THE CONSERVATION OF TEXTILES LAUNDRYOWNERS NATIONAL ASSOCIATION DEPARTMENT OF CHEMICAL ENGINEERING THE CONSERVATION OF TEXTILES . . . BY . . . HARVEY GERALD ELLEDGE AND ALICE LUCILLE WAKEFIELD INDUSTRIAL FELLOWS OF The MELLON INSTITUTE o/ INDUSTRIAL RESEARCH OF THE UNIVERSITY OF PITTSBURGH PUBLISHED BY LAUNDRYOWNERS NATIONAL ASSOCIATION LA SALLE, ILLINOIS Extra copies of this Book may be had for $1.00 per copy upon application to W. E. FITCH, Manager of the Laundryowners National Association, Drawer No. 202, La Salle, Illinois COPYRIGHT, 1921, BY LAUNDRYOWNERS NATIONAL ASSOCIATION LA SALLE, ILLINOIS Applications for permission to 'use any of the material in this Book should be addressed to W. E. Fitch, Manager of thelLaundryowners National Association, Drawer Ko. 202, La Salle, Illinois. Mlrdoch-Kerr Press Pittsburgh, Pa. Contents PAGE Preface 7 The Development of the Power Laundry Industry — Textile Work of the Department of Chemical Engineering — Causes of Wear in Fabrics — Attitude of Laundry Industry to Damages — Failure of Curtains — Impartiality of the Department of Chemical Engineering. CHAPTER I. Fibers 13 History of Clothing — Skins — Rushes — Development of Fabrics — Development of Spinning — Cotton — Mercerized Cotton — Schreiner Finish — Linen— Wool — Silk — Artificial Silk and True Silk— Test for Vegetable Fibers— Differen- tiation of Artificial Silk — Test for Animal Fibers — Use of the Microscope — Identification of Fibers by Physical Appear- ances. CHAPTER II. Weaves ^^ Plain — Fancy — Use of "Floats" — Advantages and Disadvan- tages Accruing from Use of Floats — Ideal Fabric — Variations from the Ideal — Loose Spinning — Long Floats — Relation Between Fiber Lengths and Float Lengths — Satin Weave — Short Fibers and Loose Spinning — Pile Fabrics — Weaving Flaws — Use of Poor Materials — Influence of the Finishing Process on Fabrics. CHAPTER III. Mechanical Sources of Damage 82 Snagging — Knives — Razor Blades — Bed Springs — Mice — Poor Tailoring. CHAPTER IV. Colored Garments 90 Types of Dyes — Classification of Dyes — Direct — Acid — Basic — Salt — Mordant — Vat — Sulfur — Aniline. CHAPTER V. Corrosive Materials 98 Claim Adjuster — Settlement of Claims — Identification of Type of Damage — Chemical Tendering — Tendering by Launderer — Tendering by Wearer — Table of Materials Cor- rosive to Fabrics (Table I.)— Table of Corrosives Encountered in Various Professions and Employments (Table II.) — Dis- cussion of Tables — Tendering by Manufacturers. Contents — Cont. CHAPTER VI. PAGE The Treatment of Stains 129 Treatment of Stained Fabrics — Need of Trained Employee for this Work — Equipment — Table of Reagents Used in Stain Removal — Oxalic Acid — Acetic Acid — Hydrochloric Acid — Caustic Soda — Ammonia — Javelle Water — Hydrogen Di- oxide — Potassium Permanganate — Sodium Perborate — Sodium Bisulfite — Oleic Acid — Sodium Thiosulfate — Potas- sium Cyanide — Removal of Stains (following L N. A. Pro- cedure Chart, See insert, page 135). CHAPTER VII. The Conservation of Fabrics 142 Length of Life of Fabrics — Hotel Fabrics — Collars — Mechani- cal Effect of Power Machinery — Effect of Standard Wash- room Reagents — the Model Laundry of the American Insti- tute of Laundering — Work of the Salvage Branch of the U. S. Army — Agencies of Responsibility — Retail Merchant — Dyes — Styles — Education of the Public — Abuse of Fabrics by the User — Responsiblity of the Laundry. CHAPTER VIII. Pure Fabric Legislation and the Department of Chemical Engineering, J. Clair Stone 153 The Creation of the Committee on Legislation for the Correct Labeling of Fabrics — Purposes of the Committee — Protec- tive Legislation — The Interest of the Laundry Industry in this Endeavor — Educational Responsibilities of the Com- mittee — The Study of Textile Conservation — 1917 National Textile Conference — Co-operation of Department of Chemical Engineering with the Textile Committee — The Laundr>'- owner's Knowledge of Textiles — Present Activities of the Committee on Legislation for the Correct Labeling of Fab- rics — Assistance Required of the Individual Laundryowners. Foreword THE chapters in the succeeding pages of this book present the results of five years of painstaking re- search into a subject that is of the keenest interest to laundryowners. The authors of this book have not only handled their subject from an analytical and scientific standpoint, but they have succeeded in putting it together in a truly readable and interesting literary style. The subject "The Conservation of Textiles" is one with which every laundryowner should be familiar. Our knowledge of textiles has been more of an intuitional nature than of one of positive understanding of their origin, compositiop and peculiarities. A positive and sympathetic understanding of the goods we are called upon to renovate is of the greatest importance to ourselves