S UMMAR Y Indentation and recovery tests made on six common floor coverings indicate some differences in both total and residual indentation of these materials due to temperature, humidity and load differences. Material thickness affects the total indentation character- istics of rubber, vinyl-asbestos and cork tile. The total indentation was smaller under the heavy and medium loads for the thinner materials. Little effect was noted under the light load. Differences in residual indentation of materials due to material thickness was significant for cork and vinyl-asbestos tile. Tests indicated that residual indentation was greater for the thicker samples. The thinner gage of rubber tile tended to retain more residual indentation than the heavier gage. Temperature increases tended to increase total indentation of all materials under all loads, but some materials showed a more rapid increase in indentation due to a temperature increase than others. Only standard gage linoleum and three-sixteenth-inch cork showed a significant increase in total or residual indentation with a humidity increase from 48 to 92 percent. Increases in load did not cause the same relative increases in total indentation for all materials. The interaction of loads and materials was significant for both total and residual inden- tation. No material appeared to have the best characteristics with respect to both total and residual indentation under all conditions. Under most conditions no significant differences were found among asphalt, vinyl, rubber and vinyl-asbestos tile. Linoleum and cork, on the other hand, were generally significantly sepa- rated from the other materials as well as from one another. (*- Contents Summary ------------------------------------ --"---- Introduction .................................. ..t Test Equipment and Procedure? Results and Conclusions ........... .. Application of Findings ............ Acknowledgments ....................... .. f oor coverings constitute approximately 3 to 6 4 of the total cost of the home. The cost of f nance and replacement of floor coverings con- e heavily to the total cost of home maintenance. dentation of resilient floor coverings is a major q of the floor covering industry. This is indi- by a survey made in 1958 by the Building i ch Institutel to determine the repair and main- _. e problems encountered with resilient flooring. of the survey indicated that indentation was ading problem with asphalt tile and cork tile, '5 as the second most frequent problem with Qbestos tile, linoleum and rubber tile. Indenta- as the third most frequent problem encountered ‘omogeneous vinyl tile. (dentation and recovery tests on resilient floor ‘ gs were made by the Department of Agricul- flEngineering in order to develop comparable Aation on the materials in common use. This ation should be of direct interest to the con- ' gin assisting him to select a floor covering from ‘ those types available to meet his particular ‘ ts were conducted under controlled tempera- y d humidity conditions with three different lo determine the effect of temperature, humidity ‘d on the indentation and recovery character- ‘A six common floor coverings. _t . Equipment and Procedure entation and recovery determinations were sing equipment constructed in the Department "cultural Engineering, Figure l. The inden- ’- ester, shown in the right foreground consists A of weights (A) which can be lowered onto a I (B) containing an indenting tool (C). The ple (D) was placed on the steel base plate e indenting too} and plunger. Periodic thick- dings were made by using a dial micrometer lively, assistant professor, associate professor and head, ent of Agricultural Engineering. i1; Research Institute, Installation and Maintenance of it Smooth-Surface Flooring, National Academy of Sci- ational Research Council, Publication 597, p 126, 1958. {Indentation and Recovery Tests Of Common Resilient Floor Coverings B. R. Stewart, O. R. Kunze and Price Hobgoodl‘ (E) which had its foot in contact with an actuating arm (F). The dial