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Historical Sketch Of The Textiles
Mechanical Devices For Preparation Of Textiles
Geography Of The Cotton Trade
Prices Of Cotton Goods
Classes Of Wool
Production Of Wool
Manufacture Of Wool
Geography Of Wool Production
Mohair, Its Nature And Uses
Raw Silk Porduction
Imitations Of Silk
Construction, Color, And Finish Of Cloth
Dyeing And Printing
Care Of Textiles
( Originally Published Early 1900's )
Reasons for textile tests.-Each of the commonly used textile materials has its peculiar characteristics. Each varies from the others in length, strength, diameter, elasticity, crimpiness, luster, and color-elementary qualities which determine a special result in the fabric made from the particular fiber. Hence fabrics made from the different textiles differ in strength, elasticity, luster, color, and feeling, even when manufactured by precisely similar qualities. Each textile must be carefully selected with a view to its particular purpose. Everyone, therefore, who has anything to do with the selecting or with the purchasing and sale of textiles needs to know thoroughly these fundamental qualities of the different textiles.
But not only are there these original differences in the various textiles; there are even greater differences in the qualities of fabrics due to the processes of weaving and finishing. Men continually devise new and more complicated methods of constructing and finishing the goods. The quality of the cotton fiber used may be generally the same, yet very great differences may be found in even such staple goods as cotton sheetings. "All wool and a yard wide" may mean much or little as to textile quality, according to the methods of manufacture. Silk cloths have differences as great as there are between summer and winter. Pure linen may be of great value; it may, too, be trash. The one, therefore, who handles textiles needs to know not only the elementary qualities of the textile fibers, but also enough about the processes of manufacture to determine the qualities that may be expected from each.
Finally, the one who handles textile goods needs a special knowledge of the subject in order to determine whether he gets what he pays for. The great differences in value among the textiles and their products have led to a great deal of imitation, especially by way of so manipulating the cheaper textiles as to make them look like the more expensive goods, or again by mixing higher priced with cheaper textiles, sometimes with the purpose of procuring certain very desirable qualities, at other times to produce goods with only the appearance of the higher priced textile at a cost more nearly that of the cheaper. Unscrupulous manufacturers and dealers have often been able to sell these imitations and adulterated goods at prices far above their intrinsic value simply because their customers did not know how to estimate values properly.
The buyer of textiles, therefore, needs to know textiles and textile tests in order to know positively what he is getting. A cheap textile is just as legitimate as a high priced one provided the purchaser knows what it is and pays only its value. The value of a textile lies in the service that it will perform, whether that be for wear, for appearance, or for style. Waste occurs whenever more is paid for a textile than it is worth as compared with other textiles in the market. Waste occurs again whenever a textile is put to a use for which it has no desirable qualities and for which it was never intended. Buying textiles for the service they will render demands that the purchaser should know textile values and the means or tests of determining those values.
Those who sell textile goods need this knowledge in even higher degree than consumers since they are usually called upon to handle a greater variety of textiles than any one consumer. As retailers come to see clearly that their function is to supply what will satisfy, instead of merely to dispose of their stock at a profitable figure, they will increasingly recognize the need for special textile knowledge on the part of salespeople and others who serve customers. A salesman's word upon his goods should be authoritative; his service should consist in supplying each customer with what will give the most satisfaction for the money.
Necessity for simple tests.-Knowledge of textiles and textile tests are then all-important for the store buyer, the salesman, and the consumer. For practical purposes the tests need to be both reliable and simple. The methods of the laboratory will hardly do for the average store or home. There is neither time nor equipment for elaborate chemical or microscopical examinations. The tests must require little time, labor, expense, or equipment. The results must be made as evident as possible. Something, therefore, must doubtless be sacrificed in the way of accuracy, but this may be atoned for by the common sense and experience of the one making the test. An experienced eye and hand will go far in helping to determine textile qualities, especially when checked by a few simple chemical or other scientific tests.
THE KINDS OF TESTS TO BE MADE
The following are the classes of necessary textile tests that may be applied readily in any retail store or home, and with very slight expense of time or money:
1. To determine the quantity, the length and width, the thickness and weight.
2. To determine the strength, firmness, flexibility, and durability.
3. To determine fastness of color and permanency of finish.
4. To determine the kind of material used in the construction of the fabric.
5. To determine the presence and quality of any adulterations used in the fabrics.
Length and width.-It is to be presumed that all who buy textiles will give the needed attention to the facts of measurement. The matter of length is simple, but probably not enough attention has been given to width properly to recognize qualities of the various widths into which fabrics are made up. Those who make up men's and women's clothing have in some cases made careful investigations of the possibilities of cutting up the various widths of suitings. According to some large manufacturers of ladies' garments, cloth made in fifty-four-inch widths cuts up to the best advantage; that is, leaves the least waste, with the present styles. Not enough study has yet been given to this point to assure an authoritative statement covering the general textile uses. It is clear, however, that the width of a cloth is a matter to be considered by all who have to cut it up. A consideration of width in relation to price is another important matter. This calls for no more knowledge than an application of simple arithmetic. For example, which is the more economical to buy (assuming that both widths cut up with about equal amounts of waste), twenty-seveninch cloth at sixty cents or thirty-six-inch cloth at seventyfive cents a yard? The twenty-seven-inch cloth will cost (60c divide 7/36 or 3/4 eighty cents a square yard, or five cents more a yard than the thirty-six-inch cloth, which costs seventy-five cents a square yard.
