 0.2 to 0.5 per cent dyestuff is used,
and for full shades up to 3 per cent dyestuff, calculated on the
weight of the dry skins.
For gray : silver gray N, which is dyed with the addition
of | to 1 per cent alum without any other addition.
Dyeing with chromate colors. — This method of dyeing
is valuable in all cases where the demands for fastness are
exacting. Most fancy shades can be produced with chromate
colors, but for black it is necessary to use acid colors.
The preparation of the skins is the same as in dyeing with
WOOLSKINS AND FURS 519
acid colors, except that the treatment with chloride of lime
may be omitted, as the hair absorbs the chromate dyestuffs
well enough without this treatment. For particularly full
shades, however, the treatment with chloride of lime is use-
ful also. The dyeing is carried out as follows :
The dyestuff is dissolved in the regular manner, and half as
much sodium dichromate as dye is dissolved in a separate ves-
sel, and the two solutions are mixed in the dye-bath. The
temperature of the liquor at the start should be 170° F., and
the furs are dyed at this temperature for 1 to 2 hours. An
addition of 1 to 3 per cent acetic acid is then made, and the
skins are worked for another half -hour, rinsed and hydro-
extracted. To ensure good leveling on felted wool it is ad-
visable to use 3 or 4 per cent monopole soap. Many shades
of yellow, brown, green, blue, red, gray, etc., are obtained by
using the anthracene chromate dyes alone or in various com-
binations, according to the shade desired.
Acid and chromate colors are dissolved by pouring boil-
ing water over them, and boiling if necessary. The solution
should then be passed through cheese-cloth or a fine sieve, and
any particles remaining undissolved are brought into solution
by pouring more boiling water over them.
Dyeing furs black with furrol dyes: Preparation of the
skins. — Fur skins that are to be dyed are first subjected to
the "killing" process, which cleans and de-greases the hair;
this is done in various ways as follows :
1. Drum killing with soda solution. — The skins are soaked
for 3 hours in a cold solution of 1 lb. of soda ash in 10 gal-
lons of water. They are then washed, feebly acidified with
acetic acid, and rinsed again.
2. Drum killing with milk of lime. — One pound of freshly
slaked lime is mixed with 10 gallons of water. The skins
are treated in this cold liquor, then acidified with acetic acid,
and rinsed.
3. Drum killing with caustic soda lye. — A liquor is pre-
pared, according to the nature of the skin, with 6 oz. to 2\
lb. of caustic soda lye of 77° Tw. for 10 gallons of water,
520 PRACTICAL TANNING
and the skins, the flesh side of which has been spread with
starch paste, are treated therein at ordinary temperature for
about 3 hours. Furs with very hard hairs, such as raccoon
skins, are left somewhat longer in the caustic soda lye. They
are then feebly acidified with acetic acid and rinsed.
4. Brush killing zvith caustic soda lye. — According to the
quality of the skins, prepare a caustic soda lye solution of
2 to 12° Tw., and brush it onto the hairs. For some special
kinds of fur, foxskin, for instance, a stronger lye is applied
on the belly portion and a weaker one on the back. The furs
in this state are left lying bundled, fur-to-fur, for 3 to 8 hours,
when they are dried, brushed, or cleaned. The skins are next
given a drum killing as directed under 1 and 3.
^Mordanting the furs. — The dyeing operation consists of
two processes, namely, the mordanting and the dyeing proper.
Mordanting of the hair is required to effect a quicker and
fuller absorption of the coloring matter in the dye-bath, and
is done by immersing the previously cleaned and killed skins
in the solution of mordant, the time required depending upon
the nature of the hair and the temperature of the bath. The
following solutions are used as mordants :
Quantity of Water
Solution salt, ounces gallons
Alum 16 10
Copper sulphate 8 10
Sodium dichromate 4 10
Chrome-alum 16 10
Iron sulphate 4 10
These mordants are used without further additions, or else
with the addition of 3 oz. of tartar or 2 to 3 oz. of 30 per cent
acetic acid. The mordanting solution is best applied at a
temperature of 68 to 77° F. For less delicate furs, the solu-
tions may be heated to 95° F. to allow of more rapid working.
The duration of the mordanting depends on the quality of
the skins and the results desired; when working at a tem-
perature of 68 to 77° F., 6 to 12 hours will be sufficient as
a rule, and if a higher temperature is maintained the time
may be reduced. The skins are then rinsed, and if an acid
WOOLSKINS AND FURS - 521
mordanting bath has been used, some soda should be added
to the rinsing bath, the goods being once more well rinsed.
They are then dyed.
Dyeing black.— Black is dyed by brushing in the following:
three ounces of furrol S and J oz. of phenylene diamine
powder are dissolved in 1 gallon of water, and immediately
before use, add 3 lb. of hydrogen peroxide. This solution
is brushed on the skins three times, allowing them to dry after
each application.
Raccoon {imitation skunk). — These skins are brush-killed
with caustic soda lye of 40° Tw. or drum-killed with 1 lb.
caustic soda lye of 77° Tw. per 10 gallons water.
The mordant solution consists of 1$ oz. of copper sulphate,
4-1 oz. of iron sulphate, and 4 oz. of tartar in 11 gallons of
water.
Dyeing is done with 4^ oz. of furrol gray R and 3 oz. of
ammonia. The black dye is brushed on in solution prepared
as above directed.
Lambskins. — These are drum-killed with 1 lb. of lime in
10 gallons of water; and mordanted with 8 oz. of copper sul-
phate in 10 gallons of water.
Dyeing black is then done with 4| oz. of furrol S and |
oz. of phenylene diamine powder, and 12 to 15 times the
weight of the dyestuff of hydrogen peroxide is added to all
the other ingredients.
Red-haired fox.— This is dyed black by being first brush-
killed with caustic soda lye of 2 to 3° Tw., or drum-killed
with 12 oz. of lye of 77° Tw. in 10 gallons of water.
The mordant solution is 1 lb. of chrome alum and 3 oz.
of tartar per 10 gallons of water.
The dyeing is done with 10 oz. of furrol gray R, i oz. of
phenylene diamine powder and 20 oz. of ammonia, and hydro-
gen peroxide, 12 to 15 times the weight of the dyestuff.
The black dye is brushed on the skins three times, allowing
them to dry after each application. This dyes the furs in
imitation Alaska.
Red-haired fox is also dyed black in the following man-
522 PRACTICAL TANNING
ner: The furs are brush-killed with caustic soda lye of 2 to
3° Tw., or drum-killed with 12 oz. of caustic soda lye of 77°
Tw. in 10 gallons of water. The mordant is 7 oz. of copper
sulphate and 3 oz. of tartar in 10 gallons of water.
The dyeing is done with 4|- oz. of furrol S and f oz. of
phenylene diamine powder and hydrogen peroxide 12 to 15
times the weight of the dyestuff, per 10 gallons of water.
Seal rabbit {English imitation of seal). — These furs are
drum-killed with 1 lb. of lime in 10 gallons of water. The
mordant is 8 oz. of copper sulphate, and 3 oz. of tartar in 10
gallons of water.
The first dye-bath consists of 3 oz. of furrol yellow-brown
G, 3 oz. of ammonium chloride, and -J oz. of ammonia. The
second bath consists of 1| oz. of furrol S, 7 grains of pheny-
lene diamine powder, 3 oz. of ammonia, and hydrogen perox-
ide 12 to 15 times the quantity of dye, in 10 gallons of water.
Black seal rabbit is dyed as follows : Drum-killed with 1
lb. of lime per 10 gallons of water; mordanted with 6 oz. of
copper sulphate and 3 oz. of tartar in 10 gallons of water;
dyeing with 5 oz. of furrol S and 1^ oz. of phenylene dia-
mine powder in 10 gallons of water, with hydrogen peroxide
12 to 15 times the quantity of dyestuff.
Tanning for robes, coats, etc. — Hides of horses and cat-
tle that are to be tanned with the hair on them and used in
the manufacture of coats and robes should be soaked in fresh
water before they are tanned, in order to soften and rid them
of dirt, blood, and other undesirable substances. They should
be soaked long enough to become thoroughly softened, the
length of time ranging from 12 to 24 hours.
Dry hides are more difficult to soften than salted hides.
Borax, salt, and formic acid are all useful in softening such
hides. When borax is used, from 5 to 6 lb. dissolved in hot
water, is mixed in 1000 gallons of water. The effectiveness of
this soak is increased by raising the temperature to 90° F.
The hides may be left in the soak for 12 hours, then worked
on the beam or milled in a drum in a solution of borax and
water; or they may be softened in a hide mill. After the
WOOLSKINS AND FURS 523
milling, they usually require further soaking to bring them
to the proper condition.
When a salt soak is used, enough salt is added to the water
to make it decidedly salty. The hides may be left in the
brine from 12 to 24 hours, next drummed in salt water for
30 minutes, and then re-soaked until soft enough to be tanned.
Formic acid added to the soak water hastens the softening,
and, being antiseptic, prevents decay of the hides; a suitable
strength is 1 or 2 lb. in 100 gallons of water. After soak-
ing is completed, the hides should be fleshed and all flesh and
lumps of fat removed before they are tanned.
Alum and salt process. — In applying this process, the hides,
after they have been fleshed, are placed in a fairly strong so-
lution of alum and salt, care being taken to expose all parts
of the flesh side to the liquor, so that the hair roots may be-
come firmly set and hair-slipping avoided. The penetration
of the liquor is hastened by warming to 85° F. before the
hides are entered. The hides should be given plenty of room
in the liquor so that they can be handled occasionally and their
positions changed. It is good practice to hang them on sticks
and suspend them in the liquor. Hides may be well struck
through with a liquor made up of 6 lb. of alum and 12 lb. of
salt for every 100 lb. to be tanned. They should be left in
the tanning liquor until they become permeated with it, the
length of time required depending upon their thickness and
the strength of the liquor. They should then be soaked for
a half-hour in cold water and hung up to dry. When about
two-thirds dry they should be laid in piles for a few days to
become uniformly soft and moist before they are dressed
down. While the hides are in piles it is advisable to watch
and handle them occasionally, especially in warm weather, to
prevent heating, which causes more or less damage according
to the degree of heat developed.
The cutting down to a light substance is done by hand,
work which requires considerable skill and judgment in order
that the hide may be smooth, of even thickness, and free
from holes. After the hides have been dressed down it is
524 PRACTICAL TANNING
advisable to re-tan them. They may be returned to the alum
and salt liquor; or they may be re-tanned with alum and salt
in a drum; and they may be re-tanned with chrome liquor.
Re-tanning is also sometimes done with gambier or quebracho.
One method of re-tanning is as follows : The hides are put
in a drum with 6 lb. of aluminum sulphate and 8 lb. of salt
in 39 gallons of water for each 100 lb. of hides. The goods
are drummed in this for an hour. A solution of 10 lb. of
sodium thiosulphate in 5 gallons of water is then poured into
the mill and drumming is continued for 30 minutes, thus
securing fixation of the tanning material on the fibers of the
hides. The goods are then rinsed in water and hung up.
When nearly dry, they are stuffed with oil or grease, dried
thoroughly, then worked out soft and clean.
By re-tannage with gambier and salt the unpleasant fea-
tures of alum-tanned stock are prevented, and the hides are
made soft and strong. The liquor may be applied in a drum
or in a vat, the process being carried along until the liquor
has thoroughly permeated the hides. They are then placed
in piles for 48 hours, drained well, and hung up to dry.
Softening and cleaning the stock. — For imparting softness
to the goods, oils of various kinds may be used, also com-
binations of tallow, soap, and oil. Mineral oils are also satis-
factory. A heavy coat of oil should be applied to the flesh
side, and the goods then allowed to dry slowly and kept in the
dry condition some time before they are finished. The longer
they are kept in the dry condition the softer they will be when
finally finished.
Softening and cleaning of the hides is best accomplished
in revolving wheels or drums. The oil, grease, and dirt are
taken up by dry sawdust in a closed drum; or in an open or
latticed drum, the sawdust, carrying the oil and grease with it,
is thus cleaned out of the stock. The cleaning process ought
to be repeated two or three times to get the goods perfectly
clean and soft. Some yellow ocher added to the sawdust
gives the flesh side a desirable yellow color.
Dyeing may be done with acid or furrol dyestuffs in the
same manner as furs, which has been described.
CHAPTER XVII
VEGETABLE. TANNING MATERIALS
In the manufacture of leather, advantage is taken of the
fact that certain substances have the property of combining
with hide substance and in so doing form a new compound
not susceptible to decomposition. The various processes al-
ready described plainly indicate that fact, so in this chapter
we will consider those organic substances derived from vege-
table matter, and which contain tannin as their active
constituent.
The chemistry of the tannins has not been exhaustively
studied, so it is impossible to go deeply into the scientific side
of the problem. Suffice it to say that the tannins are divided
into two groups, one class being such substances as contain
pyrogallol tannin and the other catechol tannin.
It does not follow, however, that two substances contain-
ing the same kind of tannin will produce the same kind of
leather; in fact, the various tanning materials differ widely
from each other in their chemical and physical constitution,
but they all have the common property of precipitating gela-
tine from solution and of combining with hide substance. Not
only do the tannins present combine with the animal tissues
to form leather, but the non-tannins have a decided effect
upon the appearance and physical properties of the finished
product.
Those tanning materials which give a bloom to the leather
are usually of the pyrogallol class, while those producing no
bloom are of the catechol group.
Many tanning materials contain certain quantities of in-
soluble or partly soluble tannins which are known as "reds."
These are more pronounced in acid liquors, especially sul-
phuric, and many are completely soluble in alkaline liquors.
These reds are taken up to a greater or less degree during
the tanning process, and in the case of sole or heavy leather,
S2S
526 PRACTICAL TANNING
have a decidedly beneficial action, causing firmness in the
stock.
In the production of commercial tannin solution, the bark,
leaves, twigs, or wood form a great variety of vegetable sub-
stances. The material is first reduced to the form of chips
and then lixiviated with water. This lixiviation formerly was
carried out at the tannery by leaching the bark in a series of
tanks. As the supply of tannin material near at hand be-
came scarce, it was found necessary to go farther away for
it. Transportation is a considerable item, especially as the
tannin content in most materials is comparatively small. As
a result, manufacturers have found it more economical to leach
the bark or wood nearer the source and to furnish the con-
centrated extract to the tanner. Thus the manufacture of
tanning extracts is a new industry which has sprung into ex-
istence through force of necessity. These extracts have the
advantage of being in a concentrated condition and are ready
for use by simple dilution. Thus also a weak liquor can be
quickly strengthened by adding extract, while by the old proc-
ess it would have to be returned to the leach.
Since the advent of concentrated extracts, the old-time
leach-house has become a thing of the past, and although many
tanners still leach certain barks, they all depend upon ex-
tracts for bringing up the strength of the liquor and also use
them to hasten the tannage. In the production of ordinary
tanning liquor or concentrated extract the preliminary opera-
tions are the same, and it will therefore save space to give a
description of the two processes at the same time, carrying,
of course, the thin liquors through the evaporation in order
to make the commercial extract.
Grinding. — To extract the tannin from any material it must
first be reduced to a fine state of division, the degree of fine-
ness depending upon the material, and may be either chips or
powder, as found suitable. The actual method of grinding,
as well as the machinery employed, will vary with the ma-
terial and method of leaching chosen.
Cone mill. — The cone mill works on the same principle as
VEGETABLE TANNING MATERIALS 527
the ordinary coffee mill, and is used almost exclusively for
grinding barks. This mill (figure 115) consists of a casing,
on the lower part of which is a toothed cone, which rotates
within the lower part of the casing. The action may be lik-
ened to the cutting effect of a pair of shears. The upper
part of the casing opens up into a hopper which holds the
Figure 115. — Eureka bark mill.
bark. As the bark works down through the cone it becomes
ground, the degree of fineness being regulated by adjustment
of the cone. This machine is designed to work on dry ma-
terial, but can be used for wet bark with no danger of
clogging.
Another type of mill designed for the same purpose con-
sists of a horizontal conical runner, set with breaker knives,
which cuts the bark into small pieces, and drops it into the
circular casing adjoining. This also is set with knife-blades
across which the bark is forced by the rotation of heavy
cast-iron arms and is shaved to any degree of fineness. The
ground bark then passes out through the base to the conveyor.
528 PRACTICAL TANNING
For certain materials, such as myrabolans and the like, the
bark mill cannot be used to the best advantage. It has been
found that these materials can be best crushed by using a
disintegrator or some form of roller mill. The disintegrator
is a cage-like machine having heavy arms, which travel at
high speed in a cylinder. This machine produces an exces-
sive amount of dust and is rather a dangerous fire hazard.
A better type of mill for this purpose consists of two corru-
gated rollers through which the material is passed. The dis-
tance between the rollers determines the fineness of the
product.
The grinding of wood is usually accomplished in two
stages, first by chipping the wood at an angle or directly
across the end with machines of which two types are most
commonly used. What is known as the "hog" is in general
use in the United States.
The hog chipping machine consists of a cylinder cast with
a deep V-shaped depression on each side of which the knives,
twelve in number, are set, through slots placed alternately and
equidistant. Fitting the V depression is a throat or shearing
plate bolted to the foundation frame, relative to which the
knives must be set so they will just clear to obtain a clean
cut instead of a smashing or splintering action. The shear-
ing plate being adjustable, any degree of knife-set may be
obtained. Just what this set should be is a matter of indi-
vidual judgment and requirement. The greater the set the
greater the capacity of the machine and also the power re-
quired to drive it; the chip is, of course, larger and requires
larger machines and more power to reduce it to a suitable size
in the second stage. A fair knife-set gives not only a smaller
chip, but one better shaped, as splintering is avoided.
The capacity for chipping cord wood varies from 2 to 5
cords per hour, and here we have an illustration of the im-
portance of small things in manufacturing, for a variation
of an eighth of an inch in the set of the knife will vary the cut
of the machine almost the full extent of the capacities just
mentioned, besides seriously interfering with the secondary
VEGETABLE TANNING MATERIALS 529
reducing machine and the ultimate yield of extract. The hog,
for a capacity of about 4 cords per hour, or 160 cu. ft., re-
quires about 200 h.p. to drive it.
Disc chipper.— The other type of chipping machine is
known as the disc chipper, and consists essentially of a heavy
cast-iron disc, about 6 feet in diameter, mounted on a shaft.
The knives, usually six in number, are set in slots cut
radially or tangentially through the disc, and work against a
shear plate on the same principle as the knives of the hog.
The wood, however, is fed to the machine at right angles to
the direction of rotation, and at a point about mid-distance
between the center and outside edge of the disc, whereas
with the hog the wood is fed against the faces of the cylin-
der. The wood may be fed either at an angle inclining to
the disc or horizontally, the method depending to some extent
upon the final disposition of the spent chips. In any event
the best results are obtained only with a forced feed, most
suitably of the "shotgun" type, which is nothing more than
an elongated engine cylinder with a ram on the end of the
piston, and fitted with an automatically operated slide-valve
to secure the quick return of the ram after the stick in proc-
ess of being chipped has been cut up. The capacity of this
machine is only about half that of the hog; but it requires
much less power in proportion to the quantity of wood cut,
and also gives a cleaner cut, with less dust, and consequently
a chip which more readily yields its tannin. The importance
of this will be seen later. It also reduces the work of the
secondary machine to a minimum.
In both types of machine the quantity and quality of chips,
to say nothing of economy of power, are not a little depend-
ent upon keeping the knives and shear plates sharp, so the
knives must be changed at least every 6 hours— and oftener if
necessary— and the shear plate as frequently as the edge be-
comes rounded, which, considering that it is case-hardened,
is astonishingly frequent.
Secondary reduction.- -From the chipping machines the
wood passes to the second stage of reduction which is neces-
530 PRACTICAL TANNING
sary not only to further comminute the chips, but also to ren-
der them of uniform size before extraction. The importance
of this will be understood if we assume that the extractors
have a capacity and efficiency based upon chips of a given
size. If the size is too large or the chips are irregular the ef-
ficiency is no better than the effective extraction of the largest
chips, and some chips are over-extracted, others scarcely wet
through, resulting not only in loss of yield but also irregu-
larity of product.
The machines used for secondary reduction are of the
swinging hammer type. The operating part of the machine
consists of a central shaft carrying a series of plates, to which
the beaters or hammers are loosely suspended, so that they
hang or cluster around the center when the machine is not
running. Upon starting the machine, the centrifugal force
causes the hammers to assume a radial position. Just clear-
ing the ends of these hammers a bar grating is set, conform-
ing to the circle described by the hammers when at full speed.
The bars cross at right angles to the direction in which the
hammers rotate. This bar grating performs the double func-
tion of acting as a series of shear plates and as a screen,
which is designed to permit chips of the proper size only to
pass to the conveyors which carry them to the extracting
department, the size of chip being determined by the width of
space between the bars.
The efficiency of these machines is largely governed by the
condition in which they are maintained. Both hammers and
rack bars must have the shearing edge kept in condition,
which means a rather heavy repair account, as the edges in
neither case last more than a few days ; which is not surpris-
ing when we realize that during a day's run of 24 hours, the
rack bars receive the impact of the wood between them and
the hammers over three million times.
As good yields of extract, combined with economy, cannot
be obtained unless the preparation of the wood is kept under
constant control, to this end the chips should be tested at least
three times during the 24 hours. A convenient method of
VEGETABLE TANNING MATERIALS 531
doing this is to screen two or three pounds of chips through
a set of three screens superimposed in a tight box. The
size of the openings is best at f inch, -| inch, and 12 holes
per lineal inch; and the frame 9 by 12 inches inside
measurement. The weighed chips are placed on the top (f
in.) screen and shaken with a rotary motion until all that will
pass through it. The screens are then taken out and the
four divisions are weighed separately, and the percentage of
each is calculated.
A good preparation should leave no chips in the f-in. screen,
not over 20 per cent in the \ in., and 70 per cent on the 12-
mesh ; and there ought not to be over 10 per cent of dust in
the bottom of the box. An excellent preparation should
show no chips on the two upper screens, while the particles
passing through the lower should not exceed 10 per cent at
any time.
Leaching. — Having been reduced to the required degree
of fineness the material is next treated with hot water to dis-
solve or extract the soluble portions.
The common method of extraction, and the one that is
simplest in operation, is the press leach. This consists of a
number of tanks arranged in what is known as a battery,
usually six in number. The liquor from one tank is forced
by gravity to flow into the next in order and so on through
the series, the same idea being carried out as described under
the press system in making sole leather. A better concep-
tion of the process of leaching may be secured by following
the process through the different stages :
Assume that the leaches have been working for some time,
and the strongest liquor has been run off to the cooler or to
the evaporator : This leaves six tanks full of bark, of which
five contain liquor. The tank from which the liquor has just
been drawn holds the least-extracted chips. Calling this tank
No. 6, the liquor in No. 1 pit is pumped to No. 2. This
forces the liquor from No. 2 into No. 3 and so on until No.
6 is full. In tank No. 1 now remains the bark which has
been extracted with six different liquors, and in so doing prac-
532 PRACTICAL TANNING
tically all of the tannin has been removed. The spent bark in
No. 1 tank is now removed or "pitched" and the tank is filled
with fresh bark. Fresh water or spent liquor is run into tank
No. 2 which causes an overflow into tank No. 3 and so
on through No. 6 into No. 1, which by means of proper con-
nections now becomes No. 6. The liquor from what was at first
No. 1 tank, but now is No. 6, is pumped to the cooler or evap-
orator and the liquor in what was No. 2 tank, but now is No.
1, is pumped to the next in series and the spent bark pitched.
The tank containing the strongest liquor is called the head
leach, while that containing the weakest liquor is known as
the tail leach.
The leach tanks are generally round, and are provided with
a false bottom under which are steam pipes for the purpose
of heating the liquor. In pressing the liquor from one leach
to the next, the same precaution is taken as in a press-layer
system; that is, the liquor must run downward through the
leach in order that the incoming liquor may enter the bottom,
thus forcing the outgoing liquor off the top. The transfer
of the liquor is made either through wooden troughs or cop-
per tubes by means of plugs or valves. The flow may be di-
rected into any tank desired.
The cooler mentioned above is a large tank or number of
small tanks where the liquor may be held until cool enough
for use in the yard.
The heat during leaching should be moderate, as excessive
heat tends to darken the liquor and produce a dark leather.
For very light-colored stock, leaching is often carried out in
the cold.
Sprinkler leaches. — Some tanners and extract manufactur-
ers use a sprinkler leach. In this system the liquor is pumped
from the bottom of the leach, and by means of a revolving
sprinkler is allowed to spray onto the top of the bark in the
next in series. Although the system no doubt produces a
strong liquor, there is danger from oxidation and consequent
loss of tanning material.
Autoclave system. — The systems mentioned above are all
VEGETABLE TANNING MATERIALS
533
conducted at ordinary atmospheric pressure. Ap«*W
fusion unit on the other hand consists of a serie of from 6
to 8 cylindrical copper vessels or cells, usually of about 200
cubic feet capacity capable of working under a pressure of
if to 50 lb which may be operated either on the decoction
or the continuous diffusion basis, the final results in either case
not differing much. ,
Ea h unit or battery is piped for steam, water, and a,r
in a manner which permits of its being operated in the same
way aTopen leaches 'the difference being that after filling with
wood, the cover is bolted down and the leachmg .s performed
under a pressure of 15 to 30 pounds. ,
The time of treatment in the autoclave varies with the kind
of wood and the degree of fineness. The time, of course^
much shorter than in open leaching, being reduced to a min-
imum, from 36 to 48 hours being required to accomplish the
complete extraction of the wood. Liquors made by the
autoclave system contain much more sugar than those made
tn the open leach. Just what causes the increase in sugar >s
s"il somewhat of an open question. The liquors, as they
come from the autoclave, go to the cooler, the clarification
tanks or the evaporators. .
Clarification.-Following extraction, the next step is that
of clarifying and de-colorizing the liquors. If a simple bark
extract is desired it is only necessary to remove the dust
and small particles of wood carried through the false bottoms
or strainers of the extractors. This may be and is usually
done by precipitation in large receiving tanks, although a
more desirable method is to filter the liquor through a rough
filter after which it is ready for concentration.
One important point should not be overlooked, that is the
temperature of the liquor should be maintained as nearly as
possible to that at which the liquor is run off. Cooling entads
a waste of heat, and, unless pre-heat.ng is practiced the ca-
pacity of the evaporating apparatus is much reduced. The
temperature can, oHourse, only be maintained by rap.d han-
dling and adequate insulation to prevent radiation.
534. PRACTICAL TANNING
In case of de-colorizing, and by that is meant the actual
removal of the coloring substances by means of a coagulant,
either chemical or organic, the process is somewhat more
complex. Chemical reagents capable of precipitating coloring
matter are comparatively numerous, but are not in general
use in the United States. Most of them are defective on ac-
count of the residual acids or bases left in the extract, which
render them injurious to the leather. The only advantages
they possess are that it is unnecessary to cool the liquors to
bring about the desired precipitation, also their cheapness
The best de-colorized extracts are unquestionably produced
by the use of blood albumen, for which the dried packing-
house blood of commerce is employed. The usual mode of
procedure is to cool the liquor to about 90° F., and, while it is
being agitated, add a strained solution of the blood in a series
of fine sprays, the quantity depending upon the degree of de-
colorizing desired. After the mixture is homogeneous, the
temperature of the liquor is raised to 125° F. to ensure com-
plete coagulation. It is then allowed to stand until clear,
when it is drawn off for concentration. The precipitate is
usually drawn from the bottom of the tank and passed through
a filter-press to recover all the liquor possible. While by this
means it is possible to produce an excellent product, possess-
ing superior tanning qualities and suitable for tanning almost
any kind of leather, it is somewhat expensive on account of
the high cost of blood and the unavoidable loss of tannin.
In addition to blood albumen, several other substances such
as lead acetate, aluminum sulphate, barium chloride, and casein
have been employed, all of which, however, combine to some
extent with and cause a loss of tannic acid.
An old method, but one which is time-consuming, consists
in allowing the extract to stand undisturbed for several days.
In this way the insolubles settle and the clear liquor may be
drawn from the top.
A method frequently used to brighten extracts consists in
treating them with sulphurous acid. To accomplish this, sul-
phur dioxide gas is allowed to bubble through the liquor.
VEGETABLE TANNING MATERIALS 535
Bleaching in this way does not actually destroy the color, but
simply reduces it to a colorless compound which may re-ap-
pear when the leather made from it becomes dry.
Certain tanning materials, such as hemlock and quebracho,
contain more or less insoluble tannin, which may be rendered
soluble with alkalies or alkaline sulphites. Several brands of
clarified extracts containing sodium bisulphite are therefore
on the market.
These extracts, as a rule, are not effective, excepting when
applied to heavy leather in the stronger liquors of the yard.
Applied in the tannage of light leather they are more effective,
and a proper bleaching agent, intelligently added to the ex-
tract, not only improves the color, but renders the tannage
much more rapid and mellow, also giving greater tensile
strength, pliability, and less danger from grain troubles.
Clarification and de-colorization being completed, the next
step toward finishing the process of making extract is that of
concentration to a heavy syrup or powder, in which form the
product is delivered to the tanner.
Concentration. — From both an economic and quality stand-
point, proper concentration is as important as any of the pre-
vious stages, and the same principles of rapidity and low
temperature govern success or failure in producing a high-
grade article.
Concentration of the extract involves the removal of the
excess water from the light liquors, and, when it is consid-
ered that with the open system of extraction the quantity of
water to be evaporated is about 17, to 1 of extract, and by
the closed system say 10 to 1, the provision for doing so must
be quite liberal. A plant producing 10,000 gallons of 25 per
cent tannin extract per day has to evaporate from 100,000 to
170,000 gallons, or from 833,000 to 1,416,000 lb., of water
daily. Should this have to be done under atmospheric pres-
sure or open boiling it would require from 50 to 85 tons of
coal, or its equivalent, daily. However, concentration in these
days is accomplished altogether by boiling in vacuo or under
536 PRACTICAL TANNING
reduced atmospheric pressure, so that much less heat is
necessary.
The apparatus employed is usually known as a multiple-
effect evaporator, of which there are several types, the most
used being known as the standard type, which consists of
3 or 4 copper vessels or pans, which, for the capacities previ-
ously mentioned, would be about 9 ft. in diameter and 12 to
14 ft. in height. These pans are arranged so that the vapor
arising from the boiling in the first is carried to the second, and
so on in order to the third or fourth, as the case may be. The
lower section of each effect consists of a drum, fitted with
two heads, which are tubed in a manner similar to a vertical
steam boiler, but the tubes are much more numerous, a 9-ft.
drum containing from 1000 to 1200 tubes, the number de-
pending upon their diameter.
Steam is admitted through the shell of the drum, and the
heat communicated to the liquor from the outside of the tubes.
In the center of the drum is a large tube from 18 to 24 inches
diameter known as the well or down-take. The purpose of
this- is to maintain a proper circulation of the liquors; any
fluid will always move away from the hottest part or point
of a heated surface, which, in this case, is the wall of the
tubes. The result is that, when the liquor has become suf-
ficiently heated to boil, it ascends the tube and is projected
some distance above it. This gives the vapor generated in
the tube an opportunity to escape, with the surface evapora-
tion induced by the reduction of the atmospheric pressure.
The liquor confined by the walls of the pan then falls through
the down-take to the bottom to re-ascend the tube and con-
tinue the process, the liquor gradually increasing in density
as it passes from one pan to the next.
The space above the drum, known as the vapor space, con-
sists of two parts, namely, the belt and the breast or dome.
This space is necessary for the liberation of the vapor with-
out extrainment, which means the carrying over of any finely
divided spray of liquor to the next drum or the condenser,
where it would be lost with the water of condensation. Sur-
VEGETABLE TANNING MATERIALS 537
mounting the tubular neck of the breast is a separator, con-
sisting of two concentric tubes with side openings diametrically
opposite each other, the idea being to cause the stream of
vapor to impinge upon the walls and thus cause a final sep-
aration of vapor and liquor.
The first effect is heated with live or exhaust steam, the
condensation from which is usually returned to the boiler.
The second, third, and fourth are heated with vapor from the
preceding phase. The vapor from the last passes to the con-
denser, usually of the spray type, and escapes with the con-
densing water.
Vacuum in the first two or three effects is maintained by
a vacuum-pump, which also removes the water of condensa-
tion. The last effect is connected by way of the condenser to
an independent pump, which in all large apparatus operates
on what is known as the dry system.
After concentration, it only remains to cool and give the
extract time for a final settling, when it may be pumped into
tank-cars or barrels for shipment.
In recent years some demand has sprung up for powdered
extract, and, should this be desired, the liquid extract is dried
by means of a film dyer, which consists of an internally steam-
heated drum enclosed in an air-tight casing. While the drum
revolves, it comes in contact with a trough of extract, and,
picking up a film, carries it along the greater part of the
revolution (during which time it is thoroughly dried) until
it comes in contact with a scraper set against the drum, which
removes and drops it into a suitable receiver. During the
process the vapor is removed by a vacuum-pump.
A recent innovation in producing solid extracts consists of
spray drying. In this process the material to be evaporated
is forced hot through a small opening into a high-vacuum
chamber. The fine spray readily gives up the moisture con-
tent, the solid material falling to the bottom of the drum.
Powdered extract has no advantage over the liquid, except
in saving freight charges. In fact, rather the reverse is true,
538
PRACTICAL TANNING
as every exposure to heat has a deleterious effect on the prod-
uct, both as to color and decomposition of the tannin.
Having described the general methods employed in leaching
or extracting vegetable tanning materials let us consider some
of their most important sources.
Chestnut wood. — Botanically known as the castanea vesca,
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Figure 116. — Chestnut trees; giants of the forest.
it belongs to the oak family (figure 116),- and is easily dis-
tinguishable by its narrow, pointed, serrated leaves, its fra-
grant flower which grows in slender axillary catkins, and its
fruit, the latter two of which are unlike those of any other
tree. It may also be readily recognized when out of leaf by
its bark, which, when young, is gray and smooth, but is
heavily ridged in the mature tree. It is found from Maine
to Alabama and Georgia* and west as far as Kentucky and
Michigan. It does not, however, grow in great abundance
over the entire territory mentioned, and, considered from
VEGETABLE TANNING MATERIALS
539
a tanning-material standpoint, it is nearer correct to describe
its bounds as within the environs of the Appalachian Moun-
tains. It is one of the most beautiful of American trees,
growing in great profusion and to considerable dimensions.
Where it stands close, the tendency is toward height rather
than girth and spread, and trees 80 to 100 feet in height are
Figure 117. — A flume on the chestnut wood operations.
not unusual. As to girth, it varies greatly, this being a mat-
ter of age, but, as it grows rapidly, it often attains great size.
Referring to the quick growth of the chestnut tree, it is
so rapid that it has been termed the weed of the forest.
Numerous cuttings in various localities show that it will grow
as much as 6 to 8 inches diameter in 10 years, and from 15
to 20 inches in 25 years. Besides this feature, it is repro-
duced with great facility, a characteristic unfortunately not
possessed by any other tannin-bearing wood of importance.
After cutting the virgin forest it will spring up again in great
540
PRACTICAL TANNING
abundance, not only as saplings but as offshoots from the de-
caying stump left after felling the virgin tree (like the red-
wood of California) ; and not infrequently the stems on one
stump will aggregate more wood than the virginal trunk, so
in 20 to 25 years a second cutting may be made. With
proper care such a system could be continued indefinitely,
Figure 118. — Flume terminus for chestnut wood.
and comparatively small areas be made to yield a large supply
of tannin for generations.
In Virgina, West Virginia, Tennessee, and North Carolina,
chestnut timber grows in great abundance, and large tracts of
well-timbered land exist upon which 75 per cent or more of
all the timber standing is chestnut. It is in these States that
the production of chestnut tannin is mostly conducted.
The air-dried wood, the operations of handling being shown
in figures 117 and 118, contains an average of about 8 per
cent of tannin, but it varies a great deal and may run as high
as 14 per cent. The age of the tree, exposure, and climatic
VEGETABLE TANNING MATERIALS 541
conditions all have their effect upon not only the tannin but
the other extractive constituents of the wood.
Besides tannin, it contains considerable quantities of gal-
lic acid, the pre-existence of which is doubtful, as it may
result from the decomposition of the tannin.
The extractive matter obtained in the manufacture of chest-
nut tannin extract usually contains about 60 to 65 per cent
tannin and 35 per cent to 40 per cent non-tannin substance.
The tannin is distinctly of the pyrogallol group, yielding pyro-
gallol when heated, and remaining soluble when tested with
bromine water and hydrochloric acid- formalin solution. When
pure, it also gives the blue-black color said to be characteristic.
The non-tannin substances consist chiefly of sugars, which
reduce Fehling's solution, gallic acid, pectose compounds, resin
and ash, but they are no better understood than the tannins.
Their quantity and composition in the tanning extract are
largely a question of manufacture, and much remains to be
done before we can say much about them. The sugars of
chestnut wood, in common with those of barks, are valuable
in the tannery on account of the acid they produce ; thus their
presence adds to the value of chestnut tannins.
As a tanning material, chestnut tannin has been chiefly con-
fined to the production of sole, belting, and other heavy leath-
ers; but there is no reason why it cannot be employed for
many other classes of leather when properly made and used.
On account of its abundance, cheapness, and excellent quali-
ties, chestnut tannin bids fair eventually to become the staple
basis for the tannage of all heavy vegetable-tanned leather.
A few years ago the chestnut blight struck the trees along
the North Atlantic coast, and before steps could be taken to
retard its ravages, thousands of trees were destroyed. It is
felt, however, that proper treatment has been discovered and
that the danger is now past.
Oak wood. — The wood of all the oaks yields considerable
though varying quantities of tannin, the American oaks rang-
ing from 3 to 5 per cent in the air-dried woods. In Europe,
tanning extracts are made from a number of the oak woods,
542 PRACTICAL TANNING
the product being held in much favor, if one may judge from
its value, which is from 20 to 25 per cent higher than the
chestnut extracts.
Among the oaks employed for this purpose are the Q.
robur, Q. cerris, Q. pubescens and their varieties. These
grow chiefly in southeastern Europe, Austria, Hungary, and
Jugo-Slavia being the chief sources of supply. In America,
no oak-wood extract is produced. Attempts were made years
ago to utilize the wood of the chestnut oak or rock oak, O.
prinits, the wood and bark being all ground up together. The
composition of the extract, however, did not, apparently, meet
the ideas of the American tanner at that time, so the attempt
failed, and no further investigation has been made up to this
time.
In Europe, only the waste material from the sawmills is
utilized for extract, the body of the tree being more valuable
as lumber; and, in order to produce a merchantable article,
the bark, which contains red coloring matter, is carefully dis-
carded. The tannin of the oak woods is similar in most re-
spects to that of chestnut. It belongs to the pyrogallol group
and gives the same reactions.
Extract made from oak wood appears to differ little in
composition and color from American chestnut, but it usu-
ally contains more soluble non-tannin than the average Euro-
pean chestnut. A recent analysis of a sample of southeastern
Europe oak-wood extract gave approximately 38.6 per cent
total solids, ^25.0 per cent tannin, and 13.2 per cent soluble
non-tannin. The purity was 65 per cent, or almost identical
with American chestnut.
Barks.- — Tanning in all countries, until recent times, was
conducted with native materials derived from the most con-
venient sources of supply, and as in Europe and North
America, the immense forest areas, now sadly depleted, fur-
nished what was at one time considered an inexhaustible sup-
ply of oak and hemlock bark, it naturally followed that the
tannins derived from these barks formed the basis of all tan-
nages on both continents for a very extended period.
VEGETABLE TANNING MATERIALS 543
In Europe and Great Britain the oak barks predominated,
while in North America hemlock bark has been more exten-
sively used, although oak bark has been, and is used where
plentiful, especially in the Southern States.
Speaking of the oak barks, it seems that the source of sup-
ply of tannin is not confined to any one species, and almost
any oak bark that would tan has been employed. There are
altogether over 30 species and varieties of oak trees.
Abroad, the Q. robur, or English oak, has been most exten-
sively used. This tree bears a greater resemblance to the
American white oak than any other, though it is interesting
to note that the bark of the latter is scarcely recognized here
as a tanning material. This tree, which is more valuable now
for its timber than for its bark, grows throughout Great
Britain and Europe and still furnishes, through reforestation,
a considerable quantity of tan bark. In Europe, the custom
is to peel the bark from the tree while it is still young enough
to be smooth, the age of the tree being from 12 to 20 years.
The bark, it is claimed, then has a greater tanning efficiency
and yields a better color than that from mature timber.
Many plantations have been started during the past 50 or
60 years, which are said to have yielded profitably. In
handling these plantations,, the system is to divide them into
as many sections, as it takes years to produce bark suitable for
peeling. When the bark has grown sufficiently, the first sec-
tion is peeled, the timber removed, and the land re-planted or
allowed to sprout from the stump of the first growth. The
next year the second section is harvested, and so on in rota-
tion, so that a continuous supply is secured. Europe is much
in advance of the United States in the line of conservation,
the necessity for such expensive development not yet having
arisen on the American continent. In fact, it is doubtful if
such a system could be successfully applied here, as it is
obvious that the labor and attention must be costly, and, as
long as tanning material is as cheap as it is now, it is not
likely to appeal to the investor.