micrometer foot was depressed at the beginning of a test and was extended by spring pressure as the actuating arm and indenting plunger moved downward while the sample was being in- dented. Recovery measurements were made with a depth gage micrometerz (G) mounted on a steel plate, in such manner that the gage rod could contact the base plate (H). Indenting loads were varied by changing the size and number of weights. The in- denting tool was a flat-ended cylindrical steel rod, 0.125 inch in diameter. Indentation tests were made with pressures of 298.2, 2,015.8 and 3,995.2 pounds per square inch. Recovery measurements were made with the load removed. Six common resilient floor coverings were tested. All of these materials were in tile form. A list and brief description of the materials follows: Asphalt tile-Composed through full thickness of asphaltic or resinous binder with asbestos or other fibers, fillers and pigments formed under pressure. Vinyl-asbestos tile—Composed through full thick- ness of vinyl resins, plasticizers, pigments, fillers and asbestos fibers formed under pressure while hot. Homogeneous vinyl tile-Composed through full thickness of vinyl resin, plasticizers, pigments and fillers formed under pressure while hot. Rubber tile—C.omposed through full thickness of vulcanized rubber compound binder. Linoleum tile-Composed of oxidized linseed oil, fossil and other resins or other oxidized oleo-resinous binder mixed with ground cork, wood flour, mineral fillers and pigments and pressed on saturated felt backing. Cork tile—Composed through full thickness of compressed granulated cork, bonded with a heat processed resinous binder. Two thicknesses each. of rubber, vinyl-asbestos and cork tile were used. Eight 2x 2-inch samples of each material and thickness were cut from standard 9x9-inch tiles. Each sample was conditioned and tested under a particular temperature-humidity con- 2608 RS Browne and Sharpe Micrometer Depth Gage, Browne and Sharpe Manufacturing Company, Providence, Rhode Island. 3 dition. Temperatures of 50° F., 72° F. and 94° F. were used in eight combinations with humidities of 48, 70 and 92 percent, Figure 2. Three replications of each test load were made on each sample. Nine test spots were marked on each sample to accommo- date three replications of each test load. Test loads were applied to the samples for 30 minutes, with indentation readings being made 15 seconds and 1, 2, 3, 5, 10, 15, 20 and 30 minutes after the load was applied. Recovery readings were made l5 seconds and '1, 2, 5, l0, 20 and 30 minutes after the test load was removed. Residual indentation as referred to in this work is that indentation remain- ing at the end of the 30-minute recovery period. A final recovery reading was taken '72 hours after re- moval of the test load. Before the beginning of each test, the sample to be tested was placed in the test chamber and conditioned for 24 hours at a particular temperature-humidity combination. Throughout the testing, spots on each sample to be subjected to light, medium and heavy loads were selected at random. Three replications of one load were run on all the samples before another load was applied. Tests were run using the light load first, medium load second and heavy load last. Prelimi- nary trials indicated this order was necessary because some materials buckled or curled when subjected to the heavy load. Figure 1. Indentation tester (right foreground) and re- covery measuring apparatus (left) set up in the controlled temperature and humidity chamber. A Friez Hygrothermograph (left background) was used to record temperature and humidity. (See page 3 for identification of code letters.) 4 l/B"RU8BER TILE-MEDIUM anown .oao"nuaazn rut: 4450mm enseu I/B"VINYL ASBESTOS TILE-LIGHT can 1200 '- I/IG‘ VINYL ASBEISTOS TILE-LIGHT GRAY STD. GAGE LlNOLEUM-MEDIUM GRAY é O l ua" souo vmvt- wan: s/ls‘ coax "m: - uern anowu us‘ coax TILE - umrr anovm l/VASPHALT TILE-LIGHT can s s 8 <> 1 P ' 3‘ THIRTY MlNUTE INDENTATION UNCHES) 2 O O l uunmuu ummumuu- I w .0200 i i ‘IQIIIIIIIIIIIIIIIIIIIIIIIII ¢u'-' a‘?! axwavxarrm r . I!