Which will cost the more, eighteen-inch fabric at $1.30 a yard, or twenty-seven-inch fabric at $2.10 a yard? Reducing both to denominations of square yards, we find the first costing ($1.30 divide 18/36 or 1/2) $2.6o a square yard, and the second costing ($2.10 divide 27/36 or 3/4) $2.80 a square yard. The narrower fabric is, therefore, twenty cents cheaper for each square yard than the wider. These two illustrations will probably suffice to show what care the buyer of textiles must exercise.
Weight.-The weight of the fabric, especially when ;ree from adulterations or weighting materials, is a fair guide to the value of the fabric, other things being equal. Woolen goods, blankets, suitings, and dress goods should be weighed on scales, and should be sold by weight, after the construction, style, and quality of the textiles have been determined. The mere sense of touch is not accurate enough. Large consumers of such goods almost invariably have the goods weighed, and base their purchases upon standard weights for each yard of goods. Other goods such as silks, cottons, and linens could also be weighed with profit were it not for the prevalence of weighting substances in such fabrics. Simply weighing a piece of silk gives no idea as to the amount of pure silk in its construction. It would show the amount of silk if it were pure, but cannot reveal ' possible adulterations. Other tests have to be employed for such goods.
Durability, a relative term.-A universal requirement of all textile fabrics is a certain amount of durability, or ability to withstand wear. This quality may vary greatly according to the use to which the goods are to be put. Millinery trimming fabrics are not used so roughly as dress goods; hence, they need not be so strong as dress goods. Considering their purposes, they may be equally durable, since they may both last equally long in use. Cloth intended for men's wear is usually made stronger than that for women's wear, for the obvious reason that in use men's goods are often subjected to greater wear and strain than are women's goods.
Durability is often sacrificed to secure certain fashionable or artistic effects, thus causing some higher priced goods to be less strong than cheaper goods. The higher qualities represented by higher prices to the yard are by no means always qualities of greater durability. But, in any case, whoever has anything to do with textiles is likely to desire a certain degree of strength and durability as a matter of course. As stated before, buying or selling cloth is essentially nothing more nor less than buying or selling the service that cloth performs. This service may be either a fashionable or pleasing appearance in use, or a durability in wear. Sometimes these two factors work together, sometimes they are in opposition. In some cases it may be impossible to preserve a reasonable amount of durability while producing a fabric entirely desirable in appearance. It has been most difficult to do this in many of the women's dress goods where extreme sheerness, filminess, or laciness was considered essential to good looks. In some other cases, fashion swings to the other extreme, calling for appearance and strength far beyond the actual needs of the garment; wherefore many clothes go out of fashion long before they wear out. Good value, so far as durability is concerned, is laid away in chests, hung up in closets or clothes presses, or sold to second-hand dealers and ragmen, to be reduced to shoddy, paper pulp, or what not. With fashion and its effects we are not here concerned. We shall simply give our attention to some of the causes or conditions of durability and the methods or tests applicable to determine durability and strength.
Quality of fiber.-It is clear that the strength of the fabric depends upon a great number of things. Primarily the quality of the fiber used in making the yarns must be considered. No matter what the textile may be, short, damaged, weakened fibers do not make as strong yarns, and therefore not as strong fabrics, as long, healthy, fresh fibers. Something of the quality and of the fiber may be learned by simply unraveling a few yarns drawn from the fabric and examining each little fiber carefully and testing its strength by pulling it to pieces. With experience in this, a person may become a very good judge of the fiber quality.
Quality of yarns.-Cloths made from two-ply or three-ply yarns, that is, yarns which have been made by twisting two or more simple yarns together, are, as a rule, more durable than single yarns. Cloths made from combed yarns, such as worsteds, are stronger and more durable, pound for pound, than cloths made from carded yarns, such as woolens. The combing principle is applied to cottons as well as wools ; hence, this point needs consideration in dealing with cotton goods, especially in hosiery and knit goods, in which lines combed cottons are mostly used now.
The difference between carded and combed yarns may be determined by simply untwisting the yarn and noting the arrangment of the fibers in the yarn. Worsted yarns are made from fibers that have been combed and the fibers therefore all lie parallel. Woolens are made from carded wool yarns. In this class the fiber runs in every possible direction and with absolutely no order of arrangement.
