Historic, archived document Do not assume content reflects current scientific l .u AGRICULTURAL RESEARCH SERVICE J UNiTED STATES DEPARTMENT OF AGRICULTURE CONTENTS Page Summary 3 Purpose and scope of the study 4 Review of literature 4 Dryers and drying methods studied 5 Experimental procedures Selecting and preparing fabrics for drying. . . 5 Evaluation criteria 7 Measurement of temperature 8 Analysis of data 8 Effect of drying method on fabrics White fabrics 8 Page V Effect of drying method on fabrics — Continued * Dyed fabrics 15 Effect of certain factors on performance of dryers A Voltage of dryers 22 1 Type of drum 25 Thermostat setting 26 Composition and weight of load 26 Moisture content of load 27 Operating characteristics of dryers 27 Time used by operator 28 Literature cited 28 This report is part of a research study on the functional requirements, use, and care of the home and its equipment, and supplements research in the Clothing and Housing Research Division on the care of fabrics in the home. Acknowledgment is made to the following members of the Division for contribu- tions in various phases of the investigations: Verda McLendon, Homoselle Jarvis, Bernice Brooks, and Jacqueline Riddick Parris. Acknowledgment is also made to Glenn Burrows, formerly of the Agricultural Marketing Service, as statistical con- sultant. Washinston, D. C. Issued October 1958 For sale by the Superintendent of Documents, U. S. Government Printins OfFice, Washinston 25, D. C. Price 20 cents 2'49B2't automatic clothes dryers — their performance and effect on certain Fabric properties I By Enid Sater Ross/'Katherine Taube, Nada Poole, and Lenore Sater Thye, household equipment specialists, Clothing and Housing Research Division, Agricultural Research Service. SUMMARY Automatic clothes dryers, their various design features, and factors affecting performance were investigated in evaluating home drying methods and their effect on fabric properties. Operating . characteristics of the dryers were also determined. In the study, fabrics were dried in automatic gas and electrically heated tumbler dryers, in an : electrically heated cabinet dryer, and, for com- ' parison, on indoor racks, and on outdoor lines protected and unprotected from the sun. The , automatics included dryers with perforated and nonperforated drum, single and selective thermo- stat settings, and dryers designed for operation on 120- and 240-volt circuits. Tests were made with 14 white fabrics and 21 dyed fabrics in a variety of colors. All the fabrics ' were types commonly laundered in the home — sheetings, towelings, and clothing fabrics. Fibers '' included cotton, linen, acetate, viscose rayon, and nylon. In some of the experiments the samples were t prepared for drying by soaking in clear water; in ' others they were washed in a detergent solution and rinsed. Moisture content of the wet load was ■* controlled to within 85 ±2 percent of the dry weight, except when moisture was an experimental variable. J The effects of different dr3ring methods on fabrics — were evaluated in terms of measured color changes, chemical degradation, bursting strength, and *■ dimensional change ; in some instances visual ob- servations were also made. Effect of drying method. — Results of 100 dryings l_ of 14 white fabrics that had been soaked in cold ^; water between dryings showed that no one method consistently caused the least or the most change in aU of the fabric properties analyzed. In out- door drying occurred the most chemical degrada- tion in 13 of the fabrics, and the most graying and loss of bursting strength in the largest number of fabrics. Tumbler dryers caused the greatest shrinkage and visible wear; the gas dryers caused the most yellowing. Inside rack and electric cabinet drying usually caused the least change in any fabric property. In the study of white fabrics washed in a detergent solution between dryings, gas and elec- tric tumbler dryers, and outside line and inside rack were used for drying three cottons, a nylon, and an acetate-viscose rayon. Washing between 50 dryings, compared with soaking only, lessened but did not completely eliminate graying in all fabrics, and decreased yel- lowing in cottons but not generally in the other 2 fabrics. Judges' scores indicated that the washed cottons dried by all methods were satis- factory, but some of the nylon and acetate-viscose rayon samples were not. Usually the higher the acceptability score, the less the fabric had yel- lowed. From the standpoint of bursting strength no one drying method stood out as best or poorest. The dyed fabrics, washed in detergent solution and rinsed, were dried 50 times on outdoor lines unprotected and protected from the sun, and in gas and electric tumbler dryers. Most of the fabrics were lighter in color, as indicated by gain in reflectance, when dried outdoors in the sun or shade than when dried by the other methods. In the greatest number of the fabrics, particularly the greens and reds, the most color change was brought about by sun drying. In some of the blues, gas drying made the most change. For the washed dyed fabrics, bursting strength differences between methods were not significant. As with the white soaked fabrics, dimensional changes in the warpwise direction, mainly shrink- age, were usually least for the samples hung on the line or rack and greatest for those tumbled. Effect of dryer design features.