and to the public. We all are or should be deeply concerned with the "conservation of textiles." Our reputations as launderers are at stake — not only that but the reputation and ad- vancement of our industry are greatly influenced by the degree of accuracy with which we classify the goods we are to launder, and by the degree of accuracy with which we prescribe the treatment they are to receive. The Department of Chemical Engineering, the Director and Associate Director of which Department are the authors of this treatise on textiles, has already given to the members of this Association its Standard Formulas for Washroom Practice. It is most fitting now that we should be told of the nature of the goods to which these formulas are to be applied. In fact, it seems that many of us would have understood the formulas better if we had studied the "conservation of textiles" first. Science is not something to be afraid of or ridiculed or classed as "high-brow stuff." It is nothing more or less than "organized knowledge and classified common sense." Through its use and application to social, in- dustrial and agricultural problems, our greatest progress as a nation is being brought about. And so, then, let us take this little book at even more than its face value. It will help us to know more about the goods we are handling. It will familiarize us with certain practices on the part of certain textile manu- facturers, which practices are detrimental to the interests of the public and to our interests and cause many of the claims that are presented to us for payment through failure of some of these goods. Let us learn how to use this book intelligently in the adjustment of claims. Let us read it thoroughly and preserve it carefully, remembering that there is no similar book in the world, and that, while it is not a large book, its preparation represents extensive study on the part of its authors; and last, but not least, let us remember that the book comes to you as an enduring testimonial to the value of organized effort through our membership in the Laundryowners National Association. W. E. Fitch. La Salle, Illinois. Preface THE development of the power laundry industry has been, until comparatively recent times, coincident with the popularity of the starched, detachable collar. The time is well within the memory of many men, today actively engaged in the laundry business, when white, stiff-bosomed shirts, white cuffs and collars constituted the chief articles laundered. Conditions have been, and still are, rapidly changing. In the early periods of the development of the industry the laundry manager was required to know the characteristics of few fabrics; one grade of cotton and one grade of linen, both of plain weave, were encountered. Dyes did not concern him. Later, he was required to wash and iron colored shirts and collars; still later silk and fine flannels. Today, with the variety of styles in men's shirts and with the laundry catering to family service, a knowledge of textiles and dyes is needed by everyone interested in good laundering. Some suggestions which will prove helpful in securing this desired knowledge appear in the following pages. The phase of the activities of the Department of Chemical Engineering of the Laundryowners National Association Service Bureau that has attracted the greatest interest during the period of the last year or so, has been in connection with textile articles for which claims for damage have been made against the laundry for one cause or another. Some of these exhibits show the failure of the fabric in the typical manner of the natural wearing function. The fact that textiles are perishable cannot be too strongly impressed on the minds of the patron of the The Conserz'ation of Textiles laundry, the management of laundries, and the owners of laundries. It is true that under some circumstances cloth may be and has been preserved through long periods of time. Such incidents, however, are rather the excep- tions that prove the rule. Textile fabrics wear out. Sunlight, some dyeing materials, water and friction are their natural enemies. In addition to these natural enemies, there are incidental enemies which are acquired by accident or rather by uncommon incident during the designated use of the fabric. Medicines, household toilet articles and cosmetics, and industrial materials are acci- dentally acquired during the ordinary use of the cloth, which, according to fairly well understood chemical laws, cause weakening of the individual fibres and a consequent shortening of the serviceable life of the fabric. Through correspondence with various members of the Association and other communications from this Department, discussion has been presented on many specific examples of the type of cases mentioned above. The general interest which has been attracted by the diagnosis of the cause and responsibility for the condition exhibited by the many cases of textile failures and the special interest of some of the members of the Association have prompted the preparation of this book on the subject of textile defects and failures.