The same arrangement of fibers in yarns is also to be noted in cottons. The highest grade silks are made from thrown silk yarn threads, which in turn are made from several strands of cocoon silk, all lying parallel. All but the poorest waste silks are combed and prepared much the same as worsted yarn, and hence show the parallel arrangement, but differ from thrown silk in the fact that the fibers are short. The poorest grades of silk are carded and spun much like carded wool. The arrangement can be traced easily in any of these cases by simply untwisting a strand and noting how the fibers lie.
Nature of weave.-To determine the character of weave requires some knowledge of the general classes of weaves. The cloth to be tested is simply carefully examined to see how the threads are interlaced. As an aid to this process it is best, whenever possible, to unravel a few threads in both directions of the cloth. A magnifying glass can be used to good advantage, especially a little glass known as a "linen tester." These magnifying glasses are made in sizes permitting one to study the cloth surface in spaces from a quarter inch square up to an inch square. They cost little and very materially aid the eye. Every textile goods salesman should own one.
The "counts."-The number of threads or yarns running each way-that is, the number of "counts"-may be determined by marking off an inch square on the cloth and actually counting the threads running each way within the square. Using a pin or other sharp-pointed instrument in separating the fibers one by one assists considerably in the counting. A "linen tester" magnifier can be of great assistance in determining the count since the space magnified is either a quarter, half, or full inch, so that no time need be lost in marking off an inch on the cloth with a ruler or tape. If a few yarns are unraveled under the glass, their sizes can be noted, and also how hard they are twisted and whether they are single or two-ply; with care, too, the length of fibers used in making the yarns can be determined.
The higher the number of "counts" per square inch, the yarn remaining the same in size and quality, the more durable the cloth. Cotton sheetings may run from thirtyfive to seventy counts to the inch in either direction, and other cloths vary in the same manner. The counts are not usually the same for both ways in the cloth.
As illustrations rather than as standards, the following figures are given showing the counts as found in certain samples of cloth:
Long cloth 70 x 64
Nainsook 83 x 76
Lawn 77 x 76
Persian lawn 79 x 82
Fine shirting 93 x 88
Percale 66 x 58
Madras shirtings68 x 48
Calico 61 x46
Fine gingham 86 x 84
Organdy 67 x 64
Marquisette 51 x 34
Pique 135 x 83
Table damask 66 x 57
Curtain scrim 24 x:24
Poplin 103 x 46
Closeness of weave.-Holding the cloth up to the light and looking through it will be of assistance in determining whether the weave is close or loose, whether any filling or weighting materials such as starch have been added, and whether the yarns are uniform or not.
Filminess.-Another test, used to determine the firmness of the weave, is to scrape the thumbnail diagonally across the weave. If the construction is loose, there will be a pathway of loosened threads made across the cloth after the thumbnail. This test can be applied very well to cottons, linens, and silks.
Elasticity.-The elasticity of the fabric, a quality much desired for certain uses and one which usually adds to durability, may be determined by crumpling a small portion of the cloth in the hand and then noting its behavior when the pressure is removed. If it springs back into its former shape quickly, its degree of elasticity is very high. This is a characteristic that may best be seen in good grades of all wool fabrics. But the test may also be applied to other textiles in the same manner.
Weighting.-Rubbing between the fingers white goods that are suspected of being weighted with starches, China clay, or other heavy materials, will often reveal the weighting substances in the form of dust. When tearing causes a dust to fly, this may be taken as a sign of heavy weighting.
Strength.-The easiest method of determining the relative strength of fabrics is by comparing the amounts of strength necessary to pull them apart with the hands. Care should be exercised to make the conditions of the tests as nearly equal as possible. About the same width of cloth should be grouped in the thumbs and fingers preparatory to the pull in each case and the pull should be exerted in the same direction for each fabric, either in the direction of the warp threads or of the weft or filling. In fact, the best way to test the strength of a fabric is by comparing the pull necessary to tear the fabric both in the direction of the warp and of the filling. In some cases it may be found that a cloth is much weaker in one of these directions than the other. The cloth should be judged by its weakest points rather than its strongest, for in use it will wear out or go to pieces at its weakest point first. Samuel S. Dale, editor of the Textile World Record and one of America's greatest textile experts, says that the proper way to apply this test is to grasp the cloth in both hands about an inch apart and then to pull steadily, rather than to draw the cloth tight in the hands and then to place the thumbs together and press them into the cloth. "By the former method there is a direct strain on the hands, enabling the resistance offered by the cloth to be fairly judged. By the second method there is a powerful leverage by means of the contact of the two thumbs, producing a high tension of the fabric with comparatively slight effort."