‘IIII/IIIIIIIIIII/I/I/I/ l‘ 1: . i Ia i 70% an 92v. an. 10% an. v 92% rm. 48v. ma. 10% an i 50° F, 72° F. 94° F. -\\\\\\\\§\\‘ WIII IIIIIIIIIIIIIIIIIIII .';'.°Z'Z'Z~Z-! \\\\\\\\\\\\\\ \\\\\\\\\\\\\\\‘ IIIIII llllllllllllllll -.-.-:. ' v .\\\\\\\\\\\\\ n\\\\\\\_\\\\\\ RWEQMIYSLT IIIIIIIIIIIIIIIIIIII/I/l ~.V\_§\\\\\\\\\\\\\\\ i \ \ \ i \ R‘\\\\\\\\\‘ Iilflik I s\\\\\\\\\\\ iii VIII/III TEMPERATURE — HUMIDITY CONDITION Figure 2. Average total 30-minute indentation of j floor covering tested, resulting from three replications of medium and heavy loads when applied under the tempe humidity combinations shown. Results and Conclusions k Average total 30-minute indentation of the covering materials tested is shown in Figure 2. 1 results indicate the tendency for all floor cove tested to indent more deeply as temperature or 1ty increases. e A statistical analysis of the resulting total residual indentation was made. The analysis sh that a temperature increase from 50° F. to 94 caused a significant increase in total indentatio: all materials tested. An increase from 50° F. to 7 caused a significant increase in total indentati- three-sixteenth-inch cork tile and standard linoleum tile. Figure 3 shows the effects of temperature humidity increase on residual indentation of the r coverings tested. Considering all humidities, res' indentation of rubber and vinyl tile were not‘ nificantly affected by a change in temperature .2 though the general tendency was for the res indentation to increase with temperature. A temi ture increase from 50° F. to 94° F. caused a signi :1 increase in residual indentation of all other mat tested. In addition, a significant increase in res indentation of linoleum tile was caused by a 2 A increase in temperature from either 50° F. t0 or from 72°" F. to 94° F. The thicker sample of? tile retained significantly more indentation V’ subjected to the 72° F. temperature than when; jected to the 50° F. temperature. There was nificant increase in residual indentation of a 1 tile when the temperature increased from 7 to 94° F. 3 A significant increase of total and residu dentation of linoleum and three-sixteenth-inchi tile was caused by the high humidity only. All i fls tested were not significantly affected by a ity increase. High humidities caused linoleum i‘ to warp during the conditioning period. A pity increase did not cause cork tile to warp. e preceding conclusions were reached when all 1fi1W€r€ considered. Under the light load, no pant difference in total or residual indentation iifiierials was caused by temperature or humidity t. Figures 4 and 5 show the effect of load ijtotal and residual indentation of the common lggcoverings considering all temperatures and 'ties used. There were only small differences t, the materials when tested under the light the load increased, both total and residual tion increased. These increases varied not _'th the different materials but also with the erent thicknesses of the same material. The particularly true of cork and vinyl-asbestos ; res 2 and 4 show that for these two materials dentation increases were smaller for the thin- fples of each material. This same characteristic w‘ g residual indentation may be seen in Figures i. The total indentation increase was less for i, er of the two samples of rubber tile, but gdual indentation increase was slightly more fthinner sample. erally, those materials which indented most ‘ y condition also retained the most inden- This is an undesirable combination of char- tive ratings of the materials. The most de- » oor covering should indent readily but retain tation upon removal of a load. A floor cover- indents readily will present a more com- ‘surface for walking. A minimum amount of i. indentation is desirable in maintaining ce and in preventing wear. abilities of the floor coverings to indent ere compared by measuring the amount of 'on which occurred l5 seconds after the appli- a load of 298.2 pounds per square inch to if e materials. The average