* The attitude of mind entertained by the management and personnel of the laundry industry toward these problems is reflected to the patronage of the industry. Recognition of the truth of this proposition constitutes the actuating motive for the elimination of words and expressions of objectionable connotation from the trade language. It likewise constitutes the incentive toward research on problems that are only qualitatively under- stood. Every thoughtful person knows that the useful period of service to be had from any textile article is ♦Some of the material pres;nted herein was induded in a paper on this same sub- ject delivered before the Chicago Convention and published in the 1918 "L. N. A. Year Book." Preface limited. Just how long a period constitutes a reasonable expectancy for various grades of materials is an un- answered question. This Department is making an effort to place at the disposal of the industry some definite knowledge concerning the wearing qualities of cloth. Even a casual inspection of any back-yard on washday noon affords a clear demonstration of the qualitative facts. Do clothes wear out, is not so much the question as is, how rapidly should fabrics of a certain quality wear out under ideal conditions of wearing and washing? The experience of the housewife who does not send any of her work to the power laundry has taught her that lace curtains fail more quickly when the window-shades are left up, exposing the curtains to sunlight. She has also observed that the line of failure is determined by the position of the window-shades and she is therefore very apt to keep the shades down most of the time in order to protect her lace curtains. If, however, she is a patron of a power laundry, she is inclined to forget about the effect of sunlight on fabrics and, in case the curtain has failed, she is inclined — not always with intentional dishonesty, but through prejudice against power laundries — to want an adjustment with the laundry for alleged damage done the fabric in washing. The experiments conducted by the Department have shown just how much tendering a certain amount of exposure to summer sunlight does to a fabric in a certain length of time. An interesting contri- bution to the knowledge of the effect of sunlight is had from the experience of the British Army with airplane fabrics when exposed to the tropical sun.* It is a part of the favorable publicity campaign for the laundry industry to make the people engaged therein understand more thor- oughly the facts. Knowledge of the truth is good for all concerned and especially will a correct understanding of textile knowledge be beneficial to the salesmen and pro- ducers of laundry service. ♦Charles Doree and Joseph W. W. Dyer, Journal of the Society of Dyers and Colour ists, January, 1919. Tlic Conservation of Textiles Successful salesmen usually know something concern- ing the production of their commodity. It is the practice of the United States Steel Corporation to give their sales- men a brief course of instruction in the chemistry and technology of steel. Progressive automobile distributors make it a practice to send their salesmen to the factories to learn something of the construction of the machine they have to sell. It was with the idea of furnishing some of the information suggested above, and, if possible, of providing a stimulus to careful study of the production and sale of laundry service, that the writing of this book was undertaken. If the purpose is accomplished in the broader sense, it will be done through the sympathetic co- operation of its readers. The readers that the authors have had in mind during the preparation of the text are first of all the members of the Laundryowners National Association. In addition to these, it has been the aim to interest the foremen of the washrooms and other departments of the laundry plant organization and especially those persons who come in contact with the customers, the salesmen and claim adjusters. In the accumulation of the information which the authors have endeavored to present, they have come in contact with the most progressive men of the industry. This progressiveness is evidenced by the fact that they have taken the time and trouble to file their data with the Department of Chemical Engineering, where it is available to every member of the Association. In view of this fact, no feeling of self-complacency should be inspired in the minds of the thoughtful men of the laundry industiy to know that, of the exhibits submitted to the authors' Department, less than five per cent, have represented cases wherein the laundry has been at fault. 