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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 )
Recent development of textile dyeing.-Nature riots in color. The dyeing process generally consists in taking some object of nature rich in a certain color, some plant, some animal substance, or some mineral, extracting the essential coloring substance therefrom, and then applying this coloring matter to the white or light-colored textile materials. During the last sixty years, however, there has been a great development in methods of extracting coloring substances from minerals, particularly from coal tar, a substance which in its crude state appears to contain none of the hundreds of beautiful colors, tints, and shades which chemical processes reveal. In fact, nearly all other coloring matters have lost ground before this new and powerful rival. Certain vegetable dyes of great importance in former days have been entirely replaced by coal-tar dyes.
The principle of dyeing.-The principle of dyeing can be simply stated. The coloring substances are mixed with some liquid, usually water, in proper proportions. Into this mixture, known as the dye liquor, the undyed textile is placed; whereupon the cloth or yarn becomes soaked with the dye. The coloring matter either fastens itself upon, or combines with, the textile in more or less permanent fashion. This transfer of the coloring matter from the dye liquor to the textile has been explained by the chemists as being caused by definite affinity or attraction between the dyes and the textiles.
For the dyer a knowledge of chemistry is necessary. He must know of what chemical substances his textiles are composed, and for what other substances these textiles have affinities. With this knowledge he seeks the combination of dye materials that will give the color desired and at the same time have the proper attraction for the textile. The greatest difference exists between the animal fibers, wool and silk, and the vegetable fibers, cotton, linen, ramie, and so on. Wool attracts and takes a deep color from some substances that give cotton no more than a fleeting tint. The converse is equally true. Hence different textiles imperatively demand different dyes and different dyeing methods.
Production of fast colors.-The fastness of color so desirable in the textile fabrics depends solely upon the strength of the affinity between the textile and the coloring substance. Fastness to washing indicates that the affinity between the textile and the dye is stronger than any affinity that might exist between the dye and the water, or between the dye and the soapsuds. Perspiration affects the dyes in some fabrics; that is, there is a stronger affinity between the dye and perspiration than between the dye and the fabric, as a consequence of which the textile becomes discolored or fades. The oxygen in the air, especially in the sunlight, has a powerful affinity for many substances. Its power is demonstrated by the fading of many colors when exposed to air and sunlight. The active oxygen pulls the color out of the textile, leaving a sadly faded material.
Problems in the chemistry of dyeing.-The chemist in charge of the dye process must not only find the coloring matter that will give his textile material the right tint or shade and have a strong affinity for it, but he must also make sure that the affinity between the coloring matter and the textile is stronger than the affinity between that coloring matter and other substances with which it is likely to come into contact, such as water, soap, light, air, and perspiration. He must, furthermore, consider how the requisite dyes and methods may be made applicable at reasonably low cost.
The processes through which the textile must pass and the purposes for which it is to be used are all considered by the chemist. For example, materials to be heated, steamed, washed, or scrubbed in the finishing processes must have dye materials in them that are not affected by these processes. Fabrics to be made up into underwear are not subjected to strong light as a rule, but must stand perspiration and washing in soapsuds. Hence the chemist selects dyes that have no affinity for perspiration, water, or soap when preparing dye materials for underwear goods. Cloth to be made up into shirts, aprons, house dresses, children's dresses, and similar uses must stand light, air, washing, and perspiration. Suitings that are not to be washed may be dyed so as to be fast to light and air, but not to water or soap. Fabrics intended for stylish evening wear need not be made fast to sunlight nor washing; therefore the happy chemist is free to concentrate his attention on producing a very brilliant or unusually delicate tint or shade. Formerly, hosiery for women was dyed to stand fast against washing, friction, and perspiration, but lately low shoes and high skirts have made it necessary to make hosiery colors fast to light also. Winter goods need not have colors so fast to light as must summer goods, for the winter light is far less bright and active. Goods for street wear are likely to be spattered with dust or mud. This street mud is likely to contain lime or other substances that may have a strong affinity for textile coloring matters; therefore such goods need dyes which are dust proof, mud proof, and shower proof. These are some of the many problems of the textile chemist in the modern dye works.
Natural dyes.-Let us now see what the common dyestuffs are. As already suggested, dyes are usually classified as natural or artificial. Natural dyes include such vegetable colors as logwood, indigo, fustic, cutch, butternut, sumac, madder, brazilwood, quercitron, safflower, sapanwood, peachwood, camwood, Persian berries, turmeric, saffron, henna, cudbear, and litmus. Cochineal, an insect, yields another natural dyestuff. Several minerals are used, as, for example, Prussian blue, chrome yellow, and iron buff.