QUALITY OF TESTS.-It should be remembered that such tests as those given above are only relative, and the results must be considered only as approximations. For example, to determine the breaking strength of a fabric by pulling it to pieces in the hands is far from an accurate test. Our judgment as to the amount of pull that we exert is bound to vary according to our physical condition. What may seem like a comparatively easy pull at one time may seem like a hard pull at another. Large users of textiles, institutions which cannot afford to make any mistakes on such points as these, measure the breaking strength by taking strips of equal widths and testing them in machines that register every pound and ounce required to pull the cloth apart. Such instruments are called dynamometers and work on the same principle as a spring balance. Firms using them usually have certain standards which all cloth must reach before being considered acceptable.
Tests for flocks.-Finally, there remain, especially applicable to woolen and worsted goods, tests which deter-, mine whether flock or pulverized wool en`ters into the construction of the fabric, whether the cloth will turn shiny easily, whether the nap will wear well, and whether the cloth will keep its shape.
Flocks or very short wool fibers obtained from shearing the surface of wool or worsted cloths are often worked into woolen cloths in the fulling process. They are nearly always applied to the back of the cloth, sometimes to both sides. When the fulling is well done, these short fibers have penetrated the body of the cloth deeply and do not come out easily: But when imperfectly fulled, or when too much of this kind of material is used, it comes out easily in wearing. Its presence may be determined by brushing the back of the cloth briskly with a good stiff brush. If flocks have been used, a number of short fibers will come out in the brushing.
Tests to determine whether wool will turn shiny.-Many otherwise excellent wool fabrics are objectionable because they easily turn shiny. One can tell to a certain extent in advance whether this objectionable quality will develop or not. The sheen or shiny surface on a worn wool fabric is due to the fact that the loose fibers, fuzz, or nap is pressed down or worn off completely, exposing only the surfaces of fibers lying lengthwise in the yarns of which the fabric is composed. From this it will be clear that worsteds are more likely to wear shiny than woolens. Cloths made from the long, lustrous, straight fibers are far more liable to turn shiny than shorter, softer, and more crinkly wools, there being fewer ends exposed. Fulling or felting tends to prevent this objectionable feature; but fulling also changes the character of such a material as serge. If the loose fibers are simply pressed down they may be raised, removing the shine by steaming, rubbing with a similar material and then pressing carefully. Dark-colored or hard-woven fabrics seem to become shiny more easily than light-colored or soft-woven varieties.
Estimate of durability of nap.-The durability of the nap on such wool goods as kerseys may be estimated by first determining which way the nap lies. This may be done by rubbing the hand over the cloth in various directions. It will be found that in one direction the cloth feels smooth while in the opposite direction the ends of the fibers strike the hand noticeably. Moving the hand in the direction that offers the least resistance is called "with the nap." The opposite direction is said to be "against the nap." By wetting the end of the thumb and rubbing it against the nap, the character of the nap can readily be ascertained. A poor construction that will wear out easily is readily displaced and becomes frowsy looking after but little handling. However, if the nap consists of short, thickly set fibers that offer considerable resistance to rubbing with the wet thumb, the cloth will stand hard wear without the nap becoming rough or loose. A long, loose, wavy nap is never very durable. Heavily napped goods, whether intended for dresses, overcoats, blankets, or what not, should not be expected to wear as well as lighter napped fabrics.
Tests to determine whether cloth will hold its shape or not.-Whether or not a cloth will hold its shape is due entirely to the body of the fabric. Firmly woven goods hold up much better than soft or loosely woven goods. Coupled with firmness should go a high degree of elasticity. Draping qualities may be tested easily by noting how the fabric acts when thrown into loose folds or in a jumbled heap. Draping qualities are dependent primarily upon flexibility.
Fastness of color, a relative term.-Absolute fastness of color is not a possibility in textile manufacture. All that can be done is to produce colorings which will be fast under the ordinary conditions of use; that is, fast in some degree to light, air, washing, soap, rubbing, street wear, perspiration, and so on. In addition to these qualities, manufacturers are often under the necessity of providing for still other features which do not concern us here, such, for example, as fastness to alkalies, acids, heat, and finishing processes, since the cloth must pass through such conditions before reaching the finished stage.
To produce colors that are very fast requires considerably more time, material, and expense than to produce colors not so fast. This is a general rule. Where a less fast color will serve the purpose fully as well in use, it seems unwise to assume the additional cost of producing a very fast color. Military cloths, for example, which are intended for much exposure to sun, air, and rain, need to be dyed with much more attention to fastness than fine silks in delicate shades for evening wear, that is, for use under artificial light. The latter colors might be very fleeting in bright sunlight, but since the fabric is not intended for wear under such conditions, its service is not reduced by using the weaker colors. Fabrics of weak material or loose weave do not need and do not receive the fast colors required by strong, durable fabrics. Curtains and carpets should both be dyed fast to light, but carpets should also be dyed fast to friction and the wear of feet, while curtains should be dyed fast to washing in hot water and soapsuds. Hence, the same coloring substances may by no means serve for both classes of fabrics. Underwear and stockings should be dyed fast to washing, soap, perspiration, and wear. Linings must be dyed fast to friction and perspiration. In the same manner every sort of textile should be dyed with special reference to its use if the best results are to be obtained at the lowest costs. Students applying the following tests should bear these facts in mind.