indentation, con- geall temperatures and humidities, is shown " vertical axis of Figure 6. lhorizontal axis of Figure 6 shows the com- abilities of the floor coverings to resist it indentation when subjected to a load of funds per square inch. This load was f" being representative of loadings commonly Jed. Although cork and linoleum showed g to indent reaidily, they also retained a large if indentation “when compared to the other j Vinyl tile, on the other hand, indented 'd showed an ability to recover very well antation. Asphalt tile showed the poorest idepress readily but retained a considerable i; indentation. m which caused some difficulty in evaluating . n/a"nuaaen ‘rute-uzouun aaowu .oao'auaaea rut: meouuu cases ‘0600- |/8'VlNYL ASBESTOS TILE-LIGHT can T |/|s'v|nv|. ASBESTOS ‘m: -ucnr can - sro. use LINOLEUM-MEDIUM can us‘ souo vmvt- vmrr: 8 8 I 3/16‘ coax TILE - LIGHT aaoum us‘ com: TILE- usur anovm [- - urasriutn TILE-LIGHT aan i t l | I é I .0200 — RESIDUAL INDENTATION (INCHES) OIOO — .\ 4$ /\ /.\ /§ /§_ 7\§.;:;, f =_-<._ ,\;.. . \ ‘ - l 92% RH 48% RH. 70% RH. 92% RH. 0° F. 72' F TEMPERATURE - HUMIDITY ‘CONDITION Figure 3. Average residual indentation of each floor cover- ing resulting from three replications of light, medium and heavy loads applied under the temperature-humidity combinations shown. Considering all temperatures, humidities and loads, the floor coverings tested ranged in the follow- ing order from least to most total indentation: 1/16-inch vinyl-asbestos tile 1 / 8-inch asphalt tile 1 / 8-inch vinyl tile (homogeneous) l / 8-inch vinyl-asbestos tile 0.080-inch rubber tile 1 / 8-inch rubber tile Standard gage linoleum tile 1 / 8-inch cork tile 3 /16-inch cork tile The difference between any two materials as listed was not necessarily significant but there was a significant difference among several of them. The following differences between the materials listed were significant: The thinner vinyl-asbestos tile showed less total indentation than asphalt tile. n/afiwaasn TILE-MEDIUM enowu .OBO"RUBBER TILE -MEDIUM east-m "200 _ |/a"vmY|. ASBESTOS TILE-LIGHT GRAY uns‘ VINYL ASBESTOS rut: -uetn can sro. us: LINOLEUM utsotum can us‘ souo vmn. - wmra 8 o o 3H6‘ CORK TILE - LIGHT BROWN l/B. CORK TILE - LIGHT BROWN l/O. ASPHALT TILE - LIGHT GRAY .0800 I§IIIEIIIIIII_%E§ INDENTATION (INCHES) .0600 .0400 ' .0 200 THIRTY MINUTE 3995.2 PSI. 298.2 P.S.l. 20l5.8 P.S.I. INDENTING LOADS Figure 4. Average total 30-minute indentation, on each floor covering, occurring under all temperature-humidity com- binations when subjected to the loads shown. D600 I/l' VINYL ASBESTOS TILE-LIGHT GRAY I III6' VINYL ASBESTOS TILE-LIGHT GRAY urnuaazn TILE-MEDIUM snows EQ .oao'nuusn ‘m: -usmuu snszn _ § srn. us: tmoLzuu-usnnuu can 3 I us‘ éouo vmvt- vmrr: l] ans‘ coax TILE - uem unoum ‘ ‘ 0400 — II] us‘ cum: "mz- LIGHT anovm ‘ - l/Q'A8PHALT TILE-LIGHT GRAY - -I 3 RESIDUAL INDENTATION (mcngs; '9 b - 8 § 3995.2 RSJ. 298.2 RSI. ZOISE P.S.l. INDENTING LOADS Figure 5. Average residual indentation on each floor cover- ing that occurred under all temperature-humidity combinations when subjected to the loads shown. Linoleum tile and the two thicknesses of cork tile indented more than any of the other materials and were also different from one another. The 15-inch sample of rubber tile indented more than the 15-inch sample of asphalt tile. A statistical analysis was made of residual inden- tation, considering all loads, temperatures and hu- midities. The materials ranked in the following order from least to most residual indentation: l / 8-inch vinyl tile 1/16-inch vinyl-asbestos tile 1/8-inch asphalt tile 1 /8-inch vinyl-asbestos tile l / 8-inch rubber tile 0.080-inch rubber tile 1 / 8-inch cork tile Standard gage linoleum tile 3/ 16-inch cork tile Again, the materials were not all significantly different from one another. However, the following .010 A l. I/O INCH RUBBER TILE— MEDIUM BROWN 3 2. .080INCH RUBBER TILE-MEDIUM GREEN I 3. l/BINCH VINYL-ASBESTOS TILE -LIGHT GRAY Q .008 _4. l/IG INCH VINYL-ASBESTOS TILE - LIGHT GRAY E O 5. STD. GAGE LINOLEUM-MEDIUM GRAY v g 6. I/OINCH HOMOGENEOUS VINYL-WHITE . Z .J Z 3H6 INCH CORK TILE -LIGHT BROWN 7 2 __~ ‘O06 "B. l/B INCH CORK TILE -LIGHT BROWN -8 l; (Ii S l/B INCH ASPHALT TILE -LI8HT GRAY I-— ‘*5- E w 9°‘ 5. 