The natural dyes are the oldest. The Bible has numerous references to colors and dyes; among them are descriptions of Joseph's coat of many colors, of the Tyrian purple, and other colors. All of these ancient color stuffs were natural; that is, they were extracted from plants, from animal substances, or from the earth. Oriental rugs were all dyed with vegetable dyes, some prepared by secret processes if we may believe the accounts of Oriental rug salesmen. Certainly some of the Eastern natural dyes were remarkable for brilliancy and for fastness under most of the conditions of ordinary use.
Up to sixty years ago only the natural dyes were used. But to people of today the list of dyestuffs named above is little more than a list of names. Most of those color substances passed out of use in the time of our grandmothers, and their places were taken one after another by artificial dyes, much cheaper, more easily applied, and, when properly selected and prepared, fully as fast as the natural dyes of old. Of the entire list only logwood is now used very considerably.
Artificial dyes.-Artificial dyes had their beginning in 1856, when an English chemist, H. W. Perkin, working with coal tar in. his laboratory, accidentally discovered the first coal-tar color, a beautiful mauve. A little later, a French chemist discovered the way of getting magenta by means of the same substance, coal tar. This turned the attention of color chemists the world over towards the new source of dyestuffs. A great number of experiments were made. In the last fifty years several hundred colors have been produced. Gradually the principles by which coal-tar colors can be extracted were developed, until they are now so well understood that the color chemist can sit down and work out in formula almost any color or tint with almost any desired fastness.
How COAL-TAR DYES ARE PRODUCED.-These colors, or aniline dyes, are derived from coal tar, a by-product from coal in the process of making coke. When coke is being made, it gives off a great deal of smoke and gas, which is all saved and reduced to the form of a liquor. This liquor is distilled, and the residue after the lighter oils are boiled off is coal tar. A like product is made from crude petroleum. Coal tar, as now known, is a very complex chemical substance, and a great variety of materials can be derived from it besides colors. From coal tar are made some of the most delicate artificial perfumes and flavors closely imitating, for example, wintergreen, violet, vanilla, and the fruits. From coal tar are made saccharine, a substance three hundred times as sweet as sugar, an artificial form of turpentine, substitutes for linseed oil, carbolic acid, salicylic acid used as a food preservative, naphthaline camphor, photographic developers such as hydroquinone and metol, creosote, vaseline, and a variety of lubricating oils. No one looking at the crude mass would ever guess its wonderful contents. Yet with coal tar as a raw material whole industries have sprung up within the last few years, among which the manufactories of textile dyes are probably the most important. Germany has led all the rest of the world in the manufacture of aniline dyes, and it is due largely to the deep researches of German chemists that the great variety of colors and the excellent qualities of modern artificial dyes have been developed.
EARLY FAILURES IN THE USE OF COAL-TAR DYES.-Soon after their discovery it was found that the coal-tar dyes differ greatly in their affinity for the different textiles. Early carelessness on the part of manufacturers was the cause of the general dissatisfaction with coal-tar dyes in the nineties. Dyes utterly unsuitable were used indiscriminately, with the easily foreseen result that many of them quickly faded. Coal-tar dyes are still suffering from the bad repute into which they came during these years, a reputation that it may take a generation of unfailingly good qualities to live down.
DISCOVERY OF DIRECT COTTON DYES.-The colors first discovered were suited only to dyeing wool. A little later colors were produced which could be used on cotton by means of mixing with some other chemical having a strong affinity for cotton. In 1884, however, a direct coal-tar cotton dye was discovered, the so-called Congo red. After 1884, a whole flood of colors appeared. In 1885 there appeared a coal-tar color which had all of the chemical elements and qualities of indigo. This artificial indigo has practically taken the place of the natural color.
According to the chemical composition of these colors, they were grouped into various classes; for example, aniline, alizarine, benzidine, azo, sulphur, etc. There are now more than twenty such sub-classes in the coal-tar colors, each class containing a great number of colors, but each differing in behavior as a dye substance.
General classes of dyes.-Dyestuffs are now divided by dyers and chemists into the following large classes:
1. Acid dyes.
2. Basic dyes.
3. Direct or substantive cotton dyes.
4. Sulphur dyes.
5. Mordant dyes.
6. Vat dyes.
7. Developing dyes.
Other classes are sometimes given, such as the phthallic anhydride dyes, insoluble azo dyes, and some others, but the list given includes most dyes in common use. The names of these classes suggest something of the character of the dye or the method of application.