The American varieties of oak are more numerous than
54>4> PRACTICAL TANNING
those of Europe, there being about twenty-eight, but the chest-
nut oak or rock oak, (Q. prinus) is the only one which fur-
nishes tanning material in great quantity. The range of this
tree may be said to be confined, like the chestnut, to the Appa-
lachians, where it grows in great abundance; although the
supply is diminishing rapidly, and will soon be exhausted, as
it does not reproduce as rapidly as chestnut. In appearance
it is very similar to some of the other oaks, but, while in
foliage, may be readily distinguished by its leaf, which is
unlike any of the others. In appearance it is something be-
tween the chestnut and the English oak. In Winter, the
expert may distinguish it by its bark, which is smooth and of
a silvery gray color in the young tree, and rough and much
ridged in the mature tree. The bark becomes rough after
the tree has attained a diameter of 8 inches or so.
In the United States, bark is peeled from trees at all ages,
and consequently the quality and tannin content vary a great
deal.
In past years the tree was felled for its bark alone, the
timber being considered of little value. Now, however, little
is cut that is not manufactured into lumber, a Change which
has made for conservation, the peel being governed to a con-
siderable extent by the market for the timber.
Prime chestnut-oak bark contains an average of about 10
per cent of tannin, and yields 18 to 20 per cent of soluble
extractive matter, which is rich in acid-forming sugars. It
is on this account considered one of the most valuable of all
tanning materials. It has now become too scarce and costly
to use alone, but when it was available it was unsurpassed
for the manufacture of sole and belting leathers. In com-
bination with other materials, it yields a high class of car-
riage, harness, and other leathers requiring a full, mellow,
and firm tannage.
The tannin of the chestnut oak responds to the catechol
reactions, and is unlike some of the other oaks in this respect,
as several seem to contain tannins of both groups in large
proportions.
VEGETABLE TANNING MATERIALS 545
On the Pacific Coast there is another variety of oak tree
which is deserving of more study than has been given to it,
and which bears the same relation to the tanning industry
of that region that the chestnut oak does to the East: It is
the Q. densiflors or California oak. It is still abundant in
California and Oregon, growing chiefly on the lateral spurs
of the Pacific coast ranges, which makes it somewhat inaccessi-
ble. The bark from this tree is the richest of all the known
oaks in tannin, frequently containing from 17 to 20 per cent,
with as much as 30 per cent of soluble extractive matter. It
yields a rich red liquor, more like that of hemlock in appear-
ance than of chestnut oak. The sole and harness leather tanned
with it is of a distinctive character and of excellent quality,
being much more mellow and with less tendency to break than
ordinary oak-tanned stock.
It seems to differ from most other tannin in that it is
difficult to blend with other materials on account of an ap-
parent selective action. In other words, when blended with
chestnut liquors, the hide seems to take up the chestnut first,
with the result that, not only is the characteristic color lost,
but the texture of the leather is materially affected.
Chestnut bark. — In the manufacture of chestnut-wood ex-
tract, no attempt is made as a rule to separate the bark from
the wood proper, both being extracted at the same time.
There is, however, a certain demand for chestnut-oak bark
extract and when this is required it is extracted separately.
Oak bark. — Nearly all species of oak contain more or less
tannic acid in the bark and wood. Catechol tannins predomi-
nate in the bark, although this also contains a certain amount
of pyrogallol tannins, ellagitannic, and quercetannic acids.
If cut while the sap is rising, the bark separates readily,
while timber cut at other times offers some resistance in strip-
ping. The peeled bark is laid in piles several feet high and
is so arranged that the water is shed somewhat as from shingles
on a house. This is absolutely necessary to prevent damage
to the bark. When oak bark is used it is generally leached at
the tannery. No true oak-bark extract is on the market, al-
546 PRACTICAL TANNING
though a so-called extract is sometimes offered for sale. Such
extract is usually found to be modified chestnut-oak bark.
In some of the Southern tanneries and extract works a cer-
tain amount of oak-wood extract is prepared; but the quantity
is comparatively small.
Hemlock bark. — After the oak tanning woods and barks,
the bark of the hemlock tree, tsuga canadensis, ranks next in
importance and, in North America, it probably still occupies
the premier position.
The hemlock is a cone bearer of the spruce family, and is
one of the most beautiful evergreens of the forest. Con-
ical in shape, with plume-like horizontal branches, it gives an
impression of great dignity, and, in the forest, of much sol-
emn beauty. The bark is of a red color, and its leaves are
short and linear, growing on little petioles, Which distinguish
it from any other conifer. In Spring the foliage is tipped
with new growth of a light green, while in Winter it is dark
and lustrous.
It is widely scattered in one or more of its varieties all
round the world. The species are five or six in number, and
grow principally in northern latitudes. In eastern North
America it ranges from Hudson Bay to northern Georgia,
and from the East to the Mississippi. The great hemlock for-
est, however, does not extend south of Pennsylvania and West
Virginia, the timber south of those States being only found
in restricted areas, mostly following in narrow belts the small
water-courses of the mountains.
In western North America another variety of this tree, the
tsugas mertensiana, which is richer in tannin than the eastern,
flourishes along the Cascade Range and north from there along
the mountain ranges of British Columbia and Alaska, where
it is still very abundant on account of the remoteness of its
position, half a continent separating it from the great centers
of the leather industry.
In the Eastern States the supply is fast approaching the
vanishing point and of the thousands of square miles once
covered with practically unbroken hemlock forest, compara-
VEGETABLE TANNING MATERIALS 547
tively little remains, and it would doubtless have entirely dis-
appeared but for the introduction of other tanning materials,
and the increased value of the timber.
In Canada there are still considerable areas, which, however,
are so rapidly disappearing that it is only a matter of a short
time until the hemlock forest disappears from the eastern sec-
tion of the continent.
In northern Europe two species of this tree are found in
quantity, and also in Asia, while other varieties grow in India,
China, and Japan. From descriptions given by various au-
thorities it would appear that the Oriental hemlock is very
similar to the American.
The bark of the hemlock contains varying quantities of
tannin, this being governed by climate and exposure. As a
rule it will yield about 10 per cent of the weight of the air-
dried bark, with about 16 to 18 per cent of soluble extractives.
The tannins are of the catechol group, and the soluble non-
tannins are rich in sugar. The liquors are of a brilliant red
color and are soluble with difficulty, and like most of the
catechol tannin bearers, are not readily filtered clear.
As far as North America is concerned, it has been the
tanning material par excellence, and probably the only one
with which it is possible to produce excellent leather of all
kinds. It seems as well adapted for the lightest colored
fancy or upper leather as for the heaviest sole, and, previous
to its scarcity, it was used almost universally in the whole
range of leathers made on this side of the Atlantic.
Quebracho. — From the standpoint of production and con-
sumption, quebracho wood tannin is as important as chestnut
wood.
The quebracho tree is generally given in botanical books
as aspidospermia, but this name covers several varieties, which,
with one or two exceptions, are of little or no use to the
tanner. The variety with which he is chiefly concerned is
that growing in Argentina and Paraguay, and known as the
quebracho Colorado or, as distinguished by botanists, the
loxopterygium lorentzii. The common trade name quebracho
548
PRACTICAL TANNING
is said to be derived from the Spanish word quebra — to break,
and hacho — axe, or break-axe, this nomenclature doubtless
being due to the great hardness of the wood.
The quebracho is an evergreen tree, which, in common with
all others, is of all heights and sizes. It is said, however,
occasionally to attain a height of 100 feet. In the forest its
distinguishing features are its usually erect stem and its wide-
Figure 119. — Carting quebracho logs to port of shipment; trees in
the background.
spreading crown. The branches at the top grow almost ver-
tical, but, as they descend, become gradually more horizontal
until they droop, forming a somewhat umbrella-like top.
The leaves are rigid and lanceolate or spearhead-like in
shape, and the flowers occur in terminal panicles.
The bark is thick, and remarkable for the thickness of the
internal or corky layer, which often constitutes one-half of
the entire thickness.
The wood is very heavy, too heavy to float, and of a red-
dish-brown color,, which takes a fine polish.
This tree (figure 119) is of extremely slow growth, taking
VEGETABLE TANNING MATERIALS 549
from 400 to 600 years to attain a girth of 6 to 8 feet, a
characteristic which makes its disappearance only a matter of
time for it certainly is being cut much faster than it grows.
The supply, as far as at present ascertained, is confined to
Argentina and Paraguay, the Chilean supply, it is said, hav-
ing already been exhausted. There are, however, large quan-
tities still standing on the grand chaco or forest section of
the two countries first named.
Unlike the hemlock, oak or chestnut forests of America,
where immense bodies of these timbers grow almost to the
exclusion of any other, the quebracho grows scattered through-
out and mingled with the other growths, nor is the forest like
that of our mountainous country. The land on which it
grows is for the most part flat or rolling, and the forest is
divided into belts, a bek of timber alternating with a cleared
space of pampa or prairie. ■
It was estimated some years ago that there were 175 mil-
lion tons of timber standing, but, as this estimate was apparent-
ly based on the chaco being an unbroken forest, its accuracy
is open to question. #
The manufacture of quebracho tannin is conducted for the
most part in Argentina, a number of factories operating on
the Parana river and its tributaries, to which the logs are
conveyed, in some instances, hundreds of miles, by rail and
boat These logs are also transported to Germany and the
United States where the tannin extract is produced in large
^Quebracho has been used for tanning in Chile and Argen-
tina for a long time, but it is only within the la* 20 years
that Europe and the United States have utilized it to any
creat extent. In the latter country its use grew tremendously
for some years, more being consumed here than m all of
Europe At present the annual consumption of the States is
about 90 million pounds of solid extract per annum, represent-
ing about 56 million pounds of tannin, or the product from
156 000 tons of wood. The quantity used in Europe is prob-
ably not quite so great. Germany is the largest consumer on
550 PRACTICAL TANNING
the Continent, and, although some is used in France and Great
Britain, it is not looked upon as favorably as in America.
The wood contains about 18 per cent of tannin and yields
22 to 25 per cent of extractive matter, of which 80 per cent
is estimated as tannin and 20 per cent non-tannin. The tannin
belongs to the catechol group, giving a green color with ferric
alum, and precipitates with bromine water and hydrochloric
acid-formaldehyde solution. This, however, only applies to
crude and some clarified extracts. It has been found that some
of the so-called clarified do not yield precipitates with either
of the above reagents, which is due to the presence of the
chemicals used for rendering the extract soluble, or clarify-
ing it, as it is usually termed.
The non-tannins differ materially in their structure and
proportions from those of oak and hemlock barks and chest-
nut wood. Some tests show that an extract containing 10 per
cent non-tannin contains about 2 per cent gallic acid and 1.25
per cent sugars : the remaining 6.75 per cent is probably gum
and pectose matter, although that still remains undetermined.
The extracts, which are of a strong red-brown color, are
soluble with great difficulty in water, and, in order to obtain
anything like economical or satisfactory results, it is neces-
sary to resort to some one of the several methods of clarify-
ing them either by sedimentation or chemically rendering them
soluble, the most common method being to treat the extract
with sodium bisulphite.
As a tanning agent, quebracho is employed for all classes
of leather, being especially adapted when clarified for the
tannage of light leathers where weight and plumpness are
not a consideration. In conjunction with hemlock and oak
bark or their extracts, it is extensively used in the produc-
tion of bag, case, patent, and automobile leathers ; and many
satisfactory tannages are produced in the above lines where
it forms almost the entire tannage. For heavy leathers, such
as sole, belting, and harness, it is invariably used in conjunc-
tion with other materials, as it does not contain the necessary
sugars for acid- forming, which in these tannages is indispensa-
VEGETABLE TANNING MATERIALS 551
ble; nor does it make solid leather of good weight when used
alone. When clarified, however, it penetrates rapidly, and on
account of its high purity, is useful in strengthening up a
yard which has become saturated with inert non-tannins.
Valonia. — This tanning material is obtained from the acorn
cup of the Turkish oak (quercus cegilops), which grows in
Asia Minor, and, being shipped from Smyrna, is termed
"Smyrna valonia." The amount of tannin in this grade of
valonia is about 40 per cent. A lower grade of valonia grows
on the islands of the Grecian Archipelago and is known as
"Greek valonia." The tannin content of Greek valonia ranges
from 20 to 30 per cent. In both varieties the tannin is mostly
of pyrogallol derivation.
Valonia is of value to the tanner for its weight-giving qual-
ities. It also deposits considerable bloom, not only in the
leather, but on the surface. In most tanneries valonia is used
as a dusting material in the layers. The tannic acid from
valonia is found both in the cup and in the beard hair. As a
rule, however, no attempt is made to separate the two mate-
rials. In a few places where they are separated the ground
cup is used for dusting and the beard hairs are extracted. The
extract from the beard hairs produces a certain quantity of
acid in the yard, while the cup gives practically no free acid.
In the use of valonia it has been shown conclusively that
Smyrna valonia gives about 25 per cent more weight than
Greek valonia, hence the former is much more prized by
tanners.
In Asia Minor the fruit ripens during July and August,
and the acorns, which are shaken from the trees, are allowed
to dry on the ground. They are then gathered and trans-
ported by camel and rail to Smyrna, where they are placed
in storage and allowed to ferment, during which time the
acorn contracts and falls from the cup. The cups are hand-
picked, the largest and finest, known as prima, going to Trieste,
the second selection (Inglese) is shipped mostly to England,
while the remainder, known as natural, is sent to other
countries.
552 PRACTICAL TANNING
In Greece, the best fruit is gathered in April, while still
green, and is known as chamada. The second quality is beaten
from the trees in September and is known as rhabdisto, while
a third grade is collected after the fall rains, and being dark
in color, is termed charcola.
Mangrove bark. — This tanning material is derived from
the bark of the mangrove tree, which occurs widely distributed
in practically all tropical island districts. There are over
20 different species of mangrove, all of which contain more
or less tannic acid ranging from 8 to 30 per cent. The most
largely used species of mangrove is that known as rhisophora
mucronata, although bruguiera gymnorrihiza and ceriops con-
dolleana are somewhat employed. The mangrove tree re-
quires considerable moisture and is therefore found in swampy
or marshy land, also along muddy sea-coasts. The trunk is
irregular and spready, making gathering difficult. The bark is
stripped and sold as such to the tanner, or is extracted and
sold as mangrove or cutch extract. Mangrove is used by
many tanners of sole leather, mixed with other barks and ex-
tracts. In some South American countries the entire tannage
consists of this material. No doubt the difficulty of securing
the bark has been the cause for its retarded utilization. There
are thousands of acres, however, of this valuable tanning
material available, and there is no question but that eventually
it will become an important raw material in the manufacture
of leather.
Gall nuts. — Quercus infectoria is the source of Turkish
galls. The galls are caused by insects which lay their eggs
on the leaf or bud and so produce an abnormal growth. The
best gall is obtained before the insect escapes, and contains
from 50 to 60 per cent of tannin as gallotannic acid. This
material is the principal source of pure tannic acid. The
quercus infectoria sometimes bear large galls known as "Ap-
ples of Sodom" or "rove." These are caused by a different
insect. Chinese and Japanese galls are produced by the action
of an aphis on a kind of sumac.
Sumac (rhus coriaria). — Sicilian sumac is obtained from
VEGETABLE TANNING MATERIALS - 553
a bush of which the leaves and twigs are used. The bushes
begin to bear in the second year, but the best material is ob-
tained from the mature bush. Cropping is done by pruning
off the shoots or picking the leaves by hand. The leaves are
then dried either in the field or on rocks, and are afterwards
separated from the stems by heating. The leaves are then
ground to a powder under edge-rollers and shipped in bags.
Mascolino. — This is the best grade of sumac, coming from
Palermo, while feminella is a weaker grade from other parts
of Sicily.
After the sumac has been submitted to the first grinding, it
is passed through screens and the coarser particles are
re-ground.
Good sumac contains from 25 to 27 per cent of tannin,
while some samples may run much higher. The tannin is
mostly gallotannic acid, with some ellagitannic acid and a
coloring matter.
Sumac is the best tanning material known for light colors
and soft leathers, and is therefore largely used in making
Moroccos, sheepskins, and skivers. It is also largely em-
ployed to improve the color in darker tannages.
Rhus glabra. — This is a sumac found in the Southern Amer-
ican States, and is largely used in place of Sicilian sumac. It
contains about 25 per cent of tannin, but produces a much
darker leather than that made with Sicilian sumac.
Rhus typhina. — Known as "stag-horn," is a variety of
sumac found in Virginia and contains from 10 to 18 per cent
of tannin. The color produced with this sumac is nearly
equal to that obtained with Sicilian sumac.
In Virginia the leaves are collected and dried, but no at-
tempt is made at selection. The leaves are usually taken when
full of sap, sometimes being simply stripped from the twigs;
and sometimes the whole stock is cut and the leaves are
allowed to wither in the sun. In such cases the leaves, when
partly dry, are transferred to sheds and spread out in a thin
layer on a rack. The time required for drying varies with
the weather conditions and may even take a month for a per-
554 PRACTICAL TANNING
feet cure. When in proper condition they should be dry and
brittle. Although Virginian sumac is fairly high in tannic
acid it does not produce as light a color as is obtained with
Sicilian sumac.
The grinding of sumac is usually done in the edge-runner
and the resulting powder sifted to remove twigs and stems.
French sumac is obtained from a poisonous shrub found grow-
ing in the south of France called stinco. It is low in tannic
acid, and although it has no tannin value, it is used mostly
as an adulterant of true sumac.
Gambier. — This material is derived in most part from a
climbing shrub, uncaria gambier, found in the Dutch East
Indies ; or from terra japonica, also known as catechu. It is
also cultivated by the Chinese in a very crude manner. The
first crop is taken about three years after planting and the
leaves are taken two to four times annually, the life of the
shrub being about 15 years. After cropping, the leaves are
thoroughly chopped and placed in kettles with boiling water.
Concentration, with constant stirring of the liquor, is carried
out until a syrup is obtained. The leaves and twigs are then
removed with a fork and the excess liquor is allowed to drain
back into the kettle. The heavy extract is then placed in
tubs to cool, and when in a pasty condition it is again placed
on a flat surface and cut into cubes. These cubes, which are
about an inch long, are placed in a shed on bamboo trays
and dried out with wood fires. Cube gambier is dark brown
on the surface, but pale on the inside. Its tannin is a catechol-
phloroglucol derivative. It produces a soft tannage, and is
much employed in the production of glove leather. The tan-
nin content of good cube gambier is from 50 to 65 per cent.
A more common and cheaper form of gambier is that
known as "block gambier," which in place of being cut into
cubes is run into large oblong blocks weighing about 250 lb.
each. These blocks, which are of a pasty consistence, are
wrapped in matting and shipped. Block gambier contains
from 35 to 40 per cent of tannin.
Modern factories have been established in Sumatra and other
VEGETABLE TANNING MATERIALS - 555
places, which are equipped with the latest approved apparatus
for extraction and concentration. A greatly improved prod-
uct is therefore available and is known as Indragiri gambier.
Myrabolans. — This tanning material is obtained from the
unripe fruit of the tcrminalia chebula, a tree growing to a
height of from 40 to 50 feet. The content of tannin, which
runs from 30 to 40 per cent, varies with the maturity of the
fruit. Of the various kinds, the "Bombay s" are the least un-
ripe, while the "lean greens" are the most unripe. The more
unripe the fruit the higher the tannin content. Bombays are
light in color and have a smooth surface skin, with coarse
wrinkles. J's (Jubbalpores) and U's (Urigorlas) are harder
than the Bombays and have finer wrinkles. Lean greens are
the most unripe fruit and produce a color very closely re-
sembling sumac. The tannin present is of the gallotannic and
ellagitannic acid derivation. The nuts should be hard in char-
acter and not of a waxy or soft appearance, otherwise diffi-
culty is encountered in grinding. This softening is likely to
happen, however, if the nuts are stored in a damp place.
Not only does the fruit from this tree contain tannin, but
the bark is also high in tannic acid. Extracts from the bark
show high percentages, but they have not been introduced to
the trade to any extent.
Divi-divi. — This tanning material is obtained from the dried
pods of the ccesalpinia coriaria, a native tree of Central Amer-
ica growing to a height of about 30 feet. The pods con-
tain from 40 to 45 per cent of tannin of the pyrogallic and
ellagitannic variety. When used in a concentrated liquor it
produces a heavy and firm product very desirable in the manu-
facture of sole leather. In dilute liquors, and when used in the
drum or paddle, it produces a very fair color on light leather.
Algarrobilla. — This tanning material is found in Central
America and is derived from prosopis pallida. It appears
on the market as long pods with a fairly high tannin content.
Some of this material has been sent to the United States as
a mixed tanning material, but its use has not become general.
Mimosa bark. — This bark from the acacia arabica is used
556 PRACTICAL TANNING
largely in India for tanning kips. It contains from 12 to 20
per cent of catechol tannin.
Wattle bark. — The bark is from various species of Aus-
tralian acacia, and on account of the high tannin content, run-
ning in some cases as high as 50 per cent, it bids fair to be-
come a very important factor in the production of leather.
A great deal of work has been carried out with this material
during the past few years, and the results obtained look very
promising.
Palmetto. — The saw palmetto of Florida, sobal serrulata,
contains considerable tannin in the roots, and from it an
extract may be made which produces a light-colored leather.
As the supply of palmetto is very large, it offers a raw
material for extract manufacturers which should compete
closely with some of the other common extracts, In about
1904 an attempt was made to introduce this tanning material,
but for some reason it did not meet with an enthusiastic re-
ception. Recent attempts, however, have been somewhat
more encouraging, and it is now being used successfully in
tannage where a soft and mellow leather is required.
Sulphite cellulose extract. — In the manufacture of wood
pulp by the sulphite process, the ligneous matter is dissolved,
leaving the cellulose in a fibrous condition. The liquor thus
formed is purified by removing the objectionable constituents,
and the resulting product is concentrated by evaporation until
a liquor of the consistence of an ordinary tanning extract is
obtained.
This extract, when tested by the hide-powder method, shows
about 25 per cent of a substance absorbed by the hide powder.
It is not claimed by the manufacturers that' this substance is
tannic acid, but it is claimed that this absorbable material will
produce or help to produce leather. On account of its low
cost and certain other valuable properties sulphite cellulose
extract is used in large quantities with entire satisfaction.
It may be used alone, but better leather is produced by mixing
it with other tanning extracts. It finds its largest application
as a filler in extract tannage of sole leather where it seems to
VEGETABLE TANNING MATERIALS - 557
give weight and aids in producing a light-colored product.
A series of tests carried out by the author indicates that sul-
phite cellulose extract may be used to advantage as a bottom
in the manufacture of heavy leather. By so doing, the stock is
given a light colored bottom which remains even after the
treatment with other tanning materials.
CHAPTER XVIII
SYNTHETIC TANNING MATERIALS
During the past fifty years, chemists have been endeavoring
to produce tannic acid synthetically, but up to the present
time their efforts have been without success. There are, how-
ever, a number of products on the market which are spoken
of as synthetic tanning materials, but this term is incorrect
and misleading, as none of them bears the faintest relation to
true tannic acid. Practically all of these compounds are de-
rived from coal tar, and are either condensation products or
derivatives of aromatic compounds.
The first really important work along these lines was when
Stiasny succeeded in changing the well-known condensation
products of phenol and formaldehyde into a water-soluble
compound, and showed that the product possessed tanning
properties. This reaction is accomplished by acting upon two
molecules of phenol-sulphonic acid with one molecule of for-
maldehyde, and then neutralizing the resulting product with
sodium carbonate. The product at first prepared by Stiasny
was originally called "syntan" but on account of objection
was later called "neradol."
For the production of what is now sold as neradol D a
mixture of ortho, meta, and para cresol is employed. This
compound met with fairly general application before the
World War, and when the German patents were taken over
by the Chemical Foundation, it was one of those included in
the list. Several firms in the United States are now making
a similar product. Its chief use is as a pre-tan in the produc-
tion of heavy leather. The hides are usually run in a solu-
tion of this material for about 24 hours at a density of 60°
bk., when they are transferred to strong tan liquors. Nera-
558
SYNTHETIC TANNING MATERIALS 559
dol and its substitutes may also, it is claimed, be used in con-
junction with other tanning materials.
Not only has it been shown that phenol and cresol are
capable of producing compounds possessing tanning proper-
ties, but many other products have been tested with varying
degrees of success. Among these compounds might be men-
tioned />-amidophenol, chlorophenol, trinitrophenol, pyroca-
techine, resorcine, hydroquinone, benzoquinone, mono-chloro-
hydroquinone, orcine, pyrogallol, gallotannic acid, naphthols,
naphthol derivatives, anthracene, anthracene derivatives, an-
thraquinone, and anthraquinone substitution products.
Some of the above chemicals produce condensation products
having tanning properties, while others give sulphonation prod-
ucts with marked tanning efficiency.
From the first announcement of Stiasny's success in pro-
ducing a substance which would transform hide substance into
leather, chemists as well as manufacturers became interested
in further extending our knowledge of these materials. Tan-
ners are in a credulous state of mind, and are willing to give
these new substances every advantage of experimentation.
This is no doubt due to the fact that everyone realizes that
our supply of natural tanning materials is shrinking, and we
all appreciate the wonderful results that followed the synthesis
of alizarine with the consequent building up of a synthetic
dyestuff industry.
During the World War, the Germans were forced to de-
velop every source of domestic tanning material, and as a re-
sult they resorted to the following materials : Spruce bark,
chestnut wood, sumac, willow bark, birch bark, hops, pine
bark, chestnut hulls, lentiscus, walnut bark, elder bark, and
sulphite cellulose. They also resorted to the synthetic ma-
terials which were sold under the names of triumphite, nera-
dol D, neradol N, neradol ND, and ordoval, all of which are
condensation products of formaldehyde with phenol, cresol,
and naphthaline derivatives. These synthetic materials as
well as others were used alone or in combination with the
inferior vegetable tannins mentioned.
560 PRACTICAL TANNING
American chemists are producing many of these synthetic
materials, and are continually endeavoring to bring them to
a higher degree of perfection.
An article of exceptional merit, which is recommended to
the reader, is that by George Grasser in the January, 1921,
Journal of the American Leather Chemists' Association. Some
of the most striking features, however, are quoted below :
Dihydroxybenzene (pyrocatechol) yields with sulphuric acid a sul-
phonic acid, soluble in water, which assumes a deep blue color upon
the cautious addition of formaldehyde. This liquid stands heating
to 100° C. without precipitating insolubles. However, if some formal-
dehyde is again added there follows immediately a brownish-black
color with the precipitation of considerable quantities of insoluble
condensation products. On the other hand, if the sulphonic acid is
diluted a third with water, formaldehyde then added, and heated on
the water-bath, a brown color results with complete union of the
formaldehyde to the water-soluble condensation product.
The tanning test with this condensation product, which was partly
neutralized as in the above test, yielded after a 24-hour period an
intense dark coloring of the grain, while the inner part of the pelt
was white but completely pickled. After 48 hours more, this dark
color, however, penetrated the whole thickness of the pelt and tan-
ning was completed. The washed and oiled leather was soft, full,
tough, and possessed an even gray color.
Meta-dihydroxybenzene (resorcin) can also be easily converted by
concentrated sulphuric acid into water-soluble sulphonic acids of
brown color. If this sulphonation product is then diluted one-fourth
with water, cooled down completely, treated with a few drops of for-
maldehyde and heated on the water-bath for combination of the for-
maldehyde, cooled down again, treated with a very little formaldehyde,
and then heated gradually on the water-bath while stirring, a condensa-
tion product is obtained as a mass soluble in water to a brown color.
The usual tanning test proceeded extremely rapidly; and the pelt
was completely tanned through in 24 hours with a light brown color.
The lightly oiled and dried leather showed a greenish yellow color,
was plump, tough, and soft.
Para-dihydroxybenzene (hydroquinone) was converted into the
water-soluble sulphonic acid with concentrated sulphuric acid at 100°
C. ; this, treated with a little formaldehyde at ordinary temperature,
solidified immediately to a white, solid mass, which was soluble in
water, and which had completely fixed the formaldehyde. If this
mass, however, was heated for a longer time at 100° C., a light brown
color appeared and the condensation product was less soluble in water.
A small excess of formaldehyde and moderate warming leads to dark,
violet-colored, insoluble condensation products.
Tanning, carried out in the usual way, proceeded somewhat more slowly
and after a 7-day period yielded a brown-colored, tough, and soft
but rather thin leather.
Of the trihydroxybenzenes, only pyrogallol and phloroglucine were
used in this investigation. Pyrogallol, upon sulphonation with con-
centrated sulphuric acid, yielded a violet-colored, water-soluble sul-
phonic acid, which, when treated with formaldehyde, at first while
SYNTHETIC TANNING MATERIALS 561
cooling and finally while warming, solidified and yielded a deep red-
brown, water-soluble mass.
Tanning carried out in the usual manner, yielded after 24 hours a
dark-colored grain and white, pickled interior. The dark-colored part,
however, penetrated the whole pelt quickly and was complete in 7
days. The resulting leather possessed throughout a dark color, was
plump, soft, and tough.
In connection with the phenols, quinone may be briefly discussed,
its use as a practical tanning material being first described in German
patent 206,957 of April 30, 1907. According to this process, only
400 grams of quinone are used to 100 kilograms (kg.) of pelt, and the
pelt is tanned with it in 5 hours in a drum. Leather produced in this
manner, in the course of tanning assumes first a red, then a violet,
and finally a brown color, and its resistance to water, acids, and
alkalies will be much greater than with all other known tannages.
The chemical properties of this tannage have also given a motive to theo-
retical consideration and according to Thuau (Coll., 1909, 363, 211) in tan-
ning with quinone-like bodies, leather is formed by the quinone entering
into reaction with the amido group of the protein molecule according
to the equation:
2R.NH 2 +2C 6 H 4 <^ = C 6 H 4 <^g + C 6 H4(O.NH.R) 2
(hide) u uti (leather)
Fahrion demonstrated that during quinone tannage the content of
active oxygen in the quinone becomes smaller, and only the amido
group of the hide protein can effect this. Dianilin-quinone might be
named as a known analogy.
Distinct quantities of hydroquinone can be actually detected in a
used solution of quinone. Hide can also be tanned by saturating
with hydroquinone and oxidizing with air. When such hide is taken
from the hydroquinone bath and brought into the air, in the presence
of^alkali, it is colored, first red, then violet, blue, and finally brown,
and is converted into a quinone-tanned leather. There is still to be
mentioned that quinone is also able to effect a pseudo-tannage. If
quinone is left standing for a while in water, a nearly black, amor-
phous body is formed which is almost insoluble in water, but which is
abundantly absorbed by hide powder. However, it is not changed
into such an insoluble form as is the case with other tanning materials.
From the series of nitro compounds, trinitrophenol (picric acid)
C 6 H 2 (N02)30H was investigated. If picric acid in concentrated solu-
tion is used for a tanning experiment, the pelt is entirely penetrated
by it in a few days. However, oiling hide tanned in such a manner is
difficult, since the fat is poorly absorbed. After drying, a fairly soft,
but thin leather is obtained which easily loses color and tastes in-
tensely bitter. These disadvantages prevent the general utilization of
picric acid as a tanning material.
If picric acid is sulphonated with concentrated sulphuric acid and
formaldehyde gradually added, condensation takes place to a water-
soluble product which precipitates gelatine. By the introduction of
bromine, however, a water-insoluble product is formed.
Of the aromatic alcohols, the di-alcohols show a characteristic be-
havior because they condense with sulphonic acids with the elimina-
tion of water, without the assistance of aldehydes. Besides, mono-,
disulphonic acids and the higher sulphonated products of phenols, the
homologous cresols, xylenes, and naphthenes (German patent 300,567)
also enter into the reaction. The condensation between the com-
ponents takes place extraordinarily easily, with liberation of so much
562 PRACTICAL TANNING
heat that the process proceeds quantitatively. On the other hand,
dilute solutions must be heated to 100° C. when the process is com-
pleted in a few minutes. The products obtained are exceptionally
pure, crystalline, and with their power of precipitating gelatine show a
powerful capability to tan hide. The reaction is as follows:
2 0H>C,H a CH3+HO.C,H 3 -aminophenol, chlorophenol, picric acid, mono-
chlorhydroquinone and the mono- and disulphonic acids of beta-naphthol.
The phenols only slightly soluble in water, such as alpha- and
beta-naphthols, as well as the simple and substituted amines and
aminophenols, either when existing in salts or as free bases, do not
give precipitates with gelatine solutions. But if conditions are
provided favorable to oxidation, both phenols and aminophenols
give precipitates which are insoluble in boiling water. This fact led
the investigators to experiment with oxidation products of the phenols,
especially ordinary quinone. They discovered that the gelatine
quinone precipitate is the most stable form of insoluble gelatine at
present known, for it resists not only the action of boiling water,
but even of dilute acids and alkalies. The time required to render
gelatine insoluble by means of quinone is less than two hours at
15° C. The quinhydrones react similarly, only more slowly. On the
other hand, experiments with formaldehyde gave a product which
dissolved completely under repeated treatment with hot water and
which slowly lost formaldehyde when subjected to dry heat. Further-
more it is dissolved in the cold by hydrochloric acid and dilute
alkalies.
The same results were obtained with hide as with gelatine, either
with phenols and aminophenols in the presence of oxidizing agents,
or with quinones without oxidation.
Comparative experiments with other substances capable of reacting
with hide substance show that a liquor containing only 1 part of
quinone per 100 parts by weight of raw -pelt renders the latter
insoluble, transforming it into a leather whose resistance to the action
of water, acids, and alkalies is superior to that of any other leather
known — chrome leather included — and whose resistance to wear is at least
equal to that of the best leather tanned with oak bark.
The analysis of used quinone liquors reveals the presence of
hydroquinone, which proves that a part of the quinone was used
to oxidize the hide substance, while the remainder entered into a
stable combination with the oxidized hide. Since hydroquinone is
readily oxidizable, the yield will be greater if means are provided
to re-oxidize it. The provision of conditions favorable to oxidation
favors this tannage, and the use of catalyzers, such as the laccases,
artificial peroxidases, and acetates of Mn, Ce and La, consequently
produces a better and more rapid tannage. Meunier has pointed out
that oxidases are to be found among the soluble matters given up
by the hide during tanning.
Methods of preparation and properties of quinone. — In general, quinones
can be obtained' by oxidation of the corresponding paradiphenol compounds
and can also be produced when more than two hydroxy groups are
present, provided two of these groups are in the para position. They
are formed likewise by oxidation of numerous compounds derived
from the phenols such as />-phenol sulphonic acid and />-aminophenol,
but the method often employed in laboratories is to oxidize, by means
of chromic acid, certain mono-substituted derivatives of benzene,
such as aniline.
Among the chief properties of quinone of interest to the tanner
are the following: It is soluble in cold water to the extent of only
about 0.5 .per cent., but dissolves to a considerably greater extent
in warm or acidified solution. In practice, it is dissolved in slightly
acidified boiling water, but this should be done in a closed tank, as
the product is volatile and easily carried away in the vapor. Acid
solutions are stable for a much longer period than neutral or alkaline
solutions, and light is harmful in causing oxidation, Quinone
SYNTHETIC TANNING MATERIALS 565
solutions should not be brought into contact with metals nor put
into wooden vats which have been used previously for vegetable
tannins, as they will darken in color and lose their property of
giving a clear tannage. Quinone is readily kept in the crystalline
state either in wooden or tinned containers. It is dissolved only as
needed and not more than will dissolve.
Application in the tannery. — Quinone alone, employed to the extent
of H parts to 100 of pelt, is capable of completely tanning the stock
in a few days. It would therefore seem at first sight that quinone
tannage constitutes an ideal process -both from the standpoint of
speed and of cost. In reality this is not the case, and the reason lies
in the fact that the leather is sold by weight, a procedure which was
established in times past, when hides sold at a price reasonably
higher than that of tannin, in order to induce the manufacturer to
get enough tannin into his leather to ensure complete tannage. Since
then the situation has changed, and hides have increased in price out
of all proportion to that of tannin. The result of this has been,
especially in the case of rapid tannages, an increase in proportion of
tannin, combined or not, in the leather, until now some of the better
grades often contain not more than 30 to 35 per cent of hide
substance.
It is quite evident that under these conditions tanning with
quinone alone cannot compete with tanning with vegetable extracts,
excepting for light leathers sold by the square foot. Nevertheless,
on account of its great value as a preliminary tanning agent, it
has become an article of considerable importance. Before the ap-
pearance of quinone, formaldehyde was employed preliminary to
vegetable tanning, with the object of isolating and strengthening the
hide fibers so as to enable the hide to be put into concentrated
liquors without harm. But the formaldehyde does not remain fixed,
and experience has shown that after storing for some months these
leathers undergo change, becoming hard. No such difficulty is found
with the use of quinone, and hides first treated with quinone fix
vegetable tannins with remarkable speed, without any disadvantage either
to the leather or to the modern methods of rapid tannage. Further-
more, its use has increased rapidly in the manufacture of all kinds of
leather, particularly sole leather.
The Leather World of March 10, 1916, devoted considerable space
to the use of quinone as a preliminary tanning agent. It has been
used for sole and strap leathers, where it has been demonstrated that
such leathers possess greater resistance to wear than others not so
treated. It has also been used for upper leather and has even been
employed with chrome leather.
For box calf it is best not to shave the skins too deeply after
the beam-house work, the quinone giving them sufficient suppleness.
The operation consists in adding to a soak of 100 kilos of skin 600
grams of quinone and 300 grams of 80 per cent lactic acid. If
the stock has been bated, the acid is unnecessary. For ordinary
leathers, acetic acid is preferable. The tannage is then carried out
with a one-bath chrome liquor, using only 60 per cent of the usual
amount of chrome and neutralizing agent. Box calf made in this
way is better than the ordinary in that it is more permeable to air
and gives a shoe which is more hygienic and cooler in Summer; it
is more supple and has a finer grain; and in dyeing, the black is
distributed more uniformly, not only over each skin, but over all
skins in the same lot, thus increasing the number of first-grade
skins. When used for colored calf, the proportion of sumac and
gambier can be greatly reduced and the grain is never hard or brittle.
The same holds true for smooth calf, whether black or colored.
566 PRACTICAL TANNING
Preliminary quinone treatment of kidskins intended for shoes makes
possible the use of one-bath liquors and makes the sorting for colors
unnecessary.
During the past two years attention has been called to
the use of several other organic compounds which possess tan-
ning properties and which promise to open up a new field for
the preparation of synthetic bodies for leather manufacturers.
Most of the compounds are sulphonated products of the higher
hydrocarbon compounds.
CHAPTER XIX
UNUSUAL TANNING PROCESSES
Electric tanning. — The first attempt to utilize electricity
as an aid to tanning was by Crosse in 1850. Later, Ward
continued the researches of Crosse, but without any marked
success. From time to time since that date investigations
have brought out new suggestions, but they all depend upon
electrolysis of the tanning solution.
The first process which was at all successful was intro-
duced by Meritens in 1874. In this process the usual tan-
ning solutions were employed. On the bottom of the pit was
placed a plate of graphite connected to the positive pole, the
hides were entered, and a zinc plate was placed in the top of the
solution. The zinc plate was connected to the negative pole and
the current allowed to pass through the liquor, a regular 110-
volt current being used. Tanning by this treatment was said to
be complete in 35 days. The cost of the current in this process
is an item which must be considered, and unless it can be ob-
tained cheaply it is prohibitive.
Although other attempts were made, the next large-scale
experiments were undertaken in Sweden, when an alternating
current was employed and copper electrolysis used. The time
required was 45 days. In 'this process the hides were sus-
pended parallel to the electrode. The current was thus caused
to pass through the hides.
A process devised by Worms and Balle consists in the use
of ordinary drums. On the inside of the drum, on opposite
sides, were placed copper disks connected by rods to the source
of current. From 1000 to 1200 lb. of hides were placed in
the drum and about 75 gallons of chestnut liquor added, and
the drum set in motion. Through the trunnion 1^ gallons of
oil of turpentine was introduced, and the current turned on.
567
568 PRACTICAL TANNING
The intensity of the current was 10 amperes with a tension
of 70 volts. The tanning bath was strengthened from time
to time. When well struck through, the current was turned
off and the drum run for another interval.
It was claimed that bull hides could be tanned in 5 or 6
days by this process, while lighter hides required a shorter
period.
A process devised by Place consisted in placing the hides
in closed vats provided with agitators, and along the bottom,
a series of comb-like conductors. The hides were placed in
the vats containing a liquor standing at about 5° Be. The
first treatment extended over a period of 8 hours with an in-
tensity of current of 20 amperes. The hides were then thrown
into another vat with 5° Be. liquor, but no current was passed
through the liquor. Agitation, however, was employed, and
the process for the heaviest hide was complete in about 100
hours.
Although other processes have been and still are constantly
being suggested, no process has as yet been sufficiently success-
ful to warrant serious consideration.
Vacuum tanning. — Many attempts have been undertaken
to make this commercially feasible, but up to the present time
none of the vacuum processes have met, with success.