5 O O z g; 2,.I 3 AVERAGE _| D02 4 - ALL rzmrznnruass E .9 ALL HUMIDIT as E '" o 4 1a :2 ls 2o 24 2a a2 as 4o RESIDUAL INDENTATION -THOUSANDTHS 20l5.8 RS1. LOAD Figure 6. Overall comparison of materials tested. Vertical axis shows ease of indentation, and horizontal axis shows resist- ance to permanent indentation. 6 differences between the materials listed were sj cant: The thicker cork tile indented more tb: linoleum tile. Linoleum indented more than the thinner s of cork tile. Both cork tiles and linoleiim indented more any of the other materials listed. The thinner sample of rubber tile indented; than the thinner sample of vinyl-asbestos Vinyl tile indented less than the thicker of rubber tile. Recovery readings made 72 hours after re of the test load indicated that practically all ,3 covery occurred within the 30-minute recovery p‘ Visual inspection of the test samples over a 9- period following the tests indicated that a, indentation of all samples remained as appar at the end of the 30-minute recovery period. I Application of Findings; Although all floor coverings tested exhibite ability to resist permanent indentation under of 298.2 pounds per square inch, consideration‘ l be given to the fact that this load was appli only a 30-minute period. Longer loading peri sf cause excessive additional indentation. ‘ The selection of a proper type and size gli furniture support is most important in pre , indentation to resilient floor coverings. The { contact between a floor covering and a glider a area should be large enough to prevent e pressures. Where floor covering manufacturers’ Q mendations are followed, there should be no p‘ with indentation. Many glider sizes and types are available j on household furniture. Figures 7, 8 and 9 sh types which are commonly used. The glider in 7 is the three-prong type with an overall di u five-eighths inch. This photograph illustra curved surface of the glider. The area of co this glider with the floor covering is only V mately three-sixteenth inch in diameter. If th is installed on the legs of a 25-pound chair ' occupied by an individual weighing only 125 i’ an initial pressure of 1,359 pounds per squf would be applied to the floor covering t’ leg. An equal size glider with a flat contact; five-eighth inch in diameter applied to the s ’ would subject the floor covering to a pressur 122 pounds per square inch. ' A three-prong type glider seven-eighth diameter was installed in the same manne f five-eighth-inch glider. Figure 8 shows the s_ j re 7. Five-eighth-inch diameter three-prong gliders, jling their small contact area when new. ea of this glider due t0 the curvature of the lit surface. “he contact area of these gliders was determined Flying ink t0 the glider and making an imprint igsheet of paper. The glider was placed on the l} in the same manner that it would contact a hovering when installed on a chair. The contact the seven-eighth-inch glider was approximately in as that of the five-eighths-inch glider. Like- fa flat-surfaced glider seven-eighths inch in er installed on a chair with a total load of unds would subject a floor covering to an initial e of only 62.4 pounds per square inch. Figures pl 8 both show the relatively large amount of Q tion that must occur before the contact area . leciably increased. second type of glider, Figure 9, has a rubber ich allows the glider face to adjust to the floor Lglider face and floor are not parallel. Again, f" of contact of the glider with the floor is jjly small due to the curvature of the glider i’ This glider offers a flatter surface than those in Figures 7 and 8. The initial contact area l‘, glider was only one-fourth inch in diameter. fie 8. Seven-eighths-inch diameter three-prong gliders, ‘i; g small contact area of glider when new. Figure 9. Single-prong gliders with rubber