TEXAS AGRICULTURAL EXPERIMENT STATION
R. D. LEWIS, Director, College Station, Texas

 

757

g Characteristics and Spinning Performance
of Mechanically-stripped Cotton
on the High Plains

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 The TEXAS AGRICULTURAL  _ME€'HANICEAL CQLLEGE SYSTEM
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[Blank Page in Original Bulletin]

Preface

This bulletin gives information 0n the fiber properties
and spinning performance 0f machine-stripped cottons of the
High Plains. All samples of the 1949 and 1951 crops were on
seed cotton machine-stripped after frost. The samples of the
1950 crop also included cotton hand-pulled before frost. All
the samples of the 1949 crop and 60 percent of those of the
1951 crop were from field-stored machine-stripped seed cotton.
The samples were obtained at or near the time of ginning
from storage stocks.

Hand pulling of cotton before frost is more selective and
includes only the more mature bolls. Stripping after frost is
the kind of mechanical harvesting done on the High Plains.
The mechanical stripper gathers 90 to 98 percent of the cotton.
Mechanical stripping results in a mixture of bolls of various
stages of maturity. Hence, the lint from machine-stripped
bolls has finer fibers than lint from bolls harvested by hand
earlier in the season. According to spinning tests of the 1949
crop, 74-inch cotton of finer and weaker fiber made yarn as
strong as 75-inch cotton of coarser and stronger fiber. The
strength of the yarns made from the weaker, finer cotton was
increased by packing more fibers into a bundle and thereby
obtaining greater cohesiveness when twisted. The behavior
of cottons of 1950 and 1951 was similar to that of the cottons
of 1949.

A high percentage of the cottons of the High Plains has
fine fibers and relatively low tensile strength. This study
indicates the importance of fiber and spinning tests in mer-
chandising High Plains cotton as such tests disclose the best
utilization.

- Contents

Page
Preface ............................................................................................................ .. 3
Introduction .................................................................................................... .. 5
Length 0f Growing Season as Related to Stripping .............................. .. 5
Seasonal Operation of Strippers ............................................................... .. 6
Collection of Seed Cotton Samples, 1949 .......................  ........................ .. 6
Collection of Seed Cotton Samples, 1950 ................................................. .. 7
Collection of Seed Cotton ‘Samples, 1951 ................................................ .. 7
Quality and Fiber Characteristics, 1949 ....................  ........................... .. 7
Quality and Fiber Characteristics, 1950 .................................................. .- 9
Quality and Fiber Characteristics, 1951 ................................................... .. 10
Spinning Performance of 1949 Samples ................................................. .. 10
Spinning Performance of 1950 Samples ................................................ .. 12
Spinning Performance of 1951 Samples ................................................ .. 12
Summary ........................................................................................................ .. 17
Explanation of Terms ................................................................................ .. 19

Acknowledgments ........................................................................................ .. 20

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J. M. Ward, L. E. Hessler and W. E. Paulsonl

THIS PROJECT was initiated to determine the effects of
mechanical harvesting 0n the ginning business. Ginning
capacity even with hand harvesting has frequently been in-
adequate t0 keep up with the rate 0f harvesting. It was
anticipated that ginning capacity would be strained during
periods when machine picking and stripping were done at
full capacity.

This study was confined to the High Plains because
mechanical stripping is done extensively in this area. Samples
were collected in Dawson, Lynn, Terry, Crosby, Lubbock,
Hockley, Cochran, Bailey, Lamb, Hale, Floyd, Swisher and
Castro counties. The mechanical stripper gathers 90 to 98
percent of the cotton. The amount of waste varies with the
efficiency of the machine and the variety of cotton. Harvest-
ing by this method results in a mixture of bolls of various
stages of maturity. Mechanically-stripped cotton usually
contains more immature (therefore finer) fibers than hand-
harvested cotton. High Plains cottons vary widely in fineness
because of variations in growing conditions due largely to
differences in altitude which range from 2,900 to 4,000 feet.