10 Preface It should be pointed out in this connection that the industry is being watched, not only by the patrons but also by the textile manufacturers, the fabricators of garments and some of the larger dealers in fabrics. Many of these maintain their own research departments. Through these agencies the L. N. A. ofificials, and this Department in particular, are learning of undeniable instances of the shortcomings of the industry. The most flagrant cases of the violation of the rules of good laundry practice are from the less progressive plants and from those outside the National Association. These conditions should stimulate the management of the better plants to more consistent consideration of helpful advice, not only in the application of it to their own work, but also in an endeavor to interest the less progressive. It is quite obvious, as has been called to the attention of all so many times, that the good laundry suffers the bad effect caused by the poor quality of service rendered by the nonprogressive. In the analyses of textile exhibits this Department has always maintained an impartial stand, considering only such evidence as would be acceptable in a court of law. No attempt has been made to shield the laundryowner when the evidence submitted showed that he had been at fault. If, on the other hand, the evidence indicated the fault of the fabric or abuse of the fabric by the user, it has been the pleasure of the Department to help the laundryowner to convince the patron of the facts and thereby ultimately to increase the store of good will toward the industry. Some of the facts presented in the first few chapters may appear to the busy launderer to be of academic rather than of practical interest. However, these par- ticulars are furnished in view of the conviction enter- 11 The Conservation of Textiles tained by the authors that the information contained therein constitutes a helpful background for the appli- cation of the facts brought out in the technical portion of the book. Harvey Gerald Elledge, Alice Lucille Wakefield. Mellon Institute of Industrial Research, University of Pittsburgh, September, 1920. 12 CHAPTER I. Fibers A SHORT review of the history of clothing will not be wholly out of place here. The records obtained by archeologists date back as far as 2600 B.C. and show the arts of spinning and weaving to be in a late stage of de- velopment at this time. Beyond this date nothing definite is known because no records have been found; in fact, no records are expected of the very earliest stages since these arts appeared long before man began to express himself by means of writing. However, from our present knowledge of man and the progress of his ideas and intellect from infancy to manhood, it has been possible to imagine the first steps taken by primitive man in the evolution of the art of cloth manufacture. When the first desire or need for body covering arose, our ancestors took what lay nearest at hand and clothed themselves with the robes which nature had furnished their less highly endowed brothers, the four-footed, fur-bearing animals. To do this, imple- ments for obtaining the skins were necessary, and the cleverness displayed in their preparation soon found expression in another way. Rushes and fibrous grasses were plaited or woven into mats that were found to be much lighter and more suitable for purposes of clothing in certain climates and seasons than were the animal skins. Continued use of the grasses demonstrated that an exceedingly wide field of application of heretofore useless materials had been opened to ingenious minds. Experience proved that for purposes of covering or decorating the 13 The Conservation of Textiles body some plants were more desirable than others. The desirable features of these plants were found to be confined to one section of the stalk, the section lying between the bark and the woody portion ; these features were toughness, pliability and greater ease of bleaching. Primitive man was even more prone to personal decoration than civilized man and early realized that white cloth gave him clearer and more brilliant colors than gray or cream cloth did. The fibers that resulted from the manipulation of rushes and reeds by the ancients are the linen fibers of today, and by virtue of their descent from reed weaving, and the fact that reed weaving goes back beyond any other type of weaving, linen fibers may be called the oldest of the textile fibers. Long after grass fibers were first used, but before their use had reached any great degree of perfection, the pos- session of herds had brought a knowledge of wool. Wool originally did duty as a body covering in the natural form of an undipped skin, and the real value of wool fibers became apparent only after the discovery was made (by accident rather than by intent) that by simultaneously