— The effect of operating voltage on performance was compared by use of two pairs of dryers, in each of which the dryers were identical except that one was operated on 120 volts and the other on 240 volts. The 120-volt dryers took about twice as much time but used about the same amount of electrical energy as their coimterparts operating on 240 volts. The differences between the 120-volt dryer and the 240-volt in graying, yellowing, chemical degradation, biu-sting strength, and scores for appearance of the fabrics did not indicate a superiority of one operating voltage over the other. A comparison of the effects of perforated- and nonperforated-drum dryers used to dry 14 white fabrics indicated no conclusive superiority of one type over the other. The thermostat setting — high, medium, or low — made little difference in graying, yellowing, loss of bm-sting strength, and dimensional change in fabrics dried in a gas and an electric dryer. Differences in chemical degradation, although sometimes statistically significant, were relatively small except for the two nylon fabrics in the gas dryer. They showed increased damage as the thermostat settings were changed from low to high. Effect of Jactors related to load. — The study in- cluded investigation of the possible advantage with respect to use of time and electrical energy that might be gained by separating loads of mixed fabrics into single-fabric loads for drying. With two 6-pound loads, each consisting of 3 pounds of terry towels and 3 pounds of sheets, both time and electrical energy were saved when the items were separated after water extraction and dried as one 6-pound load of towels and one 6-pound load of sheets rather than as two mixed loads. In contrast, one mixed 6-pound load required less time and energy when dried without separa- tion than when dried as one 3-poimd load of towels and one 3-pound load of sheets. After the time necessary to dry an 8-pound mixed load wet to 50 percent of its dry weight had been determined, it was found that additional 5-minute intervals dried 15 percent moisture increments up to 140 percent. Each additional 5-minute interval required approximately 0.4 kilowatt-hour of electricity or 1.7 cubic feet of gas. Operating characteristics of dryers. — As indicated by thermocouple readings, in all dryers maximimi exhaust temperatures were lower than those inside the drmn near the door. Temperature- indicating crayon marks on fabrics indicated higher fabric temperature than that of the air near the door for some dryers and less for others; at both locations the high settings were approxi- mately from 30° to 50° F. higher than the low with the medium setting falling between. Further research is needed on methods to determine ac- ciu-ately the maximimi dryer and fabric tempera- tures reached and their duration within the dryers. Efficiency of dryer operation, as measured by the units of heat energy used per 1,000 grams of moisture removed from loads, was not affected by thermostat setting or by operating voltage. However, differences in operating efficiency were found among the individual dryers studied. Time for drying the same load varied only shghtly -^j when dryers were operating under like conditions, A Time used by operator. — To place and remove a f load from a tiunbler dryer took about 10.5 minutes less than to hang and remove it from * racks, and 12.6 minutes less than to hang and remove it from the mnbreUa-type outdoor line. ' PURPOSE AND SCOPE OF THE STUDY , 1 Although the automatic clothes dryer for the ^ home laundry has been generally available for several years, only a few studies of its performance and effect on fabric properties have been pub- lished. The work reported here was conducted to de- termine the effect of automatic dryers on selected c fabrics ordinarily washed in the family laundry. ^. As a basis of comparison, the effect of conventional « drying methods was also investigated. To obtain quantitative data, experiments were de- signed to measure changes from the original in color, chemical properties, strength, and dimen- sions in the fabrics dried in various ways. In addition, the effect of certain factors on the • efficient use of dryers was investigated ; these , factors included size, composition, and moisture content of the load and special design features of the dryers. Operating and performance char- acteristics of dryers were also studied. REVIEW OF LITERATURE In 1953 Weaver and Thomas (7) ^ reported that drying washed articles in dryers gave more satis- factory results than drying on an outside fine ia,^ respect to the following factors: Loss of tensUe^^ strength, weight, and color except for certain -^ 1 Italic numbers in parentheses refer to Literature Cited, p. 28. blues, retention of whiteness, and time required for handling clothes after they were washed. Shrinkage was less for line-dried than for dryer- dried clothing. Energy costs for drying 8-pound loads averaged 2.7 kilowatt hours for electrically operated dryers and 9.6 cubic feet for gas dryers. Poole ^ found that when clothes were dried in automatic clothes dryei-s, some fading and shrink- age of decorative bands occmred in terry towels and wash cloths, but no appreciable shrinkage occiirred in cotton socks; pillowcases yellowed slightly; and clear plastic buttons became dis- torted. In a preheated dryer the average time for drying an 8-pound load from a wringer-type machine was 52 minutes. Drying a 6-pound and a 12-pound load required practically the same time and heat energy per pound of moistm-e removed. However, an 8-pound load made up of 4 pounds of sheets and pillowcases and 4 pounds of towels and wash cloths required less time and heat energy per pound of moisture removed than did two 4-pound loads, one of sheets and pillow- cases and the other of towels and wash cloths. Leavitt {4) in 1954, discussing the dimensional stability of viscose-rayon, stated that shrinkage during tumble drying results from overdrying and can be remedied by removing clothes from dryer while slight moisture remains. DRYERS AND DRYING METHODS STUDIED Effects of repeated drying of fabrics in auto- matic gas and electric dryers, on racks indoors, and on lines outside, protected and unprotected from the sun, were investigated. In design the dryers used were representative I of the types available on the market.