Cotton grown on the High Plains is practically all one
inch or less in length and the best utilization of this cotton
requires a knowledge of the physical properties of the fiber.
If the classer’s grade and staple length are supplemented by
fineness and maturity data, it is possible to select the cotton
best fitted for a specific purpose.

Length of Growing Season as Related to Stripping

The High Plains area growing season is 217 days in the
southern section, 206 days in the central and 197 days in the
northern part. Average date of first frost is November 4 at
Lubbock in the central part of the area. There are more
cloudy days and cool nights in the northern section which

‘Respectively, assistant professor, Department of Agricultural Economics
and Sociology, College Station, Texas; research associate, Cotton Re-
search, Texas Technological College, Lubbock, Texas; and professor, De-
partment of Agricultural Economics and Sociology.

_5_

produces conditions less favorable than is indicated by the
small difference in growing season. According to the Census
Bureau, ginnings by November 1 account for 40 percent of the
crop in the southern section, 35 percent in the central section
and 28 percent in the northern section. After the coming of
cold Weather, defoliation occurs and the opening of the bolls
is hastened. Acceleration of boll opening also may be obtained
by chemical defoliation before frost. Defoliation by natural
or artificial means leaves the plants in suitable condition for
stripping.

Seasonal Operation of Strippers

Experience indicates that stripper harvesting can be
started 5 to 10 days after a first killing frost. The desirable
interval between the dropping of the leaves and the beginning
of stripper harvesting varies according to the moisture con-
tent of the plants and bolls. If the plants have been chemically
defoliated 2 to 3 Weeks prior to frost, machine stripping can
be started sooner than if the plants are allowed to stand until
the leaves are removed solely by frost. Strippers are more
efficient and less wasty when the stems of the plants are
pliable. As the cotton plants reach the proper condition for
stripping, the period during which the machine may be
operated to the best advantage is strictly limited. The plants
become brittle soon after a heavy frost. Under such circum-
stance, the machine-stripped bolls are mixed with much
foreign matter in the form of stem and stalk fragments.

The 1949 cotton crop of the High Plains exceeded one
and one-half million bales. The first freeze occurred October
31. With the beginning of mechanical stripping on a large
scale, the daily rate of stripping greatly exceeded the capacity
of the gins. During such times the gins usually operate on
a 24-hour basis. Beyond the point of stripping up to full gin
capacity, growers are faced with the alternative of storing
the surplus seed cotton on the farm or at the gin, or of
leaving the cotton unharvested in the field for later stripping
as ginning service becomes available. Most of the cotton
growers of the High Plains in 1949 chose full scale stripping
and farm storage of the supply in excess of ginning capacity.
Perhaps as much as 90 percent of the storage was on the
ground in the cotton fields.

Collection of Seed Cotton Samples, 1949

Three hundred and two samples were collected from
farm-stored cotton of the 1949 crop. Stormproof and open-

_7_

boll varieties were represented. The samples Were represen-
tative of the counties in which machine-stripped cotton Was
farm-stored prior to ginning. The samples were ginned 0n a
small, one-stand gin after the close of the ginning season.

Collection of Seed Cotton Samples, 1950

During the 1950 cotton harvest on the High Plains, the
bulk of the cotton stripped by machines was of the stormproof
varieties. Sufficient labor was available to “hand pull” the
open-boll varieties the first time over. Of 147 seed cotton
samples collected, 105 were of the stormproof varieties, me-
chanically stripped. Less than 10 percent of the 1950 crop
was held in storage between the time of stripping and ginning.
All the seed cotton samples were collected at or near the
time of custom ginning. All were ginned on a small, one-
stand gin in late January 1951.

Collection of Seed Cotton Samples, 1951

One hundred seventy-seven seed cotton samples were
collected from the 1951 crop. They were stored in a shed as
collected and were ginned later in the same manner as the
samples from the two previous crops. The expansion of
cotton growing now in progress on the High Plains made
possible the collection of several samples from a section having
a shorter growing season than sections of the area previously
sampled. These samples were obtained in Castro county.
Sixty-five seed cotton samples were taken directly from
trailers at the time of harvest, and 104 were from field storage
at or near the time of ginning from storage stocks. The
remaining samples were obtained from seed cotton stored
in barns or gin seed cotton houses prior to ginning.