Seymour-Jones method. — By this method the de-haired
and washed hides are placed in a 0.5 per cent solution of for-
maldehyde, where they are allowed to remain 4 days. The
grain is then fixed by placing on frames in liquor of mixed
tanning material standing at 45° bk., a rocker system being
employed. The hides remain in this liquor for 48 hours. They
are then transferred to a drum and enough liquor at 75° bk.
to cover the stock is introduced. A small quantity of turpen-
tine is added to prevent frothing. After the hides have been
entered the drum is set in motion and run for 2 hours. The
door is opened and the drum allowed to remain at rest for
4 hours. It is then run again for 3 hours and allowed to
rest over night. The next day the drum is run in the same
manner as on the first day, when by night the stock should be
UNUSUAL TANNING PROCESSES 569
tanned through. The hides are dried in a fairly warm room,
sammied, scoured, oiled off, and dried in the cold. They are
then re-tanned with strong extract in a mill, running for 15
minutes. The hides are next oiled off with a sulphonated oil
on the grain and again set-out. Another coat of oil is ap-
plied and the stock dried in a cool loft. When dry, they are
waxed, rolled, and finished.
This method is especially successful on heavy calf and is
claimed to be applicable to heavy hides as well.
Organ leather. — The principal uses of leather in the manu-
facture of organs have been thoroughly investigated by the
United States Bureau of Standards, and are as follows :
1. Bellows
(a) Gussets
(b) Hinges
(c) Valves
2. Pneumatic pouches or diaphragms
3. Pneumatic valves
Alum-tanned sheepskin appears to be used by most manu-
facturers for bellows, gussets, and hinges. Leather for the
hinges of the folds of the bellows is required to be firm and
well stretched. A soft, pliable, unstretched leather is required
for the gussets or corners where it is necessary that the leather
fold in or out as the bellows move up or down. It is neces-
sary that the leather be free from any groan or squeak while
in motion.
A small, rectangular piece of leather is used for bellows
valves. This leather is held over the valve-opening in the side
of the bellows by tacks or a strap. The leather should be
firm and well stretched so that it will lie flat and not curl
up on the edges. Bark-tanned sheepskins, chrome-tanned
cowhide, and chrome-tanned calf are used for this purpose.
For box or pouch pneumatics, sheep or lambskin skivers
are generally used. A skiver is defined as the grain split
of a sheep or lambskin. The split is taken off when the skins
570 PRACTICAL TANNING
are in the rawhide state. These are mostly vegetable-tanned,
but occasionally some alum-tanned skivers are used.
A variety of leathers are used for pneumatic valves. The
most common are alum-tanned and chrome-tanned calf or
cowhide leather. Some sheep and goat leathers are also used.
For miscellaneous joint packings, bark-tanned or chrome-
tanned sheep fleshers are generally used, while in some cases
seal fleshers are employed.
Leather for player-pianos. — The uses for leather in player-
pianos follow the same general classifications as described
for organs, the chief difference being the leathers used on the
pneumatic valves. While a variety of goat, sheep, cowhide,
and calf leathers are used, the most common is chrome calf
re-tanned in a vegetable-tanning material. Leather used for
this purpose should be firm, similar to calf for shoe uppers.
The flesh side generally rests on the valve-seat, which is metal,
and forms an air-tight joint. The grain side is glued to a
wooden disk on the valve-stem and is preferably napped to
facilitate the gluing. This leather should be free from acid,
as, if this is present, corrosion of the valve-seat may occur,
causing sticking. It should also be dry to prevent sticking to
the valve-seat, which thus prevents the quick and positive
action necessary for successful operation.
Any kind of leather that will not harden in hot climates,
will not stick to the valve-seat, does not contain acids which
cause corrosion of the valve-seat, and is firm, can be used
satisfactorily on valves. No definite standard has been
adopted, and the same manufacturer often uses different kinds
of leather, according to what may be obtained to the best
advantage.
Pneumatic pouches. — Manufacturers have experienced their
greatest difficulty in securing leather of the desired qualities
for use on pneumatic pouches. Sheep or lambskin skivers
are almost universally used for this purpose.
Briefly, the operation of the action of a player-piano may
be described as follows : Air is pumped in from the room
through the openings in the tracker-bar and is exhausted into
UNUSUAL TANNING PROCESSES 571
the room through the bellows valve. When one of the per-
forations on the music-roll passes over its corresponding open-
ing on the tracker-bar, air is pumped through a tube or duct to
a chamber directly beneath the pneumatic pouch or diaphragm.
This causes the pouch to be raised. A small cardboard disc
mounted on the center of the pouch engages with the valve-
stem, raising it, together with the leather disc, which has been
seated on the valve. This action allows the air to be exhausted
from the small wing-bellows by suction, which causes the bel-
lows to collapse. The collapsing of the bellows in turn allows,
through suitable mechanical devices, the particular note to be
sounded. When the opening on the music-roll has passed
over its opening on the tracker-bar the suction is relieved, the
pouch falls, the valve is closed and the wing-bellows fills again
with air.
It will be seen that this leather diaphragm is a most im-
portant part of the action. If it is too tight, stiff, heavy, or
leaky, the valve movement will lag and difficulty will be
experienced.
A skiver for this purpose must be soft, pliable, light in
weight, uniform in thickness, and as free as possible from
"pin-holes" or larger openings. It is not required to -be air-
tight, and leather of this type is naturally porous on account
of the holes left when the wool is pulled. These holes are
partly filled in the process of manufacture, but there are
often many holes remaining through which light is plainly
visible, and which would allow a sufficient volume of air to
pass so as to affect seriously the positiveness of the action.
On this account the skivers are carefully examined in the
factory and those portions unsuitable eliminated.
It is difficult to secure skivers tight enough and of the
thickness desired. On some small pneumatics skivers not
more than 5/1000 or 6/1000 of an inch thick are required,
while on larger pneumatics the thickness may reach 10/1000
or 12/1000 of an inch.
The leather must also be soft and stretchy, as it is formed
into a pouch by a mold of spherical shape. The pouch is then
572 PRACTICAL TANNING
placed over the chamber in the player-board and the edges
are glued to the board.
The quality of a skiver is entirely dependent upon the type
of sheey from which it is taken. The nearer the animal is
to a hair type the better the skiver will be, in that it will be
finer grained and will have smaller pores or hair-holes, which,
of course, will make it tighter.
The majority of the sheep are of the fine, heavy-wooled
merino type, or closely approaching it. In order to allow
sufficient space for the wool to grow on fine-haired sheep,
nature provides ridges on the pelt so that it resembles a cor-
rugated surface. These ridges are so high that they affect
the quality of the leather produced and make it impossible to
secure a skiver from these pelts suitable for piano manufac-
turers. Thus, the original source of skins for suitable skivers
is from animals of the hair type, which, as a rule, are ob-
tained from foreign countries.
Skins imported for this purpose are preserved by pickling,
and are split after having the pickle withdrawn, but still con-
tain some sulphuric acid which cannot be eliminated from the
fiber. This necessitates the use of tanning liquors of such
nature as to make the resulting leather feel" relatively harsh.
Foreign manufacturers can split the fresh skins directly in the
limes and then drench or "puer," as the case may be, and
send the splits directly to -the tanyard. So-called '"sweet liq-
uors" can be used, thereby producing a soft and pliable leather.
It is believed that there is no factor in the working of the
pickled pelts in the United States which would produce pin-
holes in the leather. The question of obtaining compara-
tively tight skins is chiefly a matter of selection. England
splits more lambskins than are split in the United States, and
thus has a larger volume of skins from which to make a
selection. Also, there are tanners in England who make a
specialty of preparing leather for the organ and piano trades,
while in America no tanner does this on any large scale.. In
order to emphasize the importance attached to the selection,
one manufacturer states that out of an annual production of
UNUSUAL TANNING PROCESSES 573
75,000 to 100,000 dozen skivers, he would not feel safe in
offering over 1000 dozen suitable for use in piano actions.
The volume of business represented by the use of skivers
in this industry has been considered relatively small It is
probable that the largest manufacturer would use about 2000
dozen per year, while the smaller manufacturer would use
only 100 dozen per year, or even less. If the total were
known it would probably represent a sizable volume of busi-
ness. The American tanner generally, therefore, has not
thought it worth while to solicit this business on account of
its relatively small volume. Considerable work would be re-
quired in making the necessary selection, which would add to
the cost. On -this account it has been thought that the Amer-
ican tanners cannot compete with foreign tanners on the same
price basis for the same quality.
Substitutes. — Rubberized fabric has replaced leather for
covering bellows and pneumatic wing-bellows. This material
possesses the advantages of being uniform and air-tight
when first placed in use. It is necessary, however, to replace
these fabrics, which fail in from 3 to 10 years' time, according
to the operating and atmospheric conditions. This failure is
due to the deterioration of the rubber which cracks and thus al-
lows air to leak through.
A very thin, rubberized silk has been tried for pneumatic
pouches in place of skivers, but its use was not successful.
Its life is short, and in time the rubber coating hardens, thereby
causing a loss in pliability. Leather is ideal for this pur-
pose, and if the quality is right, it will last a lifetime.
The use of tanned cattle guts has been proposed, and some
alum-tanned colons have been used. One manufacturer states
that the alum-tanned guts are so affected by moisture that
they dry out as tight as drumheads. One supply dealer has
produced a vegetable-tanned colon which, it is claimed, will
retain its pliable condition. This material is produced only
in small pieces about 8 by 16 inches. It possesses the distinct
advantage, however, of being practically air-tight under the
pressures used in the instruments. Some difficulty has been
574
PRACTICAL TANNING
experienced in making and gluing pouches from this material,
but it is believed a little study and care in handling will
obviate this objection. The possibility of the use of whale and
porpoise intestines is now being investigated.
The author has developed a process for making leather
from the so-called bung gut, which answers all requirements
for piano leather and is being favorably regarded by the trade.
Shark-skin leather. — For several years the author has been
interested in the utilization of shark and porpoise skins for
Figure 120. — Hauling in netted sharks.
leather manufacture, and has investigated the methods of
handling this class of raw material. Through this work he
became acquainted with Alfred Ehrenreich, president of the
Ocean Leather Co., who has also spent many years in the study
of this subject, and through whose efforts the establishment
of an entirely new industry has been made possible.
During several recent visits to the Everglades of Florida
UNUSUAL TANNING PROCESSES
575
and to Morehead City, North Carolina, the shark and por-
poise have been studied in their native haunts, and the fact
demonstrated beyond a doubt that it is possible to handle
these fish in a commercial manner. As a result, the
Ocean Leather Co. has now in operation at Morehead City
a modern plant where the hides are removed and salted. In
addition, the livers are rendered for their oil and the flesh is
Figure 121.— Roping a shark.
Figure 122.— -Landing a shark. Note
skins on pier.
converted into a high-grade fertilizer stock. Another station
at Sanabal Island, Florida, is also operated by the same
company.
Catching and handling. — The sharks are caught in nets of
3-inch mesh, 360 yards long and about 12 feet deep. As the
boat picks up the buoy, one man standing in the stern pulls
in the cork line, (figure 120), while another hauls up the lead.
When the shark is brought up, a rope is placed over the tail
(figure 121), or, in some cases, a hook is placed in the mouth.
576 PRACTICAL TANNING
If the fish is alive, it is killed by a sharp blow with an axe,
and then lifted on board by means of a block-and-fall. In an
average haul from 10 to 20 sharks are taken from each net.
On arriving at the dock, the fish are unloaded (figure 122),
and the work of dressing is started at once. The first opera-
tion is to remove the fins and tail. The former are tacked on,
a rack and allowed to dry in the sun; they are used by the
Chinese for making soup. The fish is then cut down the back,
and a circular cut made over the neck and around the gills.
The skin is finally removed in such a manner that only the
holes of the pectoral fins and rectal opening remain in the
pelt. The flayed skins are placed in salt for 24 hours, fleshed
on the beam or machine, and placed in bundles for shipment
to the tannery.
The livers are thrown into barrels, where they are al-
lowed to remain for several days to disintegrate, and are then
placed in steam- jacketed kettles and heated to boiling for
about an hour. From the kettles the oil is run into washing
and settling tanks, where the gurry is separated from the oil.
The oil is then drawn into a second tank, again washed, and
finally run to a third tank, where it is stored until ready for
shipment. Exposure to the sun and rain effects more or
less bleaching.
The carcass at present is used in the manufacture of fish
scrap for fertilizer stock. Briefly, it is thrown into the
hopper of a specially designed mill, where the flesh and bones
are ground to a fine pulp, which is dried in a rotary dryer.
This grade of fish scrap contains on an average 15 to 17 per
cent of nitrogen expressed as ammonia.
Treatment of skins. — The shark skins as they arrive at the
tannery, are soaked in water to remove the salt and are again
fleshed. Skins for bag leather are limed and bated in the
usual manner and tanned in bark. The tanned skins are then
treated to remove the shagreen, and after washing and color-
ing are ready for the finishing process.
The skins to be used for shoe leather are not limed or
bated, but are at once treated for the removal of the sha-
UNUSUAL TANNING PROCESSES . . 577
green. This so-called shagreen is a hard layer which covers
the whole fish ; it has the appearance of coarse sand paper,
and is almost impossible to remove by mechanical means. The
elimination of shagreen from the raw skins is a problem which
has remained unsolved until recently. A process developed
by the author consists in soaking the skins in an acid solution
which accomplishes the removal of the shagreen in about two
hours. By leaving skins in this solution for a week no dam-
age is done. The skins are neutralized in a salt solution, to
which soda ash is added from time to time. When free from
acid the stock can be tanned by any of the methods now in
vogue.
Porpoise leather. — Although porpoises are not as plentiful
as sharks they deserve brief mention. Porpoises travel al-
most exclusively in schools, and are, therefore, usually caught
in the purse seine (net). The method consists in surrounding
the fish and then landing them on the beach. These fish vary
in size from 3 to 30 ft. Their skin carries a heavy layer of
blubber, which is split off and rendered to obtain lubricating
oil. On the face of the porpoise is an extra heavy blubber
known as junk, which, when rendered separately, yields a
more valuable oil than ordinary blubber oil. In the jaw cavity
is about 1 oz. of oil, known as jaw oil. This oil is carefully
rendered and brings from $30 to $80 per gallon.
The top layer of hide from which the blubber has been
split is limed to remove the rubbery surface and open up
the fiber bundles. It is then tanned by either the oil or the
vegetable process as applied for other kinds of leather.
CHAPTER XX
ARTIFICIAL LEATHER, DOPE SPLITS, AND PYROXYLIN
FINISHES
Pyroxylin. — The application of pyroxylin finishes to cloth
and leather has become a very important industry. This sub-
ject was well set forth in a lecture by Gillett Wyncoop, of the
Anderson Chemical Co., before the tanning and leather chem-
istry students of Pratt Institute, Brooklyn, N. Y.
The uses of pyroxylin for coating fabrics, leather, and pa-
per materials is an industry which has grown largely within
the last 20 years. A chemist in England discovered that by
mixing pyroxylin with castor oil or various other oils, and
putting certain colors, either dyes or pigments, in the solu-
tion, coating this on a fabric, and then running it through a
roller with a certain pattern engraved on it, gave a fabric
which looked much like leather. It was pliable and did not
crack easily, was waterproof, and would stand a great deal of
wear and exposure to the atmosphere. About the same time
certain industries in Newark, N. J., discovered these same
properties, and in this manner began the manufacture of arti-
ficial leather and finished splits.
In the manufacture of artificial leather, pyroxylin, as a
rule, is dissolved in a mixture of alcohol and amyl-acetate
in about the proportion of 1 to 1| lb. of pyroxylin, according
to the grade of artificial leather desired, to a gallon of solvent.
Solvents. — One reason why the use of pyroxylin did not
receive recognition earlier was on account of the solvents
used in its manufacture. There were a great many solvents
for pyroxylin, but few that would make a good film. Nearly
all of the ethers, alcohols, aldehydes, and some of the hydro-
carbon oils are solvents for pyroxylin, but only a few give
proper results. Among the best solvents should be mentioned
amyl-acetate, acetone, acetone oil, butyl-alcohol, ethyl-alcohol,
578
ARTIFICIAL LEATHER _ 579
and methyl-alcohol. As a rule, however, a mixture of two
or more of the above solvents is used rather than a single
compound, a favorite mixture being amyl-acetate, acetone,
and wood alcohol.
To dissolve cotton in wood alcohol it is necessary to have
a grade of alcohol that is at least 94 per cent.
There are a number of substitutes for amyl-acetate, how-
ever, which can be used to advantage. One of the most ex-
tensively used today is ethyl-acetate. It has a boiling point
near grain alcohol, around 79 or 80°, and if a solution is ap-
plied to leather or imitation leather, and the film is warmed
by placing over hot pipes, the ethyl-acetate will attract very
little moisture and thus will work satisfactorily. But unless
it is 100 per cent pure it has' little use as a substitute for
amyl-acetate in dope finish. It is employed, however, fairly
extensively in the artificial leather industry where goods, after
spreading, are run over steam pipes or run through a chamber
in which a blast of hot air is driven.
Ketones 'are very active solvents for the cotton, and will
dissolve the cotton quicker than any other substance. Acetone
is the most rapid solvent, but in practical use it is unsatisfac-
tory, on account of its low boiling-point, about 56°, and quick
evaporation. It will evaporate before the goods can be spread.
All of these solvents may be cheapened somewhat by dilu-
tion with naphtha or benzene. Pure amyl-acetate will stand
nearly 50 per cent dilution with naphtha or benzene and still
be a solvent.
Procedure.— After the pyroxylin is dissolved in the amyl-
acetate and wood alcohol, a certain amount of castor oil or
other oils is added (in artificial leather about 1-| to 2 lb, of
castor oil to 1 lb. of pyroxylin is added to the solution).
They are either dissolved separately and mixed or all are dis-
solved together. After the oil is added the color is intro-
duced. In artificial leather the color should be a dry insolu-
ble pigment. There is nothing especially objectionable about
the dyes except that they are likely to "crock," that is, when
rubbed with a wet cloth the color will rub off.
580 PRACTICAL TANNING
In the United States there are 8 or 10 large manufactur-
ers of artificial leather. The pyroxylin solution is spread on
all grades of material, some not much heavier than cheese-
cloth, up to heavy cloth weighing 2 lb. to the yard. At the pres-
ent time some of these higher grades of cloth with a heavy
coating are being used for even such high-grade leather sub-
stitutes as automobile cushions, but the chief use of artificial
leather is for upholstering for indoor work. It can, how-
ever, be substituted for nearly every use to which leather is
put, but, of course, is used as a cheaper product. It will wear
as a rule as long or perhaps better than some of the cheaper
grades of leather.
Acid formula. — Pyroxylin is a low-nitrated guncotton. In
its manufacture not quite as strong an acid mixture is used as
for the guncotton employed for explosives. The acid formula
employed in making pyroxylin, that is, the grade which is
used for artificial leather, is about 60 per cent sulphuric acid,
21 per cent nitric acid, and 19 per cent water.
This may be varied in a number of ways to suit the con-
ditions and qualities' of the pyroxylin required, for nearly
every industry requires a slightly different grade of pyroxylin
as to solvents and what is termed "viscosity." The higher
the temperature at which it is nitrated the higher the viscosity.
Anything much under the percentage given will not dis-
solve cotton. Methyl-alcohol, or wood alcohol, has little effect
on soluble cotton when it is absolutely pure. In technical
work we usually specify to the manufacturer of the wood al-
cohol that it shall contain 10 to 15 per cent of acetone, this,
as already stated, being one of the best solvents.
The general division of soluble cottons is as follows : A
cotton that is insoluble in ether and alcohol or a mixture of
the two (the latter is the old solvent that has been used for
50 years or more in making what is known as collodion solu-
tion), is classed as guncotton. In other words, guncotton is
insoluble in ether and alcohol solution. This mixture can
vary from 1 to 3 parts, respectively, or up to 3 parts to 1, re-
spectively. The nitrated cotton is roughly divided into gun-
ARTIFICIAL LEATHER 581
cotton and soluble cotton. A cotton with a high percentage
of non-soluble is classed as insoluble cotton. Cotton of less
nitration, soluble in ether, is called collodion cotton or pyroxy-
lin. The dividing line is not distinct. Certain cottons, when
highly nitrated, are soluble in this solution, whereas perhaps
nitrated in another way with slightly less nitrogen in the
cotton would not be soluble.
The coatings on cloth for making artificial leathers are pro-
duced in various colors. They are finished bright and dull,
the treatment for obtaining the bright finish being the same as
in finishing bright leather; that is, varnish is applied after the
last coat and a bright finish thereby produced.
Coating real leather. — This industry started about 20
years ago. At that time a firm at Newark, N. J., which was
coating a large amount of leathers, shipped several carloads
of the coated hides to their customers, and when the users
tried to unwrap the packages they could not be cut apart with
an axe. The hides were ruined. This practically killed the
use of pyroxylin on splits for a number of years, and only
recently have the tanners been willing to run the chance, as
they expressed it, of using pyroxylin instead of japan for fin-
ishing their hides or splits.
Improper coating was the cause of the hides sticking, or
the introduction of some oil that should not have been em-
ployed with the pyroxylin. There are various oils even now
used in the trade, such as boiled rape-seed oil or boiled linseed
oil. It is believed by many that neither one of these oils
should be used in a pyroxylin coating for the reason that lin-
seed, being a drying oil, will cause the goods to crack; rape-
seed oil is perhaps not so dangerous, and may last very well,
but in any case there is a question, and most manufacturers
are afraid to take a chance.
It is well known, however, that castor oil will stand almost
indefinitely, as it is a non-drying oil. It is true that goods
coated with pyroxylin to which castor oil has been added, if
kept rolled up, will sometimes dry out and something hap-
pens to the oil, and the goods will crack, snapping almost like
582 PRACTICAL TANNING
a match. However, that does not often occur, and only when
kept rolled up for a long time away from contact with the air.
If these goods that have gone bad are again given one or two
coatings of pyroxylin, they will become as soft and pliable and
as tenacious as they were before.
In making a pyroxylin for the split leather trade, the solu-
tion used is considerably thinner than the ordinary solutions,
because splits have to be coated by hand with a swab and
the liquor cannot be spread as easily or as economically under
these conditions. In split leathers, the common method for
the first coat is to use a soft, heavy brush, 2\ in. wide and
about 6 or 7 inches long, with a strap over it. This is dipped
into the solution and passed evenly over the goods ; the hides
are hung on a pole, preferably in a warm room, free as pos-
sible from moisture, as this is the one element that gives the
greatest trouble in working with solutions of pyroxylin.
For the first coat an 8 to 12-oz. solution is used. Splits
often have a heavy nap on them, and a thin solution spread
over will leave the nap standing; whereas a heavy solution
without putting nearly as much on, will, as it were, cement
the nap down. The heavier the solution the less solvent is
required, a saving, as the solvent is simply a carrier.
For the first coat on such leather, therefore, it is well to
use a 12-oz. solution. With this should be mixed for each
gallon, 3J lb. of oil, according to the softness of the leather
desired. The usual run of split leather is employed for or-
dinary carriage cushions, upholstery, etc. The color of most
of the hides coated with pyroxylin is black, this color requir-
ing 2 lb. of dye to about 50 gallons of the solution. Pigments
can be used, but as few tanners have proper mills for grinding
them, dyes are more commonly used. An advantage in dyes is
that they remain in solution almost indefinitely, whereas
when pyroxylin is mixed with pigment it is necessary to keep
stirring continually to prevent the pigment from settling out.
Having prepared a 12-oz. cotton solution to which 3 lb. of
castor oil and 2 or 3 oz. of a soluble dye has been added for
each gallon, it is spread over the goods in a warm, moisture-
ARTIFICIAL LEATHER 583
free room. About 3 lb. of this solution is required as the first
coat on a 50- foot split. A change is made in the second coat,
in order to keep the oil away from the surface. If the same
amount of oil were used in the second coat as in the first, the
goods would dry out sticky, and with very little heat it would
fry out and the color would be spoiled. The second coat is
made up with about half the amount of oil as in the first coat.
As a rule, a 10-oz. cotton is used, to which is added 2 lb. of
oil, the object being to smooth off the stock with the least
amount of material. About 2 lb. of this solution is required
for each 50-foot split. The hide is hung up to dry, and the
third coat consisting of a 12-oz. cotton, to which 6 oz. of oil
is added, is applied. When it is desired to produce a better
grade or a brighter finish a fourth coat is spread on the hide.
Having applied the necessary number of bottom coats the
goods are embossed with any design of grain desired.
To obtain a bright finish, the goods, after embossing, are re-
coated with a very thin solution of pyroxylin, say about 2 oz.
to the gallon. Care should be taken that it contains the full
amount of amyl-acetate or a substitute to keep it from having
any tendency to become whitish, as even a black color has a
tendency to show a grayish tinge if this precaution is not ob-
served. This thin coat is generally applied with a sheepskin
swab tacked over a board about the size of the brush, say 2\
by 6 inches. Bright finishes may also be improved by giving
a final coat of linseed-oil varnish.
To make a dull shade, take a solution of pyroxylin, prac-
tically 2 oz.^ to the gallon, and add 4, 5, or 6 oz. of ground
pigment to it. To be in proper condition this pigment must
be ground in some oil medium. For artificial leather, tons
of pigments are ground in castor oil. There is an objection
to the use of castor for the top coat, as it does not give as dull
a finish as it would if the color were added without any oil.
The material best suited for dull finish is crude birch tar oil.
It is made from the birch tree, and has somewhat the odor
of wintergreen oil. It can be purchased in the wholesale
584 PRACTICAL TANNING
market at 10 or 12 cents per lb., whereas the refined birch
oil costs more than that per ounce.
The crude is perhaps better than the refined oil on account
of the fact that in grinding it has less tendency to evaporate.
If not used in too large quantities this also gives a pleasant
odor to the leather. The amyl-acetate odor for leather is
rather objectionable, as even the most refined will leave behind
an amyl or fusel oil odor for a long time, even for years,
if the goods are not exposed to the air.
CHAPTER XXI
ANALYTICAL METHODS*
Water analysis. — It is quite evident that chemical con-
trol of the tannery should start with an analysis of the water
that is to be used in practically every operation which the
hides undergo while being made into leather. According to
Procter, the most important determinations are total solids,
ash, organic matter, sulphates, chlorides, iron, temporary hard-
ness, permanent hardness, magnesia hardness, free carbonic
acid, and sodium carbonate.
As a general statement, the purer the water the better it
is suited for use in the tannery. It is evident, therefore, that
the lower the total solids and ash the better for this purpose.
Organic matter is liable to be accompanied by putrefactive bac-
teria, the action of which might cause serious damage to the
hides or skins in all the beam-house operations up to the actual
tanning process. Sulphates and chlorides to some extent tend
to prevent the necessary swelling of the heavier leathers in
the tanning liquors. Also, if present in large quantities, they
interfere with the extraction of tanning material ; for example,
water containing a large amount of chlorides has been found
to cause a considerable loss of tannin in the case of oak bark,
pine bark, and sumac. Iron would unite with the tannins,
forming bad stains, and would thus make the water unsuitable
in all cases except where only black leather is to be made.
Hardness in general is objectionable, temporary being more so
than permanent. Temporary hardness slows up the soaking
process, decreases the efficiency of sodium sulphide solution
as a depilant, interferes with de-liming due to the formation
of CaCOs in the hide, and causes loss of tannin in the leach-
ing and tanning process. Owing probably to its alkalinity,
*Many of the methods given in this chapter were compiled by Ernest Little while
instructor in chemistry at Pratt Institute, Brooklyn, N. Y.
585
586 PRACTICAL TANNING
calcium carbonate causes oxidation of the tannin and con-
sequent darkening of the leather. It will react with the fat-
liquor, precipitating insoluble calcium and magnesium soaps,
as well as precipitating some of the aniline dyes. The action
of temporary hardness in forming boiler scale is well known.
Permanent hardness is as objectionable in boiler water as
temporary hardness. It would act the same as the latter in
the fat-liquors, but will cause a much smaller loss of tannins
and dyestuffs. Carbonic acid and sodium carbonate would
cause CaCOs to be precipitated in the hide during the de-
liming process. Sodium carbonate, like other alkaline salts,
will cause oxidation of vegetable tanning liquors with a con-
sequent bad color.
Total solids. — 100 cc. of sample is evaporated to dry-
ness in a weighed platinum dish on a water-bath, then dried
to constant weight at 100° C, cooled in a desiccator, and
weighed. Increase in weight X 1000 = parts total solids
per 100,000 parts of water.
Ash. — The above residue is ignited until the ash is white
and weight is constant, cooling the dish in desiccator as usual,
before weighing. Weight of dish -f- ash — weight of dish
= grams of ash. Grams of ash X 1000 = parts per
100,000.
Organic matter. — Moisten the ash in the platinum dish with
ammonium carbonate solution. This solution is then evap-
orated to dryness, dried at 100° C, and weighed. This
weight, subtracted from the weight of the dish -\- total sol-
ids, gives the weight of organic matter in the sample, then
grams of organic matter X 1000 = parts per 100,000.
The ammonium carbonate solution is added in order to cor-
rect for any carbonates which may have been decomposed by
overheating.
Sulphates. — 250 cc. of filtered sample is acidified with 2
cc. of concentrated hydrochloric acid. The solution is heated
to boiling, and 15 cc. of 10 per cent barium chloride solution
is added very slowly with constant stirring. Boil the solution
ANALYTICAL METHODS 587
gently for 10 minutes, allow the solution to stand about 30
minutes, filter, wash thoroughly with hot distilled water, ig-
nite, and weigh. Weight of BaS0 4 X 0.342X400 = parts
of S0 3 per 100,000.
Chlorides. — 100 cc. of sample is placed in a small porcelain
casserole and 2 drops of potassium chromate solution ( free
from chlorides) added. Run in N/10 silver nitrate solution
(4.25 grams AgNC>3 per 250 cc.) from a burette until one
drop causes a permanent red-brown tinge in the solution, then,
cc. N/10 AgNO s solution used X 0.00355 X 1000 = parts
of chlorine per 100,000.
Iron. — 500 cc. of sample is made acid with sulphuric acid,
and evaporated to dryness in a porcelain casserole. Add a
few drops of concentrated nitric acid and ignite gently until
all organic matter is destroyed. Warm the residue with 15 cc.
distilled water and 5 cc. 1 : 1 HC1, and wash the filter-paper
thoroughly. Add dilute potassium permanganate solution
drop by drop until slight pink color remains 5 minutes. Avoid
adding too much dilute potassium permanganate solution. To
this colorless solution add 10 cc. of 2 per cent potassium
sulphocyanide, put in Nessler tube and dilute to 100 cc. and
stir thoroughly. Into a second Nessler tube add 15 cc. of
distilled water,, 5 cc. 1 : 1 hydrochloric acid, then treat with
dilute potassium permanganate and potassium sulphocyanide
exactly as above, dilute to a little less than 100 cc. (about 99.5
cc.) and add standard iron solution drop by drop until in the
well-mixed solution is the same depth of color as in the first
tube.
The iron solution is made by dissolving 0.1 gram of pure
iron wire in a little dilute hydrochloric acid, to which a few
drops of concentrated nitric acid have been added. This so-
lution is then diluted to 1000 cc, and 1 cc. of solution =
0.0001 gram of iron.
Temporary hardness. — 200 cc. of sample is titrated with
N/10 acid until faint pink color appears, using methyl-orange
as an indicator. 1 cc. N/10 acid = 0.005 gram CaCO.3 ; re-
port parts per 100,000. N/50 acid will give a better titration.
688 PRACTICAL TANNING
1 cc. N/50 acid = 0.001 gram CaCOs- If N/50 acid is
used, 100 cc. of sample should be titrated.
(Note: If alkaline hardness is present, the amount of N/10
acid necessary to neutralize it should be subtracted from the
above volume of N/10 acid before temporary hardness is
calculated.)
Permanent hardness. — Measure 200 cc. of sample into a
porcelain casserole, boil to expel CO2, add 25 cc. of N/10
sodium hydroxide, and evaporate to about 50 cc. Cool, filter,
wash the filter-paper thoroughly, dilute the filtrate to about
100 cc, add a few drops of methyl-orange, titrate to faint
pink, point with N/10 acid.
The number of cubic centimeters of N/10 acid used, sub-
tracted from 25 = cc. of N/10 acid, corresponding to perma-
nent hardness in 200 cc. of water.
1 cc. of N/10 acid = 0.005 gram CaCOs- Report perma-
nent hardness as parts of CaCOs per 100,000.
Magnesia hardness. — This is calculated as follows : remove
temporary hardness from 100 cc. sample with N/10 acid, as
described above. Boil to about 85 cc. to expel all CO2.
Transfer to 200 cc. glass-stoppered graduated flask; add 100
cc. of lime water, the value of which is known in terms of
N/10 acid. Heat nearly to boiling; cool, and make up to
mark with boiled distilled water. Pipette off 100 cc. of clear
supernatant liquid, and titrate with N/10 acid, using phenolph-
thalein as an indicator; then cc. of N/10 acid necessary to
neutralize 50 cc. lime water — cc. N/10 acid used in final ti-
tration = cc. N/10 acid corresponding to magnesia hardness
in 50 cc. sample. 1 cc. N/10 acid = 0.005 gram MgC0 3 .
Report magnesia hardness as parts of MgCOs per 100,000.
Free carbonic acid. — 100 cc. sample are titrated with N/10
sodium carbonate, using phenolphthalein as indicator. When
all of the carbonic acid has been converted to NaHCOs by
the Na2COs, and there is slightest excess of Na2COs, the
solution will turn pink.
Alkaline carbonates. — In the determination of permanent
ANALYTICAL METHODS 589
hardness, if the alkali found by the final titration is in excess
of the alkali added, this excess is due to alkaline carbonates,
and should be calculated as Na2COs.
Cc. N/10 acid used in titration — cc. N/10 alkali added =
cc. N/10 corresponding to alkaline carbonates in 200 cc. of
sample. 1 cc. N/10 acid = 0.0053 gram Na 2 C0 3 . Report
alkaline carbonates as parts of Na2CO.s per 100,000.
Soaks. — The only determination of any importance in the
analysis of soak water is that of hide substance, this being a
measure of the extent to which the hides are being decom-
posed.
Stiasny's method. — 200 cc. of soak water is poured into
a 250 cc. graduated flask; 20 cc. of a 5 per cent solution of
zinc sulphate is now added, and the solution made up to the
mark. Allow the solution to stand 5 minutes and filter
through a 15 cc. pleated filter. Titrate 50 cc. of filtrate, as
a blank, against N/10 sodium hydroxide, using phenolphtha-
lein as an indicator. To another 50 cc. portion add 10 cc. of
40 per cent formaldehyde, which has been treated with pure
barium carbonate, and titrate as above. The difference in the
two burette readings is due to the amino acids which are
formed by the decomposition of the hide substance. These
acids condense with the formaldehyde, forming methylen-
amino acids, which give a good titration and a sharp end-point
when phenolphthalein is used as an indicator.
cc.N/lONaOHX 0.00786X25X3.785 J pounds of hide substance
453.6 P er gallon
or
cc. N/10 NaOHX 0.00164 = pounds of hide substance per gallon.
The hide substance in soak water can be more accurately
determined by the Kjeldahl method, but the above procedure
is much quicker and more satisfactory for control.
Lime. — The most important determination in the analysis
of lime is that of available lime. The determination of iron,
calcium, magnesium, and alkalinity of a saturated solution
may also be of great importance in individual cases. As a
590 PRACTICAL TANNING
general statement, a good lime should -contain about 90 to
95 per cent available CaO. The presence of MgO in quan-
tities greater than 2 per cent is objectionable, owing to the
fact that improper slaking may result and the hides may be
burned by the small lumps of CaO. The objections to iron
in any but small traces are well known.
Available lime. — Weigh 1 gram of a uniform sample and
transfer it to a 1 -liter graduated flask. The flask is then filled
to the mark with well-boiled hot water. The flask is stop-
pered at once and shaken frequently during the next few
hours to ensure complete solution of the lime. When the
solution is cold, it is again made up to the mark, shaken, and
allowed to settle; then 50 cc. of the clear liquid is pipetted
off and titrated with N/10 hydrochloric acid, using phenolph-
thalein as an indicator.
cc.N/l OHCl X 20 X 0-0028 X 100 _ M K1 n n
weight ot sample
Iron, calcium, and magnesium. — A 5-gram sample is
weighed into a porcelain dish, and 25 cc. of concentrated hy-
drochloric acid is added. Cover dish with a watch-glass and
boil until solution is complete. Rinse off the watch-glass and
evaporate to dryness on the water-bath. The residue is treated
with dilute hydrochloric acid and filtered into a 250 cc. grad-
uated flask. Wash the filter-paper thoroughly. Cool the fil-
trate, make up to mark and mix well ; 25 cc. of this solution
are taken and Fe, Ca, and Mg are determined by the usual
analysis. The Fe being precipitated by NH4CI -f- NH4OH
in hot solution, the calcium is precipitated as CaC^C^ in a
weak NH4OH solution ; and magnesium is precipitated as
MgNH4P04 in a faintly ammoniacal solution, then one-third
of its volume of concentrated NH4OH is added, and the solu-
tion is allowed to stand over night before filtering. Re-pre-
cipitation is necessary in each operation.
The iron can also be determined by taking 25 cc. of the
above solution, making acid with nitric acid, boiling a few
minutes, and transferring to a 100 cc. graduated flask; make
ANALYTICAL METHODS 591
up to mark and determine iron colorimetrically with potas-
sium sulphocyanide as outlined under water analysis.
Alkalinity of saturated solution. — This determination is of
importance owing to the fact that an impure lime may possibly
show greater alkalinity than a pure one, as the impurities may
react with the lime to form more soluble bases than Ca(OH)2.
One gram of lime is shaken thoroughly with 100 cc. of
water, and the method proceeded with as in the determination
of available lime. [50 cc. of a saturated solution of pure lime
at room temperature (15° C.) will neutralize 23.6 cc. of
N/10 HO.] If more hydrochloric acid than this is required
it will be for the reasons given above.
Sodium sulphide. — Commercial sodium sulphide is usu-
ally obtained either in the crystalline form or fused. The
first form has the formula Na2S.9HoO, and contains about
32.5 per cent Na2S; the other salt contains less water and
about 60 per cent NasS. The most common impurities of so-
dium sulphide are Na 2 C0 3j Na 2 S0 4 , Na 2 S20 3 , NaOH, and
polysulphides.
The percentage of Na2S.9H20 (or sulphide sulphur) and
the NaOH in the sodium sulphide are the determinations usu-
ally made.
Na^S.^H-jO. — Twelve grams of the sample is dissolved
in water and made up to 1000 cc ; 10 cc. of this solution are
pipetted into a 200 cc. beaker, diluted to about 100 cc, and
titrated at once with an N/10 zinc sulphate solution until one
drop gives no dark turbidity with nickel sulphate (or purple
color with sodium nitro-prusside) used as an outside indicator.
The zinc sulphate solution is made by dissolving 3.27 grams
of c.p. zinc in dilute hydrochloric acid (the zinc being in con-
tact with a piece of clean platinum), then adding an excess of
ammonium hydroxide, 50 grams of ammonium chloride, and
making up to one liter. Or, dissolve 14.35 grams of pure
ZnS0 4 .7H 2 in water, add NH 4 OH until the precipitated
Zn(OH) 2 re-dissolves, add 50 grams of NH4CI, and make up
to one liter.
592 PRACTICAL TANNING
cxt nnirn cc.N /10 Z11SO4 sol. X 100X0.012 X 100
Percentage of Na2b.9-H.2U = —cr — 7- — ■ — i ;
& weight of sample
or
£ >T cc.N /IOZ11SO4 sol. X 100X0.0039X100
Percentage of N a 2 b = ^rr — 2 — ~n
& weight of sample
Polysulphides, sulphates, or thiosulphate are not included in
this determination, only those sulphides which would yield
hydrogen sulphide and hydrochloric acid.
Total alkalinity and NaOH in the Na?,S. — Pipette 50 cc.
of the above solution into a 200 cc. beaker, dilute to 100 cc,
and titrate with N/10 hydrochloric acid, using- methyl-orange
as an indicator. This gives total alkalinity. The sodium hy-
droxide in the Na2S.9H20 can be calculated as follows:
Percentage of NaOH =
cc. N/10HC1— 5(cc. N /10ZnSO 4 sol.) X 20X0.004
weight of sample
When Na2S is dissolved in water it is hydrolyzed consid-
erably into NaOH + NaSH, as shown in the equation
Na 2 S+H 2 = NaOH+NaSH
Both of these products of hydrolysis, as well as the non-
hydrolyzed Na 2 S, react with the N/10 HC1.
(1) NaOH+HCl = NaCl + H 2
(2) NaSH + HC1 = NaCl + H 2 S
(3) Na 2 S + 2HC1 = 2NaCl+H 2 S
Any free NaOH originally present in the sample will also
react according to equation ( 1 ) . Therefore the number of
cubic centimeters of N/10 hydrochloric acid used in this tritra-
tion were used in reacting with Na2S, NaSH, and NaOH
formed by hydrolysis and NaOH originally present as such.