Acid dyes.-The acid dyes are what the name indicates. The number of artificial dyes in this class is very great, all characterized by being easily soluble in water and easily applied to cloth. Since these dyes have only slight affinity for cotton, they are not much used on that textile. Not all of the acid dyes are equally good for wool; some are very fast, while others are fleeting. According to one authority in textile chemistry, over seventy-five per cent of the dyed wools in the market are colored with acid dyes. To some extent, also, these acid dyes are used for dyeing silk.
Basic dyes.-Basic dyes differ from acid dyes in that they are basic in character and have the power of neutralizing acids. Basic dyes are the oldest among the artificial dyes. These dyes work well with wool because there are in the wool fibers certain acid properties with which the basic dyes combine easily. The combination is not usually very fast, however; hence basic dyes are passing out of use and giving place to more stable coloring substances. The basic dyes have no effect on cotton until the cotton has been treated with tannic acid. The basic dyes combine well with the tannic-acid-cotton combination, and the resulting colors are both brilliant and fast to light, water, and soap. Used in this way, the dye is called a mordant dye.
Direct dyes.-The direct or substantive cotton dyes originated with Congo red in 1884. The peculiarity about these dyes is their affinity for cotton as a direct dye. There are now more colors and varieties of dye in this class than in any other. Practically every color has been developed in this class. These colors constituted a great textile discovery, saving much time and. trouble in dyeing cottons. All that is necessary with a direct or substantive dye is to dissolve it in water, bring it to the temperature at which it works best, and then immerse the cotton cloth in the solution for a short time. Before this invention, cotton dyes, both of the natural and artificial varieties, had to be applied indirectly or with a mordant, that is, through the medium of a third substance, such as tannic acid, that had an affinity both for cotton and the dye substance. The discovery of the direct dye cheapened the dye process greatly, and shortened it too, a very important consideration when certain colors or patterns attain a seasonal vogue that cannot be foreseen and may be brief. The direct dyes vary greatly in fastness; many of them require that the dyed cloth be put through other solutions, such as copper sulphate or blue vitriol and water. Since 1902, however, a number of very fast direct dyes have been discovered and have largely supplanted all others for cotton goods. Direct dyes are also used on linen and, to a certain extent, on wool. The common household dyes that may be purchased in small packages, such as "Diamond Dyes," are of this class. The large dye-producing concerns of Germany have given to their direct dyes distinctive names which are well known to all commercial dyers. The Leopold Cassela Color Company call their colors "diamine colors." The Farben Fabriken Company uses the terms "benzo," "chloramine," and "katigen." The Badische Anilin & Soda Fabrik dyes are known as "pyramine," "oxamine," and "indanthrene," the last-named a remarkably fast series of colors, but not properly belonging to the class of direct dyes. The American Dyewood Company calls its dyes "tetrazo colors." The Berlin Anilin works denominate their dyes "Congo," "Columbia," and "Chicago." Several other brands besides these are used, most of which are, like these, of German manufacture.
Sulphur dyes.-The sulphur dyes contain sulphur in one form or another. Nearly all colors except reds have been produced in this chemical group. The sulphur blacks, blues, and browns are among the fastest produced. They are used only in cotton and other vegetable fabrics and are fast to light, washing, and acids, or perspiration. Sulphur colors are excellent for dyeing cotton hosiery and other knit goods in dark colors or blacks. Some of them require some after-treatment to fix them permanently in the fiber.
Mordant dyes.-Mordant colors are sometimes called adjective colors, because they are not applied directly but always through the means of some other substance applied to the textile first. Some substance or chemical called a mordant, having a strong affinity for both the textile and the coloring matter, is first applied. When the color is added, the result is a combination that may be expressed in the following manner: Textile+mordant +adjective dye = colored textile. The mordant clinging to the textile forms a combination with the dyestuff that dyers call a "color lake," a substance not soluble in water; hence it remains fast in the textile. Mordant dyes are the fastest known. They include most of the natural dyestuffs, such as logwood, cochineal, catechu, fustic (but not indigo), and a great number of artificial dyes. Uniforms for armies, navies, railroad companies, and large corporations are frequently finished with dyes of this class by contract specification. Very fast wool colors are obtained by means of mordants. Turkey red is an example of a cotton mordant dye.