pulling and twisting the clipped wool a long continuous strand could be obtained. This process of pulling and twisting (later called spinning) was quickly applied to other fibers, and, by means of it, many fibers, hitherto useless for weaving, by reason of their extreme shortness, were added to the list of useful natural products. Cotton was the most important of these later additions, but, like silk, was not used extensively for a long period and was regarded as a rare luxury. Today, however, the relative economic values have changed so that cotton heads the list as the one fiber used most universally and in largest quantity, while linen, wool and silk take their places in the order named. It is interesting to note that these four fibers, known now for ages, still remain the best and most useful aids to 14 Fibers man's physical comfort. They are also the ones in which the laundry industry is most interested and for that reason we must know them so well that we will recognize them wherever we meet them. They are grouped as vegetable fibers (cotton and linen) and animal fibers (wool and silk), on account of the sources from which they are derived. The vegetable fibers are further differentiated as seed and bast fibers; i. e., fibers from the seed pod and fibers from that portion of the stalk known as the bast region, lying between the outer bark and the inner woody portion. Cotton. — This fiber (which is useful only when ripe) belongs to the class of seed fibers and is disclosed in the ripe burst seed pod as numerous white hairs or fibers at- tached to the seeds. Before spinning, these fibers must be removed from the seed and, previous to the invention of the cotton gin by Eli Whitney, this was done by hand. Microscopic examination shows the individual fiber to be a long, slender, flat tube, spirally twisted about its axis. Figure 1 is a photomicrograph (a photograph taken through a high power microscope) of cotton showing the details of its structure. One end will be found closed and pointed; this is the loose end of the fiber as it grew within the seed pod. The other end will be«found blunt and ragged where it has been torn from the seed. The fibers vary con- siderably both in length and width, the longer ones being best suited for spinning and weaving because when spun greater intertwining of the individual fibers occurs, resulting in a yarn of greater strength than that spun from shorter fibers. Actual measurements show the variation in length of the fibers to be, on the average, from eight-tenths of an inch to one and eight-tenths inches, although some fibers come as short as one-half inch. These extremely short fibers are usually combined with longer fibers to insure for the finished yarn a reason- 15 The Conservation of Textiles Fig. 1. — Cotton,* approximately, x 300 diameters. The appear- ance of cotton fibers, which is said to be like a "twisted ribbon," is shown very clearly in this photomicrograph. The middle fiber is an especially good illustration of this description, although the other two fibers are of value as demonstrating the fact that all fibers do not twist to the same degree. ♦Copied from the "Encyclopedia Britannica." i6 Fibers Fig. 2. — Cotton, Mercerized Under Tension,* approximately, X 300 diameters. By treatment with hot caustic soda solution while under tension, cotton fibers are changed into untwisted cylinders that reflect the light to a greater degree than the untreated fibers do and, consequently, possess a higher gloss. ♦Copied from "A Manual of Dyeing," by Knecht, Rawson and Loewenthal. 17 The Conservation of Textiles able tensile strength. Such is not always the case, how- ever, and many damages exhibited by fabrics submitted to the Laundryowners National Association's Department of Chemical Engineering for examination are the direct result of the use of these short fibers alone, without the reinforcement of a percentage of longer fibers. Mercerized Cotton. — A variation of the natural cotton is mercerized cotton. The difference between the two is physical rather than chemical, although it is brought about through the action of caustic soda. Mercerization causes the fiber to become transparent and to lose its flat spiral form to become a nearly straight cylinder having an increased power of light reflection and consequently a higher gloss. This change in form is illustrated by Figure 2. The mercerized fiber is even stronger than the raw fiber when the conditions of mercerization have been carefully guarded and overtreatment avoided. The only part of the change that is apparent to the eye, unaided by a magnifying instrument, is the increased gloss. Schreiner Finish for Cotton. — A high luster, simi- lar to that appearing on mercerized cotton, can be given to a piece of cotton cloth by subjecting it to a process called calendering. This process consists of passing the