^ They included an electrically-heated cabinet-type dryer with metal rods for hanging the fabrics, and automatic tumbler-type dryers with perforated .. and nonperforated drums heated with gas and • electricity. Both 120- and 240-volt dryers were included. Drums were of galvanized, porcelain- enameled, and synthetic-enameled metal. Timer controls were of two types — one provided a single temperature, the other selective temperatures. Controls provided drying times ranging from 1 to '■3 hours. Detailed descriptions of individual dryers are given in table 1. The electric tumbler dryers were connected to circuits with voltage controlled to within ±2 volts by an automatic regulator. The gas dryers were connected with pressm-e regulators in the gas lines. Electric and gas meters were the integrating type with scales reading to 0.01 kilowatt-hour and 0.01 cubic foot, respectively. The dryers were installed with no outside venting in a large laboratory fairly open for air circulation. The indoor drying racks had collapsible frames with wood bars. For outdoor drying, umbrella- type racks with plastic lines were used; swatches of fabrics were hung with clothespins. One rack was completely unprotected; the other covered with a shelter that provided shade during all seasons. The drying periods extended through- out the entire year. Although some drying days were not sunny, no samples were placed outside if there was precipitation. Outdoor racks were located approximately 1,000 feet from a coal-burning heating plant, which was provided with a precipitator for filter- ing the smoke. Similar conditions might exist in home drying yards. EXPERIMENTAL PROCEDURES Selecting and Preparing Fabrics (or Drying Fabrics selected for the study were of types commonly laundered in the home — sheetings, towelings, and clothing fabrics. They were ob- tained from manufacturers and local merchants. For each experiment each fabric purchased as yard goods was from the same bolt and sheets and terry towels were of the same brand and quality. A total of 14 white * and 21 dyed fabrics was used in different phases of the study. Fibers in the white samples were cotton, linen, nylon, ace- tate, and viscose rayon. Most of the dyed ma- terials were cotton; a few were acetate-viscose rayon. Test fabrics were cut into swatches, varying in size from one-half to a yard square, and were marked with consecutive numbers as they were cut. To remove finishes that might affect origi- nal measurements, the samples were hemmed, 2 Poole, Nada D. Use of different combinations OF LAUNDRY APPLIANCES. DrYER AND CONVENTIONAL WASHER FOR WEEKLY FAMILY LAUNDRY. (ThesiS, M. S. Iowa State College, Ames, Iowa.) 1951. ' Dryers for use in the study were obtained in the period 1951-1953. 4 In this publication, white is used to denote fabrics which were purchased as white goods. =0 o n 1 1 h t4 1 .. 1 tD a> mufac urer's ting of lothes pacity -^ ... e . +3 ^ -u O t, p & S t, t- 3; 0 to ti. 33 0 g^g„g C^ -« 00 00 00 -« -« 3 •"• 3 —' 00 ^ rt rt o o f^ f^ 73 g 1 (N (N (N '^ O ^^ ^ 0) " 1 ^< ^^ ^^ ^^ lO 10 10 a ^ 1 cc fti ; 1 -o "O -a ' ' 1 a> CD oj ' ' 1 ^ +J +5 1 1 a 1 ^ ^ 1^ _' _J 1 t-. 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J u t.1 oj i3 -IJ .3 ,43+3 -f3 -i.3 t-< 3 Ph o a 0 al i^ '^ m W w 0 W H 0 0 0 0) to S w o 0 Q H P^ 0 a hH ^ o a t i 41 ZCi then washed through a cycle of an automatic washer and dried on racks in the laboratory. The samples were randomized to make up the loads to be dried in different ways; loads were randomized to determine the sequence of drying methods from day to day. In some of the tests, samples were prepared for drying by soaking in clear water; in others they were washed in a detergent solution and rinsed. Excess water was removed by spinning the load in an automatic washer; in all tests except those in which moisture content was a variable, mois- ture was controlled to within 85 ±2 percent of the dry weight of the load by the length of the spin. The dry weight of the load was established by taking the mean of several preliminary daily weighings of each load after the dry swatches had hung on a rack in the laboratory overnight. The wet samples were tied in a plastic square for weighing, after which they were dried in the specified manner. The tumbler dryers were placed on platforms equipped with hydraulic jacks which permitted raising and lowering the dryers onto a scale rolled under the platform. This device made it possible to weigh them intermittently as drying progressed to determine the dry point of a load while it was in the dryer. This procedure was used in the early stages of experimentation. After a number of dryings, a length of time for drying the load was established for each dryer and intermittent weighings were discontinued. As the number of dryings increased, all loads became lighter. Dry weights were therefore adjusted from time to time to compensate for this loss in weight. Loads dried on outside lines and on inside racks were allowed to hang untU they were dry to the touch. After being dried, the swatches were bundled into the plastic square without being folded, weighed for determination of the exact amount of moisture removed, and placed in a cabinet drawer until the next drying. Evaluation Criteria As a basis for evaluating the effects of the different drying methods on fabrics, data were X obtained on changes that occurred in fabric properties during drying. Part or all of the following measurements were made on the test fabrics before the first test dry- ing and at intervals as reported. Color. — A Hunter Color and Color-Difference Meter was used to measiu-e the color. The Hunter instrument measured R^, diffuse reflect- ance; a, redness in the plus direction and greenness in the minus; and b, yellowness in the plus direction and blueness in the minus. The overall color change, AE, in the NBS unit (a measure of an average, minimum perceptually important color difference) was calculated from the change in Ra, a, and b by the formula supplied with the instru- ment where: AE^^|AII+Aa-\-Ab'^, AL=AR(1 X factor to determine lightness change At least three readings were made per sample. Values of a for the white fabrics are not reported, since they contribute so small a part to the total color. The printed materials, where not allover prmts, were placed on the instrument in such a manner that chiefly the background color was measured. Chemical degradation. — Viscosity of nylon fabrics was measured in an m-cresol solution by a method similar to that of Boulton and Jackson (^, 8). A conditioned weight of nylon equivalent to 0.400 gm. dry weight was dissolved in 10 ml. m-cresol in a 50 ml. glass-stoppered erlenmeyer flask. With continuous shaking, solution was usually complete in 30 minutes. The solution was then transferred to a calibrated Ostwald-Fenske viscom- eter and the viscosity measured at 25° C. Results are expressed in centipoises. Fluidity (reciprocal viscosity) of cotton, linen, acetate-viscose rayon, and viscose rayon fabrics was measured in cuprammonium hydroxide solu- tion according to the specification developed by the American Society for Testing Materials — ASTM Designation: D 539-53 (i)— with the following changes: 80-mesb copper gauze was used instead of powdered copper in making up the solution and samples were dissolved in mixing vials similar to those used by Mease (5) and then transferred to the viscometers for measurement. Bursting strength.