Therefore the cc. of N/10 zinc sulphate solution necessary,
subtracted from cc. of N/10 HC1 for the same size sample,
gives the cc. of N/10 HC1 necessary to neutralize the free
NaOH. This may be clearer if we look at the problem in
this way: The number of cc. of N/10 zinc sulphate solution
is the same as it would have been had there been no hydrol-
ANALYTICAL METHODS 593
ysis. This number of cc. of N/10 zinc sulphate solution is
exactly equal to the number of cc. of N/10 acid necessary to
react with NaoS, NaSH, and NaOH formed by hydrolysis.
Therefore, the cc. of N/10 zinc sulphate solution subtracted
from the cc. of N/10 acid used in the determination of total
alkalinity gives the cc. of N/10 acid necessary to neutralize
the free NaOH. • Methyl-orange is not sensitive to H2S, so
it does not interfere with the titration.
Analysis of arsenic sulphide. — Red arsenic is composed
chiefly of AS2S2, with some AS2S3, and containing AS2O3
and free sulphur as impurities. These substances are use-
less as depilating agents, only sulphide sulphur being
available for this purpose. For a complete analysis, deter-
mine the percentage of arsenic and the amount of soluble sul-
phides produced by the action of sodium hydroxide on the
sample.
Arsenic. — 5 grams of the powdered sample are weighed in
a beaker and boiled with concentrated nitric acid, covering
the beaker with a watch glass. This nitric acid treatment
dissolves the arsenic and oxidizes it to H3ASO4. When solu-
tion is complete, evaporate off most of the acid on the water-
bath, dilute, and filter. To the filtrate add an excess of am-
monium hydroxide and about 20 cc. of clear magnesia mixture.
Allow it to stand 24 hours, filter, and wash with 3 per cent
ammonia water. Dry the MgNFLiAsC^ and separate from
the filter-paper. The paper is ignited in a weighed porcelain
(not platinum) crucible. The precipitate is then added to
the same crucible and the whole gradually heated to a red
heat, which is maintained for 10 minutes. The Mg2As207
in the crucible is now weighed, and the weight of the empty
crucible subtracted.
, . „ grams Mg 2 As 2 7 X 0.6985X100
Percentage of As 2 S 2 = r-7— — 7 i
fe weight of sample
Sulphide sulphur (Procter's method.) — One gram of the
sample is digested for 3 hours with 50 cc. of 10 per cent so-
dium hydroxide solution, with frequent shaking. Make up
594 PRACTICAL TANNING
to 100 cc. with distilled water and filter; 50 cc. of the filtrate
is titrated with N/10 zinc sulphate solution as described under
analysis for sodium sulphide.
Percentage of active sulphur =
cc. N /10 ZnS0 4 sol. X2 X0.0016 X 100
or
Percentage of active sulphur = cc. N/10 ZnS0 4 sol.X0.32
Lime liquors. — The most important determination in the
analysis of limes is that of hide substance. Too high a hide
substance content indicates putrid limes and loss of stock.
Soluble lime, available lime, and CaC03 are also factors that
are sometimes useful.
Soluble lime and hide substance. — The sample of lime liq-
uor (which has been collected after thorough plunging of the
limes) is well shaken and carefully mixed. About 100 cc. of
this liquor is filtered at once through a dry filter-paper into a
clean, dry beaker; 50 cc. of this filtrate is pipetted into a 500
cc. graduated flask and diluted to the mark with water free
from CO2. Difficulty is often experienced in filtering this
lime liquor. Colloidal hide substance will fill up the pores of
the filter-paper and make filtration a very slow process. Also
finely divided particles of lime sometimes pass through the
filter-paper, giving a cloudy filtrate. Under these conditions
it is better to allow the lime liquor to stand over night in a
stoppered bottle, then filter the clearer upper portion of the
lime liquor through a dry paper. This filtrate is well mixed,
100 cc. are pipetted off and titrated with N/10 acid, using
phenolphthalein as an indicator. When the phenolphthalein
end-point has been reached, add a couple drops of methyl-
orange and then add N/10 hydrochloric acid, drop by drop,
until solution turns pink.
Percentage of soluble Ca(OH) 2 =
cc. N/10 phenolphthaleinX0.0037XlOO
10
The amount of acid used after reaching the phenolphtha-
lein end-point until the methyl-orange end-point is reached
ANALYTICAL METHODS 595
is a rough measure of the hide substance present. This is
due to the fact that the calcium salts of many of the prod-
ucts of decomposition of hide substance, as albuminates, and
amino acids, do not change methyl-orange, although they do
destroy the pink color of the salt of phenolphthalein. Ap-
proximately 0.0053 gram of hide substance when in solution
would in this way furnish enough alkalinity to neutralize 1
cc. of N/10 acid; therefore,
cc N /10 HC1 (m.o.) X 0. 0053X100
Percentage of hide substance = 7q
Ten cubic centimeters of a saturated solution of pure Ca
(OH) 2 will neutralize 4.72 cc. of N/10 HC1. If more than
this amount of HC1 is used in the above titration (phen-
olphthalein -f- methyl-orange together) the reason is the pres-
ence of NH 3 resulting from the decomposition of the hide
or to added salts reacting with the lime to form other alkalies.
Two other more accurate methods of determining hide sub-
stance in lime liquors are taken up later.
Available lime and CaCOz- — Available lime constitutes the
dissolved lime and the lime not in solution ; CaCO.3 is usually
present in small amount and is not of great importance of
itself, but it must be considered in order to get an accurate
determination of available lime.
The sample is thoroughly mixed, and 10 cc. of unfiltered
liquor are pipetted out, washed into a liter flask with water
free from CO2, and diluted to the mark; 100 cc. of this
solution (1 cc. of original lime liquor) are measured into a
200 cc. beaker and titrated with N/10 HC1, using first phe-
nolphthalein and then completing the titration with methyl-
orange as an indicator.
(a) cc. N/10 HC1 used for the phenolphthalein titration
were used in neutralizing all the available Ca(OH)2 +
^CaCO.3 present.
(b) cc. N/10 HC1 used for the methyl-orange titration
were used in neutralizing ^CaCC>3 + hide substance.
(c) Therefore from (b) we get cc. of N/10 HC1 necessary
596 PRACTICAL TANNING
to neutralize |CaC03 = cc. of N/10 HC1 used in above
methyl-orange titration, — 1/10 the number of cc. of N/10
HC1 found necessary to react with the hide substance in the
above determination of soluble lime and hide substance.
Therefore :
Percentage of CaC0 3 =
2Xcc. N/10 HC1 for \ CaCOsX 0.005X100
From (a) we get — cc. N/10 HC1 to neutralize available
Ca(OH)o=cc. N/10 HC1 used in the above phenolphthalein
titration — cc. N/10 HC1 necessary to neutralize \ CaCOs-
[This was found in (c).]
Therefore the percentage of available Ca(OH)2=cc. N/10
HC1 used in the above determination — cc. N/10 HC1 neces-
sary to neutralize ICaCOs [found in (c)] X 0.0037 X 100.
Hide substance continued. — The following approximate
method may be of some use for control work. The chem-
istry involved is that the amino acids do not affect phenol-
phthalein, but when treated with formaldehyde they are con-
verted into more strongly acidic compounds which can be
titrated with N/10 NaOH, using phenolphthalein as an
indicator.
Twenty-five cubic centimeters of filtered lime liquor is just
neutralized with N/10 acid and a faint pink color (using
phenolphthalein as an indicator) produced with a couple of
drops of N/10 NaOH; 10 cc. of 40 per cent formaldehyde
(neutral to phenolphthalein) is now added, and the solution
titrated with N/10 sodium hydroxide.
No accurate factor is known to convert this reading into
hide substance, but the cc. of N/10 acid used may be of value
in comparing the relative amounts of the products of decom-
position of hide substance in different limes.
Kjeldahl method for hide substance. — Filter a sample of
the lime liquor to remove hairs or other suspended particles
containing nitrogen. Pipette about 150 cc. of this filtrate
into a Kjeldahl flask, and boil gently until the volume is re-
duced to a few cubic centimeters. Thirty cubic centimeters
ANALYTICAL METHODS 597
of concentrated sulphuric acid and 15 grams of potassium
sulphate, together with about three glass beads are now added
and the solution, heated gently at first, is then boiled until all
organic matter is destroyed and the solution is colorless. Cool
and pour slowly with stirring into 100 cc. cold water. Trans-
fer this to a 200 cc. graduated flask, rinsing out the beaker
thoroughly and make up to mark with distilled water. Pipette
out 50 cc, transfer to Kjeldahl flask, dilute to 100 cc. and
make the solution strongly alkaline with a saturated solution
of sodium hydroxide. Connect to a straight condenser by
means of a Hopkins distilling head, and distill for about an
hour. The distillate is caught in an Erlenmeyer flask con-
taining 50 cc. of N/10 HC1 + 2 drops methyl-orange. The
end of the delivery tube extends below the surface of the acid.
After about 75 to 100 cc. have distilled over, distillation is
stopped, and the condenser and delivery tube are carefully
rinsed with distilled water. The acid is now titrated with
N/10 NaOH in order to determine the amount of acid not
neutralized by the ammonia.
1 cc. N/10 acid = 0.0014 gram of nitrogen or 0.00786
gram of hide substance; 5.62 grams of dry hide substance =
1 gram of nitrogen.
cc. N /10 acid X 0.00786 X 100
Percentage of hide substance = 275
or
Percentage of hide substance = cc. N/10 acid X 0.02096
Sulphide lime liquors: Sodium sulphide. — 50 cc. of fil-
tered liquor is pipetted off, diluted to about 150 cc, and
titrated with N/10 zinc sulphate solution as described under
analysis of sodium sulphide.
_ cc. N /10 ZnS0 4 sol. X 0.0039 X 100 ■
Percentage of Na 2 S = ■ ^0
or
cc.N/10 ZnSQ 4 sol.X 0-012 X 100
Percentage of Na 2 S. 9H2O— jj-q
\
598 PRACTICAL TANNING
The following is a good method, but is much longer than
the method given above. The sample is filtered, and 25 cc.
of the filtrate is pipetted into a 200 cc. beaker; 25 cc. of
5 per cent cadmium chloride and 15 cc. of acetic acid are
added, and the solution is boiled and filtered. Wash the
precipitate with hot water, dissolve in dilute hydrochloric
acid, and titrate with N/10 iodine solution using starch as
an indicator.
, >T _ cc. N /10 iodine X 0.0039 X 100
Percentage of Na 2 S = ^
or
r at o nu n CC - N / 10 iodine X 0012 X 10 °
Percentage of Na 2 S. 9H 2 = ^
Soluble lime and hide substance. — The analysis is carried
out exactly as that indicated under lime liquor. In this case
the phenolphthalein end-point gives not only the dissolved
alkalies, but also half of the Na2S due to its hydrolysis:
Na 2 S + H 2 = NaOH + NaHS.
Percentage of soluble Ca(OH) 2 =
cc. N/10 HC1— V 2 cc. N/10 ZnSQ 4 sol. X 0.0037 X 100
10
The cc. of N/10 acid used after reaching phenolphthalein
end-point to the methyl-orange end-point are used in neutral-
izing the calcium salts of the decomposition products of the
hide (so-called dissolved hide substance) -f- half of the Na 2 S
present.
Percentage of hide substance =
cc. N /10 HClQn.o.)— 1 / 2 cc. N /10 ZnSQ 4 sol. X 0.0053 X 100
10
The above method for hide substance determination is only
approximate and should not be relied on when the Kjeldahl
method can be made. The latter method is run exactly as
outlined under lime liquors, and is much more dependable.
In running the formaldehyde method for hide substance,
the sulphides must first be oxidized to S, otherwise they will
ANALYTICAL METHODS 599
react with the formaldehyde, forming compounds which
greatly increase the alkalinity of the solution. The method
as outlined by Stiasny is given below :
The liquor is filtered, 50 cc. pipetted into a beaker, diluted
to 150 cc, and two drops of phenolphthalein added. Make
slightly acid with acetic acid, and add N/10 iodine in slight
excess. Titrate with N/10 NaOH until the solution becomes
pink, then add 10 cc. of neutral 40 per cent HCHO ; add
N/10 NaOH until the phenolphthalein end-point appears.
The cc. of N/TO NaOH used in this last titration is a measure
of the amino acids in solution.
Available lime and CaCOz. — The method can be run ex-
actly as outlined under lime liquors. Here the phenolphtha-
lein end-point will give available Ca(OH)2 -f- 4CaCO:-,
+ -i-Na2S. Therefore, subtract from the total number of
cc. of N/10 acid used, half the number of cc. of N/10 zinc
sulphate solution used for the same size sample, and proceed
with the calculation of available lime as outlined under lime
liquors.
The cc. of N/10 HC1 used after reaching the phenolphtha-
lein end-point until the methyl-orange end-point is reached
are used up in neutralizing ^CaCOs -f- hide substance -f-
-}Na2S. Therefore, subtract from the total number of cc
of N/10 acid used, half the number of cc. of N/10 zinc sul-
phate solution used for the same size sample, and proceed with
the calculations of CaCOs as outlined under lime liquors.
De-liming test. — In de-liming limed hides and skins by
means of acids it is customary to determine the completion
of the process by applying a solution of phenolphthalein to a
freshly cut section of the pelt. If such a solution is applied
to a limed pelt, the section shows red; if to a completely
de-limed pelt, there is no change of color. A partly de-limed
pelt will show red in the middle and colorless on either side.
Most tanners usually allow the de-liming to proceed to a given
point. For some purposes complete de-liming is necessary,
while for others a mere surface de-liming is sufficient, the
600 PRACTICAL TANNING
depth depending upon the nature of the subsequent tanning
process. For example, if it is a question of sheepskins which
are first de-limed with acid, then bated or puered, the first
actual acid de-liming is usually carried out only to such an
extent that a streak of free lime is left in the middle. With
heavier goods, such as sole leather, the extent of the acid
de-liming depends upon the nature of the liquors into which
the goods are next placed. If the tail suspension liquors are
very acid in character, it is not as important to neutralize
as much lime as if these liquors were only slightly acid. The
phenolphthalein test can be applied with almost any acid, but
there is one caution that might be mentioned in its use, and
that is that its action is more qualitative than quantitative.
A trace of lime will give as strong a coloration as a large quan-
tity of free lime, and cases have been known where this has
led to confusion. To make the matter clear, it may be well
to take a definite example :
Suppose that fully limed sole butts are being de-limed with
one of the ordinary acids, and that the amount of acid present
in the liquor is not quite sufficient to neutralize the whole of
the lime; at the beginning of the process the whole section
will show red on application of phenolphthalein, and after a
short time the cut section will show red in the middle and
colorless at the outsides. The depth of the outside strips will
increase as the process goes on, until almost the whole of the
acid has been neutralized by the free lime in the hides. When
this point has been reached there will be a minimum red sec-
tion in the center, but afterwards the free lime in the center
will gradually diffuse out to the extremities, and so, on applica-
tion of phenolphthalein, the whole section will show red. In
this way it is possible for an almost completely de-limed hide
to appear as though it were not de-limed at all. It is in this
sense that the test is qualitative rather than quantitative. By
taking cut sections at different stages of the process, and not
only at the end, it is possible to determine exactly the actual
extent of the de-liming.
Salt. — For moisture determination dry 5 grams of the sam-
ANALYTICAL METHODS 601
i
pie in a tared dish at 100° C, over night. Weigh the loss in
weight as water.
Calcium oxide (CaO). — Pipette 50 cc. of a solution made
from 25 grams of the sample in 250 cc. water, into a 250 cc.
beaker, make alkaline with ammonia, and bring to a boil on
hot plate. Add an excess of ammonium oxalate and digest
the solution for a half -hour. Filter the precipitate, and wash
free from chlorides. Ignite, blast, cool, and weigh quickly
as CaO.
Sulphates (SO3). — Dilute 50 cc. of the above solution to
about 100 cc, acidify with HC1, bring to a boil on a hot plate,
and precipitate the sulphates with barium chloride. Digest for
a half-hour, filter, and wash free from chlorides. Ignite,
cool and weigh as BaSCU. Calculate to SO3. Test for traces
of iron and magnesium. The NaCl is found by difference.
Aluminum sulphate. — Weigh out 6 grams of the pulver-
ized sample, dissolve in water, and dilute to 250 cc.
Aluminum oxide (AI2O3). — Pipette 25 cc. of the above
solution into a 250 cc. beaker, add 2 cc. of concentrated hydro-
chloric acid, dilute to about 100 cc, and bring to boil. Pre-
cipitate the aluminum from the boiling solution with a slight
excess of ammonia. Boil until the solution smells but faintly
of ammonia, filter, wash the precipitate, and ignite. Blast
the precipitate, cool, and weigh, and repeat until the weight
is constant. Calculate as AI2O3.
(Note: — If iron is present in the sample, the amount found
under Fe203 must be subtracted from the precipitate.)
Total sulphuric acid (H2SO4). — Pipette 25 cc. of above
solution into a porcelain casserole, dilute with about 150 cc.
of water, and add a little phenolphthalein. Run in N/10
NaOH till the pink color remains on stirring. Heat and boil
for one minute. Run in more N/10 NaOH and repeat the
boiling, finally titrating to the end-point. This determination
gives the sulphuric acid combined with the aluminum and any
free acid present.
Free sulphuric acid (H2SO4). — From the two above de-
terminations, the sulphuric acid necessary to form the normal
602 PRACTICAL TANNING
salt may be calculated. Formula: Al2(S04)3-18H20. Any
excess of acid is figured as free sulphuric acid.
Ferric oxide (Fe 2 Os). — The sample should be tested for
iron with potassium sulphocyanide. If present, proceed as
follows: Weigh 25 to 50 grams, according to the amount
of iron present, into a large Jena flask. Dissolve in about
500 cc. of water and make strongly acid with sulphuric acid.
Add 5 grams of powdered zinc and heat on the steam bath
till the action ceases, then test for ferric iron with
K 4 Fe(CN)6. If the zinc contains iron, a blank must be run.
Remove the flask from the bath if the iron is reduced,
filter quickly, cool, and titrate with standard potassium
permanganate.
Pickle. — The reagents are as follows :
Sodium hydroxide: N/10 solution, 1 cc. = 0.0049 gram
H 2 S0 4 .
Silver nitrate : 2.9 grams per liter, 1 cc. = 0.001 gram NaCl.
Phenolphthalein : 1 gram per 100 cc. of alcohol.
Potassium chromate : 1 gram per 100 cc. of water.
Sulphuric acid. — Pipette 10 cc. of pickle into a 250 cc.
casserole, to which add 100 cc. of water and 3 drops of phen-
olphthalein. Run in standard NaOH solution from burette
with constant stirring until the liquid shows a faint pink color.
cc. N/10 NaOH X 0.0049 X 10 = x; x = grams of
H2SO4 per 100 cc,
Jo^^L orx X 0.0835 = y;y = pounds of H 2 S0 4 per gallon.
453.6 X 100
pounds of commercial H2SO4 per gallon.
0.935
(Note: — 3785 cc. = 1 gallon; 453.6 grams in 1 pound.)
Sodium chloride. — Dilute 10 cc. of pickle with water to
500 cc. in a 100 cc. graduated flask. Shake well and pipette
10 cc. into a 250 cc. casserole, then neutralize the acidity by
a very slight excess of pure calcium carbonate. Then add
five drops of potassium chromate solution and run in silver
nitrate from burette, with constant stirring until the yellow-
ish-white color changes to a slight reddish-brown.
ANALYTICAL METHODS 603
cc. AgNOs X 0.001 X 500 =x; x = grams of NaCl per
100 cc.
x X 3785 or x X 0.835 = pounds of NaCl per gallon.
453.6 X 100
Some standard of concentration should be adopted in the
preparation of pickle and 1 lb. of salt per gallon of water
is a convenient strength. The ratio of sulphuric acid to so-
dium chloride should be 1:8; there should be therefore $ lb.
or 2 oz. of sulphuric acid per gallon of pickle.
Formaldehyde: Romijn's method. — 25 cc. of the dry
formaldehyde solution is weighed accurately in a tared weigh-
ing bottle with a well-ground stopper, and washed without loss
into a 500 cc. flask. The solution is made up to the mark, and
5 cc. is accurately measured into a bottle with a well-ground
stopper; 30 cc. of N/1 NaOH, which need only be measured
in a graduated cylinder, is added rapidly. About 50 cc. of
N/5 iodine is immediately run in from a burette, with fre-
quent shaking, until the liquid is deep yellow. The bottle is
stoppered, well shaken for a half a minute, and the contents
acidified with 40 cc. of N/1 sulphuric acid (measured in a
graduated cylinder), and after a short time, during which the
bottle is kept stoppered, the excess of iodine is titrated with
N/10 sodium thiosulphate.
HCHO + I 2 + 2H 2 = HCOOH + 2HI.
Each cc. of N/5 iodine equals 0.003 grams of HCHO.
Two-bath chrome liquors: Determination of Cr as
Cr*Oz, NaiCriOi, or NaiCrO^. — 10 cc. of the liquor is placed
in a 250 cc. graduated flask and diluted to the mark. After
thorough mixing, 50 cc. is pipetted off and run into a 500 cc.
beaker; 5 cc. of concentrated hydrochloric acid and 10 cc. of
10 per cent potassium iodine solution is now added. The
solution is cooled, diluted to about 400 cc, allowed to stand
a few minutes, and the liberated iodine titrated with N/10
Na2S2C>3 solution, using starch as an indicator. Do not add
604. PRACTICAL TANNING
the starch until the brown color of the iodine is nearly
destroyed.
1 cc. of N/10 Na 2 S 2 3 equals 0.00333 gram Cr0 3 , or
0.00436 gram Na 2 Cr 2 7 , or 0.0054 gram Na 2 Cr0 4 .
Grams of CrO s per 100 cc. = cc. N/10 Na 2 S 2 3 X 0.0033
X50.
Acidity. — Take 10 cc. of liquor, dilute to 200 cc, and
titrate with N/10 NaOH, using phenolphthalein as an indi-
cator. The sodium hydroxide will be taken up by the
Na 2 Cr 2 07, the H 2 Cr 2 OT, and the free acid as HC1 or H 2 SC>4.
(262)
(a) Assume bath is all A/a 2 O 2 07. — Na 2 Cr 2 OT +6KI -f-
(762)
14HC1 = 2NaCl + 2CrCl 3 + 6KC1 + 7H 2 + 3I 2 .
262 : 762 :: 1 : x; x = 2.908 grams of I liberated by 1 gram
of Na 2 Cr 2 07. 1 cc. N/10 iodine solution contains 0.0127 gram.
2 908
Iodine. ' = 228.9 cc. N/10 I solution could be formed
from the iodine liberated by 1 gram of Na 2 Cr 2 7 . Therefore,
228.9 cc. N/10 Na 2 S 2 3 will be required to absorb the iodine
liberated by 1 gram of Na 2 Cr2.07.
(262) (80)
Na 2 Cr 2 7 + 2NaOH = 2Na 2 Cr0 4 + H 2 0.
262 : 80 :: 1 : x; x = 0.3053 grams of NaOH necessary
to react with 1 gram of Na 2 Cr 2 07.
1 cc. N/10 NaOH = 0.004 gram of NaOH.
Therefore, ( j^jj| = 76.3 cc. N/10 NaOH for 1 gram Na 2 Cr 2 7 .
228 Q
%^ = 3. When the bath is all Na 2 Cr 2 7 the cc. of N/10 NaOH
76.3
= 1/3 cc. N/10 Na 2 S 2 3 .
Strength = cc. N/10 Na 2 S 2 3 X 0.00436 X 50 = grams
Na 2 Cr 2 7 per 100 cc.
(Note: 0.00436 = grams Na 2 Cr 2 7 in 1 cc. N/10 solu-
tion. 262 (mol. wt.) Na^Cr 2 07 -f- 6 = 43.6 grams of
Na 2 Cr 2 07 in 1 liter of normal solution.)
ANALYTICAL METHODS 605
(b) Assume bath is a mixture of NaiCrzOq and Na^CrO^.
— Na2Cr04 does not react with NaOH; therefore the cc. of
N/10 NaOH = a cc . N/10 Na 2 S 2 3 .
Strength. — cc. N/10 NaOH X 0.0131 X 10 grams
Na 2 Cr 2 7 in 100 cc. bath.
(262)
Na 2 Cr 2 7 grams Na 2 Cr 2 7 in 100 cc _ . ,
— ~-^ = ■ — ; x = grams Cr in form
— ' \yc x
(104)
of Na 2 Cr 2 7 in 100 cc. of bath.
cc. N/10 Na 2 S 2 3 X 0.00173 X 50 = x or total grains
Cr in 100 cc. of bath.
x' — x = grams of chromium as Na 2 Cr04 in 100 cc. of bath.
(Note: 0.0131 = grams Na 2 Cr 2 7 in 1 cc. N/10 solu-
tion when Na 2 Cr 2 07 is acting as an acid to neutralize NaOH.)
262 (mol. wt.) Na 2 Cr 2 7 -5- 2 = 131 grams Na 2 Cr 2 7
for 1 liter of normal solution; 0.00173 = grams Cr in 1 cc.
N/10 solution when acting as an oxidizing agent.
52 (atomic weight of chromium) -— 3 = 17.3 grams Cr
in 1 liter of solution.
(218)
(c) Assume bath is all // 2 O 2 7 . — H 2 Cr 2 7 -f - 6KI -f-
(762)
12HC1 = 2CrCl 3 + 6KC1 +7H 2 + "~6I~
218 : 762 : : 1 : x; x = 3.498 grams of I liberated by 1
gram of H 2 Cr 2 7 .
n 019 - = 275.4 cc. N/10 Na 2 S 2 3 necessary to absorb the
iodine liberated by 1 gram of [see explanation in (a)] H 2 Cr 2 07.
(218) (160)
H 2 Cr 2 7 + 4NaOH = 2Na 2 Cr0 4 + 3H 2 0.
218 : 160 :: 1 : x; x = 0.7339 gram NaOH necessary
to react with 1 gram of H 2 Cr 2 7 (H 2 Cr 2 7 does not exist
out of solution).
7339
' nft . = 183.5 cc. N/10 NaOH necessary to react with 1
gram of H 2 Cr 2 7 .
606 PRACTICAL TANNING
183.5 is | of 275.4, therefore when the bath is all H2Cr207 the
cc. of N/10 NaOH = § cc. N/10 Na 2 S 2 3 .
Strength.— cc. N/10 Na 2 S 2 3 X 0.00333 X 50 == grams
CrOs (as H 2 Cr 2 07) per 100 cc. of solution.
(Note: 0.0033 = grams Cr0 3 per cc. N/10 solution.)
100 (mol. wt.) CrOs -r-3 = 33.3 grams Cr0 3 per liter of
normal solution.
(d) Assume bath is a mixture of H^CriOi and Na^Cr^Oi. —
Both of these react with the NaOH and Na 2 S 2 3 . Then cc.
N/10 NaOH = § and \ cc. N/10 Na 2 S 2 3 .
Strength. —
Let a = cc. N/10 Na 2 S 2 3 for Na 2 Cr 2 7 and H 2 Cr 2 7 .
a u _ « u u u u
" c = " " " " H 2 Cr 2 7 .'
(1) Thenb + c = a.
Let a' = cc. N/10 NaOH for Na 2 Cr 2 7 and H 2 Cr 2 7 .
u u/ __ « u a « <*
" c' = " " " " H 2 Cr 2 7 . '
(2) Then b' + c' = a.
But Na 2 Cr 2 07 requires 3 times as many cc. of N/10
Na 2 S 2 3 as it does cc. of N/10 NaOH.
(3) Therefore, b' = |
Also H 2 Cr 2 07 requires f as many cc. of N/10 NaOH as cc.
of N/10 Na 2 S 2 3 .
2c
(4) Therefore, c = -^ *
In equation (2) substitute (3) and (4), therefore
b 2c
3 + T = a or
(5) b + 2c = 3a
(6) From (1) we get b = a — c.
Substitute (6) in (5)
a — c + 2c = 3a' or a -f- c = 3a' of
ANALYTICAL METHODS 607
c = 3a' — a. This gives cc. N/10 Na 2 S 2 3 used for
H 2 2 7 .
a — c = b cc. N/10 Na 2 S 2 03 used for Na 2 Cr 2 7 .
Strength.— cc. N/10 Na 2 S 2 O a (c) X 0.0033 X 50 =
grams Cr0 3 (as H 2 Cr 2 T ) per 100 cc. of solution.
5 cc. N/10 Na 2 S 2 O s (b) X 0.00436 X 50 = grams Na 2 Cr 2 7
per 100 cc. of solution.
(e) When bath contains free acid (HC1 or H2SO4). —
Under these conditions all chromium will be in the form of
H 2 Cr 2 7 and the cc. N/10 NaOH = § cc. N/10 Na 2 S 2 C 3 .
Strength.— cc. N/10 Na 2 S 2 O a X 0.0033 X 50 = grams
Cr0 3 as H 2 Cr 2 7 per 100 cc.
Since for H 2 Cr 2 7 the cc. N/10 NaOH = § cc. N/10
Na 2 S 2 3 .
Then, cc. N/10 NaOH — § cc. N/10 Na 2 S 2 3 = x cc.
N/10 NaOH to neutralize free acid.
x X 0.00365 X 10 = grams HC1 in 100 cc.
x X 0.0049 X 10 = grams H 2 S0 4 in 100 cc.
iVajj^Os in hypo bath. — Place 10 cc. of 10 per cent potas-
sium iodide solution, 5 cc. of concentrated hydrochloric acid,
and 25 cc. of N/10 K 2 Cr 2 7 , in a 250 cc. glass-stoppered
bottle. Place the hypo solution in a burette and titrate the
liberated iodine in the bottle, using starch as an indicator.
The volume of hypo required contains 0.620 grams of pure
Na 2 S 2 3 .5H 2 0. Its strength would be
XT '^ X 100 = grams Na 2 S 2 3 .5H 2 per 100 cc.
cc. Na 2 S 2 3 used.
(Note: 1 cc. N/10 K 2 Cr 2 7 == 1 cc. N/10 iodine
solution.)
1 cc. N/10 iodine solution contains 0.0127 gram of iodine.
0.0127 X 25 = 0.3175 gram of iodine liberated.
(496) (254)
2Na 2 S 2 3 .5H 2 + I 2 = Na 2 S 4 6 + 2NaI.
496 : 254 :: x : 0.3175.
x = 0.620 gram of Na 2 S 2 3 .5H 2 in the amount of sam-
ple taken.
608 PRACTICAL TANNING
Second bath when made up of NaHS0 3 . — Determination of
NaHS0 3 : The method is the same as that for Na2S203 in
hypo bath.
0.130 X 100
ocNaHSO, solution used = gramS of NaHS ° 3 P er 10 ° cc ' of
solution.
(Note: 1 cc. N/10 K 2 Cr 2 7 = 0.0127 gram of I.)
0.0127 X 25 = 0.3175 gram of I liberated.
(104) (254)
NaHS0 3 + I 2 + H 2 = NaHS0 4 + 2HI.
104 : 254 :: x : 0.3175.
x — 0.130 gram of NaHSOs in cc. of sample taken.
One-bath chrome liquor: 1. Determination of chrom-
ium. — Reagents used are as follows:
N/10 Na 2 S 2 3 solution 1 cc. = 0.00173 gram Cr.
10 per cent potassium iodide solution.
Starch solution, 1 gram starch per 100 cc. of water, pre-
served with formaldehyde.
Concentrated hydrochloric acid.
Sodium peroxide.
Standard N/10 sodium hydroxide.
Phenolphthalein, 1 gram per 100 cc. alcohol.
(a) Determination of Cr in new or spent liquor. — Pipette
10 cc. into an Erlenmeyer flask, to which add 125 cc. of water
and 3 grams of sodium peroxide ; add the latter in small por-
tions. Boil the mixture for a half-hour, adding more water if
necessary.
Transfer the yellow solution to a 500 cc. beaker; rinsing
the Erlenmeyer several times with water. Cool thoroughly,
then add 8 cc. of concentrated hydrochloric acid and 10 cc.
of potassium iodide solution, and let stand five minutes. The
solution must now be perfectly clear and reddish-brown in
color. If black particles float on top, more potassium iodide
solution is required. If the solution is still yellow or light
brown, more acid must be added. Now run in sodium thiosul-
phate solution from a burette with constant stirring until the
ANALYTICAL METHODS 609
color has changed to a light brown. Then add a few drops
of starch indicator after which an intense blue coloration
should ensue. Dilute to 400 cc, and add more sodium thiosul-
phate solution, drop by drop, with constant shaking until the
blue color changes to a permanent light green.
No. cc. N/10 Na^Os X 0.00173 X 100
Strength. ■ ~iq
or
No. cc. N/10 Na 2 S 2 3 X 0.0173 = grams Cr per 100 cc.
(b) Determination of Cr in stock liquor.— Pipette 10 cc.
of stock chrome liquor into a 500 cc. graduated flask, make up
to the mark with water and mix thoroughly by shaking. Pi-
pette off 25 cc. of this diluted solution for analysis. Follow
the directions given above.
Strength.— No. cc. N/10 Na 2 S 2 O s X 0.00173 X 200 =
grams of Cr per 100 cc. of liquor.
(c) Determination of basicity for diluted chrome liquors —
Pipette 10 cc. original liquor into a casserole and add about 125
cc of water. Heat to boiling and add 1 cc. phenolphthalein,
then run in standard sodium hydroxide from burette with
constant stirring until the supernatant liquid shows a faint
pink coloration.
cc. N/10 NaOH X 0.0048 X 10
° cc. N/10 NaOH X 0.048 = grams of S0 4 per 100 cc.
(d) Determination of basicity of stock liquor.— Pipette
10 cc. of stock chrome liquor into a 500 cc. graduated flask,
make up to mark with water and mix thoroughly by shaking.
Pipette off 25 cc. of this diluted solution for analysis. Fol-
low directions as given above.
Strength.— cc. N/10 NaOH X 0.0048 X 200
cc. N/10 NaOH X 0.96 = grams of S0 4 per 100 cc.
2 Use of above results to obtain correct basicity of one-
bath chrome liquors.— -The best salts for tanning purposes are
the basic salts Cr 2 (OH) 2 (S0 4 )2 or Cr 2 Cl 3 (OH) 3 .
610 PRACTICAL TANNING
The ratio of Cr to SO3 is 104 : 160 or as 52 : 80. From
the analysis of the liquor determine the ratio of Cr to SO3
by the proportion
grams Cr in 100 cc. 52 . __ . . , . ,
^r~- — tt^ = — ; x = grams of S0 3 combined with
grams S0 3 m 100 cc. x
52 grams of Cr.
If the ratio is above 80 there is too much acid present, and
sodium carbonate must be added to bring down the ratio to
52:80, while if the ratio is below 80, sulphuric acid must be
added to bring the ratio up to standard.
(a) Assume the analysis shows the ratio to be 52 : 83.2. —
80
When ratio is 52 :80; 1 gram of Cr == 52 or 1.54 grams SO3 ;
83.2
and when ratio is 52 : 83.2; 1 gram Cr = 52 or 1.6 grams SO3.
1.6 — 1.54 = 0.06 gram SO3 to be neutralized for each
gram of Cr present.
(98) (286)
H 2 S0 4 + Na 2 CO 3 .10H 2 O = Na 2 S0 4 + H 2 + C0 2 + 10H 2 O.
Na 2 CO 3 .10H 2 O (286) x 286 X 1
"SO* "l80y = T ; X = ~~80— ; x = 3 - 58 S rams of
Na 2 CO 3 .10H 2 O necessary for every gram of S0 3 to be neutralized.
0.06 X 3.58 = 0.2148 gram of Na 2 CO 3 .10H 2 for each
gram of Cr.
(cc. in gal.)
grams Cr in 100 cc. X 3785 X 0.2148 , , .. __
453.6 X 100 = P ° Unds ° f Na2C ° 3
(grams in 1 lb.)
10H 2 O to be added per gallon.
Summary. — When the grams of SO3 per one gram of chrom-
ium are greater than 1.54, subtract 1.54 from this value and
substitute the result in the equation given below.
grams Cr in 100 cc. X 37.85 X ?
453.6
or
grams Cr in 100 cc. X 0.0834 X ? = pounds of Na 2 CO 3 .10H 2 O
to be added per gallon to give the desired basicity.
ANALYTICAL METHODS 611
(b) Assume the ratio is below 80, say 69.16. — Then 1
gram of Cr is combined with
69.16
52
= 1.33 grams S0 3 .
1.54 — 1.33 = 0.21 gram of SO3 to be added for each
gram of Cr.
grams Cr in 100 cc. X 3785 X 0.21 X 1 , ,
453 6 x 10() =' pounds of sul-
phuric acid to be added per gallon.
a m oun t H3SO 4i n llb .co X mm e re ,a, a c ld (0.93 51b .) = *-—
commercial acid to be added.
Summary. — When the grams of SO3 per one gram of Cr
are less than 1.54, subtract this value from 1.54 and substitute
the result in the equation given below.
grams Cr in 100 cc. X 46.366 X ?
424.1
or
grams of Cr in 100 cc. X 0.1117 X ? = pounds of commer-
cial H2SO4 to be added per gallon of solution to give proper
basicity.
Vegetable tanning materials. — The following are the
quantities of the materials to be taken for analysis :
Unextracted materials
Graves Cubic centimeters
Myrabolans 20 2000
Valonia cups 20 2000
Divi divi 20 2000
Sumac 20 2000
Oak bark 30 1000
Hemlock 30 1000
Chestnut wood 50 1000
Spent tans 50 1000
612 PRACTICAL TANNING
Extracts
Grams Cubic centimeters
Chestnut 35 to 45° Be 14 1000
45 to 60° Be 12 1000
Mynabolans to 50° Be 14 1000
50 to 100° Be 13 1000
Mangrove to 50° Be 14 1000
50 to 100° Be 13 1000
Quebracho (solid) 12 1000
Myrabolans (solid) 14-15 1000
Mangrove (solid) 14-15 1000
Cutch (solid) 14-15 1000
Quebracho (solid) 12 1000
Tan liquors
Cubic centimeters Cubic centimeters
Barkometer reading to 15° 200 1000
15 to 25° 100 1000
25 to 40° 50 1000
40 to 60° 25 1000
Above 60° bk. weigh out 15 to 20 grams, according to
strength, and dilute to 1000 cc.
The following corrections should be applied to the barkom-
eter readings: At 70° F. add 1.0 to the reading; at 75° add
1.5; at 80° add 2.0. When the reading is 30 or above, and
the temperature is 80° F. or more, add 2.5.
The following determinations are made:
1. Total solids.
2. Soluble solids.
3. Insoluble solids.
4. Tannins.
5. Non-tannins.
6. Specific gravity by Westphal balance at 15.5° C.
OFFICIAL METHOD OF THE AMERICAN LEATHER CHEM-
ISTS' ASSOCIATION FOR THE ANALYSIS OF VEGE-
TABLE MATERIALS CONTAINING TANNIN
I. Raw and spent materials
(1) Caution. — Proper care must be taken to prevent any
change in the water content of raw materials during the
sampling and preliminary operations. (See "General" under
"Sampling.")
ANALYTICAL METHODS
613
(2) Preparation of sample. — The sample must be ground
to such a degree of fineness that the entire sample will pass
through a sieve of 20 meshes to the linear inch.
(a) The temperature used for drying samples of spent
material for grinding must not exceed 60° C.
(b) Samples of raw material too wet
to be ground may be dried before grinding
as in (a). In this case a preliminary
water determination must be made ac-
cording to (IV) on the sample as re-
ceived. If the portion of the sample taken
for the water determination is in pieces
too large to dry properly, it is permissible
to reduce these to smaller size as rapidly
and with as little loss of water as possible.
(3) Water determination. — Ten grams
of the ground material shall be dried in
the manner and for the period specified
for evaporation and drying in extract
analysis.
(4) Amount of sample to be extracted.
— Such an amount of raw material shall
be extracted as will give a solution con-
taining as nearly as practicable 0.4 gram
tannin to 100 cc. (not less than 0.375 nor
more th,an 0.425). Of spent materials
such an amount shall be taken as will give
p. —Tea's a som ^ on °f as nearly as practicable the
extractor. above concentration.
(5) Extraction. — This shall be conducted in an apparatus
(figure 123) consisting of a vessel in which water may be
boiled and a container for the material to be extracted. The
container shall be provided above with a condensation chamber
so arranged that the water formed from the condensed steam
shall drip on the material to be extracted, and provided below
with an arrangement of outlets such that the percolate may
either be removed from the apparatus or be delivered to the
614 PRACTICAL TANNING
boiling vessel. The boiling vessel must be so connected that it
will deliver steam to the condensation chamber and that it may
receive the percolate from the container. The condensation
water from the condenser must be at approximately the boiling
temperature when it comes in contact with the material to be
extracted.
The material of which the boiling flask is composed must
be inert to the extractive solution. Suitable provision must
be made for preventing any of the solid particles of the ma-
terial from passing into the percolate.