Fastness to light.-To determine how fast a colored fabric may be to light and air, the samples to be tested should be cut in two and the halves carefully marked for subsequent matching. One-half of each sample should then be laid away under cover from light, while the other half should be hung out in a sunny place for several days. As to standards of fastness, it may be noted that the very strongest, fastest dyes, such as Turkey red, begin to fade between the twenty-fifth and thirtieth days in summer, while indigo blue fades between the twelfth and fifteenth day. Summer light is more powerful than winter light; hence, allowances have to be made for the season of the year. A color that remains fast a month may be termed "fast." If it fades in about two weeks, it may be called "moderately fast." If it fades in less than fourteen days, it is called "fleeting." Allowances are also to be made for the effects of moisture, particularly salt water, in the air. Such moisture makes some colors more fast, while rendering others less so.
Fastness to washing.-Fastness to washing may be determined by actually washing a sample of the fabric thoroughly in hot soapsuds and then comparing it with the same goods still unwashed. In laboratories the usual method is to make up strong hot soapsuds, using pure soap and distilled water, and to boil the colored sample of cloth or yarn in these suds for twenty minutes along with a piece of undyed cloth of the same kind. If the colors are not absolutely fast, they will "run" from the dyed fabric into the undyed and give to this piece of goods a tint. Sometimes the experiment is performed several times over on the same sample to note just how many washings are required to show any perceptible fading or running.
Fastness to friction.-Fastness to friction or rubbing is usually determined by rubbing the colored goods briskly over a clean, white, laundered cotton handkerchief. If the handkerchief is discolored in any way, it shows that the fabric is not fast to friction, and therefore not suitable for hosiery, underwear, lining material, and so on.
Fastness to street wear.-Fastness to street wear includes fastness to light, rain, dust, and friction. Light, washing, and friction tests have already been described. To determine if a fabric is proof against spotting as a result of drops of water or of dust, a sample may be sprinkled with water, preferably water in which a little lime has been added, and then dried before brushing off. Any change in color or luster is carefully noted, since this would indicate unfitness for street wear or other outdoor use.
Fastness to perspiration is best tested by wearing a sample of the fabric next to the skin for a few days. Military cloths are tested for fastness against perspiration by placing small samples in the shoes of the marching soldiers, or by placing them on a horse's back under the saddle. Several days' test in these ways shows conclusively the degree of fastness.
Permanency of finish.-Permanency of finish is determined by the same tests as those used to determine fastness of dyes. The sun, washing, and friction tests especially reveal any weakness in finish. Weighting materials used for cottons usually come out in the wash test, as do the special calender surface finishes.
Tests for kinds of textiles.-Tests for determining the kinds of material used in a piece of fabric consist mainly in recognizing by sight and feeling the easily observed characteristics of the several textiles. Difficulties arise in great numbers, however, when these textiles are combined: To tell linen from cotton, silk from mercerized yarn, natural wool from shoddy, and mulberry silk from artificial silk usually takes more careful analysis than any eye or hand unaided by other tests can yield. Here chemical or microscopic methods are necessary. Some of these tests can be made easily; the mere fact that they are chemical, for example, should in no wise discourage the untechnical salesman or consumer. The process of testing a fabric solely to determine what kinds of fibers it comprises is known in chemistry, and generally in the textile industries, as qualitative analysis.
When the presence of certain textiles has been determined in a fabric, it may often be desirable to investigate yet further in order to determine what proportions of each enter into the total make-up of the fabric. This process is called quantitative analysis. This is much more difficult outside of a laboratory, but one can frequently ascertain approximately the amounts of each substance or fiber used in the fabric.
Difficulties to be encountered.-As already indicated, each of the common textile fibers has a peculiar appearance which anyone can learn to recognize quite easily with experience. This was the chief means of telling wool from cotton and linen from cotton fifty years ago. But in the intervening period there has been tremendous progress in the textile production, much of which has taken the form of so changing the cheaper kinds of textile fibers in appearance that they closely resemble the more costly fibers.
In fact, it is now difficult for even the most experienced to tell by the sense of sight and touch alone the differences between a particular fabric and its imitation.