— Bursting strength was meas- ured in accordance with procedures outlined in the ASTM Designation: D 231-46 (1). Instead of cutting samples of specified size, measurements were made within the swatch and the resulting holes mended by machine. Initial bursting strength values are the means of measurements of only those swatches included in each experiment. Dimensional change. — Dimensional change was determined from the average of three 8-uich dis- tances marked in both warp and filling directions on each sample. The effects of the different drying methods on the dimensions of the fabric are reported only for the warpwise direction. Changes in filling measurements ^yere, in general, too small to serve as evaluation criteria. Visual judgments. — Discoloration of white fab- rics was determined visually by a judging panel. Before being judged, the samples were wet and rack-dried to eliminate differences in texture due to drying methods. Samples of each fabric were presented for judging according to a randomized pattern, fom* at a time (one of a fabric from each drying method) under daylight controlled to give a good light without glare. Intensitj^ of the light was meas- lu-ed with a Weston foot-candle meter. The four samples were displayed on a white background within an area in which differences in light intensity were no more than 10 percent. Judges arranged the samples (keeping them flat on the surface and within prescribed limits) , ranked from most to least desirable, then scored them on an acceptability scale ranging from 1, very poor, not acceptable, to 5, very good, would not attempt to improve. Visible wear. — ^Any visible wear due to drying methods was observed by the laboratory staff in the experiment in which samples were wet by soaking. Measurement of Temperature Two types of temperatm'e measiu-ements were made — of air and of fabrics. Thermocouple junc- tions located in the exhaust air at the lint trap and inside the drum about 3 inches from the center of the door, protected from the tumbling load by a wire guard, measin-ed the air temperatures. A potentiometer recorded these temperatures during the drying period. From this record the maxi- mima temperature reached in the air at each loca- tion was obtained. Fabric strips marked with temperature-indicatmg crayons were attached to pieces of the load to indicate the temperatures reached by the fabric. Cra3^ons used were designed to melt at intervals of 25 degrees. Analysis of Data Analysis of variance was used to determine differences among the data collected. Where this analysis showed significant differences, Duncan's Multiple Significance Test Method was applied to arrayed means to determine where the differences occurred. In the discussion where significant or nonsignificant differences are noted, all statements refer to the 5-percent level of probability. It is possible in some instances where statistical sig- nificances exist, that practical differences may not be present. EFFECT OF DRYING ON FABRICS White Fabrics The 14 white fabrics used in the study included 8 cottons — broadcloth, muslin, dress percale, sheeting percale, denim, buck, terry, and jersey. The other 6 were dress-weight and towel linen, nylon crepe and tricot, acetate-viscose rayon crepe, and viscose rayon crepe. In the first phase of the study the fabrics were wet for drying by soaking them in clear water. In a second series of experiments they were washed in a detergent solution between dryings. Fabrics Soaked Between Dryings All of the white fabrics were used in tests in which samples were prepared for drying by soaking only. Each was dried in the following 10 ways: On outdoor lines (60 out of 100 dryings were on sunny daj^s, September tlirough March), on racks indoors, in an electrically heated cabinet, in an electric nonperforated-drum tumbler dryer with single thermostat setting, and in a gas and an electric perforated-drum tumbler operated at each of three thermostat settings. An 8-pound load, including 2 swatches of each fabric, was prepared for drying by each method. Each load was soaked for 3 minutes in warm water (approximately 100° F.) ; then excess water was removed and the samples were weighed according to the general procedures previously described (p. 7). After the fabrics had been dried 50 times by the different methods, measurements were made to determine changes from the original in color, dimensions, and bursting strength. After 100 dryings, measurements of chemical degradation were also made. Where visible wear was noted, it was recorded. Color: — Changes in reflectance, Ra, are shown in table 2. 8 U3 a . CI) > 1 1 rn fl (P o 0) O o a a o >-> 01 < +s 03 o a O) Q 41 .a 03 0) U O SI '^ to 00 2. 3 o3 -P o o P5 o 00 CO 00 -*,-! 