(A) Woods, barks and spent materials :
Five hundred cc. of the percolate shall be collected outside in
approximately 2 hours and the extraction continued with 500
cc. for 14 hours longer by the process of continuous extraction
with reflux condenser. The applied heat shall be such as to
give condensation of approximately 500 cc. in 1^ hours.
(B) Materials other than woods, barks and spent:
Digest the material in the extractor for 1 hour with water
at room temperature, and then extract by collecting 2 liters
of percolate outside in approximately 7 hours.
(6) Analysis. — The percolate shall be heated to 80° C,
cooled, made to the mark, and analyzed according to the
official method of extracts.
II. Analysis of extract
(7) 'Amount and dilution for analysis. —
(A) Fluid extracts: These shall be allowed to come to
room temperature, mixed thoroughly, and such quantity
weighed for analysis as will give a solution containing as
nearly as possible 0.4 gram tannin to 100 cc. (not less than
0.375 nor more than 0.425). Precautions must be taken to
prevent loss of moisture during weighing. Dissolve the extract
by washing it into a liter flask with 900 cc. of distilled water
at 85° C.
ANALYTICAL METHODS 615
Cooling :
(a) The solutions prepared as above shall be cooled rapidly
to 20° C. with water at a temperature of not less than 19° C,
be made to the mark with water at 20° C. and the analysis
proceeded with at once, or
(b) The solution shall be allowed to stand over night, the
temperature of the solution not being permitted to go below
20° C, be brought to 20° C. with water at not less than 19°
C, be made to the mark with water at 20° C, and the analysis
proceeded with.
(B) Solid and powdered extracts: Such an amount of
solid or powdered extract as will give a solution of the strength
called for under liquid extracts shall be weighed in a beaker
with proper precautions to prevent change of moisture. One
hundred cubic centimeters of distilled water at 85° C. shall
be added to the extract and the mixture placed on the water-
bath, heated, and stirred until a homogeneous solution is ob-
tained. When dissolved, the solution shall immediately be
washed into a liter flask with 800 cc. of distilled water at 85°
C, be cooled, etc., as under (A) above.
(Note: It is permissible to make up 2-liter instead of 1-liter
solutions, dissolving by washing into flask with 1,800 cc. water
at 85° C. in case of fluid extracts and 1,700 cc. water at
85° C. in case of solid or powdered extracts.)
(8) Total solids. — Thoroughly mix the solutions; pipette
100 cc. into tared dish, evaporate and dry as directed under
"Evaporation and Drying." (See IV.)
(9) Water. — The water content is shown by the difference
between 100 per cent and the total solids.
(10) Soluble solids.— S. & S. No. 590, or Munktell's No.
IF, 15 cm. single-pleated filter-paper shall be used for the
filtration.
The kaolin used shall answer the following test: 2 grams
of kaolin digested with 200 cc. of distilled water at 20° C.
for 1 hour shall give not more than 1 mg. of soluble solids
per 100 cc, and shall be neutral to phenolphthalein. To 1
616 PRACTICAL TANNING
gram of kaolin in a beaker add sufficient solution to fill the
paper, stir, and pour on paper. Return filtrate to paper when
approximately 25 cc. has collected, repeating operation for 1
hour, being careful to transfer all kaolin to the paper. At
the end of the hour remove solution from filter-paper, dis-
turbing the kaolin as little as possible. Bring as much as
needed of the original solution to exactly 20° C„ as described
under (7), re-fill the paper with this solution and begin to
collect the filtrate for evaporating and drying as soon as it
comes clear. The paper must be kept full, and the tempera-
ture of the solution on the filter must not fall below 20° C.
nor rise above 25° C. during this part of the filtration. The
temperature of the solution used for re-filling the paper must
be kept uniformly at 20° C, and the funnels and receiving
vessels must be kept covered.
Pipette 100 cc. of clear filtrate into tared dish; evaporate
and dry as under (8).
(11) Insolubles. — The insoluble content is shown by the
difference between the total solids and the soluble solids, and
represents the matter insoluble in a solution of the concentra-
tion used under the temperature conditions prescribed.
(12) Non-tannins. — The hide powder used for the non-
tannin determination shall be of wooly texture, well de-limed,
and shall require between 12 and 13 cc. of N/10 NaOH to
neutralize 10 grams of the absolutely dry powder.
(a) Digest the hide powder with 10 times its weight of
distilled water till thoroughly soaked. Add 3 per cent of
chrome-alum (Cr 2 S04)3K 2 S04.24H 2 0, in 3 per cent solution
calculated on the weight of the air-dry powder. Agitate fre-
quently for several hours, and let stand over night. Squeeze
and wash by digesting in the cold with 4 successive portions
of distilled water, each portion equal in amount to 15 times
the weight of the air-dry powder taken. Each digestion shall
last for 15 minutes, and the hide powder shall be squeezed
to approximately 75 per cent water after each digestion ex-
cept the last, a press being used if necessary. The wet hide
powder used for the analysis shall contain as nearly as pos-
ANALYTICAL METHODS 617
sible 73 per cent of water, not less than 71 per cent nor
more than 74 per cent. Determine the moisture in the wet
hide powder by drying approximately 20 grams (see IV).
To such quantity of the wet hide as represents as closely as
practicable 12} grams (not less than 12.2 nor more than 12.8)
of absolutely dry hide, add 200 cc. of the original analysis
solution and shake immediately for 10 minutes in some form
of mechanical agitator. Squeeze immediately through linen,
add 2 grams of kaolin (answering test described under 9)
to the de-tannized solution and filter through single- folded filter
(No. IF Swedish recommended) of size sufficient to hold
the entire filtrate, returning until clear. Pipette 100 cc. of
filtrate into tared dish, evaporate and dry as in (8).
The weight of the non-tannin residue must be corrected
for the dilution caused by the water contained in the wet
hide powder.
Funnels and receiving vessels must be kept covered dur-
ing filtration. Flasks graduated to deliver 200 cc. are rec-
commended for measuring the analysis solution to be
detannized.
(b) Digest the hide powder in the cold with the amount
of water and add the amount of chrome-alum in solution
directed under (a).
Agitate by some form of mechanical apparatus for 1 hour.
and proceed immediately with washing and subsequent opera-
tions as directed under (a).
(Note: In order to limit the amount of dry hide powder
used, determine the moisture in the air-dry powder and cal-
culate the quantity equal to \2\ grams of actual dry hide
powder. Take any multiple of this quantity according to
the number of analyses to be made, and after chroming^and
washing as directed, squeeze to a weight representing as
nearly as possible 73 per cent of water. Weigh the whole
amount, and divide by the multiple of the \2\ grams of
actual dry powder taken to obtain the weight of wet hide
powder for 200 cc. of solution.)
618 PEACTICAL TANNING
(13) Tannin. — The tannin content is shown by the dif-
ference between the soluble solids and the corrected non-tan-
nins, and represents the matters absorbable by hide under the
conditions of the prescribed methods.
III. Analysis of liquor
(14) Dilution. — Liquors shall be diluted for analysis with
water at room temperature so as to give as nearly as pos-
sible 0.7 gram of solids per 100 cc. of solution. Should a
liquor be of such character as not to give a proper solution
with water of room temperature it is permissible to dilute
with water at 80° C. and cool rapidly as described under
(7, A, a).
(15) Total solids. — To be determined as in Extract
Analysis.
(16) Soluble solids. — To be determined as in Extract
Analysis.
(17) Insolubles. — To be determined as in Extract Analysis.
(18) Non-tannins. — To be determined by shaking 200 cc.
of solution with an amount of wet chromed hide powder,
containing as nearly as possible 73 per cent water, correspond-
ing to an amount of dry hide powder shown in the following
table :
Tannin range per 100 cc. Dry powder per 200 cc.
Gram Grams
0.35—0.45 9.0—11.0
0.25—0.35 6.5— 9.0
0.15—0.25 4.0— 6.5
0.00—0.15 0.0— 4.0
Solutions to be shaken for non-tannins as in Extract An-
alysis and 100 cc. evaporated as in Extract Analysis.
IV. Temperature, evaporation and drying, and dishes
(19) Temperature. — The temperature of the several por-
tions of each solution pipetted for evaporating and drying,
that is, of the total solids, soluble solids and non-tannins, must
be identical at the time of pipetting.
ANALYTICAL METHODS 619
(20) Evaporation. — All evaporations and dryings shall be
conducted in the form of apparatus known as the "combined
evaporator and dryer" (figure 124) at a temperature not less
than 98° C. The time for evaporation and drying shall be
16 hours.
(21) Dishes. — The dishes used for evaporation and drying
^^
>5>
It •
i
jfcti *m
JH
i
Figure 124. — Combined evaporator and dryer.
of all residues shall be flat-bottomed glass dishes not less
than 2f inches nor more than 3 inches in diameter.
V. Determination of total acidity of liquors
(22) Reagents. — (a) One per cent solution of gelatine
neutral to hematin. The addition of 25 cc. of 95 per cent
alcohol per liter is recommended to prevent frothing. If the
gelatine solution is alkaline, neutralize with tenth normal acetic
acid, and if acid, neutralize with tenth normal sodium
hydroxide.
(b) Hematin. A solution made by digesting hematin in
cold neutral 95 per cent alcohol in the proportion of ^ gram
of the former to 100 cc. of the latter.
620 PRACTICAL TANNING
(e) Acid-washed kaolin free from soluble matters.
(d) Tenth normal sodium hydroxide.
Directions. — To 25 cc. of the liquor in a cylinder that can be
stoppered, add 50 cc. of gelatine solution, dilute with water
to 250 gc., add 15 grams of kaolin and shake vigorously.
Allow to settle for at least 15 minutes, remove 30 cc. of the
supernatant solution, dilute with 50 cc. of water, and titrate
with tenth normal soda, using hematin solution as the indi-
cator. Each cubic centimeter of tenth normal soda is equiv-
alent to 0.2 per cent acid as acetic.
VI. General
(23) When materials containing sulphite cellulose extract
are analyzed, the fact that the material contains this extract
shall be noted in the report.
(24) The test for the presence of sulphite cellulose in a
liquor or extract shall be as follows: 5 cc. of a solution of
analytical strength shall be placed in a test-tube, 0.5 cc. of
aniline added and the whole well shaken ; then 2 cc. of strong
hydrochloric acid added and the mixture again shaken. If at
least as much precipitate remains as is obtained when a com-
parison solution prepared as below is similarly treated, the
material shall be held to contain sulphite cellulose. (Neradol
D gives the same reaction.)
The comparison solution shall consist of sulphite cellulose
in the proportion of 1 part total solids to 2,000 cc. of solu-
tion, and as much tanning material, similar to that being
tested, but known to be free from sulphite cellulose, as will
make up the solution to analytical strength.
(25) On public analytical work by members of this As-
sociation the fact that the official method has been used shall
be stated.
OFFICIAL METHOD FOR SAMPLING TANNING MATERIALS
General. — Extract, whether liquid or solid, and tanning ma-
terials in general, all contain moisture. The amount of mois-
ANALYTICAL METHODS 621
ture varies with climatic conditions, but especially in liquid,
and in most solid extracts becomes less as the extract is ex-
posed to the air. As the value of any material shown by
analysis is directly dependent upon the amount of moisture
contained, and as an exposure of a comparatively few mo-
ments may alter appreciably the amount of moisture, it is ap-
parent that the sampling in all its details should be done as
quickly as consistent with thoroughness and with great care to
expose the material as little as possible to the air. The por-
tions taken as samples should be placed at once in containers
as nearly air-tight as possible, and preferably of glass. Wood,
cardboard, poorly glazed crockery, etc., are all porous and
more or less absorbent and not suitable for retaining samples.
Liquid extract cannot be accurately sampled when it con-
tains any frozen material. A sample of extract taken after
live steam has been run into the extract has not the same
concentration as the original extract. A sample of spent
bark which has been standing where dust from freshly ground
bark has sifted into it does not represent the degree of ex-
traction of the spent bark. Samples of liquor which have been
kept with no preservative in them for some time do not rep-
resent the condition of the liquor when sampled.
All extracts and crude tanning materials shall be sampled
as nearly as possible at time of weighing, and for every 50,000
lb. or less sampled, a sample shall be drawn.
(1) Solid, powdered and pasty extracts. — The number of
packages to be sampled out of a given lot shall be ascertained
by taking a percentage of the total number of packages in
the lot obtained in the following manner : Divide the total
number of packages by 100, multiply by 0.02, and subtract
from 4.
Thus 4,700 -=- 100 = 47
47 X 0.02 = 0.94
4 — 0.94 = 3.06 per cent
4,700 X 0.0306 = 144 packages
622 PRACTICAL TANNING
Provided that for lots of 200 packages and under, 5 per
cent of the number of packages shall be sampled; and for lots
of 10,000 packages and over, 2 per cent of the number of
packages shall be sampled.
Whenever possible every iVth package shall be set aside for
sampling while the extract is being moved. When this is not
possible, the packages shall be selected from as uniformly
distributed parts of the bulk as possible.
Samples of as nearly equal size as practicable shall be taken
from each package, and these samples shall represent as nearly
as may be, proportionally the outer and inner portions of the
extract. These sub-samples shall be placed in a clean, dry,
closed container. When sampling is completed, the whole
composite sample shall be broken up until it will pass through
a sieve of 1-inch mesh; it shall be reduced to the required bulk
by successive mixings and quarterings. From this bulk, du-
plicate samples of at least 6 ounces shall be drawn from op-
posite quarters by means of a small flat scoop (and not by
selecting a handful here and there). The sample shall be
enclosed in the smallest clean, dry, glass receptacle, sealed
and properly labeled.
(Note: Whenever possible, the sample should be wrapped
in paraffin paper and placed in the smallest straight-side glass
receptacle ; especially is this desirable during the warmer
months of the year.)
Sampling at place of manufacture shall be conducted by
running a portion from the middle of each strike into a mold
holding at least 2 lb. These sub-samples shall be preserved
with proper precautions against evaporation, and be sampled
for analysis as above.
(2) Liquid extracts in barrels. — The number of barrels of
extracts to be sampled out of any given lot shall be not less
than 10 per cent of the whole number of barrels for every
50,000 lb. or fraction thereof. The barrels to be sampled
shall be rolled and shaken from end to end until the contents
are homogeneous. Whenever this is not possible the heads
ANALYTICAL METHODS 623
of the barrels shall be removed and the contents stirred until
homogeneous, a sample of equal size to be taken from each
barrel. These sub-samples shall be put together in a suitable
closed container and thoroughly mixed. From this bulk, du-
plicate samples of at least 4 oz. shall be drawn and preserved
in clean, dry, glass containers; sealed and labeled with such
distinguishing marks as may be necessary.
(3) Liquid extract in bulk. — The extract shall be agitated
with air, plunged or mixed by some other efficient means until
homogeneous. Equal samples shall then be taken from dif-
ferent parts of the bulk, placed in a proper container, thor-
oughly mixed, and sampled as described in (2).
(4) Liquid extract in tank-cars. — The following methods
are permissible :
(a) The extract shall be unloaded into clean, dry contain-
ers and sampled according to (3).
(b) The extract shall be mixed until homogeneous, by
plunging through the dome or other effective means, then
numerous equal samples shall be taken from as widely scat-
tered parts of the bulk as possible. These samples shall then
be placed in a suitable container, be mixed and sampled as
in (2).
(Note : As it is almost impossible to secure a homogeneous
mixture of the extract in a tank-car, this method should be
used only when no other is possible.)
(c) The extract shall be sampled as follows while the car
is being unloaded: A quart sample shall be taken from the
discharge three minutes after the extract has begun to run;
another quart sample shall be taken three minutes before the
extract has all run out, and three other quart samples shall be
taken at equal intervals between these two. These five sam-
ples shall be transferred to a suitable container as soon as
taken, be thoroughly mixed and sampled as in (2).
(5) Crude tanning materials. — (A) Shipments in bags,
mats or other similar packages.
A number of packages shall be sampled representing 2 per
624 PRACTICAL TANNING
cent of the weight for every shipment of 50,000 lb. or frac-
tion thereof, by taking representative portions from each
package. These sub-samples shall be mixed together and the
bulk reduced by mixing and quartering to the desired size.
Duplicate samples of not less than 5 lb. each shall be preserved
in air-tight containers properly labeled.
(B) Shipments in bulk, bark, wood, etc., in sticks.
Sticks shall be taken from at least ten uniformly distributed
parts of the bulk, sawed completely through, and the sawdust
thoroughly mixed and sampled as in A.
(C) Materials prepared for leaching.
Samples of equal size shall be taken at uniform intervals
as the material enters the leach and be kept in a suitable con-
tainer till sampling is completed. This bulk shall then be
thoroughly mixed, be reduced by mixing and quartering, and.
duplicate samples for analysis of at least 2 lb. in size be pre-
served in air-tight containers, as in A.
(6) Spent materials from leaches. — Samples of spent ma-
terial shall be taken from the top, middle, and bottom, and in
each case from the center and outer portions of the leach.
These sub-samples shall be thoroughly mixed, reduced in bulk
by mixing and quartering, and duplicate samples of at least
1 quart in size preserved for analysis.
(7) Tanning liquors. — The liquor shall be mixed by plung-
ing or other effective means till homogeneous and then sam-
ples of at least 1 pint be taken for analysis. The addition of
0.03 per cent of thymol or other suitable anti-ferment to the
sample is essential to keep the liquor from altering its orig-
inal condition.
When routine samples are taken from day to day and a
composite sample analyzed, samples of equal size shall be taken
from each vat after thorough mixing, preserved in covered
containers in as cool a place as possible, and kept from fermen-
tation by the addition of suitable anti-ferment, as above. This
bulk shall be mixed till homogeneous, and samples of not less
than 1 pint each preserved for analysis.
ANALYTICAL METHODS 625
When a sample is taken by a member of this Association
in accordance with the above method, it is requested that he
state on the label of the sample submitted and on the analysis
blank that "this sample has been taken in accordance with the
official method of sampling of The American Leather Chem-
ists' Association."
OFFICIAL METHOD FOR ANALYSIS OF VEGETABLE-
TANNED LEATHER
(1) Preparation of sample.— The sample of leather for
analysis shall be reduced to as fine a state of division as prac-
ticable, either by cutting or grinding.
(2) Moisture. — Dry 10 grams of leather for 16 hours at
a temperature between 95 and 100° C.
(3) Fats.— Extract 5 to 10 grams of air-dry leather in
a Soxhlet apparatus until free from grease, using petroleum
ether boiling below 80° C. Evaporate off the ether and dry
to approximately constant weight.
Or, if preferred, extract 30 grams of leather as described
above. In the latter case, the extracted leather, when freed
of solvent, may be used for the determination of water-solu-
ble material.
(4) Ash. — Incinerate 10 to 15 grams of leather in a tared
dish at a dull red heat until carbon is consumed. If it is
difficult to burn off all the carbon, treat the ash with hot
water, filter through an ashless filter, ignite filter and residue.
Add the filtrate, evaporate to dryness, and ignite.
(5) Water-soluble material. — Digest 30 grams of leather
in a percolator over night, then extract with water at 50° C.
for 3 hours, the total volume of the solution to be 2 liters.
Determine total solids and non-tannins according to the of-
ficial method for Extract Analysis.
(6) Glucose. —
Solutions
Copper sulphate. — Dissolve 34.639 grams of CuS0 4 .5H 2
in distilled water and dilute to 500 cc. Filter through asbestos.
626 PRACTICAL TANNING
Alkaline tartrate solution. — Dissolve 173 grams of Ro-
chelle salt and 50 grams NaOH in water and dilute to 500 cc.
Allow to stand 2 days and filter through asbestos.
Normal lead acetate solution. — Prepare a saturated solution
of normal lead acetate.
Determination
Place 200 cc. of leather extract of analytical strength in
a -|-liter flask, add 25 cc. of a saturated solution of normal
lead acetate, shake frequently (5 to 10 minutes), and filter.
(The funnels and beakers must be kept covered to prevent
evaporation.) Add to the filtrate an excess of solid potas-
sium oxalate. Mix frequently for 15 minutes and filter, re-
turning the filtrate until clear. Pipette 150 cc. of this filtrate
into a 600 cc. Erlenmeyer flask, add 5 cc. of concentrated
HC1 and boil under a reflux condenser for 2 hours. Cool,
neutralize (place a small piece of litmus paper in the flask)
with anhydrous sodium carbonate, transfer to a 200 cc. grad-
uated flask, and make to volume. Filter through a double
filter (the filtrate must be clear). Determine the dextrose in
the solution immediately.
Place 25 cc. of the copper solution and 25 cc. of the alkaline
tartrate solution in a 400 cc. beaker. Add 50 cc. of the clar-
ified and neutralized solution above mentioned, and heat to
boiling in exactly 4 minutes and boil for 2 minutes. 1 Filter
immediately without diluting, through asbestos, 2 wash thor-
oughly with hot water, then with alcohol, and finally with
ether; dry for ^ hour in water-oven, and weigh as cuprous
oxide, determine the amount of dextrose by the use of Mun-
son and Walker's table, and report in percentage on leather.
1 The rate of heating of the Bunsen burner used should be regulated before sugar
determinations are started. This is best done by adjusting the burner so as to
bring 25 cc. copper solution + 25 cc. alkaline tartrate solution + 50 cc. H 2 in
a 400 cc. beaker to 100° C. in exactly four minutes.
2 The finely divided, long-fibered asbestos to be used in the glucose determination
should be digested with HN0 3 , washed, then digested with NaOH and washed.
When Gooch filters are prepared, they should be washed with boiling Fehling's
solution, then with HNO3. The mats thus prepared can be used for a long time.
ANALYTICAL METHODS
627
Munson and Walker's Table
(Bulletin 107 [Revised], Bureau of Chemistry, page 243.)
(Expressed in milligrams.)
Cuprous
oxide
Copper
Dextrose
Cuprous
oxide
Copper
Dextrose
(Cu 2 0)
(Cu)
(d-glucose)
(Cu 2 0)
(Cu)
(d-glucose)
10
8.9
4.0
45
40.0
19.1
11
9.8
4.5
46
40.9
19.6
12
10.7
4.9
47
41.7
20.0
13
11.5
5.3
48
42.6
20.4
14
12.4
5.7
49
43.5
20.9
15
13.3
6.2
50
44.4
21.3
16
14.2
6.6
51
45.3
21.7
17
15.1
7.0
52
46.2
22.2
18
16.0
7.5
53
47.1
22.6
19
16.9
7.9
54
48.0
23.0
20
17.8
8.3
55
48.9
23.5
21
18.7
8.7
56
49.7
23.9
22
19.5
9.2
57
50.6
24.3
23
20.4
9.6
58
51.5
24.8
24
21.3
10.0
59
52.4
25.2
25
22.2
10.5
60
53.3
25.6
26
23.1
10.9
61
54.2
26.1
27
24.0
11.3
62
55.1
26.5
28
24.9
11.8
63
56.0
27.0
29
25.8
12.2
64
56.8
27.4
30
26.6
12.6
65
57.7
27.8
31
27.5
13.1
66
58.6
28.3
32
28.4
13.5
67
59.5
28.7
33
29.3
13.9
68
60.4
29.2
34
30.2
14.3
69
61.3
29.6
35
31.1
14.8
70
62.2
30.0
36
32.0
15.2
71
63.1
30.5
37
32.9
15.6
72
64.0
30.9
38
33.8
16.1
73
64.8
31.4
39
34.6
16.5
74
65.7
31.8
40
35.5
16.9
75
l 66.6
32.2
41
36.4
17.4
76
67.5
32.7
42
37.3
17.8
77
I 68.4
33.1
43
38.2
18.2
78
69.3
33.6
44
39.1
18.7
79
1 70.2
34.0
628
PRACTICAL TANNING
Cuprous
Cuprous
oxide
Copper
Dextrose
oxide
Copper
Dextrose
(Cu 2 0)
(Cu)
(d-glucose)
(Cu 2 0)
(Cu)
(d-glucose)
80
71.1
34.4
115
102.2
. 50.0
81
71.9
34.9
116
103.0
50.5
82
72.8
35.3
117
103.9
50.9
83
73.7
35.8
118
104.8
51.4
84
74.6
36.2
119
105.7
51.8
85
75.5
36.7
120
106.6
52.3
86 -
76.4
37.1
121
107.5
52.7
87
77.3
37.5
122
108.4
53.2
88
78.2
38.0
123
109.3
53.6
. 89
79.1
38.4
124
110.1
54.1
90
79.9
38.9
125
111.0
54.5
91
80.8
39.3
126
111.9
55.0
92
81.7
39.8
127
112.8
55.4
93
82.6
40.2
128
113.7
55.9
94
83.5
40.6
129
114.6
56.3
95
84.4
41.1
130
115.5
56.8
96
85.3
41.5
131
116.4
57.2
97
86.2
42.0
132
117.3
57.7
98
87.1
42.4
133
118.1
58.1
99
87.9
42.9
134
119.0
58.6
100
88.8
43.3
135
119.9
59.0
101
89.7
43.8
136
120.8
59.5
102
90.6
44.2
137
121.7
60.0
103
91.5
44.7
138
122.6
60.4
104
92.4
45.1
139
123.5
60.9
105
93.3
45.5
140
124.4
61.3
106
94.2
46.0
141
125.2
61.8
107
95.0
46.4
142
126.1
62.2
108
95.9
46.9
143
127.0
62.7
109
96.8
47.3
144
127.9
63.1
110
97.7
47.8
145
128.8
63.6
111
98.6
48.2
146
129.7
64.0
112
99.5
48.7
147
130.6
64.5
113
100.4
49.1
148
131.5
65.0
114
101.3
49.6
149
132.4
65.4
ANALYTICAL METHODS
629
Cuprous
oxide
(Cu 2 0)
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
Copper
(Cu)
133.2
134.1
135.0
135.9
136.8
137.7
138.6
139.5
140.3
141.2
142.1
143.0
143.9
144.8
145.7
146.6
147.5
148.3
149.2
150.1
151.0
151.9
152.8
153.7
154.6
155.5
156.3
157.2
158.1
159.0
180
159.9
181
160.8
182
161.7
183
162.6
184
163.4
Dextrose
(d-glucose)
65.9
66.3
66.8
67.2
67.7
68.2
68.6
69.1
69.5
70.0
70.4
70.9
71.4
71.8
72.3
72.8
73.2
73.7
74.1
74.6
75.1
75.5
76.0
76.4
76.9
77.4
77.8
78.3
78.8
79.2
79.7
80.1
80.6
81.1
81.5
Cuprous
oxide
(Cu 2 0)
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
Copper
(Cu)
Dextrose
(d-glucose)
164.3
165.2
166.1
167.0
167.9
168.8
169.7
170.5
171.4
172.3
173.2
174.1
175.0
175.9
176.8
177.7
178.5
179.4
180.3
181.2
182.1
183.0
183.9
184.8
185.6
186.5
187.4
188.3
189.2
190.1
191.0
191.9
192.8
193.6
194.5
82.0
82.5
82.9
83.4
83.9
84.3
84.8
85.3
85.7
86.2
86.7
87.1
87.6
88.1
88.5
89.0
89.5
89.9
90.4
90.9
91.4
91.8
92.3
92.8
93.2
93.7
94.2
94.6
95.1
95.6
96.1
96.5
97.0
97.5
98.0
630
PRACTICAL TANNING
Cuprous
oxide
(Cu 2 0)
Copper
(Cu)
Dextrose
(ti-glucose)
Cuprous
oxide
(Cu 2 0)
Copper
(Cu)
Dextrose
(d-glucose)
220
195.4
98.4
255
226.5
115.2
221
196.3
98.9
• 256
227.4
115.7
222
197.2
99.4
257
228.3
116.1
223
198.1
99.9
258
229.2
116.6
224
199.0
100.3
259
230.1
117.1
225
199.9
100.8
260
231.0
117.6
226
200.7
101.3
261
231.8
118.1
227
201.6
101.8
262
232.7
118.6
228
202.5
102.2
263
233.6
119.0
229
203.4
102.7
264
234.5
119.5
230
204.3
103.2
265
235.4
120.0
231
205.2
103.7
266
236.3
120.5
232
206.1
104.1
267
237.2
121.0
233
207.0
104.6
268
238.1
121.5
234
207.9
105.1
269
238.9
122.0
235
208.7
105.6
270
239.8
122.5
236
209.6
106.0
271
240.7
122.9
237
210.5
106.5
272
241.6
123.4
238
211.4
107.0
273
242.5
123.9
239
212.3
107.5
274
243.4
124.4
240
213.2
108.0
275
244.3
124.9
241
214.1
108.4
276
245.2
125.4
242
215.0
108.9
277
246.1
125.9
243
215.8
109.4
278
246.9
126.4
244
216.7
109.9
279
247.8
126.9
245
217.6
110.4
280
248.7
127.3
246
218.5
110.8
281
249.6
127.8
247
219.4
111.3
282
250.5
128.3
248
220.2
111.8
283
251.4
128.8
249
221.2
112.3
284
252.3
129.3
250
222.1
112.8
285
253.2
129.8
251
223.0
113.2
286
254.0
130.3
252
223.8
113.7
287
254.9
130.8
253
224.7
114.2
288
255.8
131.3
254
225.6
114.7
289
256.7
131.8
ANALYTICAL METHODS
031
Cuprous
Cuprous
oxide
Copper
Dextrose
oxide
Copper
Dextrose
(Cu 2 0)
(Cu)
(rf-glucose)
(Cu 2 0)
(Cu)
(d-glucose)
290
257.6
132.3
325
288.7
149.7
291
258.5
132.7
326
289.6
150.2
292
259.4
133.2
327
290.5
150.7
293
260.3
133.7
328
291.4
151.2
294
261.2
134.2
329
292.2
151.7
295
262.0
134.7
330
293.1
152.2
296
262.9
135.2
331
294.0
152.7
297
263.8
135.7
332
294.9
153.2
298
264.7
136.2
333
295.8
153.7
299
265.6
136.7
334
296.7
154.2
300
266.5
137.2
335
297.6
154.7
301
267.4
137.7
336
298.5
155.2
302
268.3
138.2
337
299.3
155.8
303
269.1
138.7
338
300.2
156.3
304
270.0
139.2
339
301.1
156.8
305
270.9
139.7
340
302.0
157.3
306
271.8
140.2
341
302.9
157.8
307
272.7
140.7
342
303.8
158.3
308
273.6
141.2
343
304.7
158.8
309
274.5
141.7
344
305.6
159.3
310
275.4
142.2
345
306.5
159.8
311
276.3
142.7
346
307.3
160.3
312
277.1
143.2
347
308.2
160.8
313
278.0
143.7
348
309.1
161.4
314
278.9
144.2
349
310.0
161.9
315
* 279.8
144.7
350
310.9
162.4
316
280.7
145.2
351
311.8
162.9
317
281.6
145.7
352
312.7
163.4
318
282.5
146.2
353
313.6
163.9
319
283.4
146.7
354
314.4
164.4
320
284.2
147.2
355
315.3
164.9
321
285.1
147.7
356
316.2
165.4
322
286.0
148.2
357
317.1
166.0
323
286.9
148.7
358
318.0
166.5
324
287.8
149.2
359
1
318.9
167.0
632
PRACTICAL TANNING
Cuprous
Cuprous
oxide
Copper
Dextrose
oxide
Copper
Dextrose
(Cu 2 0)
(Cu)
(d-glucose)
(Cu 2 0)
(Cu)
(d-glucose)
360
319.8
167.5
395
350.9
185.7
361
320.7
168.0
396
351.8
186.2
362
321.6
168.5
397
352.6
186.8
363
322.4
169.0
398
353.5
187.3
364
323.3
169.6
399
354.4
187.8
365
324.2
170.1
400
355.3
188.4
366
325.1
170.6
401
356.2
188.9
367
326.0
171.1
402
357.1
189.4
368
326.9
171.6
403
358.0
189.9
369
327.8
172.1
404
358.9
190.5
370
328.7
172.7
405
359.7
191.0
371
329.5
173.2
406
360.6
191.5
372
330.4
173.7
407
361.5
192.1
373
331.3
174.2
408
362.4
192.6
374
332.2
174.7
409
363.3
193.1
375
333.1
175.3
410
364.2
193.7
376
334.0
175.8
411
365.1
194.2
377
334.9
176.3
412
366.0
194.7
378
335.8
176.8
413
366.9
195.2
379
336.7
177.3
414
367.7
195.8
380
337.5
177.9
415
368.6
196.3
381
338.4
178.4
416
369.5
196.8
382
339.3
178.9
417
370.4
197.4
383
340.2
179.4
418
371.3
197.9
384
341.1
180.0
419
372.2
198.4
385
342.0
180.5
420
373.1 '
199.0
386
342.9
181.0
421
374.0
199.5
387
343.8
181.5
422
374.8
200.1
388
344.6
182.0
423
375.7
200.6
389
345.5
182.6
424
376.6
201.1
390
346.4
183.1
425
377.5
201.7
391
347.3
183.6
426
378.4
202.2
392
348.2
184.1
427
379.3
202.8
393
349.1
184.7
428
380.2
203.3
394
350.0
185.2
429
381.1
203.8
ANALYTICAL METHODS
633
Cuprous
Cuprous
oxide
Copper
Dextrose
oxide
Copper
Dextrose
(Cu 2 0)
(Cu)
(d-glucose )
(Cu 2 0)
(Cu)
(d-glucose)
430
382.0
204.4
460
408.6
220.7
431
382.8
204.9
461
409.5
221.3
432
383.7
205.5
462
410.4
221.8
433
384.6
206.0
463
411.3
222.4
434
385.5
206.5
464
412.2
222.9
435
386.4
207.1
465
413.0
223.5
436
387.3
207.6
466
413.9
224.0
437
388.2
208.2
467
414.8
224.6
438
389.1
208.7
468
415.7
225.1
439
390.0
209.2
469
416.6
225.7
440
390.8
209.8
470
417.5
226.2
441
391.7
210.3
471
418.4
226.8
442
392.6
210.9
472
419.3
227.4
443
393.5
211.4
473
420.2
227.9
444
394.4
212.0
474
421.0
228.5
445
395.3
212.5
475
421.9
229.0
446
396.2
213.1
476
422.8
229.6
447
397.1
213.6
477
423.7
230.1
448
397.9
214.1
478
424.6
230.7
449
398.8
214.7
479
425.5
231.3
450
399.7
215.2
480
426.4
231.8
451
400.6
215.8
481
427.3
232.4
452
401.5
216.3
482
428.1
232.9
453
402.4
216.9
483
429.0
233.5
454
403.3
217.4
484
429.9
234.1
455
404.2
218.0
485
430.8
234.6
456
405.1
218.5
486
431.7
235.2
457
405.9
219.1
487
432.6
235.7
458
406.8
219.6
488
433.5
236.3
459
407.7
220.2
489
434.4
236.9
490
435.3
237.4
634 PRACTICAL TANNING
(7) Nitrogen. — Gunning modification of the Kjeldahl
method, A. O. A. C. Bulletin, No. 107 (1907).
Reagents
Standard acid solutions. — Hydrochloric or sulphuric acid,
the absolute strength of which has been accurately deter-
mined : For ordinary work half-normal acid is recommended.
For work in determining very small amounts of nitrogen,
tenth-normal is recommended. In titrating mineral acid
against hydroxide solution use cochineal as indicator.
Standard alkali solution. — The strength of this solution
relative to the acid must be accurately determined; tenth-
normal solution is recommended.
Sulphuric acid. — The sulphuric acid used should have a
specific gravity of 1.84 and be free from nitrates, also from
ammonium sulphate.
Sodium hydroxide solution. — A saturated solution of so-
dium hydroxide free from nitrates.
Potassium sulphate. — This reagent should be pulverized be-
fore using.
Indicator. — A solution of cochineal is prepared by digest-
ing and frequently agitating 3 grams of pulverized cochineal
in a mixture of 50 cc. of strong alcohol and 200 cc. of dis-
tilled water for a day or two at ordinary temperature; the
filtered solution is employed as indicator.
Determination
Place 0.7 gram of leather in a digestion flask. Add 10
grams of powdered potassium sulphate and from 15 to 25 cc.
(ordinarily about 20 cc.) of concentrated sulphuric acid.
Place the flask in an inclined position and heat below the
boiling point of the acid from 5 to 15 minutes, or until froth-
ing has ceased (a small piece of paraffin may be added to pre-
vent extreme foaming).
Then raise the heat and boil briskly until the liquid has
ANALYTICAL METHODS 635
become quite clear and nearly colorless (the digestion should
take from 4 to 5 hours).
After cooling, dilute with about 200 cc. of water. Next
add 50 cc. of soda solution, or sufficient to make the reaction
strongly alkaline, pouring it down the side of the flask so
that it does not mix at once with the acid solution. Connect
the flask with the condenser, mix the contents by shaking,
and distil until all ammonia has passed over into the stand-
ard acid. The first 150 cc. will generally contain all the am-
monia. The operation usually requires from 40 minutes to
1^ hours. The distillate is then titrated with standard alkali.
Previous to use, the reagents should be tested by a blank-
experiment with sugar, which will partly reduce any nitrates
present that, otherwise, might escape notice.
Chrome-tanned leather. — In an ordinary analysis of
chrome-tanned leather the sample is analyzed for fat, ash, and
chromium.
Fat. — About 15 grams of the leather is weighed out and
dried at a temperature of 105° C. for 2 hours. This dry
sample is put in a Soxhlet extractor and extracted on the water-
bath with petroleum ether for 3 hours. Distil off the ether
and remove the last traces by heating in the water-oven at a
temperature of 105° C. Weigh and subtract weight of the
empty flask to get the weight of. the fat residue.
Percentage of fat - g^ms fat residue X 100
weight of sample
Free sulphur. — If there is free sulphur in the leather it can
be determined by extracting a sample as described above, sub-
stituting carbon disulphide for the petroleum ether, and the
residue calculated to fat and sulphur. This fat and sulphur
residue is now covered with fuming nitric acid and allowed
to stand over night, thus oxidizing the S to SO4. Evaporate
nearly to dryness in an evaporating dish, add 100 cc. water,
boil and filter. Make the filtrate acid with hydrochloric acid
and precipitate the sulphuric acid with barium chloride solu-
tion in the usual way.
636 PRACTICAL TANNING
weight BaS0 4 X 0.137 X 100
Percentage or b = r-rr — j ; "
weight of sample
Percentage of fat = percentage of fat + S — . percentage
of S.
Ash. — A 5-gram sample is weighed into a platinum dish
and ignited, gently at first, then at high heat to constant
weight.
. , weight of residue X 100
Percentage of ash = ^j— — t i
& weight ol sample
Chromium. — The ash from the above determination is
transferred to an iron crucible and intimately mixed with
about five times its weight of sodium peroxide. Heat gently
at first then fuse well for about 10 minutes. (Warning:
Keep face away from fusion mixture. ) Cool, place in a small
casserole, cover with water and boil for about 20 minutes.
Cool, filter into a 500 cc. graduated flask. Wash the paper
well, allowing the washings to run into a flask. Pipette off
100 cc. into a 400 cc. beaker and add 25 cc. of hydrochloric
acid, some 10 per cent potassium iodine solution and titrate
with N/10 hypo in the usual way, using starch as an indicator.
, „ ' cc. N/10 Na 2 S 2 3 X 0.00253 X 5 X 100
Percentage of Cr 2 3 = . ,. , -,
fe weight of sample
( Note : — In place of the sodium peroxide the ash may be
heated with four times its weight of equal parts of magnesium
oxide and sodium carbonate, stirring frequently with a plat-
inum wire, or fused with about five times its weight of a mix-
ture consisting of equal parts of sodium and potassium car-
bonate with a small quantity of potassium nitrate.)
If the leather contains a large amount of grease, the G*203
is best calculated to the weight of leather obtained after the
fat is extracted. A well-tanned chrome leather should con-
tain at least 2.8 per cent of Cr2C>3.
Complete analysis. — While the above determinations are
usually sufficient, additional determinations are sometimes
needed. The following is a scheme given by Procter for a
complete analysis, using four different samples :
ANALYTICAL METHODS 637
A. (1) Water (7) Tannins
(2) Ash (8) Sugar
(3) Chromium (9) Sulphates
(4) Alumina (10) Chlorides
B. (5) Fat (11) Barium
(6) Sulphur (12) Lead
Water solubles C. (15) Alkaline salts
Water insolubles D. (16) Hide substance
A. A 5-gram sample is weighed out and the following
determinations made :
Water. — The percentage of water is determined by heating
the sample to constant weight at a temperature of 105° C.
loss in weight X 100
Percentage of H 2 =
Ash. — The above c
Percentage of ash =
5
Ash. — The above dry sample is ignited to constant weight,
weight of residue X 100
5
Chromium and aluminum. — The ash is fused as described
under chromium determination. The fused mass is then
boiled with water and filtered into a 250 cc. graduated flask.
The residue on the filter-paper is well washed with hot water,
and the washings run into the flask. The solution is cooled,
made up to the mark, and 50 cc. pipetted off and analyzed
iodometrically for chromium as described above. Calculate
to O2O3.