Quality and Fiber Characteristics, 1949

Stormproof varieties have finer fiber than open-boll
varieties grown in the area. Stormproof varieties are better
adapted to mechanical stripping. This increases the propor-
tion of cottons with fine fibers. In stormproof cottons, the
locks are held closely in special type bolls which open partially
and remain intact before and during the stripping operation.
The structure of the stormproof boll is such that the penetra-
tion of dust and moisture into the seed cotton is held to a
minimum. These desirable properties of stormproof cottons
are not characteristic of the more common or open-boll cottons.
The locks of the open-boll cottons tend to string out and
result in considerable wastage during stripping.

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_9__

In classing the lint cotton samples of the 1949 crop
according to official standards, it was found that 75 percent
of the stormproof, but only 47 percent of the non-stormproof
cottons, was graded middling light spot, strict low middling
and strict low middling plus. These were high grades for
the time and method of harvesting. All these samples were
from cotton stripped mechanically.

Fineness, maturity and tensile strength of the cottons
sampled in 1949 are summarized in Table 1. It is evident
that a high percentage of these cottons had fine fibers with
average or better maturity, and tensile strength below average.
These cottons were mixed for spinning on the basis of simi-
larity in fiber properties.

Quality and Fiber Characteristics, 1950

Forty-six percent of the stormproof cottons mechanically
stripped in 1950 were in the highest grade group, middling
light spot, strict low middling and strict low middling plus.
This compares with 75 percent in the same group in 1949.
Weather conditions in 1950 were less favorable for the pro-
duction of desirable grades.

A total of 498 samples were collected to compare the
fiber properties and spinning performance of pre-frost hand
pulled cottons with after-frost machine-stripped cottons. Of
these, 351 samples were pre-frost hand-pulled and fiber tests
were run on 331 and spinning tests on 20 of them. The after-
frost machine-stripped samples contained 122 fiber tests and
25 spinning tests.

Fineness, maturity and tensile strength of cottons har-
vested before and after frost are shown in Tables 2 and 3.
The pre-frost hand-harvested cottons were much coarser and
more mature, but the difference in tensile strength was not
so pronounced.

In the two southern counties, Lynn and Dawson, 90
percent of the samples from the pre-frost harvested cottons
were in the average and coarser class with respect to fineness.
The longer, warmer growing season of the central and south-
ern parts of the area produce coarser, stronger cotton fibers
than the cooler, shorter growing season of the northern sec-
tion. A large part of the cotton acreage in the northern sec-
tion is irrigated. This produces finer, less mature fibers. A
larger acreage of stormproof varieties also is a factor. In
the northern section of the area, 61 percent of the cottons
were in the average and coarse group. This is confirmation

_._]_()_..

of generally accepted facts regarding High Plains cottons.
The tensile strength of 47 percent -of the cottons from the two
southern counties were in the average or above group but only
15 percent from the northern counties were in this group.

Quality and Fiber Characteristics, 1951

Seventy-six percent of all cottons from field storage of
the 1951 crop were low middling equivalent or better in grade;
69 percent of the cottons from trailers Were in the same group.
Major differences in grade can be attributed largely to
variations in growing conditions, variety and season. Samples
from field-stored seed cotton which received one inch of
moisture composed of rain and snow when in storage during
the first week in January 1952, were of satisfactory grade.

As indicated in Table 1, the 1951 cottons were coarser
and stronger with a greater percentage of immature fibers
than those of the two previous crops.

Spinning Performance of 1949 Samples

Twenty-five spinning tests were run on the 1949 machine-
stripped cottons. Twist multipliers of 3.75, 4.25, 4.75 and 5.25
were used over a range of yarn numbers of 7’s to 28’s (see
definition of terms). Neps varied closely with fineness; it
is believed that on the coarser yarns the effect of neps on
yarn appearance grade was not significant. Twist per inch
is more important in the coarser cottons than in the finer.
The finer cottons take more twist before reaching a shearing
point than the coarser cottons.