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The experiment was conducted from January to August of one year. The following dyed fabrics were selected for the study: Cotton broadcloth — coral, light blue, and green chambray — green and yellow percale prints — predominating colors, pur- ple, red, blue, and green plisse prints — pink and blue backgrounds sheeting — pink and blue terry towels — yellow, rose, light blue, green, and pink Acetate-viscose rayon crepe — medium blue, rose, and violet ASTM classifications by a launderometer and a fadeometer and manufacturers' information are given in table 8. The fadeometer did not predict the performance of the fabrics in the drying methods studied. Terry was pm-chased as towels and sheeting as sheets; the other fabrics were purchased by the yard from one bolt. All but the towels were cut into swatches of approximately 18 by 36 inches. To remove excess dye and sizing, fabrics were sorted and washed separately according to color. Areas to be measured for dimensional change or for color readings were marked with ink or with stitching, and the fabrics were again washed to remove soil of handling. Color readings were made; the samples were then conditioned in an atmosphere of controlled humidity and temper- ature, and dimensional and bursting strength measurements were made. Two samples of each fabric and color were randomly assigned to each test load. In preparation for dryings, test loads were washed in an automatic washer for 5 minutes in a 0.05-percent solution of detergent at 120° F. and rinsed twice in water at 100°. Loads were dried in random order, with the exception that those dried outside were hung in the morning so they could be put away by the end of the day. Between dryings unfolded swatches were bundled together and tied into plastic squares, in which they were held until they were used again. In the dryers loads were dried to a predetermined weight. After each of the 6 loads had been dried 50 times, Rj, a, and b were measured with the Himter Color and Color-Difference Meter and compared with the original readings (table 9). Data are arranged in this table by groups of fabrics similarly affected by drying methods. Total color change. — Since 1 NBS unit is con- sidered a perceptually important color change, a difference of less than 1 between the color changes for 2 drying methods would indicate no appre- ciable difference in their effects. For 4 of the 21 fabrics the differences in AE resulting from various drying methods were in general not enough for importance when evaluated by this criterion. For green percale print there was less than 1 unit difference in AE between any 2 methods. No single method of drying blue per- cale print, green broadcloth, and pink sheeting produced an effect as much as 1 unit greater than every other method, although in some instances there was more than 1 unit difference between 1 method and another. In 10 of the remaining 17 fabrics, sun drying brought about a AE perceptually different from that caused by the other 5 methods. These changes were chiefly made up of a loss of the pre- dominant color, accompanied by a large gain in reflectance, except in piu-ple percale print where the reflectance increase was accompanied by an increase in red and in blue (probably as some of the print colors changed), and in yellow chambray where the change was mainly loss of yeUow. In those fabrics most changed by the sun, shade drying or drying in electric dryer I brought about changes next in magnitude. In general, the changes, except those caused by the sun, were not of such magnitude as to set any method apart as being different from the others. In both gas dryers, five fabrics predominantly blue showed more color change than when dried by the other methods. All lost blue and gained reflectance, with substantial increases of green in blue broadcloth. Gas dryer H caused the greatest change in the violet acetate-viscose rayon crepe. Loss of blue from this fabric was greater from the gas dryer than from outside drying, but outside drying caused a greater increase in reflectance. Electric dryer I caused the greatest change in yellow terry, owing chiefly to losses of yeUow and reflectance. The effects observed here in the gas dryers are probably similar to those that prompted a study by the American Association of Textile Chemists and Colorists (6) of the destructive action of home 17 gas-fired dryers on certain dyestuffs. These re- searchers singled out oxides of nitrogen as the likely causative factor and reported that the result was not confined to any group of dyestuffs. Bursting strength and dimensional change. — Bursting-strength measurements showed no differ- ences between methods after 50 dryings. Changes in dimensions were similar to those reported for white fabrics, where tumbling caused the most and hanging the least warp-wise shrinkage. Table 8. — AS TAI classification and manufacturers' inform^ation on 21 dyed fabrics Classification iby— Fabric and color Launderometer (wash fastness) Fadeometer (light fastness) Information from manufacturers SOLID COLOBS Acetate- viscose rayon crepe: Blue Fast to laundering without bleach. Class 4 ... fClass 4 ] Class 5 [Class 4 Class 5 Class 4 Class 6 Class 5 Class 5 Class 5 Class 5 Class 7 Class 4 Class 4 Class 6 Class 6 Class 7 Class 7 Class 6 Class 4 Class 8 Class 6 Rose Disperse dye, with inhibitor; hand-washable. Violet.. ... Cotton broadcloth: Blue ._ _ _ Vat dye. CoraL _._ _ __ _ _ Class 3... ... .. Azoic dye. Green Class 4 _ _ _ _ Vat dye. Cotton chambray, dress weight: Green.. Class 4 .. [Vat dye. Yellow Class 4 Cotton sheeting: Blue Class 4 - ^Vat dye. Pink Class 4 Cotton terry toweling: Blue Class 4 Green _ _ Class 4_. Pink __ __ Class 4 >Vat dye. Rose Class 4 Yellow Class 4 ._ PATTEBNED COLOBS Cotton percale: Blue Class 4 _ _ Resin-bonded pigment^ — blue ground, green. Green . Class 4 • yellow; azoic dye — red. Vat dye — green ground; small white dots. Azoic dye — ^red ground; resin-bonded pig- ment— blue, green, yellow. Azoic dye — purple ground, red; resin-bonded pigment — blue green. Vat dye — blue ground; azoic dj^e — red, pink; resin-bonded pigment — -blue, green. Vat dye — pink ground; azoic dye — scarlet, wine; resin-bonded pigment — blue, char- treuse. Red Class 4 Purple Class 4 Cotton plisse: Blue Class 4 Pink Class 4 1 Wash fastness: Cottons, ASTM Designation: D 435-42, classes 1-4; acetate-viscose rayon, D 436-37 {1). Light fastness: ASTM Designation: D 506-55, classes 1-8 {1). 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G to a . « a -H 0 ID G ,„ -3 T3 2 .^ ' -S 3 1 ■= 0) «H X} 1 . c y^ o ^ « ID a; 3 -i-3 G m 0) D --; --H ^ 1 C (D (U D --; --; qH G 0 fS 0 t— 4 ^ 4J -1-3 _p X! J2 ,„_( "H -S ->J ^ ,12 ,Q 1 03 "rH .H ?