For aluminum, 50 cc. of above solution is pipetted into a
250 cc. beaker, the solution made strongly acid with hydro-
chloric acid. Alcohol is then added and boiled to reduce the
chromium to the three-bonded condition. The solution is
now made alkaline with ammonium hydroxide and boiled until
the odor of ammonia is very faint. Filter hot, wash well with
hot water, ignite, weigh, and calculate as per cent of O2O3 -j-
A12O3. The percentage of AI2O3 is found by subtracting
from the percentage of O2O3 + AI2O3 the percentage of
Cr2C>3 found iodometrically.
B. The 20-gram sample is weighed out, dried at 105° C,
and the following determination made :
Fat and sulphur are determined from the above sample as
previously outlined.
638 PRACTICAL TANNING
Water solubles. — The 20-gram sample from which the fat
and sulphur have been extracted is heated to 105° C. for 2
hours to drive off all petroleum ether or carbon disulphide.
The water solubles are dissolved from this dried sample in
the manner described under vegetable-tanned leather, 500 cc.
of the extract being collected. Small samples of this extract
are then tested for the following:
Tannins. — Vegetable tannins are tested for with iron alum
(getting blue or green precipitate) and if present are deter-
mined quantitatively as outlined under vegetable tannin
analysis.
Sugar. — A small sample of water-soluble material is treated
with basic lead acetate to precipitate the tannin, and the excess
of lead precipitated as PbC2C>4. The solution is then boiled
with dilute hydrochloric acid, neutralized with sodium car-
bonate and boiled with Fehling solution. The presence of
sugar is shown by the reduction of copper sulphate to red
C112O. If sugar is found to be present it can be determined
quantitatively as outlined under vegetable-tanned leather.
Sulphates. — A small sample boiled with hydrochloric acid
and barium chloride gives a white precipitate if sulphates are
present. Determine quantitatively in the usual manner.
Chlorides. — A white precipitate with nitric acid and silver
nitrate shows the presence of chlorides. It should be deter-
mined quantitatively in the usual manner, filtering on a Gooch,
washing, drying, and weighing as AgCl.
Barium. — In the absence of sulphates, barium may be pres-
ent. It can be tested for by adding a little sulphuric acid to
a part of the solution. A white precipitate, insoluble in KOH,
proves barium. A white precipitate soluble in KOH or
NH4C2H3O2 indicates lead.
Water insolubles: Sulphates. — After extraction with hot
water, the leather is soaked in 10 per cent sodium carbonate
solution, ashed, and fused. The fused mass is boiled with
water, filtered, washed, and the sulphates in the filtrate deter-
mined by precipitating with barium chloride.
Barium and lead. — The fused ash insoluble in water is
ANALYTICAL METHODS 639
boiled with dilute hydrochloric acid and filtered. The barium
and lead are precipitated from the filtrate with sulphuric acid.
The BaS0 4 and PbS0 4 are weighed together. The PbS0 4
is then dissolved with NH4C2H3O2, the BaS0 4 weighed up,
and the PbS0 4 obtained by difference.
C. Alkaline salts. — Fifteen grams of leather is extracted
with carbon disulphide, and the excess driven off. It is then
covered with 100 cc. of fuming nitric acid and allowed to
stand over night. It is finally evaporated to dryness, dissolved
in hot water, filtered, and made up to 250 cc. From this
solution total soluble sulphates and alkaline sulphates can be
determined.
(a) Total soluble sulphates. — 100 cc. is pipetted off, the
solution acidified with hydrochloric acid, and the sulphates
precipitated with barium chloride in the usual manner.
(b) Alkaline sulphates. — 100 cc. is pipetted off, evaporated
to dryness, and ignited to remove organic matter. The resi-
due is boiled with hydrochloric acid, evaporated to a small
volume and traces of chromium removed by boiling with am-
monia. Filter, add a few drops of concentrated sulphuric
acid to the filtrate, evaporate, ignite at not too high a tempera-
ture, and weigh as alkaline sulphates.
D. Hide substance. — This is determined by the Kjeldahl
method, as outlined under vegetable-tanned leather.
PROVISIONAL METHOD FOR THE ANALYSIS OF CHROME
LEATHER
Chrome determination. — (a) Ash 3 grams of leather. Mix
the ash well with 4 grams of a mixture of equal parts of so-
dium carbonate, potassium carbonate, and powdered borax
glass and fuse for 30 minutes. Dissolve the cooled fusion in
hot water with enough hydrochloric acid to make the solution
acid. Filter, and if there is any residue on the paper, ash it
and treat the ash with 1 gram of the fusion mixture in the
same manner as is the original ash, adding the solution to the
first, and make up to 500 cc. To 100 cc. of this solution in
640 PRACTICAL TANNING
an Erlenmeyer flask add 5 cc. hydrochloric acid, and determine
CraC>3 as above under the analysis of one-bath chrome liquors,
(b) If it is not desired to determine Fe or Al, the ash of
3 grams of leather may be transferred to an iron crucible,
mixed with '3 grams of sodium peroxide and fused 10 min-
utes. Place the cooled crucible in 300 cc. water in a casserole
and boil 20 minutes. Wash into a 500 cc. flask, cool, and
make up to the mark. Filter through a dry filter. Place 100
cc. of filtrate in an Erlenmeyer flask, neutralize with hydro-
chloric acid, add 5 cc. excess and proceed as in (a).
PROVISIONAL METHOD FOR SULPHONATED OILS
Moisture. — Weigh between 30 and 40 grams (depending on
amount of water present) into a flask of 250 to 300 cc. ca-
pacity and add 75 cc. water-saturated xylol, prepared by heat-
ing a mixture of water and xylol with frequent shaking and
subsequently removing the water in a separatory funnel. Con-
nect to a Liebig condenser and place the flask in a bath of
paraffin or a heavy lubricating oil. Distil moderately until
the distillate becomes clear. Collect the distillate in a tube
graduated to 1/10 cc. and wash the condenser with a stream
of xylol from a wash-bottle. Place the graduated tube in hot
water and when the distillate is clear, cool. The percentage
of moisture is obtained by dividing the volume of water in
the distillate by the weight of oil taken.
(Note: — For the graduated tube Eimer and Amend's No.
3812 is recommended.)
Ash. — Weigh any convenient quantity into a dish or cruci-
ble. Ignite gently, allowing the oil to burn until all carbon
is consumed.
Non-sap onifiabie. — Weigh approximately 10 grams of oil
into an 8-oz. Erlenmeyer flask and add 5 cc. aqueous KOH
solution (50 grams KOH in water and dilute to 100 cc), 45
cc. ethyl-alcohol, and a few glass beads. Boil one hour with
reflux condenser. Add 100 cc. water and cool. Transfer
to separatory funnel and shake at least three times with petrol-
ANALYTICAL METHODS 641
eum ether (B. P. 40 to 75° C. ) using 50 cc. each time. Wash
ether layer at least three times with 50 cc. water containing"
10 cc. ethyl-alcohol. Use alcohol to break emulsion. Evaporate
ether extract in tared vessel, cool and weigh.
(Note: — If the contents of the flask bump violently during
saponification add 25 cc. petroleum ether, and proceed.
Combined SO3. — (a) Weigh approximately 4 grams into
an Erlenmeyer flask and boil for 40 minutes with 30 cc. HO
(1 : 5). Shake frequently. Cool, transfer to separatory fun-
nel, and shake out with petroleum ether. Draw off aqueous
layer and wash ethereal layer with water. Combine wash-
ings with main aqueous portion and determine the sulphuric
acid as barium sulphate. From the amount thus found, the
quantity as determined in (b) is subtracted and the difference
calculated as SO3.
(b) Dissolve 4 grams in ether and shake out several times
with 25 cc. of concentrated brine free from sulphates. Com-
bine the washings, dilute, filter, and determine the sulphuric
acid as barium sulphate.
Total fatty oil. — The total fatty oil shall be the difference
between 100 per cent and the sum of moisture, ash and non-
saponifiable.
(Note: — The results obtained by these methods shall be
reported only to one decimal place.)
PROVISIONAL METHOD FOR ANALYSIS OF MOELLONS
Moisture. — Weigh accurately 3 grams of the sample in a
wide platinum dish, and heat with a low flame until the mois-
ture is all driven off. This point can be determined by the
appearance of smoke, and a slight crackling sound. Place
the dish in a desiccator, cool and weigh.
Ash. — Ash the moellon remaining in the dish after the
moisture determination in the usual manner, cool, and weigh.
Unsaponifiable. — Weigh accurately in a 300 cc. flask, 5
grams of the moellon, add 2.5 grams of caustic potash dis-
solved in a little water (or 5 cc. of a 50 per cent KOH solu-
642 PRACTICAL* TANNING
tion), and 25 cc. of 95 per cent alcohol, boil with reflux con-
denser for 1 hour, shaking occasionally. Glass beads may be
used to prevent bumping. Add 50 cc. of hot water, cool,
transfer to a separatory funnel, and extract three times, using
40 cc. of petroleum ether for each extraction. A little alco-
hol may be added to break persistent emulsions. Wash the
combined ether solutions three times with a moisture of 30
cc. of water and 10 cc. of alcohol, transfer to a tared dish,
evaporate to dryness, cool and weigh. Excessive drying must
be avoided.
Oxidized fatty acids. — Boil the soap solution remaining
from the unsaponifiable determination until all the alcohol is
expelled, then dissolve in hot water, transfer to a separatory
funnel, rinse the beaker thoroughly into the funnel, bringing
the volume to approximately 300 cc, and immediately add a
slight excess of concentrated HC1 (about 25 per cent more
than sufficient to neutralize the total alkali). Rotate the con-
tents of the flask vigorously, cool and shake out with petro-
leum ether. Run off the aqueous layer, and pour off the
ether layer, avoiding any loss of oxidized fatty acids. Wash
these acids twice with small quantities of petroleum ether and
hot water; dissolve in warm 95 per cent alcohol, filter if
necessary, transfer to a tared dish, and place in an ordinary
evaporator and dryer for 16 hours, then cool and weigh.
The entire operation should be conducted without delay.
Free fatty acids.— Weigh out 1 gram moellon, dissolve in
mixture of 20 cc. of alcohol and 20 cc. of sulphuric ether,
which has been neutralized to phenolphthalein, and titrate with
N/10 NaOH, using phenolphthalein as indicator. Test for
mineral acids or alkalies (by adding methyl-orange to the
water emulsion of the moellon), and if present, make the
necessary correction.
PROVISIONAL METHOD FOR ANALYSIS OF HARD
GREASES
Titer test. — Saponify 75 grams of fat in a metal dish with
60 cc. of 30 per cent sodium hydroxide (36° Be.) and 75 cc.
ANALYTICAL METHODS 643
of 95 per cent by volume alcohol or 120 cc. of water. Evap-
orate to dryness over a very low flame or over an iron or
asbestos plate, stirring constantly to prevent scorching. Dis-
solve the dry soap in a liter of boiling water, and if alcohol
has been used, boil for 40 minutes in order to remove it, add-
ing sufficient water to replace that lost in boiling. Add 100
cc. of 30 per cent sulphuric acid (25° Be.) to free the fatty
acids and boil until they form a clear, transparent layer. Wash
with boiling water until free from sulphuric acid, collect in
a small beaker, and place on the steam bath until the water
has settled and the fatty acids are clear; then decant into a
dry beaker, filter, using hot water funnel, and dry 20 minutes
at 100° C. When dried, cool the fatty acids to 15 or 20° C.
above the expected titer and transfer to the titer tube, which
is 25 mm. in diameter and 100 mm. in length ( 1 by 4 inches)
and made of glass about 1 mm. thick. Place in a 16-ounce salt
mouth bottle of clear glass, about 70 mm. in diameter and 150
mm. high (2.8 by 6 inches), fit it with a cork, which is perfor-
ated so as to hold the tube rigidly when in position. Suspend
the thermometer, graduated to 0.10° C, so that it can be used
as a stirrer, and stir the mass slowly until the mercury re-
mains stationary for 30 seconds. Then allow the thermometer
to hang quietly, with the bulb in the center of the mass, and
observe the rise of the mercury. The highest point to which
it rises is recorded as the titer of the fatty acids.
Test the fatty acids for complete saponification as follows :
Place 3 cc. in a test-tube and add 15 cc. of alcohol (95
per cent by volume). Bring the mixture to a boil and add
an equal volume of ammonium hydroxide (0.96 sp. gr.). A
clear solution should result, turbidity indicating unsaponified
fat. The titer must be made at about 20° C. for all fats
having a titer above 30° C, and at 10° C. below the titer for
all other fats.
Unsaponifiable. — Same as for unsaponifiable in moellons.
Free fatty acids. — Same as for free fatty acids in moellons.
644
PRACTICAL TANNING
PROVISIONAL METHOD FOR ANALYSIS OF LACTIC ACID
Free sulphuric acid. — Dissolve 50 grams of the sample in
200 cc. of alcohol, which should be neutral, and of at least
95 per cent strength. Heat to 60° C, cover, and let stand
over night in a warm place. Filter off precipitated material
and wash with alcohol. Evaporate off the alcohol, make up
the residue to 250 cc. with water, add 5 cc. strong HC1, boil,
add BaCb and determine BaSC>4 in the usual way. Calcu-
late to percentage of H2SO4 on the original sample.
Volatile acid. — Weigh out 1 gram of sample, make up to
about 50 cc. with water, titrate with N/5 NaOH. Calcu-
late the result to lactic acid: (1 cc. N/5 NaOH = 0.045
gram lactic acid.) On this basis, make up a solution con-
Table Showing the Relation of Amounts of Volatile
Acid Found in Distillate Obtained Under Stand-
ard Conditions to the Amounts Actually Present
in Distilling Flask, in Milligrams.
One Distillation
In dis-
In dis-
In dis-
In dis-
tillate
In flask
tillate
In flask
tillate
In flask
tillate
In flask
1
0.0
14
17.5
27
37.5
40
57.9
2
0.0
15
19.0
28
39.0
41
59.6
3
0.0
16
20.5
29
40.6
42
61.3
4
2.0
17
22.1
30
42.1
43
62.9
5
3.5
18
23.6
31
43.7
44
64.6
6
5.1
19
25.2
32
45.2
45
66.3
7
6.7
20
26.7
33
46.8
46
68.0
8
8.2
21
28.2
34
48.3
47
69.8
9
9.8
22
29.8
35
49.9
48
71.5
10
11.3
23
31.3
36
51.5
49
73.3
11
12.8
24
32.9
37
53.1
50
75.0
12
14.4
25
34.4
38
54.7
51
76.8
13
15.9
26
35.9
39
56.3
52
78.5
ANALYTICAL METHODS
Two Distillations
645
In dis-
In dis-
In dis-
In dis-
tillate
In flask
tillate
In flask
tillate
In flask
tillate
In flask
5
0.0
22
19.2
39
38.9
56
58.6
6
1.0
23
20.4
40
40.0
57
59.8
7
2.0
24
21.5
41
41.1
58
61.1
8
3.0
25
22.7
42
42.3
59
62.3
9
4.0
26
23.9
43
43.4
60
63.5
10
5.0
27
25.0
44
44.6
61
64.7
11
6.2
28
26.2
45
45.7
62
65.9
12
7.4
29
27.3
46
46.8
63
67.2
13
8.6
30
28.5
47
48.0
64
68.4
14
9.8
31
29.7
48
49.2
65
69.6
15
11.0
32
30.8
49
50.3
66
70.8
16
12.1
33
32.0
50
51.5
67
72.0
17
13.4
34
33.1
51
52.7
68
73.3
18
14.5
35
34.3
52
53.9
69
74.5
19
15.7
36
35.4
53
55.0
70
75.7
20
16.9
37
36.6
54
56.2
71
76.9
21
18.1
38
37.7
55
57.4
72
78.1
taining about 15 grams of acid per liter. Place 150 cc. of
this dilution in a long-necked 300 cc. Kjeldahl flask, con-
nected through a Kjeldahl bulb trap to a vertical spiral con-
denser, the total height from the bottom of the flask to the
top of the turn connecting with the condenser being between
20 and 24 inches. Distil over 125 cc. in from 47 to 53 min-
utes, counting from the time the first drop falls into the re-
ceiver, which should be a graduated cylinder. Add 125 cc.
of water to the residue in the flask and repeat. Titrate both
distillates with N/10 NaQH and phenolphthalein and calcu-
late results to grams of acetic acid: 1 cc. N/10 NaOH =
0.006 gram of acetic acid. From these figures for acid found
in distillates find actual weight of volatile acid placed in boil-
ing flask, by means of table, and calculate this result to per-
centage of volatile acid in the sample.
64,6 PRACTICAL TANNING
Free acid and anhydride. — Titrate 50 cc. of the dilution
made up for volatile acid, in the cold, with N/5 NaOH and
phenolphthalein to first full pink. Call this figure "first titra-
tion." From it subtract a number of cc. of N/5 NaOH
equivalent to the sum of volatile acid and free sulphuric acid
present in the 50 cc. of dilution. (If the sample contains free
oxalic or hydrochloric acid, the amount must be determined
by appropriate methods, and further deduction made.) Cal-
culate the remainder to lactic acid and express it as a percen-
tage of the sample. This is the free lactic acid. After com-
pleting the first titration, add 4 cc. excess alkali, or in the case
of concentrated acids, 5 cc, and stand aside at room tempera-
ture (20—25° C.) for 15 minutes. Then add 5 cc. N/5
H2SO4, boil, and titrate back with N/5 NaOH. The amount
of alkali used by anhydride is now found by subtraction and
calculated to lactic acid. Express this as percentage of lactic
acid equivalent to anhydride present in sample.
OFFICIAL FORM FOR REPORT ON EXTRACT ANALYSIS
ANALYSIS
Tannin Total solids
Non-tannins Soluble solids . .
Insolubles Ash
Water Specific gravity
Total Twaddell
Analyzed by the official f Slowly \-
method of the A.L.C.A. 1 Rapidly J
Sulphuric acid in leather: Procter and Searle method. —
This method is rapid, fairly accurate, and probably more used
than any other method.
A 3-gram sample of leather is soaked with 25 cc. of N/10
sodium carbonate and evaporated to dryness on a water-bath.
The residue is charred, pulverized, boiled out with water, and
filtered through a quantitative filter-paper. The residue is
ignited, treated with 25 cc. of N/10 hydrochloric acid and
added to the above filtrate. This combined solution is now
ANALYTICAL METHODS 647
titrated with N/10 NaOH, using methyl-orange as an indi-
cator. The amount of acid found is calculated to H2SO4.
x tt or, cc - N A° Na0H X 0.0049 X 100
Percentage of H 2 S0 4 = — 7— — -. :
weight of sample
Balland and Maljean method. — A 2-gram sample of leather
is weighed out and ashed. The ash is boiled out with water,
filtered, the sulphates in the filtrate determined by precipita-
tion with BaCb in the usual manner, and calculated to per-
centage of H2SO4. This represents the mineral sulphates in
the sample.
A second sample is weighed out, soaked with an excess of
10 per cent Na2COs solution, dried, ashed, boiled with water,
and the sulphates precipitated, as above. This gives a measure
of the free sulphuric acid plus the mineral sulphates in the
leather. Calculate the sulphates in each case. The H0SO4
in the second example minus the H2SO4 in the first sample
equals free H2SO4 in leather.
Jean's method. — A sample of leather is extracted in Soxh-
let with absolute alcohol. This dissolves the free H2SO4,
but not the mineral sulphates. Sodium carbonate should be
placed in the extraction flask to neutralize the H2SO4. The
alcohol is distilled off, the Na2SC>4 is precipitated as BaSC>4
and calculated to H2SO4.
Soap analysis. — The sample should be finely shaved and
put into a well-stoppered bottle. If the sample comes in small
cakes, cross sections should be taken through the middle. In
any case, a sample representative of the whole should be taken.
Water. — Five grams of the sample are accurately weighed
into a platinum dish containing a small glass rod, and heated
carefully on a sand-bath. The soap should be constantly
stirred with the rod to prevent burning and ensure even heat-
ing. As soon as no moisture gathers, on a watch-glass placed
over the dish it may be removed to a desiccator, cooled, and
weighed. After re-heating, it is again weighed and the process
repeated until constant weight is obtained.
Fatty acids. — A 5 or 10-gram sample is dissolved in hot
648 PRACTICAL TANNING
water and washed into a separatory funnel. The soap is de-
composed with a known quantity of standard hydrochloric
acid, and the fatty acids thus liberated are dissolved in pe-
troleum ether. The mixture should be well shaken to ensure
a perfect separation. The aqueous layer is drawn into a flask,
and the petroleum ether layer well washed with small portions
of water. The wash water is added to the drawn-off portion.
The petroleum ether solution is run into a tared dish, and
evaporated to dryness and then heated to constant weight at
100° C.
Weight obtained X 0.97 represents fatty anhydrides.
Total alkali. — The aqueous solution combined with the
washings from the fatty acids is titrated with standard sodium
hydroxide, using methyl-orange as, indicator. The difference
between the amount of acid taken to decompose the soap and
the back titration with sodium hydroxide represents the total
alkali, which should be calculated as Na20.
Insoluble in alcohol. — A 5-gram sample is dissolved in ab-
solute alcohol. If no absolute is obtainable, 95 per cent will
do. If there is much water in the soap, it must be dried be-
fore dissolving. The solution is filtered through a tared filter,
the residue washed with alcohol, dried at 100° C, and
weighed. This residue contains sodium carbonate, sodium
silicate, and other materials, which, to be determined, must be
dissolved in water and titrated with standard acid, using
methyl-orange as indicator.
Free sodium hydroxide. — The alcohol solution of soap is
titrated with N/10 acid, using phenolphthalein as indicator.
The titration represents free NaOH present.
Free oil. — A 5-gram sample is dissolved in water and ex-
tracted in a separatory funnel with petrol. The petroleum
ether extract is then washed and evaporated to constant weight
in a tared dish.
Oils. — The following methods are taken chiefly from such
standard texts as Sherman's "Organic Analysis" and Wood-
man's "Food Analysis."
A. Lubricating oil. — The color, odor, turbidity, fluores-
ANALYTICAL METHODS 649
cence, and general appearance in the standard 4-oz. sample
bottle are usually noted.
Soap. — When added to increase the viscosity, soap is
roughly tested for by seeing whether or not the ash exceeds
0.05 per cent.
Rosin oil. — The presence of this oil is determined by the
Liebermann-Storch reaction, as follows : 5 cc. of acetic an-
hydride is heated gently with 2 cc. of the oil to be tested. Cool,
and add a drop or two of 1 : 1 H2SO4 to the anhydride. A
temporary violet color indicates the presence of rosin or rosin
oil.
Saponifiablc oil {qualitative test.) — This is tested for as fol-
lows : 4 cc. of oil is heated for 15 minutes in a test tube,
in a paraffin bath with a small piece of sodium. The appear-
ance of froth or part gelatinization indicates the presence of
saponifiable oil.
The saponification number is run if saponifiable oils are
present. The saponification number in the milligrams of caus-
tic potash of KOH required to saponify 1 gram of the oil
can be determined as follows: About 2.5 grams of oil is
accurately weighed into a 300 cc. Erlenmeyer flask, and 50
cc. of alcoholic KOH solution (40 grams of KOH in 1 liter
of • alcohol and filtered) are added; 50 cc. of the alcoholic
KOH is now placed in a second Erlenmeyer flask to be used
as a blank. Both flasks are connected to a reflux con-
denser and boiled for a half-hour. Disconnect, cool, and
titrate excess KOH with N/2 HC1, using phenolphthalein as
an indicator.
Saponification No.
cc. N/2HC1 for blank— cc. N/2HC1 for sample X 0.028X1000
weight of sample
To prevent the alcohol from turning brown by. the action of
KOH it is allowed to remain in contact with the KOH for
two weeks, then distilled, and the solution made up as de-
scribed above.
Unsaponifiables. — The unsaponifiable material is determined
by weighing about 3 grams of the oil into a 150 cc. Erlenmeyer
650 PRACTICAL TANNING
flask. To this add 25 cc. of alcoholic potash (40 grams per
liter) and heat with reflux condenser for one hour. Distil
off the alcohol and add about 75 cc. of water to the residue.
Stir the solution well and extract in a separatory funnel with
75 cc. of petroleum ether. Allow the funnel to stand until
the two solutions have completely separated. Draw off the
water layer into a second separatory funnel and wash it again
with petroleum ether, also wash the etheric layer again with
water ; repeat these washings three or four times. Then com-
bine all the ether solutions in a weighed flask and combine all
the water solutions in a beaker. Distil off all ether from the
weighed flask and heat to constant weight on the water-bath,
weighing as unsaponifiable matter. The soap solution in the
beaker can be used for a saponified fatty-acid determination
by making strongly acid with concentrated hydrochloric acid,
and dissolving the precipitated fatty acids in ether, 95 per
cent of the insoluble fatty acids being obtained by this means.
Percentage of unsaponifiables
_ weight of unsaponifiable residue X 100 .
If bad emulsions are encountered in this method, the follow-
ing dry soap method for unsaponifiables can be run : About
3 grams of oil is dissolved in alcohol, and saponified as above
with 2 grams of KOH. The alcohol is distilled off and 3
grams of NaHCOs and 10 cc. of methyl-alcohol is added.
The solution is well stirred and evaporated to dryness. 5
cc. of methyl-alcohol and 10 grams of pure calcium carbonate
is now added, mixed, and evaporated to dryness at 110°
C. Extract with petroleum ether, using a Soxhlet extractor.
Specific gravity. — The specific gravity of the oil is deter-
mined by use of a hydrometer, specific-gravity bottle, pyk-
nometer or Westphal balance at 15.5° C. For liquids lighter
than water the specific gravity can be changed to Be. by use of
the following formula.
14°
°Be = sp. gr. 60 F.— 130.
60 F.
ANALYTICAL METHODS 651
The specific gravity for acids of the same series decreases
with increasing molecular weight ; in different series the spe-
cific gravity of corresponding acids increases with the number
of double bonds and OH groups.
Cold test. The cold test, or the temperature at which the
oil just begins to flow, is determined as follows : About 25
cc. of oil is placed in a tall cylindrical 100 cc. bottle, and a
thermometer is inserted through the cork so that the bulb
extends just below the surface of the oil. The bottle is now
immersed in a mixture of ice and salt. At every fall of 3°
C. the bottle is removed and inclined until a temperature is
found where the oil "sets" or just fails to flow. This is the
cold test.
Cloud test. — The cloud test or chilling point is the tempera-
ture at which the oil becomes turbid or cloudy.
Viscosity. — This is one of the most important determina-
tions for a lubricating oil. The Engler, Saybolt, and Red-
wood are the viscosimeters most commonly used. The rela-
tive viscosity, or body of an oil, is the number of seconds re-
quired for a certain volume of oil to run through a certain
orifice at a given temperature, as compared with some standard
such as distilled water or rape oil. In using the Engler vis-
cosimeter, 240 cc. of oil is poured into the reservoir. The
cover is put on, and when the temperature is just 20° C, the
plug is lifted up, and the number of seconds for 200 cc. to
flow out is determined. This number, divided by the num-
ber of seconds necessary for 200 cc. of water to flow out, is
the Engler viscosity number. Oil employed as a lubricant is
in a sense used as a cushion, to separate the two moving sur-
faces and prevent friction. It should have "body" enough to
stand up, to stay in place and withstand the maximum pres-
sure that it may be subjected to. On the other hand, if an
oil is used which has a greater viscosity than is needed, a
serious loss in power results. Oils of the same kind having
the same specific gravity and viscosity may safely be substi-
tuted for each other as lubricants.
652 PRACTICAL TANNING
Total acidity. — The acidity of a lubricating oil is impor-
tant. Organic acids up to 15 per cent (calculated to oleic
acid) are not especially objectionable, but mineral acids should
be absent.
Seven grams of oil is weighed into a 250 cc. glass-stop-
pered Erlenmeyer flask, and 50 cc. of 85 per cent neutral
ethyl-alcohol plus 2 drops of phenolphthalein are now added.
Titrate with N/10 NaOH, shaking well after each addition.
Mineral acids. — About 12 grams of oil are shaken out re-
peatedly with hot water until all of the acid is dissolved. Com-
bine these extracts, filter, cool, and titrate with N/10 NaOH,
using methyl-orange as indicator.
Flash-point. — Nearly fill a small evaporating dish or crucible
with the oil to be tested, and set it deep into a sand-bath. The
bulb of a thermometer is immersed in the oil, and the sand-
bath heated with a Bunsen flame. At every 2 degrees rise in
temperature a small gas flame (such as could be obtained at
the end of a blowpipe) is moved across the surface of the oil
at a height of about 1/10 inch. The flash-point is the tem-
perature at which the first flash is seen.
Burning point. — This test is carried out as in flash-point
and is the temperature at which the liquid takes fire.
Loss on evaporation and tendency to gum. — About 5 grams
of oil, accurately weighed on a watch-glass, is heated for
about 5 hours at the maximum temperature to which the oil
will be subjected in use. The loss in weight should not be
more than 1 per cent, and the oil should not get gummy.
Suspended matter. — Any great amount of suspended mat-
ter could be detected by diluting a sample of oil with petro-
leum ether, when the suspended matter can easily be seen. The
open cup or closed cup tests- as applied by the American So-
ciety for Testing Materials may also be used for this
determination.
Anti-fluorescents. — Three cubic centimeters of 10 per cent
potassium hydroxide solution is added to 1 cc. of oil and
boiled; a red color shows the presence of anti-fluorescents as
nitrobenzene.
ANALYTICAL METHODS " 653
B. Oil numbers for other than petroleum and lubricat-
ing oils: Iodine number. — This number is a measure of the
unsaturation of oil, of the number of double bonds. It is
determined either by the method of Hubl, Wijs, or Hanus.
Hubl uses a solution of iodine in alcoholic HgClo. The Wijs
method uses iodine chloride in place of I -f HgCl 2 , and re-
quires less time. The Llarius method uses iodine bromide.
This method has been adopted by the Association of Official
Agricultural Chemists. It is a rapid method and the solution
is easily made, as follows :
(13.2 grams of iodine is dissolved in 1000 cc. of glacial
acetic acid, and 3 cc. of bromine is added to the cold solution. )
Method. — 2.5 grams are weighed into an 8 oz. glass stop-
pered bottle; 10 cc. of chloroform is now added to dissolve
the oil and 30 cc. of Hanus solution introduced from a bur-
ette; 30 cc. of Hanus solution and 10 cc. of chloroform is
measured into a second bottle and carried along as a blank.
Let stand for 30 minutes. Add 10 cc. of 15 per cent KI,
100 cc. of water, and titrate the excess of iodine with N/10
Na 2 S 2 3 .
Percentage of iodine
cc.N /10 iodine for blank — cc. N /10 iodine sample X 0.0127 X 100
weight of sample
absorbed.
Helmer number. — This number is the percentage of insolu-
ble fatty acids.
Reichert Meissl number. — The number of cubic centimeters
of N/10 NaOH to neutralize the soluble volatile acids from
5 grams of sample.
Maumene number. — Rise in degrees Centigrade caused by
the addition of 10 cc. of concentrated H0SO4 to 50 grams of
oil. This number is dependent on the number of double bonds.
Acetyl number. — Number of milligrams of KOH to neutral-
ize the acetic acid obtained by saponification of 1 gram of
acetylated fat. It is dependent upon the number of OH groups
in the molecule.
654 PRACTICAL TANNING
Titer test. — Temperature of solidification of the mixed fatty
acids.
Acid number. — The number of milligrams of KOH to neu-
tralize the free fatty acid in a one-gram sample. It is de-
termined by dissolving 5 grams of oil in neutral alcohol, and
titrating with N/10 KOH, using phenol phthalein as an
indicator.
Ester number. — Saponification number — acid number.
Polenske number. — Cubic centimeters of N/10 NaOH to
neutralize the insoluble volatile fatty acids, distilled from a
5 -gram sample.
Analysis of titanium-potassium oxalate (TiO-z). — Weigh
accurately 10 grams of sample, dissolve in water, and make
up to mark in a 250-cc. graduated flask.
To 25 cc. of the solution add about 5 cc. of concentrated
sulphuric acid and heat to 60° C. Destroy oxalic acid by add-
ing potassium permanganate solution slowly to the hot solu-
tion until a permanent pink color results. Just enough solid
sodium bisulphite is now added to destroy the excess potas-
sium permanganate and dissolve any manganese dioxide which
may be formed; ammonium hydroxide is added in slight ex-
cess. Acetic acid is added in considerable excess (about 15
cc. 1:3 acid), and the solution digested on the hot plate for
about 20 minutes. Filter off the precipitated TiC>2 while the
solution is hot. Wash the precipitate with hot water until free
from sulphates ; ignite in a weighed crucible, and weigh as
TiC>2. This determination is accurate in the absence of iron
and aluminum, the acetic acid preventing the manganese from
being precipitated.
If iron and aluminum are present, the following modifica-
tions should be made. Carry out the precipitation with am-
monium hydroxide and acetic acid as described above, filter
and wash. Dissolve the precipitate in about 15 cc. of HC1
(sp. gr. 1.12). Stir a minute in the cold, then boil two or
three minutes. Any undissolved material can be dissolved by
adding a few drops of concentrated HNO3 and boiling. Di-
lute, filter, and evaporate to destroy excess of acid. Dilute
ANALYTICAL METHODS 655
to about 20 cc, and make alkaline with an excess of NaOH
(avoid too great an excess) . Add 5 cc. of 10 per cent Na2C03,
boil, cool, add an equal volume of water and -filter.
Aluminum remains in the filtrate in the form of NaAlC>2, and
iron and titanium become insoluble and are collected on the
filter-paper as hydroxides or oxides.
Aluminum. — This is determined in the usual way. Make
the solution acid with HC1, then faintly alkaline with NH4OH,
boil, filter, ignite, and weigh up AI2O3.
Iron and titanium. — Dissolve the iron and titanium residue
obtained above in the least possible amount of HC1 (1.12 sp.
gr.). Add 20 cc. more HC1 (1.12 sp. gr.), and transfer the
cold solution to a separatory funnel. Add an equal volume
of ether and shake vigorously. Allow the two layers to sep-
arate and draw them off into two separate beakers. Rinse
out the funnel with a little ether. Return the aqueous layer
to the funnel and treat with ether as before. Repeat this
treatment until the ether layer is colorless. Iron is now in
the ether layer in the form of FeClj. Combine these extrac-
tions, distil off the ether and determine iron in the usual way.
The titanium is found in the water extract from which it can
be precipitated as TiC>2 or TiO (OH) 2 as directed above.
Oxalate. — Acidify 10 cc. of the original solution with
H2SO4, heat to 60° C, and titrate with N/10 KMn0 4 as in
an ordinary permanganate titration.
1 cc N/10 KMn0 4 = 0.0044 gram C2O4
Ash. — One gram of sample is ignited at a low red heat in
a platinum dish. After igniting, the dish is transferred to a
desiccator and weighed as soon as cool. Repeat the heating
to constant weight ; providing other metals are absent the ash
is composed of TiC>2 and K2CO3.
Potassium. — The percentages of potassium and water are
usually obtained by subtracting the sum of the above per-
centages from 100.
The potassium may be determined as follows: A 1-gram
sample is dissolved in 50 cc. of hot water. Filter, wash the
656 PRACTICAL TANNING
filter-paper with hot water, and reject any insoluble residue.
If sulphates are present, they must be removed by precipi-
tating with BaCl2 in the usual way. The excess of barium,
and any aluminum which may be present, must now be re-
moved by making the solution alkaline with NH4OH, heating,
and adding ammonium carbonate solution until no further
precipitation occurs. Filter, wash, and proceed with the fil-
trate as follows : Evaporate the solution to 20 cc. and add
10 to 15 cc. of perchloric acid. Evaporate, with stirring, in
a porcelain dish, until the solution becomes syrupy. Dilute
and evaporate again until dense white fumes of perchloric acid
are seen. Cool, and introduce 25 cc. of 95 per cent alcohol,
to which 1 cc. of perchloric acid has been added. Stir well
and allow to settle. Decant the clear portion through a
weighed Gooch crucible and treat twice with 25 cc. of the al-
coholic wash. Throw the insoluble portion on the Gooch,
wash with 25 cc. of alcohol containing two drops of perchloric
acid. Then wash with 95 per cent alcohol. Cover the Gooch
crucible, and dry in an oven at a temperature of about 130°
C. Weigh as KCIO4. Report potassium as KoO.
Analysis of blood albumen. — The sample should be finely
powdered and put into a well-covered vessel.
Water. — Dry 2 grams of the sample in a tared dish to con-
stant weight at 100° C. Loss in weight is the water.
Ash. — Ignite 2 grams of the sample at a very low temper-
ature in a platinum dish until all the carbon is burned off.
Weigh as ash.
Insoluble matter. — Dissolve 5 grams of the sample in water
and dilute to 250 cc. Pour some of this solution into a glass,
add 2 or 3 grams of kaolin, stir well and pour into a fluted
filter. Collect 50 cc. of the filtrate as soon as it runs clear,
and evaporate to dryness in a tared dish. Evaporate 50
cc. of the unfiltered and well-shaken solution in another dish.
The difference in weight of the two residues represents the
insoluble matter.
Non-albumen. — Dilute 50 cc. of the solution used in the
above determination in water, and make slightly acid to litmus
ANALYTICAL METHODS - 657
with acetic acid. Digest on steam-bath until the albumen is
all precipitated and the supernatant liquid appears clear. Wash
into a 250 cc. flask, cool, make up to the mark, filter, and
evaporate 50 cc. in a tared dish. The residue represents non-
albumen.
Analysis of formic acid. — The specific gravity is taken at
60° F. with a Westphal balance.
Total acidity. — Between 50 and 60 grams of the sample is
dissolved in water, and diluted to 1000 cc. ; 25 cc. of this
solution is titrated with N/10 NaOH, using phenolphthalein
as indicator. The result is calculated to formic acid.
Acetic acid. — Add about 5 grams of yellow mercuric oxide
to about 10 cc. of the solution used in the above determination.
Dilute to about 150 cc. and digest on the steam-bath for about
1£ hours. Filter through a fluted filter, using kaolin if nec-
essary to obtain a clear filtrate. If acetic acid is present, a
black precipitate will form in the filtrate on the addition of
ammonium sulphide.
Mineral acids. — The S0 4 and CI ions are tested for in the
regular manner.
Analysis of egg-yolk: Water. — A glass evaporating dish
containing some purified quartz and a small glass rod is dried
in the oven to constant weight. A sample of 5 or 6 grams
is weighed from the weighing bottle and thoroughly mixed
with the sand in the dish. The dish is heated in the oven at
100° C, with occasional stirring to break up any lumps
formed, and dried to constant weight. The loss is calculated
as water.
'Ash. — A sample of 2 or 3 grams is ignited at a low tem-
perature in a platinum dish until charred. The carbonaceous
mass is extracted with hot water and filtered into a tared dish,
then evaporated to dryness. The filtrate is ignited and the
residue added to the extracted portion. The sum represents
the ash.
Fat. — The portion used for the determination of water is
removed from the dish, powdered finely in the mortar and
extracted with petroleum ether in a Soxhlet extractor. The
658 PRACTICAL TANNING
extract is evaporated to dryness at 100° C, and weighed as
fat.
Salt. — After removing the fat, the sample is extracted with
hot water, cooled, and made up to 250 cc, and 50 cc. of this
solution is then titrated with N/10 AgNOa, using potassium
chromate as an indicator.
Nitrogen or albumen. — Three or four grams of the original
sample is digested with 15 cc. of concentrated H2SO4 and 10
grams of potassium sulphate until clear. The digested portion
is diluted with water, connected to a condenser, an excess of
sodium hydroxide is added, the ammonia distilled into 50 cc.
N/10 acid, and the determination completed as previously
described under the Kjeldahl method. The nitrogen multiplied
by 6.33 equals albumen.
Analysis of acetate of iron liquor. — 25 grams of the
sample is weighed out and diluted to 250 cc.
Total acidity. — 25 cc. of N/10 NaOH is added to 50 cc.
of the above solution in a 250 cc. flask, the solution made
up to the mark, shaken, and filtered; 50 cc. of the filtrate
is titrated with N/10 H2SO4, using phenolphthalein as
indicator. The result may be calculated to acetic acid.
Iron oxide. — 50 cc. of the above solution is digested to
clearness with concentrated H0SO4 in a Kjeldahl flask to
destroy organic matter. The digested portion is made up
to 250 cc, and 100 cc. is precipitated with ammonium
hydroxide in the regular manner for the determination for
Fe203.
Ash. — Ignite 1 gram of the sample in a platinum dish.
Sulphuric acid. — Test for SO4, and if present, proceed as
follows : 10 grams of the sample is made up to 250 cc. ;
25 cc. of the solution is measured into a platinum dish with
25 cc. of N/10 Na2CO,3, evaporated to dryness, and ignited.
The residue is re-dissolved in water and titrated back with
N/10 H2SO4. The titration thus obtained subtracted from
25 represents in cubic centimeters of N/10 alkali the acid
present as free and combined H2SO4. The acid may also be
determined gravimetrically by precipitation with BaC^. Any
ANALYTICAL METHODS - 659
FeSCU present may be calculated from these two determina-
tions and the determination of acetic acid by distillation.