pad, illustrating their small contact area. . A 150-pound load appliedto four gliders of this type would subject a floor covering to an initial pressure of 764 pounds per square inch. Many items of furniture have legs which are large enough to reduce the pressure on a floor covering to considerably less than 100 pounds per square inch. However, unless the bottom of the leg is in complete contact with the floor covering, the pressures may be excessive. The corner or edge of a chair leg provides an extremely small contact area. Where flat gliders are used, a comparatively heavy piece of furniture such as a couch, which may weigh as much as 400 pounds, does not require ex- tremely large glider sizes in order to produce floor covering pressures under 100 pounds per square inch. For example, a ‘100-pound couch seating four indi- viduals whose average weight is 175 pounds would require only four contact areas 11/2 inches in diameter to reduce the pressure on a floor covering to less than 100 pounds per square inch. A floor covering which indents readily, yet re- sists permanent indentation even under large pres- sures, is very difficult to produce. With the resilient floor coverings now on the market, however, perma- nent indentation can be prevented by considering the loads that will be applied and providing proper glider sizes and types. Acknowledgments Recognition is given to the Department of Genetics, The A8cM College of Texas, which super- vised the statistical analysis of the indentation and recovery data. This research was set up in 1954 as part of the Southern Regional Housing Project S-8. Appreciation is extended to the floor covering manufacturers who furnished materials for the tests and made comments and suggestions on the report. ~ 7 i mm ITATION nu SUIITATION! : nu nrm usonxronrs A coorzurmo STATIONS Location oi field research units oi the Texas Agricultural Experiment Station and cooperating agencies ORGANIZATION OPERATION Research results are carried to Texas farmers, ranchmen and homemakers by county agents and specialists of the Texas Agricultural Ex- tension Service joalay g Kedearcé yd yOITlITlOPPOl/U 5,} WPOgPQII State-wide Research ‘ The Texas Agricultural Experiment Stati is the public agricultural research agen oi the State oi Texas. and is one oi thj parts oi the AcSM College oi Texas. I IN THE MAIN STATION, with headquarters at College Station, are 16 s p, matter departments, 2 service departments, 3 regulatory services =+ administrative staff. Located out in the major agricultural areas of Te 21 substations and 9 field laboratories. In addition, there are 14- coop { stations owned by other agencies. Cooperating agencies include the Forest Service, Game and Fish Commission of Texas, Texas Prison S U. S. Department of Agriculture, University of Texas, Texas Technol College, Texas College of Arts and Industries and the King Ranch. experiments are conducted on farms and ranches and in rural homes. { THE TEXAS STATION is conducting about 4-00 active research projects, ; ~ in 25 programs, which include all phases of agriculture in Texas. ' these are: Conservation and improvement of soil Beef cattle Conservation and use of water Dairy cattle Grasses and legumes Sheep and goats Grain crops swine Cotton and other fiber crops Chickens and turkeys g Vegetable crops Animal diseases and parasi Citrus and other subtropical fruits Fish and game Fruits and nuts Farm and ranch engineer Oil seed crops Farm and ranch business Ornamental plants Marketing agricultural pro, Brush and weeds Rural home economics , Insects Rural agricultural economi Plant diseases Two additional programs are maintenance and upkeep, and central I AGRICULTURAL RESEARCH seeks the WHATS. the i, WHYS. the WHENS, the WHERES and the HOWS oi hundreds oi problems which coniront operators oi‘, iarms and ranches, and the many industries depend- A ing on or serving agriculture. Workers oi the Main Station and the iield units oi the Texas Agricultural. Experiment Station seek diligently to iind solutions to v these problems. . '