Use of the microscope.-Under a high-power microscope the essential characteristics of each kind of fiber are, of course, more easily made out than with the naked eye; imitations may likewise be easily made out, for the original characteristics are in no case entirely changed in the processes which textile manufacturers employ in producing the imitations. But a high-power microscope is expensive, and requires some skill in manipulation as well as time for making the proper tests. Hence, its use cannot be described here. Textile students desiring to go into a study of the use of the microscope can find a number of excellent manuals which give in detail instructions in its use and its applications to textile fibers. Despite its cost and the care required in using it, the day is probably not far distant when every well-equipped dry goods house will have as a part of its equipment a textile laboratory, and in this connection the microscope will be a most useful and valuable instrument.
Detection o f adulterations o f wool.-Wool is commonly adulterated or cheapened by the addition of either cotton or shoddy (refuse wool goods reduced to fiber by shredding machines), sometimes of both. It helps somewhat to know how these cheapening substances are introduced into pure, natural wool. Knowing this, one is prepared to look for evidences of the mixing in definite places.
Cotton is often carded or combed into the wool before the spinning. The yarn then becomes a uniform mixture of cotton and wool in the proportions in which they were mixed. The cotton, when worked into the wool in this way, is often difficult to detect by the common tests.
Sometimes cotton threads are twisted in with worsted in the process of drawing before the spinning.
Again, cotton threads of the same color as the wool or worsted threads are introduced in the weaving, either as filling or warp. In some cases, the entire warp is made of cotton yarn and the entire filling is made of wool, or vice versa.
Cotton yarn is sometimes veneered with wool fibers by means of special machines which produce a yarn that outwardly resembles all wool.
Shoddy is mixed with natural wool in about the same manner as cotton, and even cotton and shoddy mixtures are sometimes made, using cotton yarn for warp and shoddy for filling.
Cotton may be distinguished from wool and discovered in the wool mixtures by the following means: Appearance.-Cotton fibers can usually be told from wool fibers by the eye, especially if assisted by a magnifying glass. Cotton fibers are straight and dull in luster, while wool is curly or crinkly and possesses considerable luster or lively appearance. However, some varieties of cotton, like the Peruvian, closely resemble wool fiber of poorer grades; hence, the need for more accurate tests than mere use of the eye.
Fire test.-Cotton is a vegetable fiber, and wool is an animal fiber. Vegetable fibers are all composed mainly of cellulose, an easily burned substance, whereas all animal fibers are composed mainly of nitrogenous materials, which burn with difficulty. Vegetable yarn can be told from ani mal fiber by setting fire to a strand of each. The vegetable fiber will burn quickly, while the animal fiber will burn very slowly and with difficulty. At the same time the burning animal fiber gives off a disagreeable odor that is characteristic of burning hair, feathers, horn, and so on. The odor that comes from burning wool is especially disagreeable because of the fact that besides the nitrogenous materials it also contains sulphur, which gives an additional, strength to the odor. The burning test is a certain means of determining whether a fiber is vegetable or animal. If the test shows that a fiber is vegetable, other methods must be employed to determine what particular vegetable. It is not likely that linen fibers would be mixed with wool; hence, any vegetable fibers detected in woolen yarn or clotli would almost certainly be cotton. Since cotton and wool are frequently spun together in the same thread, the burning cannot be used as an absolute test except for individual fibers.
Boiling-out test.-Burning is a chemical test, though a simple one. There is another chemical test that anyone can apply to determine whether or not wool yarn or cloth contains any cotton or other vegetable fiber, a test that is more valuable than the burning test, since it permits the making of an estimate of the quantity of any cotton introduced. This is known as the "boiling-out test." A solution is first prepared by dissolving one ounce of caustic potash or caustic soda in a pint of water: The water should be heated to make the caustic dissolve more quickly. This amounf may serve for several tests. Boiling a small sample of pure wool in some of this solution entirely dissolves the sample in less than fifteen minutes, but the same amount of boiling would have practically no effect on cotton or linenanother difference in effect due to the fact that vegetable fibers are cellulose, while animal fibers like wool contain nitrogen. Therefore, if a mixture of cotton and wool were to be boiled in the solution for fifteen minutes, all of the wool would be destroyed, while the cotton would remain.
Before this boiling-out test, the sample should be carefully washed, dried, and then weighed. After the test, the residue should once more be weighed; whereupon, by simple arithmetical calculation.
As stated in the case of the burning test, the only distinction made by the test is between the vegetable and animal fibers. Because of our knowledge of the costs of textiles, we feel certain that linen would not be used instead of cotton as the vegetable fiber, and the wool is recognized by its own qualities from any other animal fiber such as mohair or silk, although both of these would, like wool, dissolve in the caustic.
Acid test.-By using a strong solution of sulphuric acid (So per cent) instead of caustic, and by immersing the cotton-mixed wool in this chemical for about twelve hours, and then washing the residue in alcohol, it will be found that the cotton is dissolved instead of the wool, and comparisons can be made by weight in this experiment as well as in the former case.