^ 0 .2 (U ^ 0) o S S o 1 .H 0 c^ da 1 0) S OJ « G G 0 1 ^ S " a •- '3 1&2|55 +3 'g T) ft :g 'C 5 3 -c -g S S 2 P=^ G G •" 0 to t—i ■^^^ M ^ ^ 1—1 |t^£ S ^ ?§ SrS SjH "O "O G3 G "=> ^ -a „ „ G „ G <: O w W n' -3.5 -5.4 -.7 -1.0 + 3.5 + 3.5 -6. 6« -3.7" -2.7" -3.9 -6.0 -4. 0- -3.4 + 1.1 + 1.2" + 1.8 +.9" +.8" +.6" Change after 100 dryings -1. 8" -1.7" -1. 8" -2. 1 -6. 1 -3.6 -2.4" -3.3" -4.3 -3.6" -3.7" + 6. Ob + 8.8 -5.6 -3. l"b -1.8b -2.8 -3.8 -3.7" -3. 3" + 4. 0" + 6.2" -6.8" -3. Ob -1. 9'> -3.1'' -4.8 -.6 -.7 + 6.2" + 6. 5" -6.6" -3.4" -2.2" -3. 2"i' -5.5 -3.0 -2.6 + 3.7" + 4.6 + 12.2 + 10.2 + 3.4" + 3.7" * Yellowness in plus direction, blueness in minus direc- tion; measured with Hunter Color and Color-Difference Meter. * Yellow-blue change: Toward yellow in plus direction, toward blue in minus direction. Note. — Data for a fabric after 50 or 100 dryings marked with the same superscript were not significantly different at the 5-percent level of probability. 23 Table 12. — Initial and final bursting strength of 11 white fabrics dried in 120- and 240-volt dryers after being washed in a detergent solution Drying condition Cotton Linen Nylon Broad- cloth Denim Huck Jersey Per- cale sheet- ing Terry Dress weight Crash towel- ing Crepe Tricot Ace- tate viscose rayon crepe Initial bursting strength Pounds 115. 3 Pounds 139. 8 Pounds 180.3 Pounds 74. 4 Pounds 157. 2 Pounds 140. 4 Pounds 272.4 Pounds 245.5 Pounds 184.8 Pounds 164. 3 Pounds 93. 6 After 50 dryings D. 240-volt F. 120-volt I. 240-volt, high heat J. 120-volt, high heat 114. 0»b 127. 1» 166. 0- 74. 6« 162. 6» 145. 5» 238. 8- 197. 0» 171. 4»b 150. 7- 118. 2« 126. 9« 158. 6'' 73.3- 158. 0- 150. 4- 238. 9- 197. 6'> 175. 2» 153. 1- 109. 9b 136. 2» 159. 5« 76. 4» 158. 6- 150. 6- 234. 6« 215. 6« 166. 2° 150. 7» 117. 4» 130. 3» 155. 6" 76. 2» 163. 0» 155. 0- 242. 3» 210. 5- 168. 8b"' 149. 4» 69. 0» 72. 1 68. 1« 70. 1» After 100 dryings D. 240-volt F. 120-volt I. 240-volt, high heat. J. 120-volt, high heat. 95.5- 131. 9- 156. 9- 76. 5- 147. 8- 136. 4- 206. 9- 185. 2- 167. 7- 150. 8- 92.9- 124. 6- 134. 8- 69.7 136. 8b 135. 8- 207. 3- 159. 5b 166. 1- 150. 1- 94. 6- 126. 2- 156. 9- 74.7- 145. 0-b 134. 3- 210. 1- 180. 6-b 156.4 147. 0- 96.6- 128. 7- 153. 1- 77.6- 152. 7- 132. 9- 219. 2- 179. 8-b 165. 3- 147. 7- 64. 6- 64. 6- 58.4 64. 2- NoTE. — Data for a fabric after 50 or 100 dryings marked with the same superscript were not significantly different at the 5-percent level of probability. considered unsatisfactory, and from the other 240-volt dryer the nylon tricot and dress linen were unsatisfactory. Time and energy. — The mean time and energy consumption of the 4 dryers for 100 loads were as follows : Energy con- Time sumption Dryer: Hr. Min. Kw.-hr. D (240-v) 1 13 4.81 F (120-v) 2 58 4.85 I (240-v) 0 58 3.68 J (120-v) 2 10 3.87 The low-voltage dryers required more than twice as much time as the higher voltage dryers of like design to dry loads of the same size and moistm-e content. Each 240-volt dryer used approximately the same electrical energy per load as the correspond- ing 120-volt dryer; one pair of like design, however, used approximately 1 kilowatt-hour more than the other pair. 24 Table 13. — Fluidity of selected white cotton fabrics dried 100 times in 120- and 240-volt dryers after being washed in a detergent solution Drying condition Broad- cloth Huck Jersey Percale sheeting D. 240-volt . Rhes 7.7- 6.8b 10. 9 7.6- 6. 5b Rhes 4.8- 4.4- 7.3 4. 9- 4. 4- Rhes 5.8b 5. 5-b 7.9 6.0b 4. 6- Rhes 9. 4- F. 120-volt 9. 5- I. 240-volt, high heat.. J. 120-volt, high heat-. No treatment (original fabric) 13.8 9. 6- 8.6 Note. — Data for a fabric marked with the same super- script were not significantly different at the 5-percent level of probability. Table 14. — Judges^ scores ' of acceptability of appearance of 6 white fabrics dried 100 times in 120- 2JfO-volt dryers after being washed in a detergent solution and Cotton Linen, dress weight Nylon, tricot Acetate- viscose Drying condition Jersey Percale sheeting Terry rayon crepe D. 240-volt --- -- --- 4.5 4.5 4.6 4. 8 4.8 45 4.8 4.8 4.8 4.9 4.8 4.8 4.4 4.5 2.6 3.9 1.5 2.8 3. 1 3.8 1.2 F. 120-volt - _- 1.4 I. 240-volt, high heat _ _ - __ 3. 8 J. 120-volt, high heat _. _. 3. 6 • Scale for scoring: 1. Very poor (not acceptable). 2. Poor (barely acceptable). 3. Fair (could be considerably improved). 4. Good (acceptable, but would like to improve it). 5. Very good (would not attempt to improve it). Data are averages of the scores of 4 judges. Type of Drum Data obtained on electric dryers D and G (medium setting) in the study of the effect of dry- ing method on selected white fabrics were used to compare the performance of perforated- and non- perforated-drum dryers (tables 2, 3, 4, 5, 6). Melting temperatures of the temperature-indicat- ing crayon marks included in the loads showed these dryers to be comparable in operating temperature (table 15). Color. — The nonperforated-drum dryer caused greater loss of reflectance than the perforated in all but 2 (nylon crepe and acetate-viscose rayon crepe) of the 14 fabrics in 50 dryings and in all but 1 (nylon crepe) in 100 dryings. With 50 dryings the nonperforated drum caused significantly more yellowing than the perforated drum in half the fabrics, but with 100 dryings there were significant differences in only 2 fabrics. In one of them the nonperforated and in the other the perforated drum caused more yellowing. These differences were too small to be of practical significance. Chemical degradation. — Drying in the two types of drums resulted in fluidity values that were not significantly different in half the fabrics; in the other half the perforated drum caused more chemical degradation, although the differences were numerically small. Bursting strength. — ^The two types of drums were not significantly different in their effect on bursting strength of any of the fabrics dried 50 times; after 100 dryings differences were signifi- cant for only one fabric, nylon tricot. Dimensional change. — The effects of the two types of drums on dimensions in the warpwise direction were much alike for aU fabrics at both intervals. Table 15. — Maximum temperatures^ at three locations in automatic dryers studied Location Dryer Ex- haust 2 Inside drum 3 Strips on load< D. Electric, 240-volt E. Gas ° F. 172 169 124 131 124 120 111 114 101 131 95 o p 198 232 136 186 147 135 171 159 139 263 165 ° F. 15a 150' F. Electric, 120-volt G. Electric: High heat (=) 175- Medium heat Low heat _ _ _ 15a 125 H. Gas: High heat 2oa Medium heat 175 Low heat. __ __ _. 