Since the cottons of the High Plains vary in fineness,
spinning tests were made over the range of fineness to ascer-

Table 3. Tensile strength of High Plains cottons, 1950 crop,
harvested before and after frost

Samples
_ Number Percent of total
Tenslle Hand- Machine- Machine- Hand-
strength harvested stripped stripped harvested
before frost after frost after frost before frost

72 & below ...... ..weak 118 29 33.6 19.7
73-77 ............... ..fair 132 102 37.6 69.4
78-82 ................ ..average 83 15 23.7 10.2
83-89 ............... ..very good 18 1 5.1 .7

351 147 100.0 100.0

tain the spinnability, yarn grade and strength of these cottons.
The spinning tests revealed that 7/3-111011 cotton in the very
fine category behaved differently during processing into 11’s
yarn than did the 7/3-inch cotton that was coarser and stronger.
Maximum strength was obtained in nearly every instance with
14.2 turns per inch. Although the very fine 7/3-inch cotton
had somewhat lower tensile strength than the other 7/3-111011
cotton, the yarn made from the weaker, finer cotton was as
strong as that made from the coarser, stronger cotton. The
strength of the yarns made from the weaker and finer cotton
was increased by packing more fibers into a bundle and
thereby obtaining greater cohesiveness when twisted. Maxi-
mum strength in 14’s yarns was usually reached for both the
fine and the coarse fibers with a twist of 15.8 turns per inch.

Table 4. Yarn appearance grades 0f yarns processed from stormproof
cottons, 1950 crop, harvested before and after frost

Hand-harvested Machine-stripped
before fro-st after frost

Yarn count

Yarn No. of Percent No. of Percent

appearance tests of total tests of total
11’s 22’s 11’s 22’s 11’s 22’s 11’s

A— 2 5 28.6 71.4 3 3 20.0 20.0

B+ 3 1 42.8 14.3 11 11 73.3 73.3

B 2 1 28.6 14.3 1 1 6.7 6.7

Total 7 _7 100.0 100.0 15 15 100.0 100.0

Yarn appearance

Grade Designation . Index‘
A and above .................. ..Excellent 130
B+ ................................... _.Very good 120
B ...................................... ..Good 110
C+ ................................... ..Average 100
C ...................................... ._Fair 90
D+ ................................... ..Poor 80
D and below ................. ..Very poor 70

‘The yarn appearance index provides a means of averaging the appear-
ance grade of two or more yarn numbers, and for comparlng yarn
appearance values obtained in the testing of a specific sample with
those of the general average of cotton. A yarn appearance index greater
than 100 indicates higher than average yarn appearance, whereas‘ a
yarn appearance smaller than 100 indicates lower than average yarn
appearance. Cotton Branch, PMA, U. S. Department of Agnculture.

___]_2__

The final test of the cotton is its performance in a fabric.
Several samples 0f machine-stripped cotton of one variety
were grouped according to fiber properties for spinning
and then made into fabrics. The main purpose of fab-
rication was to determine the effect of fineness on fabric
strength and use value. Coarse fabrics, such as ducks, drills
and sheetings, were made from these cottons. The breaking
strength tests indicated that fineness of fiber is not detrimen-
tal to the strength of the finished fabrics. The fabrics Were
acceptable in appearance and were of B grade, or better. The
breaking strength data of the fabrics and previous experience
in correlating such data With wearing qualities indicate that
strong and durable fabrics can be made from High Plains
cotton.

Spinning Performance 0f 1950 Samples

The pre-frost, hand-harvested, stormproof cottons of the
1950 crop are contrasted with the after frost machine stripped
stormproof cottons in Tables 4 and 5. The after-frost, ma-
chine-stripped stormproof cottons compare favorably with the
before-frost, hand-harvested cottons in yarn appearance grade
and skein strength.