Detection of shoddy.-Shoddy cannot be distinguished from natural wool by any chemical test, since shoddy is itself wool. It differs from natural wool only in that it has been used before for textile purposes and is in most cases less strong and less elastic than natural wool. It is very difficult to distinguish shoddy from natural wool, but there are certain characteristics which indicate the presence of shoddy, such as very short fibers, fibers of various colors, lack of uniformity in size and general character of the scale structure, ends broken and uneven, scales missing on parts of the fiber. Three characteristics of shoddy that are revealed by the compound microscope cannot be seen by the naked eye:
1. Because of the wear to which most shoddy has already been subjected in some fabric and because of the shredding process which tore the individual fibers apart from the old fabric or yarn, the original scales found on all sheep's wool may be largely missing or broken down on shoddy fibers.
2. For the same reasons, the ends of shoddy fibers may not be so regular as those of natural wool clipped from the sheep's back. Shoddy, under the microscope, presents ends that are broken and torn.
3. Wherever the shoddy came from dyed fabrics it retains some of the coloring matters from the former dye even under the new dye. This makes a difference in the hues visible under the microscope, even in very dark-dyed materials. When this variation in color is to be found, one is usually justified in concluding that shoddy is present.
For the student who has not access to a microscope, there is no adequate test for shoddy. But since the chief evil of shoddy is its lessened durability, the student may fall back upon the more general textile tests for strength and durability given earlier in this book. What is most important is that the fabric purchased shall give adequate service for the money expended. It is even possible that the presence of good grades of shoddy would be preferable to the poorest grades of wool in the fabrics purchased; it all depends upon the uses to which the fabrics are to be put and the prices paid for them.
TESTS FOR DISTINGUISHING COTTON AND LINEN.-Owing to the great difference in cost between cotton and linen, it is only natural that cotton should often be used in place of linen. It is natural, too, that cotton and linen should be mixed for many purposes, and even that cotton should be substituted for linen in deceptive ways. It is not so easy to distinguish cotton from linen as it is to distinguish vegetable fibers from animal fibers. Both cotton and linen are composed almost entirely of the same substance, cellulose. Yet there are generally differences enough, physical and chemical, to allow accurate distinction between the two. Tearing test.-In general, linen is stronger than cotton. It takes more force to tear linen cloths than to tear cotton goods of equal thickness and sizes of yarns; further, the sound of tearing linen is more shrill than that of tearing cotton. The torn edge of linen cloth shows fibers that are decidedly unequal in length, parallel, and glossy. The torn edge of cotton cloth shows short, curly, rather even, luster less fibers projecting. Snapping a linen thread apart leaves the fibers remaining straight and outstretched, whereas breaking a cotton thread quickly causes the latter to curl up.
Weight and feeling.-Linen is nearly a fifth heavier than cotton, bulk for bulk. It has a leathery feeling that is absent in cotton. On the other hand, cotton feels warmer and holds the heat better than linen. It is estimated that cotton is from fifteen per cent to thirty per cent warmer than linen.
Appearance.-In construction, carded cotton yarn is much like carded wool yarn, while linen yarn is like worsted yarn. The glossy linen fibers lie more or less parallel throughout the thread or yarn.
Light test.-On holding linen cloth against light, the threads and the fibers composing the threads appear uneven and streaked. It is not possible to make linen yarn as uniform as cotton yarn; hence, this test may be used as a check on other tests where it is desired to determine the presence of linen threads.
Burning test.-Burning the end of a linen thread leaves the fibers in the same relative position as before with no change except the scorched appearance. Burning a cotton thread causes the fibers to spread out like a tuft:
Oil test.-Linen cloth freed from dressing by washing and boiling absorbs oil much better than cotton does. When, therefore, a cotton-mixed piece of linen goods is dipped in oil, the linen fibers look transparent if held against the light, while the cotton remains more nearly opaque.
Acid test.-Linen stands the action of sulphuric acid better than cotton, and a test can be made based upon this difference. The samples are first carefully washed to remove all dressing, dipped in concentrated sulphuric acid for a minute or two, and then washed in water and dried on blotting or filter paper. All that remains on the blotting paper is linen. The cotton almost immediately dissolves in the acid.
That is to say, linen and cotton - linen = cotton.
Tests for silk and its imitations and adulterations.Silk, the most valuable of all textiles, has more imitations than any other fiber. More processes have been invented to preserve the appearance of genuineness while utilizing cheaper fibers, than in any other textile industry. Silk fabrics are cheapened in at least seven ways:
1. Spun silk is introduced in place of thrown silk.
2. Wild silks, such as tussah, are used in place of mulberry silk.
3. The silk fiber is weighted with tannin and mineral salts.
4. Artificial silk has been produced which in appearance rivals true silk.
5. Cotton and linen are given finishes to resemble silk. Mercerizing is an example.
6. Silk is mixed with wool for fancy effects.
7. Silk is mixed with cotton or other vegetable fibers likewise for fancy effects, or for giving body to what might otherwise be a very flimsy silk fabric.