cloth between rollers under heavy pressure. One of the rolls is engraved with obliquely set lines, ruled fiom 125 to 600 to the inch; these lines produce a great number of parallel, flat surfaces on the cloth, which cause it to acquire a high luster. If the rollers are heated during the process, a finish is produced that closely resembles mercerized cot- ton, and is quite permanent. This finish, however, is lost to a large degree on washing. Linen. — Linen is a representative of the bast fibers and is obtained by fermentation of the whole flax plant. This process prepares those parts of the stalk that are undesirable as textile fibers so that further treatment by i8 Fibers Fig. 3. — Linen,* approximately, x 210 diameters. The jointed structure that suggests the description of "bamboo-like" is (juite ev'ident in the above photomicrograph. ♦Copied from "A Manual of Modern .'^team Laundry Work," by E. Clayton. 19 The Conservation of Textiles Fig. 4. — Wool,* approximately, x 210 diameters. The over- lapping scales that characterize the wool fiber are clearly defined in this photomicrograph. This feature is not so apparent on used wool as on the virgin wool. *Copied from "A Manual of Modern Steam Laundry Work," by E. Clayton. 20 Fibers drying and rolling removes them, leaving the long tough fibers to be used for spinning. When examined micro- scopically (see Fig. 3), a linen fiber presents a more or less bamboo-like structure, caused by the occurrence of several cells in sequence, with nodes or knots at irregular intervals where two cells are joined at the ends. An individual cell measures in length from twenty to forty millimeters (7/lOOths to 15 lOOths of an inch); conse- quently the long fibers of combed flax linen consist of a large number of cells attached end to end. These fibers, by virtue of their greater length, furnish a much stronger yarn than does cotton. Wool. — Wool and silk, though grouped together as animal fibers, are produced in entirely different ways. The term wool is usually taken to mean the hair of the sheep, although the hair of certain goats (Cashmere, Mohair, etc.) and of the camel are classed under the same name. The kind of animal from which it is obtained and the location on the body determine the quality character- istics of the wool, which may be short or long, coarse or fine, dull or lustrous. A long stapled wool fiber is one that measures over one and one-half inches in length, and its diameter is usually proportional to its length. Long stapled wool is generally combed and spun into worsted yarn and used for the best qualities of coatings, dress goods, etc., while the short fibers are carded and spun into woolen yarn, which is subjected to a fulling process subse- quent to being woven into fabrics, in order to impart thicker and fuller feel to the fabric. A close microscopical examination of wool reveals a cylindrical fiber covered with flattened, horny scales, which are funnel-like and which overlap each other in the manner of fish scales (see Fig. 4). The dimensions, uni- formity and compactness of these scales are generally conceded to determine the luster and strength of the wool. 21 The Conservation of Textiles Wool differs from the vegetable fibers in several important respects. It possesses greater elasticity and strength and is more lustrous; it is curly and has the property of becoming felted under certain conditions, which are outlined in the L. N. A. charts of Standard Procedure for Washroom Practice as including the use of too low a bath with too little soap. This property, while being useful in certain ways, is a nuisance in others, and it is well for launderers to keep this fact in mind when handling woolen articles. The exact physical change that takes place during the process of felting is still under discussion, but experiments carried out by the Department of Chemical Engineering have proved that it is the result of hard pounding in the wheel rather than of changes in temperature, which was first given as the cause of the phenomenon and was said to cause contraction of the fiber and an interlocking of the scales. The observation made by this Department upon the cause of felting is substantiated by the research findings of the United States Government workers on this problem.* Silk. — Silk is a substance secreted by several species of caterpillar for the purpose of forming a cocoon in which the change from the caterpillar stage to the moth stage of existence occurs. It is produced by two glands, situated one on each side of the body, and is carried by ducts to the head of the caterpillar where the spinneret is located. Here on coming in contact with the air the two gelatinous streams solidify and are cemeted together by another secretion which is produced by glands located near the spinneret. While all caterpillars spin cocoons in this manner, the secretions of only a few species form strands of sufficient strength to make them of value as textile fibers. When recovering these fibers for spinning, the cocoons are placed in water at a temperature of 60°C. to *A full report of this work is to be found in the laundry trade journals for the early part of 1919. 