Acetic acid. — In the presence of mineral acids, the acetic
acid should be distilled off. This is done by dissolving a
few grams of the sample in water, acidifying with H2SO4,
and distilling until no more acid is obtained in the distillate.
This will require thorough distillation.
Some simple chemical tests for leather makers.* — The
following are a few simple tests which may be applied to
several of the more common materials used in the tannery
without the aid of a specially arranged laboratory or any
expensive apparatus, in order to tell whether or not they are
adulterated.
Lime. — A good quicklime should slake well when mixed
with water. If, on the addition of a little hydrochloric acid,
it effervesces, it points to a fair amount of chalk present ; while
if after this treatment with acid much is left undissolved, it
would indicate an excessive quantity of sand or insoluble
matter.
Linseed meal (crushed linseed). — Make a solution in hot
water, and allow to cool. When cold, add a few drops of
tincture of iodine. A blue color formed would show that the
linseed had been adulterated (the blue color really indicates
the presence of starch, and pure linseed contains no starch).
Dried blood. — If the amount of ash is determined, it
should be between 4 and 5 per cent. The ash should be white,
and if it is a brick-red color the admixture of iron would be
indicated.
Gum arabic. — The likely adulterant is gum tragacanth.
Dissolve some of the gum, after finely powdering, in the
blue solution obtained by adding ammonia to a solution of
copper sulphate. If an appreciable amount is left undissolved,
tragacanth is probably present.
Dyes. — To determine whether a dye is just a simple one or
an admixture, the following procedure should be adopted :
Place a small portion of the dye on the end of a penknife,
Jour. Amer. Leather Chemists, Dec, 1916.
660 PRACTICAL TANNING
and blow it onto a piece of wet white blotting paper held
about a foot away. The small particles will adhere to
the wet paper and dissolve in the water, showing its color.
By this method one may show, for example, that a dye consists
of a mixture of a blue and a red dye.
Cod-liver oil. — This is likely to be adulterated with mineral
oil. Boil two or three drops of the oil with caustic soda
which has been dissolved in methylated spirit. If after con-
tinued boiling a perceptible amount is left undissolved this
would indicate admixture with mineral oil. This test is based
upon the fact that, under the influence of caustic soda, cod
oil is converted into soap, whereas mineral oils are not so
changed.
Glucose. — This substance may be adulterated, and if a small
piece is burnt in a tin, only a very small amount of a white
ash is left. Anything over a trace would indicate adulterants.
Salt. — Impure salt may contain a small yet undesirable
amount of iron. To test for this, make a solution of the salt
in water, and add a few drops of potassium thiocyanate. A
red color will develop in the presence of the iron. If this
chemical is not at hand, add a few drops of potassium ferro-
cyanide (yellow prussiate of potash), when a blue color will
indicate iron.
Ammonium chloride (sal-ammoniac). — This should be of a
pure white color, and perfectly soluble in cold water. If a
small amount is heated in a tin lid over a gas flame it will be
completely volatilized, no residue being left.
Caustic soda, — This substance, if left exposed to the air,
will absorb carbon dioxide therefrom, and so gradually
"carbonate." A rough test would be to dissolve a small sample
in cold water, and then add a little hydrochloric or sulphuric
acid (dilute). If gas bubbles are given off, this would indicate
carbonates, which should not be present in a good sampl
Ferrous sulphate (green vitriol). — A good sample should
be of a uniform pale green color. In a moist atmosphere it is
liable to undergo oxidation, in which case a brownish color
ANALYTICAL METHODS - 061
will develop. To prevent this, the material should be kept in
a cool, dry place, for preference in large stone jars fitted
with bungs.
Sodium thiosulphate {hypo). — It is quite unlikely that this
chemical will be adulterated, but as in appearance it resembles
soda it may be confused with it if, say, the labels became
detached from the receptacles in which they were kept. Add
a little hydrochloric acid to a solution of the substance in
water. If hypo, the solution will turn yellow (owing to the
fine precipitate of sulphur), and an unpleasant-smelling gas
will be evolved (sulphur dioxide). If, on the other hand, the
substance be soda, only bubbles of an odorless gas will be
given off (carbon dioxide).
Flour. — Alum is sometimes added to a bad quality of flour
to improve its appearance. To test for this substance, the
following reagent has to be prepared : 10 cc. of 5 per cent
alcoholic logwood solution mixed with 150 cc. of water, and
10 cc. of saturated ammonium carbonate solution (this reagent
should be mixed just before using). Some of the flour to be
tested is made into a paste with water, and then a few drops
of the solution added. Alum, if present, will be indicated by
the formation of a blue color after the mixture has been
allowed to stand for about two hours.
The percentage of ash also affords a good method of deter-
mining the quality of a flour. High-class flour yields 0.5 per
cent of ash, whereas lower qualities will give from 0.5 up to
8 per cent, according to how much bran is present. Chalk,
which some years ago was used as an adulterant, can be tested
for by adding dilute hydrochloric acid to some flour paste,
when an effervescence will take place if chalk is present.
Egg-yolk. — It is difficult to suggest any simple tests for the
purity of egg-yolk, a chemical analysis being essential. The
following tests, however, will detect the preservative present :
Ignite some of the yolk to complete ash in a porcelain basin.
If a large amount of a white ash is left, salt (sodium chloride)
is the preserving agent. Now add a few drops of sulphuric
662 PRACTICAL TANNING
acid to the ash and then some methylated spirit; warm the
whole, and then ignite the spirit. In the presence of boric acid,
a greenish tinge will appear around the edges of the flame.
Ammonia or ammonium hydroxide. — This is a solution of
pure ammonia gas in water, and at its greatest strength has a
specific gravity of 0.880. A higher gravity than this would
indicate either a weak liquor or the addition of water. If
some of the solution is boiled to dryness in a dish, no residue
should be left. Sulphates, chlorides, and other impurities are
deposited by this treatment.
Borax. — It is unlikely that this substance will appear adulter-
ated, although it is stated that soda has been used for this
purpose. This could be detected by treating some of the borax
with dilute hydrochloric acid, when, if soda is present,
bubbles of gas will be evolved.
Mineral acids. — The two acids of this class used are hydro-
chloric and sulphuric, and to distinguish between them the
following tests may be applied: Add to the acid (previously
diluted with a little distilled water) a small quantity of silver
nitrate solution. If a precipitate is formed, hydrochloric acid
will be indicated. Using a fresh sample of the diluted acid,
repeat the above experiment, using a solution of barium
chloride in place of silver nitrate. A white precipitate will
show sulphuric acid. By these tests, small amounts of impu-
rities may be detected in either acid ; for example, a very slight
precipitate in the case of the first test will show a trace of
chloride, etc. Iron may be detected in either acid bv means
of potassium sulphocyanide.
Shellac. — The only impurity which can be identified in
a simple manner is any weighting material added, such as sand,
etc., which may also be present in a dirty sample. Such sub-
stances will be left behind as insoluble residue when some of
the material is dissolved in hot methylated spirit or hot
ammonia solution. A good sample will dissolve completely in
either of these two solvents. Shellac is often adulterated with
rosin, but its detection is too complicated to include in these
tests.
ANALYTICAL METHODS 663
Soda. — Washing soda or sodium carbonate may contain
iron and salt. Take some of the sample, and dissolve it in
dilute sulphuric acid ; or better still, in some dilute nitric acid.
Divide the solution into two parts, and to one add a few drops
of silver nitrate solution, when a white curdy precipitate will
show the presence of salt (if only a white cloudiness appears,
a trace of salt is present). To the other half of the solution
add some potassium sulphocyanide, when a blood-red colora-
tion will indicate iron.
Carbolic acid or phenol. — This, sometimes used as an anti-
septic, is liable to contain an undesirable amount of iron. The
following method will apply : About half an ounce of the
sample should be burned to ash in a porcelain dish. The opera-
tion must be performed in a place where the fumes evolved
can be carried away. Then dissolve the ash in a few drops of
strong nitric acid and dilute with a little water. The usual test
for iron with potassium sulphocyanide may then be applied.
Sumac. — The purity of this material, like all other tanning-
materials, can only be determined by an accurate chemical
examination. Iron in a metallic form may sometimes be pres-
ent in an undesirable amount. This may be tested for by run-
ning a strong magnet through a sample of the sumac previously
spread out in a thin layer. The particles of iron will adhere
to the magnet and may be removed and further examined if
necessary.
Lactic acid. — If this acid has been adulterated with mineral
matter, a large amount of residue will be left when some of the
acid is boiled to dryness in a porcelain dish. To test for iron,
the residue obtained above is dissolved in a little nitric
acid diluted with a small quantity of water, and a solution
of potassium sulphocyanide added. If present, iron will give
a deep red color.
(Note: — This test also applies to acetic or formic acid.)
Soaps. — These, whether hard or soft, are very liable to
adulteration with various admixtures. The sample should be
cut into very small pieces, and a little of it boiled in absolute
alcohol (or very good re-distilled methylated spirit may be
664, PRACTICAL TANNING
used). Only soap will be dissolved by this treatment. What
is left will be alkaline carbonate, borate, silicate, together with
any "filling" material, such as starch, chalk, and, in very bad
cases, even sawdust.
( Note : — It might be added that to detect iron in any material
containing a large amount of organic matter, the following
method may always be applied: Burn the material to an ash
in a porcelain (or better still a platinum) dish, and then heat the
ash and, when cool, treat with nitric acid. The addition of this
acid is important, inasmuch as it converts all the iron present
into the ferric condition, which is essential for the final test.
Having now got the iron into solution in this form, the liquid
is diluted with a little water, and then a little 10 per cent
potassium sulphocyanide solution is added, when a red color
shows the presence of iron. If preferred, a 10 per cent solu-
tion of potassium ferrocyanide may be used instead of the
sulphocyanide. In this case, however, a deep blue color will
be produced if iron be present..
Indicators. — By means of indicators we are able to tell
whether a liquor has an acid or alkaline reaction. The fol-
lowing table gives the colors produced when using these vari-
ous indicators :
Indicator If acid If alkaline
Litmus Red Blue
Methyl-orange Red Yellow
Phenolphthalein Colorless Red
CHAPTER XXII
DISPOSAL OF TANNERY WASTE*
Tanneries are among the largest producers of industrial
organic wastes. Each day's run-off consists of many millions
of gallons of liquid material teeming with bacteria and con-
taining much organic matter, both dissolved and suspended,
and of a highly putrescible nature. Up to the present time
practically all tanneries have been discharging this waste into
streams, lakes, or sewer systems without preliminary treat-
ment. The situation, however, is rapidly becoming acute,
inasmuch as municipalities and boards of health are begin-
ning to prohibit by law the pollution, directly or indirectly, of
natural waters by industrial wastes. Where tanneries dis-
charge their waste into local sewer systems authorities are at
least insisting that suspended matter be excluded so that the
sewers shall not become clogged. Where cities are treating as
well as collecting their sewage and industrial waste, they are
stipulating that all materials harmful or burdensome to the
disposal plant processes shall be excluded, or reduced by di-
lution to such a degree that the waste can be successfully and
economically treated. In fact, the policy now followed in some
localities is to insist that no industrial effluent stronger than
the average sanitary sewage be permitted to enter the local
sewer system. Thus it is readily seen that the problem of dis-
posing of tannery waste, especially where the tanner is com-
pelled to treat his own material, is fast becoming important
and serious.
Classification and Nature of Tannery Wastes.
1. Soak liquors — containing blood, manure, hair, etc.
2. Lime liquors — containing lime and magnesia, calcium
carbonate, hair, and dissolved hide substance.
*The material contained in this chapter was furnished by Victor H
Kadish of Milwaukee, Wisconsin.
665
666 PRACTICAL TANNING
3. Bate liquors — containing bacteria, enzymes, hide sub-
stance, etc.
4. Pickle liquors — containing salt and acid in solution; and
calcium sulphate in suspension.
5. Chrome tanning liquors — containing salts in solution;
chromium compounds in solution or suspension.
6. Vegetable tanning liquors — containing tannins, "reds,"
coloring matter, etc.
7. Dye liquors — consisting of solutions of weak dyestuffs.
8. Fat-liquors — containing small quantities of oils and fats.
9. Wash waters — in large volumes containing undissolved
or suspended solids which, when removed, leave practically
pure water.
10. Condenser water.
Plain sedimentation. — This is the simplest and most com-
mon method now used. The sewage flows continuously
at a low velocity through a settling-tank or basin, properly
baffled, with the consequent settling out of a considerable
percentage of the material in suspension. The supernatant
liquor is drawn off at intervals, and the accumulated sludge
is removed from the bottom of the tank. While the plant
cost is low and operating charges are small, there are many
disadvantages in this method, a few being the large floor area
required, a serious objection in many cases; instability of the
effluent with very little if any reduction in the number of
bacteria ; difficulty in removal and disposal of the sludge which
is very offensive in odor and has little value as a fertilizer.
Mechanical sedimentation. — This is usually carried out in
a circular tank with sloping bottom by means of slowly ro-
tating arms which tend to scrub the solids towards the bottom
of the sedimentation tank where they can be withdrawn by
means of a pump or syphon. The sludge as withdrawn is in
the liquid condition, containing about 95 per cent water, which
necessitates de-watering before it can be disposed of. This
method increases the rate of settling of the solids and pro-
vides a cleaner-cut handling of the sludge, but the same ob-
DISPOSAL OF TANNERY WASTE ' 667
jections, nevertheless, maintain as above, only to a lesser
degree.
With either method further treatment of the effluent is
necessary if it is to be rendered relatively stable and low
in bacteria. This can be. accomplished by means of coarse
stone trickling niters, which again occupy much space, or the
effluent may be disinfected by means of liquid chlorine which
largely reduces the number of bacteria when sufficient chlor-
ine is used.
Activated sludge process. — This is a recently developed
rapid aeration process which produces a remarkably pure
effluent when applied to sanitary sewage. The raw sewage
flows through rectangular tanks fitted with "filtros" plates in
the bottom through which finely divided compressed air is
diffused, thereby agitating the sewage violently. About 20
per cent by volume of the thickened so-called activated sludge
is mixed with the incoming raw sewage as it enters the aera-
tion tank. This combination of air and activated sludge pre-
cipitates a large portion of the organic matter in the form of
a light, fluffy, brown-colored mass which is separated from
the clear, purified liquor in a settling tank by means of a Dorr
thickener. That portion of the sludge withdrawn from the
settling tank and not returned to the aerating system must be
de-watered by pressing or otherwise. This is no small prob-
lem when the nature of the material and its 98 per cent mois-
ture content is considered. The process as a whole is delicate
of control and costly, and while in its present stage of devel-
opment looks promising for large municipal sewage disposal
works, is hardly feasible on the small scale of tannery
operation.
Other methods of treatment. — Heretofore, in the relatively
few installations for tannery waste disposal, it has been the
practice to collect the entire flow of the tannery and treat it
at the disposal plant, disregarding the fact that fully 80 per
cent of the volume is practically clean water. Handling
large volumes means increased costs, necessity for large
ground areas— frequently not available — and generally is a
668 PRACTICAL TANNING
heavy financial burden to the tanner, without adequate return.
Advantage should be taken of this large volume of almost
clean water by laying out a dual sewer system, one for the
collection of foul and polluted waste, the other for the much
larger volume of wash and condenser water. The latter can
be merely passed through a suitable screen to remove the
coarse solids in suspension such as hair, bits of flesh, tanned
shavings, etc., after which the clear effluent can be conducted
away from the tannery. The second and smaller system
should of course collect all of the polluted waste for subse-
quent treatment. With a greatly reduced volume to be treated,
and richer in solids as well, treatment in a mechanical sedi-
mentation tank is feasible and economical. If, however, the
required ground area is not available, the use of a recently
perfected, continuously operating centrifugal machine, the so-
called "ter meer," made in Germany, is suggested. This
machine, occupying only a few square feet of floor space, will
"scrub out" 95 per cent of the suspended matter in the form
of 80 per cent moisture sludge-cake, discharged automati-
cally, and deliver at the same time a clear effluent. No
further treatment should be necessary where the tannery waste
is being run into a municipal sewer system. Where it is being
discharged into a potential water supply, final treatment of
the effluent from settling tank or centrifuge with liquid chlor-
ine is suggested.
Another recent discovery may change the recovery of tan-
nery waste from the debit to the credit side : By using the
so-called sulphide process for de-hairing, whereby the hair is
completely dissolved, it is now commercially profitable to
recover this waste sulphide liquor as fertilizer and at the same
time remove from tannery waste a large percentage of the
most obnoxious material. When spent sulphide liquors are
rendered slightly acid, the dissolved hair (proteid colloids) is
immediately precipitated in the form of a spongy, porous mass
from which the water is readily expressed. This can be
accomplished by means of a continuously operating process
which runs itself automatically, consisting of very simple
DISPOSAL OF TANNERY WASTE 669
equipment and requiring little labor. The resulting fertilizer
material is uniform in composition and averages 13 per cent
ammonia on a 10 per cent moisture basis, with 97 per cent
of the ammonia available. This material ranks with the best
grade of packer tankage, and should always command a ready
market. At present fertilizer prices the manufacturing profit
amounts approximately to 100 per cent. An interesting side-
light in this connection is that the process provides for the
recovery of a considerable portion of the original sodium sul-
phide used, which, together with the fertilizer produced, makes
the sulphide de-hairing process much cheaper per unit of
leather than the liming process.
By segregating tannery waste liquors into two classes as
indicated, and by adopting the sulphide process with recov-
ery of the spent sulphide waste as a valuable nitrogenous
fertilizer material, the tanner can clean up his back yard and
make a profit at the same time.
CHAPTER XXIII
USEFUL DATA
Thermometer conversions. — To convert degrees Centi-
grade into Fahrenheit (above freezing) multiply by 9, divide
the product by 5 and add 32 to the quotient.
To convert Fahrenheit (above freezing) into Centigrade,
subtract 32, multiply the remainder by 5 and divide the prod-
uct by 9.
To convert Reaumur into Fahrenheit, multiply by 9, divide
the product by 4 and add 32 to the quotient.
To convert Fahrenheit into Reaumur, subtract 32, multiply
the remainder by 4 and divide the product by 9.
Boiling and Freezing Points of Thermometers
Boiling
Point
Freezing
Point
Fahrenheit
212°
100°
80°
32°
Centigrade
0°
0°
FORMULA FOR CALCULATING THE WEIGHT OF PIPES
W = k(D'— d")
W = weight of 1 lineal foot in lbs.
D = outside diameter in inches,
d =• inside diameter in inches,
k ■— a coefficient, being
0.85 for aluminum.
2.43 for zinc.
2.45 for cast iron.
2.49 for tin.
2.64 for wrought iron.
2.82 for brass.
3.03 for copper.
3.86 for lead.
670
USEFUL
, DATA
671
Comparisons of Thermometers
Fahrenheit
Centigrade
Reaumur
Fahrenheit
Centigrade
Reaumur
212
100.
80.
142
61.1
48.9
210
98.9
79.1
140
60.
• 48.
208
97.8
78.2
138
58.9
47.1
206
96.7
77.3
136
57.8
46.2
204
95.6
76.4
134
56.7
45.3
202
94.4
75.6
132
55.6
44.4
200
93.3
74.7
130
54.4
43.6
198
92.2
_ 73.8
128
53.3
42.7
196
91.1
72.9
126
52.2
41.8
194
90.
72.
124
51.1
40.9
192
88.9
71.1
122
50.
40.
190
87.8
70.2
120
48.9
39.1
188
86.7
69.3
118
47.8
38.2
186
85.6
68.4
116
46.7
37.3
184
84.4
67.6
114
45.6
36.4
182
83.3
66.7
112
44.4
35.6
180
82.2
65.8
110
43.3
34.7
178
81.1
64.9
108
42.2
33.8
176
80.
64.
106
41.1
32.9
174
78.9
63.1
104
48.
32.
172
77.8
62.2
102
38.9
31.1
170
76.7
61.3
100
37.8
30.2
168
75.6
60.4
98
36.7
29.3
166
74.4
59.6
96
35.5
28.4
164
73.3
58.7
94
34.4
27.6
162
72.2
57.8
92
33.3
26.7
160
71.1
56.9
90
32.2
25.8
158
70.
56.
88
31.1
24.9
156
68.9
55.1
86
30.
24.
154
67.8
54.2
84
28.9
23.1
152
66.7
53.3
82
27.8
22.2
150
65.6
52.4
80
26.7
21.3
148
64.4
51.6
78
25.6
20.4
146
63.3
50.7
76
24.4
19.6
144
62.2
49.8
74
23.3
18.7
672
PRACTICAL TANNING
Comparison of thermometers (concluded)
Fahrenheit
Centigrade
R6aumur
Fahrenheit
Centigrade
Reaumur
72
22.2
17.8
6
—14.4
—11.6
70
21.1
16.9
4
—15.6
—12.4
68
20.
15.
2
—16.7
—13.3
66
18.9
15.1
—17.8
—14.2
64
17.8
14.2
—2
—18.9
—15.1
62
16.7
13.3
—4
—20.
—16.
60
15.6
12.4
—6
—21.1
—16.9
58
14.4
11.6
—8
—22.2
—17.8
56
13.3
10.7
—10
—23.3
—18.7
54
12.2
9.8
—12
—24.4
—19.6
52
11.1
8.9
—14
—25.6
—20.4
50
10.
8.
—16
—26.7
—21.3
.48
8.9
7.1
—18
—27.8
—22.2
46
7.8
6.2
—20
—28.9
—23.1
44
6.7
5.3
—22
—30.
—24.
42
5.6
4.4
—24
—31.1
—24.9
40
4.4
3.6
—26
—32.2
—25.8
38
3.3
2.7
—28
—33.3
—26.7
36
2.2
1.8
—30
—34.4
—27.6
34
1.1
0.9
—32
—35.6
—28.4
• 32
0.
0.
—34
—36.7
—29.3
30
—1.1
—0.9
—36
—37.8
—30.2
28
—2.1
—1.8
—38
—38.9
—31.1
26
—3.3
—2.7
—40
—40.
—32.
24
—4.4
—3.6
—42
—41.1
—32.9
22
—5.6
—4.4
—44
—41.2
—33.3
20
—6.7
—5.3
—46
—43.3
—34.7
18
—7.8
—6.2
—48
—44.4
—35.6
16
—8.9
—7.1
—50
—45.6
—36.4
14
—10.
—8.
—52
—46.7
—37.3
12
—11.1
—8.9
—54
—47.8
—38.2
10
—12.2
—9.8
—56
—48.9
—39.1
8
—13.3
—10.7
USEFUL DATA G73
Specific gravity, degrees Twaddell, barkometer, and Baume
Specific
Twaddell
Barko-
Baume'
Specific
Twaddell
Barko-
Baum£
Gravity
meter
Gravity
meter
1.000
1.205
41
205
24.5
1.005
1
5
0.7
1.210
42
210
25.0
1.010
2
10
1.4
1.215
43
215
25.5
1.015
3
15
2.1
1.220
44
220
26.0
1.020
4
20
2.7
1.225
45
225
26.4
1.025
5
25
3.4
1.230
46
230
26.9
1.030
6
30
4.1
1.235
47
235
27.4
1.035
7
35
4.7
1.240
48
240
27.9
1.040
8
40
5.4
1.245
49
245
28.4
1.045
9
45
6.0
1.250
50
250
28.8
1.050
10
50
6.7
1.255
51
255
29.3
1.055
11
55
7.4
1.260
52
260
29.7
1.060
12
60
8.0
1.265
53
265
30.2
1.065
13
65
8.7
1.270
54
270
30.6
1.070
14
70
9.4
1.275
55
275
31.1
1.075
15
75
10.0
1.280
56
280
31.5
1.080
16
80
10.6
1.285
57
285
32.0
1.085
17
85
11.2
1.290
58
290
32.4
1.090
18
90
11.9
1.295
59
295
32.8
1.095
19
95
12.4
1.300
60
300
33.3
1.100
20
100
13.0
1.305
61
305
33.7
1.105
21
105
13.6
1.310
62
310
34.2
1.110
22
110
14.2
1.315
63
315
34.6
1.115
23
115
14.9
1.320
64
320
35.0
1.120
24
120
15.4
1.325
65
325
35.4
1.125
25
125
16.0
1.330
66
330
35.8
1.130
26
130
16.5
1.335
67
335
36.2
1.135
27
135
17.1
1.340
68
340
36.6
1.140
28
140
17.7
1.345
69
345
37.0
1.145
29
145
18.3
1.350
70
350
37.4
1.150
30
150
18.8
1.355
71
355
37.8
1.155
31
155
19.3
1.360
72
360
38.2
1.160
32
160
19.8
1.365
73
365
38.6
1.165
33
165
20.3
1.370
74
370
39.0
1.170
34
170
20.9
1.375
75
375
39.4
1.175
35
175
21.4
1.380
76
380
39.8
1.180
36
180
22.0
1.385
77
385
40. 1
1.185
37
185
22.5
1.390
78
390
40.5
1.190
38
190
23.0
1.395
79
395
40.8
1.195
39
195
23.5
1.400
80
400
41.2
1.200
40
200
24.0
674 PRACTICAL TANNING
Weight and specific gravity of liquids
Water. — The weight of fresh water is, in practise, usually
assumed at 62^ pounds per cubic foot, but 62^ would be
more nearly correct at ordinary temperatures, about 60° F. A
pound of , water is equal to 27.759 cubic inches.
Specific
Gravity
Weight in
Pounds per
Cubic Inch
Weight in
Pounds per
Gallon
Water, distilled, 60° F
Water, sea
Acid, acetic
Acid, nitric
Acid, sulphuric
Acid, muriatic (hydrochloric)
Alcohol, pure
Alcohol, proof
Naphtha
Petroleum
1.000
1.030
1.062
1.217
1.841
1.200
0.792
0.916
0.848
0.878
0.036
0.037
0.038
0.044
0.067
0.043
0.029
0.033
0.031
0.032
8.33
8.55
8.78
10.16
15.48
9.93
6.70
7.62
7.00
7.39
WEIGHTS AND MEASURES
Troy weight
24 grains • • 1 pennyweight
20 pennyweights 1 ounce 12 ounces 1 pound
Used for weighing gold, silver and jewels.
Apothecaries' weight
20 grains 1 scruple 8 drams 1 ounce
3 scruples 1 dram 12 ounces 1 pound
Ounce and pound are the same as in Troy weight.
Avoirdupois weight
27 11/32 grains 1 dram 4 quarters. ... 1 hundredweight
16 drams 1 ounce 2,000 pounds 1 short ton
16 ounces 1 pound 2,240 pounds 1 long ton
25 pounds 1 quarter 2,204 pounds .... 1 metric ton
Dry measure
2 pints 1 quart 4 pecks 1 bushel
8 quarts 1 peck 36 bushels 1 chaldron
USEFUL DATA 675
Liquid measure
4 gills 1 pint 413^ gallons 1 barrel
2 pints 1 quart 2 barrels 1 hogshead
4 quarts 1 gallon 2 hogsheads 1 pipe
Long measure
12 inches . 1 foot 40 rods 1 furlong
3 feet 1 yard 8 furlongs 1 mile
53^2 yards 1 rod 3 miles 1 league
Cloth measure
234 inches 1 nail 4 quarters 1 yard
4 nails 1 quarter
Square measure
144 square inches. 1 square foot 40 square rods 1 rood
9 square feet 1 square yard 4 roods 1 acre
30J4 square yards. 1 square rod 640 acres 1 square mile
Surveyor's measure
7.92 inches 1 link
25 links 1 rod 4 rods 1 chain
10 square chains or 160 square rods 1 acre
640 acres 1 square mile
36 square miles (6 miles square) 1 township
Cubic measure
1,728 cubic inches. . 1 cubic foot 128 cubic feet. . . 1 cord (wood)
27 cubic feet 1 cubic yard 40 cubic feet . . 1 ton (shipping)
2,150.42 cubic inches 1 standard bushel
231 cubic inches 1 U. S. standard gallon
1 cubic foot about 4/5 of a bushel
METRIC EQUIVALENTS
Linear measure
1 centimeter 0.3937 inch 1 inch 2.54 centimeters
1 decimeter 3.937 inches 0.328 foot
1 foot 3.048 decimeters
1 yard 0.9144 meter
1 meter 39.37 inches 1.0936 yards
1 dekameter 1.9884 rods 1 rod 0.5029 dekameter
1 kilometer 0.62137 mile 1 mile 1.6093 kilometers
676 PRACTICAL TANNING
Square measure
square centimeter 0.1550 square inch
square inch 6.452 square centimeters
square decimeter 0.1076 square foot
square foot 9.2903 square decimeters
square meter 1.196 square yards
square yard 0.8361 square meter
hectare 2.47 acres 1 acre 0.4047 hectare
square kilometer .0.386 square mile
square mile 2.59 square kilometers
Weights
gram 0.03527 ounce 1 ounce 28.35 grams
kilogram 2.2046 pounds 1 pound 0.4536 kilogram
metric ton 1.1023 English tons
English ton 0.9072 metric ton
Volume
cubic centimeter 0.061 cubic inch
cubic inch 16.4 cubic centimeters
cubic meter 35.29 cubic feet
cubic foot 0.028 cubic meter
cubic meter 1.308 cubic yards
cubic yard 0.765 cubic meter
Capacity
liter 0.0353 cubic foot 1 cubic foot 28.32 liters
liter 0.2642 gallon, U. S. 1 gallon 3.785 liters
liter . . . .61.023 cubic inches 1 cubic inch 0.0164 liter
Multiples for conversion of quantities
To convert Multiply by
Grains to grams . 065
Ounces to grams 28 . 35
Pounds to grams 453 . 6
Pounds to kilograms . 45
Hundredweights to kilograms 50 . 8
Tons to kilograms 1016 .
Grams to grains 15.4
Grams to ounces . 35
Kilograms to ounces 35 . 3
Kilograms to pounds 2.2
Kilograms to hundredweights . 02
Kilograms to tons . 001
USEFUL DATA 677
Multiples for conversion of distances
To convert Multiply by
Inches to millimeters 25 . 4
Inches to centimeters 2 . 54
Feet to meters . 3048
Yards to meters .9144
Yards to kilometers . 0009
Miles to kilometers 1.6
Millimeters to inches . 04
Centimeters to inches 0.4
Meters to feet 3.3
Meters to yards 1.1
Kilometers to yards 1093 . 6
Kilometers to miles . 62
Multiples for conversion of capacities
To convert Multiply by
Cubic inches to cubic centimeters 16.39
Cubic feet to cubic centimeters 28320 . 00
Cubic yards to cubic meters . 7646
Fluid ounces to centiliters 2. 958
Gallons to liters 3 . 786
Bushels to hectoliters . 3524
Troy grains to milligrams 64 . 8
Troy pounds to kilos . 373
Avoirdupois pounds to kilos .4536
Square feet to centimeters 929.00
Square yards to meters 0.8361
Liters to quarts, dry measure 0.908
Liters to quarts, liquid measure 1 .0567
Square meters to square yards 1 . 196
Kiloliters to gallons 264 . 17
Liters to gallons 0. 22
APPROXIMATE METRIC EQUIVALENTS
1 decimeter 4 inches 1 meter 1.1 yards
1 liter 1.06 quarts liquid or 0.9 quart dry
1 kilometer 5/8 of a mile 1 hektoliter 2^ bushels
1 hectare 23^ acres 1 kilogram 2 1/5 pounds
1 stere or cubic meter J4 of a cord
1 metric ton 2,200 pounds
678 PRACTICAL TANNING
CAPACITY OF VATS IN GALLONS FOR EACH INCH
IN DEPTH
Circular in form
5 feet diameter 12 . 24
6 " " 17.76
7 " " 23.63
8 " " 31.50
9 " " 39.38
10 " " 48.56
11 " " 59.24
12 " * 70.50
13 " " 82.74
14 " " 95.96
15 " " 110.16
Cubic capacity of a circular vat is equal to the square of
the radius multiplied by 3.1416, multiplied by the depth.
5 feet square
Square in form
15.75
6 " "
22.31
7 " "
30.19
8 " "
40.03
9 " "
51.19
" "
62.34
Sundry Calculations
1 gallon contains 231 cubic inches.
1 gallon of water weighs approximately 8^ pounds.
8-J pounds multiplied by the specific gravity of a liquid
equals the weight of a gallon of the liquid.
Volume of a cube. — Multiply a side of a cube by itself
and that product again by a side. If contents in gallons is
desired, multiply the contents in cubic feet by 7.4805.
Volume of a parallelopipedon. — Multiply length by breadth
and that product again by depth.
Volume of a cylinder. — Multiply the square of the diameter
by 0.7854, and the product by the height.
USEFUL DATA 679
Volume of a cone. — Multiply the square of the diameter
of the base by 0.7854, the product by the Derpendicular
height, and divide by 3.
Volume of o frustum of a cone. — Add together the
square of the diameters of the greater and lesser sides and
the product of the two diameters; multiply the sum bv 0.7854,
and the product by the height; then divide the last product
by 3.
Example. — A tank is 5 feet across the base, 3 feet across
the top, and 9 feet high ; get the volume :
(5x5) + (3 x 3) + (5 x 3) = 49
49 x 0.7854 = 38.4846
38.4846 x 9 = 115.4538 cu. ft.
3
Volume of sphere. — Multiply the cube of the diameter by
0.5236. This rule applies to kettles which as a rule may be
considered one half of a sphere.
Diameter and speed of pulleys. —
D and d diameter of driving and driven pulleys
R and r number of revolutions
Then
D =— * d= 5^-- R=—- -- DR
R' r ' D' r d
Heat, steam, evaporation and electricity
Total heat of saturated steam (above $2° Fahrenheit}. —
H = 1150.3 + 0.3745 (t — 212°) —0.000550 — 212°)
where H is the total heat in B.t.u.'s above water at 32°
Fahrenheit, and t is the temperature Fahrenheit.
Latent heat of steam. — Obtained by subtracting from the
total heat at any given temperature the heat of the liquid, or
total heat above 32° Fahrenheit in water of the same
temperature..
Heat required to generate 1 pound of steam from water at
32° Fahrenheit is 1150.4 heat units.
The heat unit (B.t.u. ), is the heat required to raise a
680 PRACTICAL TANNING
pound of water from 62° to 63° Fahrenheit, or 1/180 of the
heat required to raise 1 pound of water from 32° to 212°
Fahrenheit.
French calorie = 3.968 B.t.u.'s.
1 B.t.u. = 0.252 calorie.
1 pound calorie — 9/5 B.t.u., = 0.4536 calorie.
1 B.t.u. = 778 foot-pounds of energy.
1 foot-pound = 1/778 = 0.0012852 B.t.u.
1 horsepower = 33000 foot-pounds per minute = 2545
B.t.u. per hour.
Absolute zero is — 460° Fahrenheit.
Evaporation in vacuum. — Approximate working figures :
3 gallons per square foot heating surface per hour.
1 pound of coal evaporates 8^ pounds of water — single
effect.
1 pound of coal evaporates 16 pounds of water — double
effect.
1 pound of coal evaporates 22 pounds of water — triple
effect.
1 pound of coal evaporates 28 pounds of water — quadruple
effect.
1 kilowatt hour =
1.341 horsepower hours.
2,655,200 foot-pounds.
3,415 heat units.
3.52 pounds of water evaporated from and at 212° Fah-
renheit.
22.77 pounds of water raised from 62° to 212° Fahren-
heit.
1 horsepower hour =
0.7457 kilowatt hour.
1,980,000 foot-pounds.
2,546.5 heat units.
2.62 pounds of water evaporated from and at 212° Fah-
renheit.
17.0 pounds of water raised from 62° Fahrenheit to 212°
Fahrenheit.
USEFUL DATA
(581
1 kilowatt =
1.3410 horsepower.
44,254 foot-pounds per minute.
56.92 heat units per minute.
3.52 pounds of water evaporated per hour from and at
212° Fahrenheit.
1 horsepower =
0.7457 kilowatt.
33,000 foot-pounds per minute.
42.44 heat units per minute.
2.62 pounds of water evaporated per hour from and at
212° Fahrenheit.
Boiling point of water at reduced pressure
Inches of
Temper-
ature
Temper-
ature
Inches of
Temper-
Temper-
Mercury
Degrees
Fahrenheit
Degrees
Centigrade
Mercury
Degrees
Fahrenheit
Degrees
Centigrade
212
100
15
179
81.7
1
210
98.9
16
176
80
2
208
97.8
17
173
78 3
3
207
97.2
18
169
76 1
4
205
96.1
19
165
73.9
5
203
95
20
161
71 7
6
201
93.9
21
157
69.4
7
199
92.8
22
152
66 7
8
197
91.7
23
147
63.9
9
194
90
24
140
60
10
192
88.9
25
133
56 1
11
190
87.8
26
125
51.7
12
187
86.1
27
114
45.5
13
185
85
28
100
37.8
14
182
83.4
29
77
25
682
PRACTICAL TANNING
Temperature of steam at various pressures
Pounds per
Square Inch
Temper-
ature
Degrees
Fahrenheit
Temper-
ature
Degrees
Centigrade
Pounds per
Square Inch
Temper-
ature
Degrees
Fahrenheit
Temper-
ature
Degrees
Centigrade
212
100
45
292
144.4
1
215
101.6
50
298
147.7
2
219
103.9
55
303
150.5
3
222
105.6
60
307
152.7
4
224
106.7
65
312
155.5
5
227
108.4
70
316
157.7
6
230
110
75
320
160
7
232
111.1
80
324
162.2
8
235
112.8
85
328
164.4
9
237
113.9
90
331
166.1
10
239
115
95
335
168.3
11
242
116.7
100
338
170
12
244
117.8
105
341
171.6
13
246
118.9
110
344
173.3
14
248
120
115
347
175
15
250
121.1
120
350
176.6
16
252
122.2
125
353
178.3
17
253
122.7
130
356
180
18
255
123.8
135
358
181.1
19
257
125
140
361
182.7
20
259
126.1
145
363
183.8
21
260
126.6
150
366
185.5
22
262
127.7
155
368
186.6
23
264
128.8
160
371
188.3
24
265
129.4
165
373
189.4
25
267
130.5
170
375
190.5
"26
268
131.1
175
377
191.6
27
270
132.2
180
379
192.7
28
271
132.7
185
382
194.4
29
272
133.3
190
384
195.5
30
274
134.4
195
386
196.7
35
281
138.3
200
388
197.8
40
286
141.1
GLOSSARY OF TERMS USED IN TANNING AND RELATED
INDUSTRIES
Acid dye. A coal-tar color which is applied to leather without
a mordant.
Airing-off. Slightly drying the stock after application of
finish.
Annatto. A red dye of vegetable origin.
_ Antiseptics. Preservatives which temporarily check fermenta-
tion, such as dilute solution of formaldehyde, salt, etc.
Arm-staking. A mechanical process employed to soften skins.
Bacterial action. Effect produced through the agency of cer-
tain bacteria. .
Barkometer. A special hydrometer used in tanneries only,
one degree of which is equivalent to 1.001 specific gravity. Then
30° bk.= 1.030 specific gravity.
Basic dye. A coal-tar color which requires the presence of
tannic acid to fix it on the leather.
Bate runs. Skins damaged by too violent action with bacterial
bates.
Bating. Treatment of skins with hen or pigeon manure or
other bacterial agents, to neutralize lime and render them flaccid.
Bating also opens the pores of the skin, and so assists subsequent
treatment.
Baume. An arbitrary scale for determining the density of a
liquid.
Beam. A rounded support for holding hides or skins during
unhairing or fleshing by hand.
Beam-house. That part of the tannery where the hides are
treated previous to tanning.
Bettered. Strengthened.
Bleaching. The removal of part of the surface tan to pro-
duce a light-colored stock.
Boarding. Producing a false grain on leather.
Bottoming. Filling a leather and giving a suitable foundation
for a dye.
Buffing. Removal of the grain or flesh of leather by mechani-
cal means to eliminate defects or obtain a level surface.
Butt. The best part of the skin, or hide directly over the
rump.
Cabretta. A cross between a goat and a sheep.
Casein. A product obtained from the souring of milk.
683
684 GLOSSARY OF TERMS
Castor leather. A kind of glove leather.
Centigrade. Boiling point of water, 100 degrees; freezing
point, degrees.
Chamois. Leather produced by incorporation of an oxidizable
oil, such as cod-liver oil.
Cod oil. Newfoundland cod-liver oil.
Colon. The large gut of an animal.
Copperas. Iron sulphate; ferrous sulphate.
Currying. Introducing grease into leather and giving it any
desired finish.
Deacons. Small calfskins.
De-greasing. Removal of grease either by solvents, by saponi-
fication, or by pressing.
De-hairing. The chemical removal of hair from hides; also
a general term in removing hair.
De-liming. Soaking skins in a weak acid or other solution
to remove lime.
Dermiforma. An artificial bate.
De-tanning. Extracting vegetable tanning materials by means
of borax or soda to prepare skins for re-tanning with another
agent, such as chrome.
Depilation. The process following the soaking of hides, such
as immersing them in an infusion of lime, which loosens the
hair without injuring the skin.
Depleting action. Any action which tends to loosen the hair
and epidermis.
Dermis. The true skin or that part from which leather is
produced.
Direct dye. A coal-tar color which may be applied to leather
without a mordant.