DETECTION OF SPUN SILK.-Spun silk is often very difficult to distinguish from thrown silk. Of course, the fibers are much shorter, but it is very difficult, if not impossible, to tease out the tiny separate silk fibers from silk yarn. Under the microscope the presence of spun silk can be determined by two facts. First, the fibers of waste silk are usually irregular in form; second, the sericin, or gum, is irregular in waste or spun silk. These facts are accounted for by the fact that the waste silk comes from the parts of the cocoons that do not reel off readily.
DETECTION OF WILD Silk.-When it is desired to determine whether wild silk, such as tussah, yamanai, or senegal, enters into the structure of a silk fabric, one of the best tests is to prepare a solution of chromic acid as follows:
Dissolve chromic acid in cold water until the water will dissolve no more. Add an equal volume of pure water. The result is a semi-saturated or fifty per cent solution of chromic acid. Place the suspected silk sample in this solution and bring it to a boil. True silk, that is, mulberry silk, will dissolve within a minute after boiling begins, while tussah and other wild varieties will remain insoluble for at least three minutes.
DETECTION OF WEIGHTING.-Weighting of silk can usually be detected by the burning test. Separate threads from the warp and the weft are set on fire with a burning match. Pure silk burns very badly and stops burning as soon as the burning match has been removed. Practically no ash is formed (less than one per cent), and the end of the fiber left unburned takes the shape of a little bulb. Weighted fibers, when burned, leave a considerable amount of ash, and the entire thread may keep its shape after being burned. When only the filling or the warp is weighted, applying the flame to a sample of the cloth seems to consume only one set of threads, the unweighted ones, the others keeping their form because of the heavy ash content. To determine just what weighting substances are used is a subject for a more technical treatise than this.
TESTS FOR ARTIFICIAL SILKS.-Artificial silks made from cellulose, cotton, wood pulp, or other vegetable substances can be distinguished from true silk by the fire test. All cellulose silks burn readily and give off no odor; true silk burns badly and gives off the odor of burnt feathers. Artificial silks, as a rule, are not so strong as true silk and not so elastic. When wet, artificial silks now on the market swell and become weak, whereas no such effect takes place in true silk. In a caustic potash solution, artificial silk turns yellow, while true silk remains colorless.
Another chemical test is frequently used to distinguish true silk from the artificial. Dissolve ten parts copper sulphate in one hundred parts water and add five parts glycerine. A white precipitate will form. Add enough caustic potash solution to dissolve this precipitate. To perform the test, immerse the suspected sample in this solution at ordinary room temperature. True silk will dissolve almost at once. Artificial silk will not dissolve.
Detection of cotton.-To distinguish between silk and cotton or other vegetable fiber, apply the same test that was used to distinguish between wool and cotton, namely, boiling for fifteen minutes in a caustic potash solution. The silk dissolves, but the vegetable fiber is in no way affected.
Another method is to prepare a solution of fuchsine, a dyestuff, and then decolorize it by adding caustic potash or caustic soda solution drop by drop until the color disappears. A sample of cloth made up of silk and cotton is immersed in this liquid for half an hour, and then washed carefully. When taken out, the silk, if there is any in the cloth, is red, while the cotton remains colorless.
Detection of mercerized cotton.-Mercerized cotton may be determined as follows: A solution is prepared by dissolving five ounces of potassium iodide in about a pint of water. To this solution add one or two ounces of iodine, and mix with another solution made by dissolving thirty ounces of zinc chloride in twelve ounces of water. The cloth sample should first be soaked in water, immersed in this prepared solution for three minutes, and then rinsed in water. Mercerized cotton will have a deep blue color, while unmercerized cotton will wash out white. The blue of this solution on mercerized cotton will show through quite heavy dyes.
To distinguish mercerized cotton from silk in the same fabric, use the same tests as for ordinary cotton and silk mixtures.
SEPERATION OF SILK AND WOOL.-Silk and wool mixtures may be tested by immersing the fabric sample in a solution of zinc chloride of 1.7 specific gravity. Any druggist can make up this preparation. In this solution silk dissolves, but wool is unaffected.
Another chemical method of separating wool and silk is 1>y boiling the fabric sample in strong hydrochloric acid for fifteen minutes. In that time the silk will have dissolved, while the wool will remain intact.
Use of the magnifying glass.-Silk that is mixed with cotton or wool can often be studied most easily by means of a magnifying glass or linen tester such as has already been described. The true silk fibers can usually be distinguished by sight and the proportion of true silk to adulterant or other component in the mixture fairly approximated.