Table 5. Skein strength of yarns processed from stormproof cottons,
1950 crop, harvested before and after frost

Hand-harvested Machine-stripped
before frost after frost
Average of 7 samples Average of 15 samples
Skein strength Skein strength
Twist Twist
multiple 11’s 22’s multiple 11’s 22’s
4.25 190.0 lbs. 83.7 lbs. 4.25 193.0 lbs. 83.2 lbs.
4.75 188.1 lbs. 84.5 lbs. 4.75 193.0 lbs. 83.0 lbs.

Spinning Performance of 1951 Samples

Nine varieties of the 1951 crop were tested for spinning
performance. Sixty-two spinning tests were run; 54 of these
are included in the four summary tables covering the four
principal varieties, Tables 6, 7, 8 and 9.

The nep count of the 1951 cottons was much lower than
either of the other two machine-stripped crops. The lower
nep count produced a superior yarn grade. These tests indi-
cate that the properties of the various varieties remain as
stable as climatic conditions permit.

_]_3__

Table 6. Fiber properties and spinning data, 27 tests,
Macha variety, 1951

Fiber properties

Upper half Mean Length Fiber strength Fineness Maturity
mean length length uniformity (1000 lbs. per (micrograms (percent)
(inches) (inches) (percent) square inch) i per inch)
Average .90 .64 71 75.8 3.7 60
Range .83—.98 .58-.75 66-79 71.7-81.4 2.8-4.8 40-71

Processing results
Nep count (neps per 100 square inches card web—40 gr. sliver)

Average 21
Range 8-44
Picking and carding waste (percent)
Average 21.11
Range 12.38-32.52

Yarn strength-skein (pounds)

Twist multiple
Yarn N0.

3.75 (Average)
(Range)
4.25 (Average)
(Range)
4.75 (Average)
(Range)
5.25 (Average)
(Range)

Yarn grade
Average

11’s

187.7
169.5-206.3
186.8
172.2-203.1
180.2
161.6-194.8
173.5
152.6-188.1

3+

14’s

138.3
120.2-152.1
141.4
132.3-148.9
135.8
128.2-143.6
131.6
121.0-146.2

3+

70.8-86.5

3+

28’s

57.3
43.0-64.2
60.3
52.9-68.9
59.9
50.3-66.1
59.6
50.7-64.9

3+

__14_.

Table 7. Fiber properties and spinning data, 12 tests,
Stormproof N0. 1 variety, 1951

Fiber properties
Upper half Mean Length Fiber strength Fineness Maturity
mean length length uniformity (1000 lbs. per (micrograms (percent)
(inches) (inches) (percent) square inch) per inch)

Average .87 .61 71 73.6 3.6 59

Range .80-.93 .58-.66 67-74 69.3-79.3 2.9-4.4 44-73
Processing results
N ep count (neps per 100 square inches card web—40 gr. sliver)
Average 17
Range 7-33
Picking and carding waste (percent)
Average 22.03
Range 18.53-26.33

Yarn strength—skein (pounds)

Twist multiple
Yarn No.

3.75 (Average)
(Range)
4.25 (Average)
(Range)
4.75 (Average)
(Range)
5.25 (Average)
(Range)

Yarn grade
' Average

11’s

188.8
154.9-213.3
181.5
157 .1-195.5
172.1
162.4-180.3
167.0
157.4-175.4

3+

14's

137.6
128.8-149.9
140.9
131.0-150.1
132.7
128.2-138.4
128.6
122.8-133.4

3+

71.s§s0.s

3+

57.3
52.7-62.8

3+

Table 8. Fiber properties and spinning data, 9 tests,
CA-122 Early variety, 1951

Fiber properties

Upper half Mean Length Fiber strength Fineness Maturity

mean length length uniformity (1000 lbs. per (micrograms (percent)
(inches) (inches) (percent) square inch) per inch)

Average .87 .62 71 76.8 4.2 66
Range .84-.90 .58-.66 68-77 70.8-80.8 3.4-4.9 57-72

Processing results

Nep count (neps per 100 square inches card web--40 gr. sliver)
Average 16
Range 7-26