15a I. Electric, 240-volt, high heat._ _ __ _ «275- J. Electric, 120-volt, high heat- 15a 1 Each figure is the average of at least two replications* 2 Thermocouple junction in lint trap. ' Thermocouple junction inside drum, 3 inches from door. * Temperature-indicating crayon marks on fabric strips- attached to pieces of load. Crayons included for 25° in- tervals from 150° to 275° F. More crayons melted at temperature given than at higher temperatures included. Interpret as approximate rather than absolute. ^ None of the 150° F. marks melted; no lower tempera- ture crayons were on hand. * Highest temperature-indicating crayon mark included in load. 25 Thermostat Setting To compare the effects of high, medium, and low thermostat settings, objective measurement data on dryers G and H in the work on effects of drying methods on selected white fabrics were used (tables 2, 3, 4, 5, 6). Temperatm-es at the three settings at the different locations of measurement are given in table 15. A variation of fabric temperature of about 25 degrees occiu-red between high and medium and between medium and low thermostat settings in both dryers. Color. — Comparison of data for the three ther- mostat settings indicated that there was little difference in their effect on the reflectance of fabrics dried 50 and 100 times in either the gas or electric drj^ers. After 50 dr3angs on high, medium, and low settings in gas and electric dryers, the yellowing effect was significantly different for very few fabrics. Where significant differences occurred, the high setting generally had the greatest effect. Effects of medium and low settings were rarely significantly different. After 100 dryings of the 14 fabrics in the gas dryer, high setting resulted in a yellowing effect which was not significantly different from that caused by medium and/or low settings in 11 fabrics. In the other 3 fabrics the significant difference was too small to be of practical im- portance. In the electric dryer no significant difference in yellowing occurred in 9 of the fabrics dried on high, medium, and low settings, nor was there a consistent order of magnitude of yellowing in the other 5 fabrics. Chemical degradation. — After 100 dryings in the electric and gas dryers differences in the effects of high, medium, and low heats on the fluidity of the 14 fabrics were small, even though they proved to be statistically significant in some cases (table 4). Only the 2 nylon fabrics in the gas dryer showed consistent and substantial enough damage between effects of thermostat settings to be considered a definite trend of increasing damage as the settings were changed from low to high. Bursting strength. — After 50 dryings there was no significant difference between the effects of high, medium, and low heats on bursting strength of 12 fabrics in the gas dryer and 11 in the electric. High heat in the gas dryer weakened nylon tricot more than medium and low heats; medium and high caused more loss of strength in nylon crepe than low. In the electric dryer medium and low heats were not significantly different m this effect on njdon crepe but were more damaging than high. With 100 dryings at each of the three tempera- ture settings, the bursting strengths of 10 fabrics in the gas dryer and 1 1 in the electric were not affected in a significantly different manner. In the other fabrics in which there were differences, the effects of the three temperatures were not in a consistent pattern of magnitude. Dimensional change. — The effects of the tlu-ee temperatures on the warpwise dimensions of fabrics varied slightly from each other. Composition and Weight of Load Many instruction books for the operation of clothes dryers recommend the separation of light and heavy fabrics before they are dried in order to have articles together which require about the same drj^ing time. The performance of clothes dryers with mixed fabric loads and with single fabric loads was investigated to determine the effect on drying time and the electrical energy required. Six dryers were used. Mixed fabric loads of 3 pounds of dry sheets and 3 pounds of dry terry towels were soaked in an automatic washer. Water was extracted until the moisture content was 85 ±2 percent of the dr}^ weight of the load. The loads were dried as they came from the washer. For single-fabric 6-pound loads (dry weight), two wet mLxed loads 'were separated into a terry towel load and a sheet load. Drying time and energy consumption. — The two 6-pound mixed-fabric loads required an average of 82 minutes total drying time compared with 65 minutes for the same quantity in two separate single-fabric loads (table 1 6) . The average drying time was approximately 3 minutes less for one 6- pound mixed load than for two 3-pound single- ' fabric loads. The two 6-pound mixed loads required ap- proximately 0.5 kilowatt-hour more electrical energy for drjdng than did the two 6-pound single-fabric loads. A 6-pound mixed load re- quired 0.17 Idlowatt-hour less for drying than the j two 3-pound single-fabric loads. In table 16 are shown specific times and elec- trical energy required, with quantity of moisture removed from the loads in different dryers. The 26 3 pounds of terry towels retained approximately twice as much moisture as the same weight of sheets, although they were spun together. Hence, both the 3- and 6-pound loads of terry towels required approximately twice as much time to dry as did the 3- and 6-pound loads of sheets. Table 16. — Amount of moisture removed in drying and time and energy required for drying mixed and separate loads of sheets and terry towels ^ Load Dry weight Moisture removed Electrical energy Time Mixed Terry Sheets Terry Sheets Pounds 6 6 6 3 3 Grams 2,310 2,962 1,405 1,483 757 Kilowatt- hours 2.75 3. 