22 Fibers Fig. 5. — Raw Silk,* approximately, x 150 diameters. The above photomicrograph shows the silk fiber as it is obtained from the cocoon, before the gum is removed by boiling. Each strand is really two fibers, the gum serving to cover this double nature. ♦Copied from "A Manual of Dyeing," by Knecht, Rawson and Loewenthal. 23 The Conservation of Textiles Fig. 6. — "Boiled-off" Silk,* approximately, x 150 diameters. The true silk fiber as it appears after the gum has been removed. The natural high gloss that is developed or uncovered by this process is not as evident in a photograph as in the fibers themselves. ♦Copied from "A Manual of Dyeing," by Knecht, Rawson and^Loewenthal. 24 Fibers soften the cement which binds the two fibers together. When this softening has taken place the fibers are reeled onto spools, several strands being reeled together to form a thread. Raw silk (unreeled silk or the cocoon proper) is of a creamy or yellowish color and has very little luster. When examined under the microscope it appears as two straight, transparent fibers, absolutely lacking in cellular structure, cemented together along their whole length (Fig. 5). When boiled with soap solution, theouter layer of cementis removed, and the true luster of the fiber is revealed (Fig. 6). A silk fiber varies from 500 to 1500 yards in length and in diameter from 0.01 to 0.02 millimeters (4/1000 to 8/1000 inch). Besides the advantage afforded by such ex- ceptional length, silk is extremely elastic and is the strongest and most lustrous of the natural fibers. The best silk is produced by silk-worms reared under artificial environ- ment and carefully cultivated, and is finer, whiter and more lustrous than the so-called "wild" silks obtained from the cocoons of uncultivated worms. Artificial Silk. — The demand for silk has reached such proportions that efforts to supply its beauty at a popular price have led to the manufacture of artificial silks. The most_important varieties of these fibers are prepared by the same fundamental formula, which calls for a solution of some chemical product of cellulose in an appropriate liquid. Of the two types of artificial silk on the market, the better known is made from cellulose hydrate, more commonly called viscose. The other type is manufactured from cellulose acetate, and sold under the trade-name of "Lustron." Viscose and cellulose acetate "silks" differ materially chemically but the physical differences are not marked. However, the identification of the type to which an artificial silk belongs may be readily accom- plished in the laboratory. 25 The Conservation of Textiles The process of manufacture of artificial silk is briefly as follows: A solution of v^iscose (or of cellulose acetate) in a suitable solvent and of desired concentration is ex- truded by appropriate mechanical devices in such a way as to convert the viscous solution into filament form. These filaments or threads are placed into some medium that causes immediate coagulation or hardening, and are reeled from this coagulating material and prepared for weaving in the same manner as silk, per se. None of the varieties of cellulose silk possesses the strength and elasticity of real silk nor its resistance to the process of washing; they all have to be handled with considerable care and even with such treatment the results obtained are often not entirely satisfactory. This product of the chemical laboratory can hardly be dififerentiated from real silk by microscopical examin- ation because of the absolute lack of physical character- istics that exists in both types of fiber; it happens, however, that the one physical point of difference lies in the greater luster of the artificial silk, which shows such an increase over that of real silk that identification can be made merely from an inspection of the fabrics. In case any doubt remains in the mind of the inspector recourse may be had to simple chemical tests that are infallible. Differentiation of Artificial and True Silk. — The sim- plest of these tests is burning and identifying the odor that results; an odor as of burning feathers indicates real silk, an odor as of burning wood indicates artificial silk. Another test, that improves on this test by replacing the factor of personal judgment with one of purely chemical character, is conducted by heating a portion of the fibers under examination in a dry test tube and testing the reaction of the volatile matter driven off by this treatment with a piece of moist neutral litmus paper placed at the mouth of the test tube. If