Picking and carding waste (percent)
Average 19.50
Range 16.91-24.07 ”

Yarn strength-skein (pounds)

Twist multiple

Yarn No. 11’s 14’s 22’s 28’s
3.75 (Average) 186.8 138.1 81.8 58.2

(Range) 173.4-204.2 129.6-153.0 71.6-93.4 52.9-67.3
4.25 (Average) 192.6 139.5 82.2 59.7

(Range) 177.3-212.4 133.3-150.0 76.1-86.9 55.4-68.0
4.75 (Average) 188.1 136.2 81.8 60.1

(Range) 172.7-207.2 132.5-144.0 78.6-87 6 56.1-67.9
5.25 (Average) 182.6 134.6 78.5 58.4

(Range) 1642-1992 129.2-143.0 75.0-84.2 55.0-64.3
Yarn grade

Average B+ B+ B+ B+

Table 9. Fiber properties and spinning data, 6 tests,
Northern Star variety, 1951

Fiber properties

Upper half Mean Length Fiber strength Fineness Maturity

mean length length uniformity (1000 lbs. per (micrograms (percent)
(inches) (inches) (percent) square inch) per inch)

Average .90 .63 70 75.9 . 3.9 64
Range .85-.96 .61-.65 66-72 70.9-80.3 3.6-4.3 57-68

Processing results
Nep count (neps per 100 square inches card web—40 gr. sliver)

Average 12
Range 8-19
Picking and carding waste (percent)
Average 23.56
Range 17.56-27.22

Yarn strength—skein (pounds)

Twist multiple

Yarn N0. 11’s 14’s 22’s 28’s
3.75 (Average) 192.6 141.4 82.2 62.3
(Range) 178.4-205.4 123.7-148.9 75.8-89 0 56.0-66 5
4.25 (Average) 196.2 140.8 83.0 63.1
(Range) 181.3-207.0 131.7-145.8 75-.8-87 5 58.5-66.9
4.75 (Average) 192.3 132.1 85.6 64.2
(Range) 174.3-200.6 122.3-137.0 76.9-91 9 57.7-69 4
5.25 (Average) 180.8 126.2 84.7 65.6
(Range) 169.6-188.1 116.8-132.2 76.4-89.7 54.4-80.1
Yarn grade
Average B+ B+ B+ B+

While the cotton grown on the High Plains is practically
all one inch or less in length, utilization necessitates knowing

‘the physical properties of the fiber. Cotton with a high

percentage of immature fibers does not dye uniformly. One
eastern mill operator refuses to buy any cotton from this area
of less than a specified fineness as all his products are dyed.
The savings in dyestuffs alone more than justifies the expense
of buying on specification. It is because of the importance of
fiber properties that the data presented in this report type
the cotton by variety. Thus, the purchaser of cotton of the
area can rely fully on the classer’s length and grade and the
laboratory fineness and maturity tests as the guide in obtain-
ing cotton of the required specifications.

Many. of the mills use these cottons for fabrics such as
ducks, awning materials and belting. The essential require-
ments in such products are yarn and fabric strengths. For
this reason, the yarn strengths and the ranges for each twist
are given in this report. With the strength data at the various
twists, the mill operator will be able to find the variety that
best meets his specifications. At the same time, the mill can
determine at what twist the maximum strength may be real-
ized. This is also graphically shown for 85 percent of the
varieties tested in Figure 1.

As quality and waste are competitive features which most
mills must take into account, the nep count, processing waste
and yarn grades are of vital concern to mill men. These
factors may serve as guides in organizing their production
methods for achieving results comparable with those of the
pilot plant.

Summary

Year by year an increasing percentage of the cotton on
the High Plains is being stripped mechanically. In 1949, a
year of high production, 35 to 40 percent of the crop was
stripped mechanically.

Stormproof varieties are best adapted to mechanical
stripping. Grades from such varieties are higher and wastage
during the stripping process is much lower than from open-
boll varieties.

Spinning tests make data available on cotton of known
fiber properties. These data can be used as an aid in selecting
cotton varieties with fiber properties similar to those of the
cotton spun in the tests. The results of the spinning tests
can then be duplicated__within a reasonable range.