35 1.68 1.95 .97 Minutes 41 44 21 31 13 1 Data are means from 6 dryers. Moisture Content of Load In order to note the effect of different moisture contents of a load of household laundry on the time and heat energy required for drying, 8-pound loads of sheets and terry towels were wet to range from 50 to 140 percent of their dry weight, in increments of 15 percent. The time for drying increased, on the average, 5 minutes for each 15-percent increment. The energy for drying- each 15-percent moisture increment averaged approximately 0.4 kilowatt-hour of electricity or 1.7 cubic feet of gas. OPERATING CHARACTERISTICS OF DRYERS Throughout the course of the study, data were obtained on operating characteristics of the dryers under conditions of use. They included the air temperatiu"es provided, temperatures reached by the fabrics, heat energy used in relation to amount of moisture removed from loads, and time required for drying. Temperatures. — The maximum exhaust temper- ature in all dryers was lower than the maximum recorded inside the drum near the door (table 15). Maximum temperatures of fabrics as indicated by temperature-indicating crayon marks on the strips in the load were greater in some dryers and less in others than the temperature of the air near the door. High and low thermostat settings in the electric dryer were 11° F. apart at the exhaust, 51° inside the drum, and 50° as indicated by the crayon marks. In the gas dryer the range in the exhaust was 10°, inside the drum 32°, and with the indicating crayon marks, 50°. Further research is needed on methods of measurement to yield accurate determinations of temperatures reached by the fabrics and within the dryers combined with the duration of those temperatures. Drying time. — Comparison of the data for time requirements for drying approximately equal loads at different thermostat settings shows that both of the dryers studied required less time on the high than on the medium setting (table 17). Table 17. — Summary of energy and time require- ments for drying 8-pound loads of white fabrics by different methods Energy Time for Drying condition Total B. t. u. per 1,000 grams of moisture removed dry- ing 1 Hours A. Outside line, unpro- tected from sun. 3. 8 B. Inside rack 5. 7 C. Electric cabinet 5.9 kw.-hr 6, 189 4.8 D. Electric tumbler, 4.8 kw.-hr 5,010 L2 240-volt. E. Gas tumbler 16.8 cu. ft 5,348 1.3 F. Electric tumbler, 4.8 cu. ft 5, 103 3.0 120-volt. G. Electric tumbler: High heat 4.5 kw.-hr 4,684 1.0 Medium heat 4.4 kw.-hr 4,635 1. 1 Low heat 4.5 kw.-hr 4,660 1.2 H. Gas tumbler: High heat 12.9 cu. ft 4,341 1.0 Medium heat 12.3 cu. ft 4,203 1. 1 Low heat 11. 9 cu. ft 4,070 1.6 I. Electric tumbler, 3.7 kw.-hr 3,901 LO 240-volt: High heat. J. Electric tumbler, 3.9 kw.-hr 4,103 2.2 120-volt: High heat. ' Figures given are means. For A the range was from 1.8 to 7.2 hours; for B, from 3.7 to 7.6 hours; for C, from 4.5 to 5.0 hours. For tumbler dryers, the range was within a few minutes of the mean. 27 For one dryer, time was considerably greater on the low than on the medium setting; for the other, operation on either setting made Httle difference in drying time. As has been stated previously (page 24), the dryers operated on 120 volts required more than twice as much time to dry a load as their dupli- cates operated on 240 volts. Energy requirements. — Operating data are re- ported in table 17. With the two dryers operated on high, medium, and low thermostat settings, the setting made little difference in the efficiency of operation, expressed in British thermal units of heat required per 1,000 grams of moisture removed. Data for the 120- and 240-volt dryers in each of the two pairs studied showed little difference in efficiency due to voltage. One pair of dryers (I-J) had greater efficiency than the other pair (D-F), which indicated that in this instance the design of dryers had more effect on efficiency than the voltage. TIME USED BY OPERATOR Since the operator's time is a factor to be con- sidered in an evaluation of drj/ing methods, records were made of the time required for placing wet loads on lines or racks and in tumbler dryers and for removing the loads when dried. The times noted did not include time for folding. The tumbler dryer, in comparison with the inside rack and cabinet dryer, saved 10.5 minutes of the operator's time in placing and removing a load; in comparison with the outside line, it saved 12.6 minutes. No time was recorded for covering distances between washer and line or dryer; this, of course, would vary for different homes. Neither was any account made of expend- iture of physical energy in moving the clothes to the place of drying. Cleaning lint traps in dryers required a httle more than half a minute; where emptying water and removing lint were both involved, the time was increased approximately 3 times. LITERATURE CITED (1) American Society for Testing Materials, Committee D-13. 1956. a. s. t. m. standards on textile mate- RIALS (with RELATED INFORMATION). 766 pp., illus. (2) BouLTON, J., and Jackson, D. L. C. 1943. THE FLUIDITY OF NYLON SOLUTIONS IN M-CRESOL: MEASUREMENT OF CHEMICAL DAMAGE IN NYLON TEXTILES. SoC. DyerS and Colourists Jour. 59: 21-26. (3) and Jackson, D. L. C. 1945. THE FLUIDITY OF NYLON SOLUTIONS IN M-CRESOL. PART II. Soc. Dyers and Colourists Jour. 61: 40-47. (4) Leavitt, H. J. 1954. DIMENSIONAL STABILITY OF VISCOSE RAYON. Amer. Dyestufif Rptr. 43: 472-477, illus. (5) Mease, R. T. 1941. an improvement in the method fob dissolving cellulose in cuprammo- nium solution for fluidity measure- MENTS. [U. S.] Natl. Bur. Standards, Jour. Res. 27: 511-553, illus. (6) Midwest Section, American Association of Tex- tile Chemists and Colorists. 1956. a study of the destructive action of home gas-fired dryers on certain DYESTUFFS. Amer. DyestufI Rptr. 45: 471. (7) Weaver, E. K., and Thomas, M. 1953. AUTOMATIC DRYING VERSUS OUT-OF-DOOR DRYING OF CLOTHES. Ohio Agr. Expt. Sta. Res. Bui. 734, 36 pp. 28 U. S. GOVERNUEHT PRINTING OFFICE: l9Sa ^