the litmus paper becomes red, the 26 Fibers fumes are acid and prove the fibers to be artificial silk; if the litmus paper becomes blue, the fumes are alkaline with ammonia and prove the fibers to be real silk. These are two of the few reliable tests recommended for the identification of textile fibers. Textile literature is filled with tests that are said to be good and that have been praised beyond their actual merits. It is often quite possible that these tests deserve their reputation for great delicacy of indication, provided we consider one important factor, i. e., the relation of the manipulator to the results. If the delicacy of the test is greater than the degree of d iicacy of technic that lies within the possi- bilities of tht average manipulator, the chances are that the test will fail when applied by other than the man who has worked it out. The process of evolution has gained for the originator of the test a knowledge of the reactions involved and a fineness of technic that is denied to others who may attempt to use it. It is deemed advisable to include in this chapter a discussion of the tests that have the full endorsement of the authors. Tests for Vegetable Fibers in Mixtiires.—li the presence of cotton or linen is suspected in a wool or silk fabric, proof can be obtained by boiling a small piece of the cloth in a 5% solution of caustic soda for five minutes. At the end of this period the wool or silk will be entirely dissolved and any cotton or linen that may be present will remain unaffected by this treatment. Tests for Animal Fibers. — If, on the other hand, it is desired to remove the cotton or linen and leave the wool or silk, the cloth may be saturated with a 2% solution of sulfuric acid (H2SO4) and then dried in an oven at 100°C. for an hour. This treatment chars cotton and linen fibers and they can be readily removed by rubbing the cloth gently between the palms of the hands. The wool and silk 27 The Conservation of Textiles successfully resist the action of the acid. These tests may be made quantitative by using weighed samples, carefully washing, drying and weighing the residue. The weight of the residue divided by the weight of the sample and multi- plied by 100 equals the percentage of wool or silk in the case of treatment with sulfuric acid, and of cotton or linen in the case of treatment with caustic soda. Figs. 7, 8 and 9 illustrate the application of these treatments to a fabric of cotton and wool mixture. Fig. 7 shows a piece of the whole cloth that has been dyed with an acid dye and later bleached to differentiate between the cotton and the wool. The cotton is bleached white while the wool retains its color. Fig. 8 shows the cotton threads that have resisted the action of boiling caustic solution, the open spaces having been occupied by the wool that was dis- solved out by this treatment. Fig. 9 shows the condition of the fabric after treatment with sulfuric acid, and pre- sents the unaffected wool fibers with the cotton removed. It is possible to differentiate between the two animal fibers by chemical analysis, but the procedure is too complex and the apparatus required too bulky to be at the command of everyone. There is no chemical means of differentiating between the vegetable fibers in spite of the oft-repeated statement that such differentiation may be made by treating a mixed cotton and linen cloth with concentrated sulfuric acid for one or two minutes, drying and washing. The statement is made that the linen will survive this treatment while the cotton will not. The degree of solubility of cotton in sulfuric acid approximates that of linen too closely to permit a separation by this method. For these reasons, in cases that prove difficult to decide, it is often desirable to conduct final tests with the microscope. Although the examination of a fiber with the micro- scope is the quickest and most reliable method of identify- 28 Fibers P'ig. 7. Wool and Cotton Mixture. This mixture was dyed to differentiate between the wool and the cotton in the photograph. The dark portion is the wool and the light portion is the cotton. 29 The Conservation of Textiles ."I'v' ..'-■^^&^iUiS,Ji mm ■;:iKiBi Fig. 8. Cotton that has Survived Treatment with Caustic Soda. A piece of the fabric pictured in Fig. 7 was boiled in a 5 per cent, solution of caustic soda for five minutes. This treatment dissolved the wool and left the cotton as it appears in the above photograph. 30 Fibers fjCAjm«.''< 2QU *■ -^ if tt'^H^B ■' *l J- 1 Fig. 25. Typical F.mlure of Bath Toweling. Loops of the pile are caught and the pile warp is pulled out for some distance, giving long threads that becoinc intertwined and knotted on the surface of the towel as illustrated, 57 The Conservation of Textiles ■ •iwtiKi,; '•Mifi.i;,; * '■- IIH»I,,, <>' •■ ■ >t iikI . 1 1*1 " .,.. ']^^\]v^h c ""'.r,',',',v ,'i'i'.i'n'>>