I90-

I80-

l70—

 

I50;

I40’-

I30-

 

Norfhern Star variety ———
CA—|22 Early variety ---- --
Macha variety

no-

Yarn skein strength (Pounds)

Stormproof variety ———
IOO —

90 _ 22's Yarn

80-

 

70-

_ _ __o__-__..__...___-o-

-Q-¢--_-_i.__-- 91"’-

 -<f-----——-—-<»--=== --~2:~._

50'-

I l l I I l I
3.75 4.00 4.25 4.50 4.75 5.00 5.25

if‘

Twist multiple
(Twlsf per |nch = Twist multiple Vyarn number

Figure 1. Average yarn skein stnength by twist multiples, Macha,
Stormproof No. 1, CA-122 Early and Northern Star varieties, 1951.

__19__

A high percentage of mechanically-stripped cottons of the
High Plains have fine, immature fibers and relatively 10W
tensile strength. Spinning tests of the 1949, 1950 and 1951
crops revealed that 7/8-inch cotton in the very fine category
behaved differently during processing into 11’s yarns than
did the 7/g-lIlCh cotton that was coarser and stronger. Al-
though the very fine 73-inch cotton had fibers of somewhat
lower tensile strength than the other 7/3-inch cotton, the yarn
made from the weaker, finer cotton was as strong as that
made from the coarser, stronger cotton. The strength of
the yarns made from the weaker and finer cotton was in-
creased by packing more fibers into a bundle and thereby
obtaining greater cohesiveness when twisted. Spinning tests
of stormproof cottons of the crop of 1950, harvested by hand
in the 15-day period prior to frost and tests of similar cottons
harvested by stripper after frost, show that the mechanically-
stripped stormproof cottons compare favorably with the hand-
pulled cottons in yarn strength and appearance grade.

The cottons of the 1951 crop were coarser, less mature
and stronger than those of the two previous crops. The yarn
was slightly stronger and the nep count much lower. The
lower nep count produced a superior yarn grade.

Explanation of Terms

The upper-half-mean is the average length of the longest
half of the fiber by weight and corresponds closely to staple
length as determined by the classers.

The mean length is the average length of all fibers in
the sample excluding those M; inch or under.

Uniformity is a measure of fiber length distribution and
is obtained by dividing the mean by the upper-half-mean and
expressing the result in percent. Above 80 is considered
uniform in fiber length, 80 to 76 average, 75 to 71 slightly
irregular, and 70 or below, irregular.

Fiber tensile strength is the force in 1,000 pounds re-
quired to separate the equivalent of a surface area of one
square inch. Ninety or above is considered excellent, 89 to
83 very good, 82 to 78 average, 77 to 72 fair, and below 72
is considered weak.

Fiber fineness is linear density expressed in terms of
micrograms per inch. 1.8 to 2.9 micrograms per inch is
considered extra fine, 3.0 to 3.9 fine, 4.0 to 4.9 average, 5.0
to 5.9 coarse, and above 6.0 is considered very coarse.

_2()_

Fiber maturity represents the percentage 0f thick-walled
fibers. 84 or above is considered very mature, 84 to 77 ma-
ture, 76 to 68 average, 67 to 61 immature, 6O or below very
immature.

Twist multiplier indicates the twist per inch of yarn.
The twist per inch applied to yarn is the product of the twist
multiplier and the square root of the yarn number.

Acknowledgments

The quality phases of this study were facilitated by the
cooperation of the Cotton Research Committee of Texas
through its staff of Cotton Research at Texas Technological
College, Lubbock, Texas.

The helpful assistance of the farmers and ginners of the
High Plains and the staff of Substation No. 8, Texas Agricul-
tural Experiment Station, at Lubbock, was indispensable.

MORE DETAILS AVAILABLE

For information on machinery inventory
and settings used in the spinning tests in
this bulletin, contact:

Cotton Research

Box 4159

Texas Technological College
Lubbock, Texas