Disinfectant. A purifier ; a compound which kills both bacteria
and their spores.
Drench. A mixture of bran and water which has been al-
lowed N to ferment, and so contains acetic and lactic acids. It
neutralizes and removes lime, and has a plumping effect.
Drum. An apparatus in which hides or skins are tumbled to
aid in tanning, coloring, fat-liquoring, and stuffing.
Dubbin. A mixture of oil and tallow for stuffing leather.
Effect. Part of a vacuum apparatus used in evaporating tan-
ning extracts or other solutions.
Embossing. Producing an artificial grain on leather.
Enzyme action. The result of unorganized ferment.
Epidermis. The external layer of the skin.
Fahrenheit. Boiling point of water, 212 degrees; freezing
point, 32 degrees.
Fat-liquor. An emulsion of soap and oil; a mild alkali such
as borax and oil, or a sulphonated oil, in which skins are worked
after tanning and washing.
GLOSSARY OF TERMS 685
Filling leather. Introduction of substance to give weight
and body.
Fleshing. Removal with a knife of portions of flesh, etc.,
which adhere to the hide. Fleshings contain considerable fat and
gelatine, which are recovered.
Fluffing. Producing a soft effect on grain or flesh side of
leathers.
French chalk. Talc, or magnesium silicate.
Frizzing. Removing the outer grain of skins on a beam after
long lime treatment — 30 or 40 days.
Furs. Skins tanned without removal of the hair.
Fustic. A yellow vegetable dyestuff.
Glassing. Producing a bright finish on the grain by means of
a glass slicker or roll.
Grain. That portion of the hide just under the epidermis. ^
Hair-slip. An effect produced when the grain of a pelt is
partly decomposed.
Handler. A pit containing vegetable tanning solutions in
which hides are suspended.
Hauling. Taking hides out of lime solution.
Hematin. An oxidized logwood.
Hides (green). Raw hides from the butcher.
Hides (split). A hide that is split into two layers. The
grain layer is used for one purpose, while the flesh split may
have another application.
Horsing-up. Placing the hides or skins over a horse to
drain.
Irish moss. Kelp or seaweed extract.
Iron in tanning operations. No iron should come in contact
with hides or solutions during vegetable tanning, as iron sulphate
is formed, which stains the finished goods. Wood or brass may
be used.
Jacking. Stretching the stock on boards or frames and hold-
ing it in position by means of tacks.
Kid. A small goat.
Kip. A pelt having a weight between calf and a light hide.
Kiss spot. Light-covered spots which appear on vegetable-
tanned leather when two hides have touched during the early
stages of tanning.
Knee-stake. A mechanical device used especially for soften-
ing alum-tanned glove leather.
Lamb. A young sheep.
Layaways. Pits in which heavy hides receive their first
tannage.
Logwood. A vegetable dyestuff used for producing a black
color.
Mocha leather. A kind of glove leather.
Mordant. A material used to fix a dyestuff.
686 GLOSSARY OF TERMS
Muriatic acid. Hydrochloric acid.
Oropon. A patented bate.
Osage orange. A yellow vegetable dyestuff.
Paddle. An apparatus used in bating, tanning and coloring
skins.
Patent leather. A leather with a bright varnish finish.
Pelts. Skins in the hair as received by the tanner.
Perch. A mechanical device used for softening skins.
Perching. Softening and stretching leather with a moon-
knife or on a staking machine.
Pickling. Treating de-limed, bated, or drenched stock with
salt and sulphuric acid.
Plumping. Softening and swelling of hide fibers which con-
tain little water. Plumping follows the removal of salt on treat-
ment with dilute acids and alkalies.
Plunging. Stirring up the liquors.
Puerine. An artificial bate.
Puering. Bating, but using dog manure in place of hen
manure; a term also employed when other bacterial agents are
used.
Re-staking. Further softening of leather; usually done on
the dry stock.
Re-tan. To tan again.
Saddening agent. The addition of a substance during dyeing
to produce a duller shade.
Sal-ammoniac. Ammonium chloride.
Sal soda. Sodium carbonate containing 12 molecules of water
of crystallization.
Salts of tartar. Potassium carbonate.
Salted skins. Those cured with salt.
Sammie. Half dry.
Setting-out. Removing excess of liquid and eliminating
wrinkles.
Shearlings. Sheepskins which have been sheared just prior
to killing of t,he animal.
Side leather. Leather made from hides that have been split
into sides.
Sig. A seasoning made of adhesive compounds (see section
on harness leather).
Skiver. The grain side of a split sheepskin.
Skiving. Removing superfluous flesh from the flesh side of
the leather, or separating the grain.
Slicking. Setting-out the wet leather by means of a slicker.
Slunk. The skin from an unborn calf.
Snuffing. A light buffing on the grain side.
Soaking. Washing hides with water to remove dirt, blood,
and salt, previous to liming.
GLOSSARY OF TERMS 687
Sod oil. _A product obtained by neutralizing the washing
from chamois leathers.
Spew or spue. A white exudation which sometimes appears
on the grain of finished leather.
Splits. The hide from which the grain has been removed.
Stoning. ^ Smoothing down leather with a stone.
Stoning-jack. A machine which is provided with a stone,
and is used for smoothing out leathers.
Striker. A substance applied to leather to get the color.
Struck through. When the tanning agent has penetrated
through the hide it is struck through.
Sumac. The leaf of a tree largely grown in Sicily, and con-
taining up to 30% tannin. Prices are quoted f. o. b. Palermo,
per hundredweight, Yocum's test.
Surficial. Pertaining to the surface of the hide or leather.
Sweating. A natural process of putrefaction brought about
by storing hides in a warm and damp atmosphere, so that bac-
teria grow and loosen the hair.
Talc. Magnesium silicate or French chalk.
Tan. Any material which will prevent putrefaction of hide
substance.
Tannage. A process of converting hide substance into leather.
Tannate. Such as titanium tannate, a yellowish shade, on
which bottom all shades of tan, brown, green, blue, and maroon
can be obtained.
Tannic acid. The active principle in manv vegetable materials,
which has the power of converting hide substance into leather.'
Tanning:. Treating prepared skins with an infusion containing
Tannic acid.
Tartar emetic. Antimony-potassium tartrate.
Tawing. Treating skins with compounds of aluminum.
Toggle. Fastening hides together by means of special hooks.
Trimmings. The useless parts of hides, used for glue manu-
facture.
Twaddell. An arbitrary scale for determining the density of
a liquid. J
Unhairing. De-hairing: the mechanical removal of loosened
hair after the action of the depilatory.
Wallaby. A small animal of the kangaroo family.
Weighting leather. Adding some material to produce weig-ht
and fullness, sometimes termed adulterating.
Welting. A strong thin leather cut into strips.
Welting-stock That portion of a hide not suitable for sole
leather and used for making welts.
INDEX
(For references not given under this head see Glossary of Terms
on pages 683 to 687 inclusive.)
Acetyl number, 653
Acid colors, 354, 367
hemlock, 270
Acidity of liquors, determination
of, 619
Activated sludge, 667
Adipose tissue, 51
Adjective dyes, 352
Adler, Geo. W., cited, 171
Aged oil, 342
Agras, 28
Algarrobilla, 555
Algin, 497
Algoabays, 27
Alizarine colors, 355
Alligator skin, grain of, 36
Alum and chrome tanning, 169
tannage, 138, 229
snake skins, 152
tanned lace, 136
leather, coloring, 361
Alumina-pickled grain, 177
Aluminum bisulphite reduction,
194
sulphate, analysis of, 601
and salt pickle, splitting out
of, 132
Amend, O. P., cited, 114
American Leather Chemists' As-
sociation, official method of
analyzing vegetable tannins,
612
Ammonia, simple test for, 662
Ammonium butyrate in de-liming,
115
chloride, simple test for, 660
in de-liming, 114
phosphate in de-liming, 116
Amritsars, 28
Analysis of vegetable tannin ma-
terials, 612
Analytical methods, 585
A-naphthol, 563
Anglo-American hides, 18
Antique leather, 380
Apothecaries' weight, 674
Arabian goatskins, 27
Arazym, 86
on goatskins, 106
Arm-board, 255
Arsenical limes, 92
Arsenic sulphide, 85, 91
analysis of, 593
Artificial dyestuffs, 354
coloring with, 376
leather, 578'
Autoclave system, 532
Automobile leather, 318, 336
Avoirdupois weight, 674
Backer, 10
Bag leather, 318, 322
coloring, 408
Banana liquid, 499
Bark mill, 527
mimosa, 555 _
wattle (acacia), 556
Barks, 542
Basic colors, 354
dyestuffs, 354
coloring with, 364
Bate, C. T., 116
beam-stone, 117
Bating, 119
with dog dung, 121
glucose, sulphur and yeast,
121
hen manure, 123
molasses, 120
Oropon, 125
Bavarian hides, 19
Bayonet scabbards, 134
Beam, 86
knife, 80
Beam-house, 100
in goatskin tannery, 100
work, 90
Belting, driving efficiency of
grain and flesh sides, 317
leather, 292, 293
characteristics of, 292
chrome, 183
coloring, 408
drum tannage, 289
manufacturing process for,
295
practical considerations, 298
raw materials for, 293
tanning, 301
tanning agent, 296
Belt-knife splitting machine, 131
Belt-pins, 134
689
€90
INDEX
Bend, 272
Black gambier, 554
glazed finish, 455
Blacking, 412
machine, 386
varnish, 484
Blacks on chrome leather, 359
Bleaching, 141, 238, 279, 305
machine, 281
Bleach pits, 280
Blood, 492
albumen, 492
analysis of, 656
B-naphthol, 563
Boarding, 453
machine, 325
Boiling oil, 343
point of water, 681
Bokharas, 26
Bones, disinfection of, 38
Borax in soaks, 64
neutralizing with, 172
simple test for, 662
Boric acid in de-liming, 111
Bot-fly, 14
Bower glazing machine, 460
Box finish, 471 _
Bran in drenching, 117
Brand marks, 2
Branding, 17
Brazil wood, 353
Broad flesher, 81
Bronze dyeing, 381
Brown shades, 398
Brush dyeing, 356
killing, 520
Brushing machine, 288
Buckskins, chrome, 196
tanning, 154
Indian method, 155
white, 155
Buenos Aires, 18
Buffing,_ 450
machine, 146
room, 459
wheel, 148
Bull hides, 17
Button lac, 499
Butyric acid, 61
in de-liming, 114
Calcium chloride, 96
polysulphide, 91"
sulphydrate, 86
Calf, Russia, 238
Calfskin, cross-section of, 49
fancy leather, 258
glove leather, 201
leather, 233
'white, 145
mitten leather, 201
quebracho-tanned, 233
Calfskins, 19
soaking, 62
Capacity of vats, 678
Capes, 27
Capetowns, 27
Carbonic acid in de-liming, 112
Casablancas, 27
Case leather, 322
Casein, 495
Castor leather, imitation of, 144
liming, 105
oil soap, 441
Caustic soda, 85
in depilation, 85
in soaks, 61
production of, 85
simple test for, 660
Chamois, bleaching, 141
coloring, 388
leather, 140
Checking machine, 99
Chemical Foundation, 558
soaks, 61
tests, 659
Chestnut bark, 545
tannage, 229, 283
tree, 538
wood, 538
China goatskins, black on, 516
Chinese blue, 343
goatskins, 28
Chipper, disc, 529
hog, 528
Chocolate shades, 402
Chrome alum, dissolving, 193
bag, coloring, 408
belt, coloring, 408
calfskins, seasoning for, 470
goatskins, finish for, 472
harness, blacking, 416
finishing, 417
leather, 181
kangaroo black, 405
lace leather, 201
stuffing, 445
leather, black, 403
difference in, 175
oiling, 442
sulphonated oil on, 440
liquor, analysis of, 603
one-bath, analysis of, 608
mitten leather, 178
patent leather, 187
process for acid pickled stock
177
one-bath, 159
two-bath, 158
residues, recovery of, 195.
INDEX
691
sheepskins, blacking, 372
flesh-finished, 371
side glove leather, 178
leathers, black, 409
dyeing, 409
fat-liquor for, 428
finish for, 474
sole leather, 178
strap leather, 183
tannage, 158
suggestions on, 173
new two-bath process, 171
tanned belt leather, 183
buckskin, 196
calfskins, black, 389
coloring, 390, 391
dyes for, 359
fat-liquor for, 424
goatskins, black, 402
dyeing, 395
kangaroo, fat-liquor for, 427
leather, analysis of, 635
dyeing, 358
sheepskins, coloring, 362
• fat-liquor for, 422
finishing, 454
side leather, 176
wax calf, 207
tanning, theory of, 198
velvet leather, 187
Clarification of extracts, 533
Classification of dyestuffs, 352
Clearing of grain, 398, 473
Cloth measure, 675
Cloud test, 652
Coal-tar bates, 116
Coating leathers, 581
Coats, tanning of, 522
Cod-liver oil, simple test for, 660
Cold sweat, 71
Cold test, 651
Collodion, 499
varnish, 380
Color formulas, 360
on stuffed leather, 330
Colorado steers, 17
Colored sheepskins, seasoning
for, 458
Coloring after fat-liquoring, 370
goatskins, 357
Combination process for depila-
tion, 101
tannage, 227, 247, 260
Concentration of extracts, 535
Condensation products, 558
Cone mill, 526
volume of, 679
Connective tissue, 50
Conservation of skin substance,
52
Conversion multiples, 676
Cooper-Hewitt lamp, 347
Corium, 48, 51
Country hides, 17
Cowhide, 17
cross-section of, 50
grain of, 16
Cows, spready, 17
Cropping, 275
Cross-section of calfskin, 49, 51
Crystal sulphide, 85
Cuba wood, 353
Cube, volume of, 678
Cubic measure, 675
Curing, 10, 22
Currier's knife, 308
Currying, 306
Cutch, 353
Cuticle, 48
Cutis, 48
Cut-throats, 3
Cyco powder, 11
Cylinder, volume of, 678
Daccas, 28
Dampening, 449
Dark tan shades, 401
Daub coat, 343
Deacons, 19
De-greasing by vacuum od pro-
cess, 68
fluid, gargoyle, 130
pigskins, 68
in the Krouse process, 68
De-hairing, use of term, 86
De-liming, 110
ammonium butyrate, 115
ammonium chloride, 114
ammonium phosphate, 116
boric acid, 111
butyric acid, 114
carbonic acid, 112
hydrochloric acid, 111
lactic acid, 112
sodium bisulphite, 111, 116
sodium dichromate, 115
sulphuric acid, 111
sulphurous acid, 111
test, 111, 599
zinc sulphate, 116
Dennis Co., Martin, 116
puerine, 126
Density tables, 673
Depilating glove leather, 103
Depilation, 71
methods of, 87
Depilatories, patented, 104
Depilatory compound for wool
skins, 101
paints, 104
Derma, 48
Dermiforma, 123
692
INDEX
Dihydroxybenzene, 560
Direct black, 403 ■■
colors, 355
dyeing with, 367
leather blacks, 391
Disc chipper, 529
Disinfection of bones, 38
hides, 36
railroad cars, 42
Divi-divi, 555
Dog dung, 121
Dongola tannage, 236
Dope splits, 578
Drench, mild fermented, 118
Drenching, 116
with bran, 117
Dressings, 482
waterproof, 485
Dried blood, simple test for, 659
hides, 1
skins, soaking of, 65
Driers, 345
Driving surface, 292
Drum, 56
dyeing, 356
heads, 134
tannage, 289
Drumming with sumac, 239
Dry hides, 2, 58
measure, 674
salted hides, 1
skins, soaking, 66
sheepskins, 65
skins, soaking, 62, 63
Drying, 306, 448
loft, 286
Dry-room, 450
Dry-salted hides, 58
Dull finish, 458
Dyeing, 352
leather, 352
notes on, 400
vegetable-tanned leather, 356
Dyes, simple test for, 659
Dyestuffs, acid, 354
alizarine, 355
basic, 354
classification of, 352
direct, 355
dissolving, 355
Egg albumen, 493
Egg-yolk, 435
analysis of, 657
simple test for, 661
Ehrenreich, Alfred, cited, 574
Electric tanning, 567
Electrical units, 680
Embossed sheepskins, finish for,
460
Embossing, 453
machine, 338
press, 337, 339
Epithelium, 48
Eureka bark mill, 527
Evaporation, 679
Evaporator and dryer, combined,
619
Extract, analysis of, 614
wheels, 278
Extracting, 278
Extracts, clarification of, 533, 535
Fancy colors, 379
leather, 258
Fat-liquor, applying, 428
formulas, 431
Fat-liquoring, 419
process, 421
Fats, 419
Fatty resist, 380
Fell-beater, 9
cutter, 9
Ferrous sulphate, simple test for,
660
Fig soap, 436
Fine hair, inspection for, 95
Finishing processes, 447
materials, 491
sole leather, 287
Fitz-Henry machine, 308
Flash point, 652
Flat bed glazing machine, 461
Flaying, 4
Flesher, 81
monitor, 81
Fleshers, sheepskin, 143
Fleshing, 60
knife, spring style, 81
machine, 60
automatic roller, 82
Flexible splits, 250
Flint hides, 2
Floorsman, 9
Flour paste, 488
simple test for, 661
Flume, 539
terminus, 540
Fly-blow, 34
Foerderer, Robert, cited, 433 .
Formaldehyde, 53
analysis of, 603
antiseptic action of, 53
raw stock, 70
tannage, 147
tanning with, 156
Formic acid, 59
analysis of, 657
and salt pickle, 128
in soaks, 59
INDEX
693
Fox, red-haired, 521
Fresh hides, 56
skins, soaking of, t>3
Frigorificos, 18
Frustum of a cone, volume of,
679
Full grain finish, 416
Fulling stocks, 59
Furrol dye, on furs, 519
Furs, 501
acid color on, 517
alum process on, 523
alum tannage, 506
black on, 519
chlorinating of, 517
chromate colors on, 518
chrome-tanned, 513
deodorizing, 512
dyeing, 517
dyeing black, 521
formaldehyde tannage, 504
furrol dyes on, 519
mordanting, 520
oil process, 511
soaking, 69
softening, 524
tanning, 501
vegetable tannage, 505
Fustic, 353
bottom, 368
mordant, 365
Gall nuts, 552
Gambier, 554
liquor, 139
mordant, 365, 397
tannage, 234, 240 .
Gargoyle de-greasing fluid, 129
Gelatine, 493, 494
German goatskins, 25
Glazed kid, 161
Glazing, 452
machine, 460
Glossary of terms, 683-687
Glove leather, chrome, 178
calfskin, 201
depilating, 103
kid, 147
process for, 166
Glucose, determination of, 625
simple test for, 660
sulphur and yeast, bating with,
121
tables, 626
Glue, 493, 494
stock, disinfection of, 38
Goatskins, 21, 65 ,
arazym on, 106
black, 402
buffing, 459
coloring, 357
finish for, 472
glazing, 462
grain on, 22
liming, 99
perching, 458
soaking, 65
sorting, 464
staking, 457
tannery, beam-house in, 100
tan-room, 162
warehouse, 24
Goodyear welting, 321
welts, 250
Grain, clearing, 398
Grasser, George, cited, 560
Grease, recovery of, 130
analysis of, 642
Greasy skins, washing of, 511
Green hides, 1
Green-salted hides, 1, 57
sheepskins, 65
skins, soaking, 62
Grub allowance, 15
Grubs, 14
Gum arabic, simple test for, 659
Gunmetal finish, 471
Hair, disinfection of, 40
removed by sodium sulphide, 83
Hairsheaths, 50
Hairskins, alum tannage, 515
soaking, 69
tanning, 509 .
Hand fleshing, 94
seasoning, 416
stuffing, 309
Handlers, 302
Harness blacking, 485
leather, 318, 329
chrome, 181
Heat, 679
units of, 680
Heaver, 12
Heavy rolling jack, 316
Hematin, 353
Hemlock bark, 546
leather, acid, 270
non-acid, 269
tannage, 226
Hen manure, 123
Herrars, 28
Hide structure, 48
substance, 596
conservation of, 52
Hides, 1
Anglo-American, 18
Bavarian, 19
bull, 17
country, 17
694
INDEX
cow, 17
disinfection of, 36
dried, 1
dry, 58
dry-salted, 1, 2, 58
fresh, 56
green, 1
green-salted, 1, 57
increase in weight from liming,
76
inspection of, 12
liming, 87
loss in weight during liming, 78
market, 56
packer, 3
raw, 134
selection, 16
South American, 18
spready, 16
straight, 18
Swiss, 19
taking-up, 12
washing, 57
Hog chipper, 528
Hogskins, 29
Horsehides, 19
fronts, 20
Hot stuffing, 314
Hou, T. P., cited, 214
Human skin, grain of, 36
Hyaline, 50
Hydrochloric acid and calcium
chloride pickle, 128
in de-liming, 111
Hydrated lime, 73
Hydroquinone, 560
Hydrosulphite, 335
Imitation castor, 144
India goatskins, 28
tanned skins, 28
coloring, 383
finish for, 465
re-tanning, 383
Indicators, 664
Indigo, 353
Inspection for fine hairs, 95
of hides, 12
Intestinal leather, 208
Iodine number, 653
Irish moss, 497
Iron liquor, analysis of, 658
tannage, 214
patents on, 216, 222
research in, 215
Ironing, 452
Isinglass, 495
Italian goatskins, 25
Jackson, D. D., cited, 214
Japan wood, 353
Kaffirs, 27
Kangaroo black, 405
leather, finish for, 474
skin, 67
grain of, 35
soaking, 67
vegetable-tanned, 240
Kaolin, acid-washed, 620
Keratin, 49
Kid glove leather, 147
skin, grain of, 35
Kids, sheep, 32
Killing, brush, 520
with caustic, 519
lime, 519
soda, 519
Kinney, C. B., cited, 414
Kips, 1, 18, 19
soaking, 62
sulphide process for, 95
Kjeldahl method, 596
Knee-staker, 150
Knocker, 3
Kosher, 3
Krouse process, 68
Kushtias, 28
Lace leather, 134
alum-tanned, 136
chrome, 201
oil-tanned, 135
Lacterine, 495
Lactic acid, analysis of, 644
in de-liming, 112
simple test for, 663
Lamb, M. C, cited, 102, 113
Lambskin, dyeing of, 521
grain of, 35
Lampblack, 343
Lateral stiffness, 292
Latigo leather, 135
Layaways, 303
Layer-pit, 274
Leaching, 531
Leather, color on stuffed, 330
dyeing, 352
for organ pipes, 212, 569
for player-pianos, 570
intestinal, 208
lace, 134
latigo, 135
oil-tanned, 140
picker, 138
white calfskin, 145
Legger, 4
INDEX
695
Leidgen unhairing machine, 93
unhairing on, 93
Levant grain, 467
seal, 251
Lice, 34
Ligl-rt shades, 399
dyeing, 366
Light tan shades, 401
Lime, 72
analysis of, 590
and arsenic, 97
sulphide, 88
liquors, analysis of, 594
plunger, 79
putrid, 74
simple test for, 659
splitting out of, 131
Liming, 72
after removal of wool, 105
calfskins, 96
for castor leather, 105
for mocha leather, 105
for sole leather, 94
goatskins, 99
hides, 87
thin grain, 92
Linseed meal, simple test for, 659
oil, 341
Liquefying bacteria, 52
Liquid measure, 675
Liquor, analysis of, 618
Lissom, 498
Litharge, 343
Loading wheel, 282
Logwood, 353
bottom, 368
Long measure, 675
Lubricating oils, analysis of, 648
Machine finishing, 416
Madras, 28
Mangrove bark, 552
Marbled effects, 379
suede, 413
Market hides, 56
Marrakesh, 27
Measuring, 453
machine, 463
Mechanical hoist, 273
transfer, 272
Metaderos, 18
Metallic luster, 381
'Methods of depilation, 87
Metric equivalents, 675
Mild fermented drench, 118
Milk albumen, 495
Mill coloring, 414
Mimosa bark, 555
Mineral acids, simple test for, 662
dyestuffs, 354
Mitten leather, calfskin, 201
chrome, 178
Mocha leather, liming of, 105
Mochas, 27
Moellons, analysis of, 641
Mogadors, 27
Molasses, bating with, 120
Moniter flesher, 81
Montevideos, 18
Moon-knife, 232
Mordant, fustic, 365
gambier, 365, 397
osage orange, 365
sumac, 365, 397
Mordanting furs, 520
Morocco finish, 466
Munson and Walker's table, 627-
633
Myrabolans, 555
Naphtha, 342
Napthalene condensations, 562
Native steers, 16
Natural dyestuffs, 352
coloring with, 401
Neradol, 558
Neutralizing chrome skins, 167
with borax, 172
Nihoul, E., cited, 563
Nitrocellulose, 499
Non-acid hemlock, 269
North African goatskins, 26
Oak bark, 545
leather, 265
wood, 541
Official method of tannin analysis,
613
Oil, boiling of, 343
grain, 477
process for furs, 511
tanned leather, 140
Oiling, 306
leather, 426
Oils, 419
analysis of, 648
One-bath chrome, 177
liquor, analysis of, 608
on pickled sheepskins, 166
process, 159, 197
Ooze calf, notes on, 394
coloring, 405
leather, 387
Organ leather, 212, 569
Oropon, 107, 124
Osage orange, 353
mordant, 365
Oudhs, 28
Ox-blood shades, 369, 377, 402
696
INDEX
Packer hides, 3
Paddle dyeing, 357
soaking, 61
vat, tanning in, 169
Paints, depilatory, 104
Palmetto, 556
Parallopipedon, volume of, 678
Parchment, 134
like leather, 211
Patent leather, 341
chrome, 187
drying of, 347
shoe tipping, 260
tipping, 482
Patented depilatories, 104
Patents for iron tannage, 216-222
Patna skins, 28
Peach wood, 353
Pelts, 1
classification of, 1
Perching, 458
Pernambucos, 29
Petropaul goat, 26
Phenol, simple test for, 663
Phosphine dyestuffs, 367
Picker leather, 138
Pickle, analysis of, 602
Pickled sheepskins, one-bath
chrome on, 166
two-bath chrome on, 163
Pickling, 127
Picric acid, 561
Pigment finish, 414
Pigskins, 67
de-greasing, 68
.dyeing, 412
soaking, -67
tanning, 255
washing, 68
white, 151
Pin mill, 56
Pipes, weight of, 670
Player-piano leather, 570
Plumping effect of lime, 91
sulphide, 91
Plunged up, 79
Plunger, 79
Pneumatic fleshing machine, 60
pouches, 570
Popular shades, dyeing, 368
Porpoise leather, 574, 577
Potash soap, 436, 441
Powder, cyco, 11
Press, embossing, 339
Pressing grease from pickled
skins, 128
Priest, G. W., cited, 341
Proctor dryer, 447, 448, 449
Prussian blue, 343
Puerine, 126
Puerine D, 127
Puering, 119
Pulleys, speed of, 679
Punjabs, 28
Putrid lime, 74
soaks, 60
Putting-out machine, 132
Pyro tan, 140
Pyrocatechol, 560
Pyrogallol, 560
Pyroxylin, 499, 578
solvents for, 578
Quebracho, 547
tanned sheepskins, 230
Quicklime, 72
Quinone, 563
preparation of, 564
Quirin press, 277
Rabbinical law, 3
Raccoon, 521
Rapid sole leather tannage, 281
tanning for sole leather, 263
process, 263
Raw hide, 134
Recovered grease, 130
Red-haired fox, 521
Reel, 87
Report form, official,. 646
Resorcin, 560
Re-tanning, 207
with gambier, 247
with quebracho, 239
River Plate hides, 18
Robes, tanning of, 522
Rogers' shark-liver oil process,
142
Rohm's bate, 124
Roller leather, 231
Rolling, 452
jack, 285, 316
Rosenthal, Geo. D., cited, 51
Rough leathers, finish, 480
Rumper, 9
Russia calf, 238
chrome leather, notes on, 394
goatskins, 26
Saddle-tops, 134
Saladeros, 18
Salt, analysis of, 600
pickle and aluminum, sulphate,
splitting out of, 132
simple test for, 660
stains, 3
Salting hides, 54
Sampling tanning materials, 620
Schlegel, Henry, cited, 115
INDEX
697
Schultz, Augustus, cited, 158
Schultz process, 158
Scouring, 307
Seal, imitation of, 522
Levant grain, 251
rabbit, 522
walrus grain, 252
Sealskins, dyeing, 411
grain of, 36
tanning, 250
Seasoning, 451, 458
machine, 386
Semi-chrome leather, 203
Serial table machine, 313
Set, 79
Setting-out, 284, 447
Seymour-Jones, cited, 568
Shark-liver oil process, Rogers,
142
tannage, 135
skin leather, 574
treatment of, 576
Sharks, catching, 575
Shaving machine, 164
Sheep kids, 32
Sheepskins, 30
de-greasing, 463
fleshers, 143
grain of, 34
one-bath chrome on, 166
quebracho-tanned, 230
soaking, 63
two-bath chrome on, 163
vegetable-tanned, 225
white chrome-tanned, 168
Sheep ticks, 33
Shellac, 498
simple test for, 662
Sheridan press, 337
Side leather, chrome-tanned, 176
dyeing, 409
vegetable-tanned, 242
white, 185
Sides, 9
sulphide process for, 95
Sigs for greasy leather, 486
Simple chemical tests, 659
Skins, 1
India-tanned, 28
Patna, 28
Skinning, 4
Skivers, 230
finishing, 468
for player-pianos, 570
Skiving, 308
Skunk, imitation of, 521
Slaked lime, 90
Slicker, 232
Small, F. H., cited, 292
Smooth plate press, 339
Snakeskins, 152
alum tannage, 152
tanning, 257
Snuffing machine, 146
Soaking, 56
calfskins, 62
dried skins, 65
dry-salted skins, 66
dry skins, 62, 63
fresh skins, 63
furs, 69
goatskins, 65
green-salted skins, 62
hairskins, 69
kangaroo skin, 67
kips, 62
paddle, 61
pigskins, 67
sheepskins, 63
Soaks, analysis of, 589
borax in, 64
butyric acid in, 61
caustic soda in, 61
chemical, 61
putrid, 60
sodium bisulphite in, 64
Soap, analysis of, 647
black, 488
castor-oil, 441
fig, 436
potash, 436, 441
simple tests for, 663
Soda, simple test for, 663
Sodium bisulphate and acid col-
ors, 367
bisulphite in de-liming, 111, 116
in soaks, 64, 67
dichromate in de-liming, 115
hydroxide in soaks, 61
sulphide, 82
analysis of, 591
and calcium chloride, 96
as a depilatory agent, 82
preparation of, 85
process, 89
thiosulphate, simple test for,
661
Softening furs, 524
Sole leather, 263
chrome, 178
drum tannage, 289
jack, 268
liming of, 94
sulphonated oil on, 441
Soluble cotton, 499
Sorting, 453
South African goatskins, 27
South American hides, 18
Southern Europe goatskins, 25
698
INDEX
Spanish goatskins, 23
leather, 340
Specific gravity of liquids, 674
tables, 673
Speed of pulleys, 679
Sphere, volume of, 679
Spirit black, 343
Splits for white shoes, 153
heavy, 328
vegetable-tanned, 325
white, 152
Splitting, 132
after tanning, 133
out of. aluminum sulphate and
salt pickle 132,
lime, 131
pickle, 132, 133
Splitter, Union, 246
Splits, finishing for, 486
grain leather from, 491
Sporting goods leathers, 478
Spray dyeing, 379
Spready cows, 17
hides, 16
Spring style fleshing knife, 81
Sprinkler leach, 532
Square measure, 675
Stag horn, 553
Stains, removal of, 483
Staker, knee, 150
Staking, 450, 457
machine, 456
Staling, 72
Steam, 679
temperature of, 682
Steers, Colorado, 17
uative, 16
Texas, 17
Stiasny, cited, 558
Sticker, 3
Stick-lac, 498
Stocks, 59
fulling, 59
Stoning-jack, 249
Straight hides, 18
Strap leather, 318
chrome, 183
Stretching, 315
Stripping, 451
the tannage, 204
Structure of hides, 48
Stuck-throats, 3
Stuffing chrome lace leather, 445
Sturtevant dryer, 451, 452
Substantive dyes, 352
Sudan goatskins, 27
Suede leather, 237
coloring, 392
marbled, 413
Sulphide-lime liquors, analysis of,
597
process for sides, 95
Sulphite cellulose extract, 556
Sulphonated hydrocarbons, 566
oils, 434, 437
analysis of, 640
on chrome leather, 440
sole leather, 441
vegetable-tanned leather, 440
Sulphuric acid and salt pickle,
127
in de-liming, 111
in leather, 646
Sumac, 368, 552
mordant, 365, 397
simple test for, 663
tannage, 228
Suppleness to increase, 192
Surveyor's measure, 675
Sweat glands, 49
Sweat pit, 71
Sweating, 71
Sweep tare, 13
Swiss hides, 19
Syntans, 558
Synthetic tanning materials, 558
Tacking, 451
Tail-puller, 9
Taking-up hides, 12
Tan liquors, 612
shades, 398
yard, 274, 276
Tannage, alum, 138
formaldehyde, 147
shark-liver oil, 135
Tannery waste, 665
disposal of, 665
Tanning agents for belting
leather, 295
buckskins, 154
extracts, sampling of, 620
glossary of terms used in, 683-
687
in paddle-vat, 169
materials, quantities for analy-
sis, 611
pigskins, 255
- snakeskins, 247
with formaldehyde, 156
Tanolin, 165
Tanolin T, 189
Tartar emetic, 399
Tea's extractor, 613
Tensile strength, 292
Terms used in tanning, glossary
of, 683-687
Test for de-liming, 111
Texas steers, 17
INDEX
699
Theory of chrome tanning, 198
Thermometers, comparison of,
671
conversions, 670
Ticks, sheep, 33
Titanium-potassium oxalate, 365
analysis of, 654
Titer test, 654
Toggled, 79
Tray dyeing, 356
Troy weight, 674
Tryptase, 86
Turkestans, 26
Turkish goatskins, 25
Turner embossing press, 339
serial table machine, 313
Turpentine, 342
Twisters, 161
Two-bath chrome liquors, analy-
sis of, 603
on pickled sheepskins, 163
process, 158
of chrome tannage, new, 171
Ultra-violet light, 347
Umber, 343
Unhairing, 86
machine, 80, 93
Union leather, 272
splitter, 246
United States Government regu-
lations for hides, etc., 37-45
Units of heat, 680
Unsplit sides, 177
Unusual tanning processes, 567
Useful data, 670
Vacuum evaporation, 537
tanning, 568
Valonia, 551
Varnish, 345
collodion, 380
Vaughn machine, 308
Vegechrome, 204
Vegetable tanning materials, 525,
611
grinding, 526
Vegetable-tanned calfskins, black,
390
• fat-liquor for, 432
grain, finish for, 478
kangaroo, 240
leather, analysis of, 625
blacking for, 485
dyeing, 356
sulphonated oil on, 440
light leather, 225
sheepskins, 225
side leather, 242
fat-liquor for, 428
skins, dyeing, 374
upper leather, dyeing of, 411
Velvet leather, 237
chrome, 187
coloring, 392
Vici kid, 433
Viscosity, 651
Wallaby, 67
Walrus grain seal, 252
Warble, 2
fly, 14
Warm sweat, 71, 72
Washing hides, 57
pigskins, 68
Wash-wheel, 56
Water analysis, 585
solubles in leather, 638
Waterproof dressing:, 485
filling for sole leather, 443
Wattle bark, 556
Wax calf, chrome-tanned, 207
resist, 380
Waxed splits, 329
Waxes, 419
Weight of liquids, 674
pipes, 670
Welting, 318
Wetting-back, 30?
Wheel stuffing, 311
White buckskins, 155
calfskin leather, 145
chrome, 189
chrome-tanned sheepskins, 168
furs, cleaning of, 515
pigskins, 151
side leather, 185
splits, 152
Whitening, 320
machine, 309
Wool, disinfection of, 40
Woolskins, 501
chrome-tanned, 513
coloring, 506
de-greasing, 504
dyeing, 517
formaldehyde tannage, 504
tanning, 501
Wyncoop, G., cited, 578
Zinc chloride, 52
sulphate in de-liming, 116
ADVERTISEMENTS
Chemical Specialties
for tanners
Manufactured by
The Martin Dennis Company
Claim consideration and deserve the inves-
tigation of all tanners throughout the World.
The Specialties Comprise
TANOLIN
Chrome Tanning Extract
ACIDOLENE
Superior Fat- Liquors
PUERINE
Efficient Improved Bates
KROMOID
Filler for Chrome Sole Leather
These are made according to the most exact methods
by expert workmen. Our experience of a quarter of
a century and our reputation among the best tanners
is a guarantee that users can rely on the
EFFICIENCY, UNIFORMITY and LOW COST
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Write for Particulars
The Martin Dennis Company
859 SUMMER AVENUE, NEWARK, N. J., U. S. A.
Foremost Drying Machines for
all kinds of Leather and Hair
" Proctor 7? Dryers make the drying process a
thoroughly efficient mechanical one, operating
independently of weather conditions and control-
ling uniform drying results in all seasons. They
greatly reduce the time, labor and space required
by old drying methods. They utilize exhaust
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any other drying equipment.
Our catalogue introduces ' ' Proctor ' ' Dryers
in various types for different leathers and methods
of handling. Send for your free copy.
PROCTOR & SCHWARTZ, INC
Formerly The Philadelphia Textile Mach'y Co.
PHILADELPHIA, PA.
"Colors for Leather"
<;_/! Supplementary Text-Book
on Leather Dyeing
Every leather dyer should have his copy of
"Colors for Leather.' This loose-leaf volume
describes those Du Pont Dyestuffs which are
suitable for the dyeing ot leather.
Complete directions for application, with samples
showing the results obtainable, are given for each
dyestuff.
E. I. du Pont de Nemours &* Co., Inc.
Dyestuffs Department
WILMINGTON, DELAWARE
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CODES:
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EUROPEAN BRANCHES
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ROHM & HAAS COMPANY, Inc.
Manufacturers of Chemicals
40 N. FRONT STREET
PHILADELPHIA, PA. CHICAGO, ILL.
SPECIALTIES
OROPON — Fur bating hides and skins; the recognized substi-
tute for the manure bates, the bran and acid drenches.
ARAZYM — For unhairing hides and skins by enzyme action
instead of the lime and sodium sulphide or lime and arsenic
processes.
KOREON — A one-bath chrome tan in crystal form, easily
soluble in water.
TITANENE — A titanium- sodium sulphate cantaining 14% Ti0 2 .
TITANIUM POTASSIUM OXALATE— Containing 24% Ti0 2 .
TARTAR EMETIC— Technically pure.
SYNTHETIC TANNING MATERIALS
CRESOTAN— For light leathers.
SORBANOL— A new Synthetic Tanning Agent for use on
all classes of leather in combination with Vegetable
tans— of proven merit as to safety, speed, economy
of extract, colour and quality of leather.
CHEMICALS
SODIUM SULPHIDE ACIDS
Concentrated Sulphuric
Crystals Muriatic
DEPILATORY GLAUBER'S SALT
SULPHATE OF ALUMINA „ -^ .
Iron Free BISULPHITE OF SODA
Commercial Dry
AMMONIA ALUM Liquid
POTASH ALUM HYPOSULPHITE OF SODA
G. W. BAKER MACHINE CO.
Builders of
HIDE AND LEATHER
WORKING MACHINERY
COMPLETE TANNING EQUIPMENT
Wilmington Automatic Roller Fleshing, 6'
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WILMINGTON, DEL, U. S. A.
ORIGINATORS and MANUFACTURERS of
FLESHING MACHINES
UNHAIRING MACHINES
SCUDDING MACHINES
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WHITNEY MACHINE COMPANY
Established 1844
WINCHESTER, MASSACHUSETTS, U. S. A.
Over a Century of Service and Progress "
CBENUM&
1816 iiraroirTWTfai 1922
INNIS, SPEIDEN C& CO., Inc
Established 1816
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cm™ 46 Cliff St " NeW York NIAGARA FAL ^s
BOSTON manufacturers JERSEY CITY
PHILADELPHIA
IMPORTERS AND EXPORTERS OP
INDUSTRIAL CHEMICALS
OSWEGO, N. Y.
CLEVELAND
GLOVERSVILLE II1UUO I IIIHL UIILIfllUHLO MURPHYSBORO, ILL.
LOGWOOD, HEMATINE, DYEWOOD EXTRACTS
TANNING MATERIALS
ISCO LEATHER SEASONS AND FINISHES COVER ALL LEATHERS
SURE PROFIT MAKERS
MAKES BETTER SOLE LEATHER
HARNESS AND BELTING
IN ONE -HALF THE USUAL TIME
For Perfect Results as
The Most Dependable
a Mordant on Chrome
Leathers
Oil for Mellowing and
For a Fine Smooth Grain
Strengthening Your
on Combination Tanned
Leathers
Leathers
WRITE FOR THE BOOKLET
"Modern Tanning Methods"
THE TANNADE COMPANY
1446 CUSTER STREET
CHICAGO, ILL.
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