The mordant substances include such acids as tannic acid, sumac, gall nuts, bark extracts, oleic and stearic acids, and Turkey red oil; and metallic substances such as various combinations or soluble salts of chromium, aluminum, iron, copper, and tin. The latter, the metallic mordants, are more used than the acid mordants.
Each mordant produces a different effect with each color. In general, tin produces the brightest colors and is therefore much used in fancy dress fabrics, in cotton, wool, or silk. Iron produces the fastest colors, but they are generally dark, as, for example, logwood blacks. Chromium is used extensively, especially for dark wool shades. The copper mordant also produces a fast dye.
Vat dyes.-Vat dyes include the natural dyestuff, indigo, and the artificial dyes called by the trade names, indanthrene, and flavanthrene. They are called vat dyes because, being originally insoluble in water, they undergo special preparation in large vats before the cloth is introduced; here they are made soluble, usually by the adding of caustic soda and hyposulphite. In this mixture or dye liquor the textiles are soaked. Certain chemicals are thereafter added, changing the dyestuff back to the insoluble form in the cloth or fiber. This is called the fixing process. All the vat dyes are fast, especially to washing. The artificial vat dyes have in many instances taken the places of the older mordant dyes, and their future seems promising, for they are cheaper and easier to apply than the mordants, although not so cheap and convenient as the direct dyes.
Developing dyes.-Developing dyes are color substances which, although they have some affinity for textiles, are not brought out in full hue until a developing process has been applied. One of the commonest developing agents is ice, or ice water. One of the best developing dyes is known as aniline black. It is one of the fastest and most beautiful. Sulphur blacks being cheaper have, however, taken the place of aniline black for most uses. Certain other chemicals are sometimes used as developing agents, but this group of dyes is not important and therefore requires no extended treatment here.
METHODS OF APPLYING DYES
Textiles are dyed in the form of the loose textile fiber, in the yarn, or in the woven fabric or piece. The products are known as fiber dyed, yarn dyed, and piece dyed, respec tively. Most goods are either yarn or piece dyed. But for certain purposes it seems that dyeing the loose cotton or wool is the preferable method. Each method has special machinery designed for it, such as vats, kettles, and driers, but in principle the process is the same, depending wholly upon the kind of textile and the kind of dye.
The dye process.-The first step in any case is the thorough cleansing of the material by boiling and washing with caustic soda or hot soapsuds. This removes the dirt that may be found in the fiber. Often woven goods are bleached at this point, especially if they are to be dyed with light colors or tints.
In applying the mordant dyes to cotton fabrics, the next step is soaking the cloth in the mordant vats or kettles until the fabric is properly saturated. The cloth is then dried and hung up for two or three days in a moist air chamber. This is called the "aging" process, by means of which the mordants are firmly imbedded in the fiber. Next the fabric is passed through vats containing cow dung and chalkthe "dunging" process. After the cloth has soaked in these vats for an hour or two, it is raised, dried, and generally "dunged" a second time. The mordant is now firmly fixed. Substitutes for cow dung have been tried and are now widely used in the cotton-dyeing industry; none, however, gives more satisfactory results than the old-fashioned English dunging process. After the dunging the cloth is thoroughly washed and transferred to the dye vats. After the dye proper is absorbed by the fabric for such time as may be necessary to make the particular color wanted, the cloth is taken out, washed thoroughly, run through soapsuds, and washed again. To remove any foreign stains, the last washings may contain a little bleaching powder, but not enough to harm the dye itself. The cloths are then and made ready for the finishing processes.
CONTINUOUS DYE PROCESS.-The process of applying the direct dyes is naturally simpler. After the goods are washed and bleached, they are run directly into the dye liquor vats or baths, and by means of rollers kept in continuous motion through the dye liquor until properly dyed. The cloth then passes into a rinsing box, and the dye process is completed.
Printing.--There is another method of applying color to textiles, particularly to cloth, that is much used. This method is printing. The cloth is run through a printing machine supplied with rollers, one for each color to be printed on the fabric. These rollers are engraved with the designs desired on the cloth, and the cloth passing through them receives the impression of the engraved design in the proper color or dye. The engraved rollers receive their coloring matter from troughs below or from regular inking rollers similar to those used in printing offices.
After the cloth has received the printed color impressions, it is passed on into a drying room; the dyes here become fixed in the fabric. This is followed by steaming, dunging, washing, soaping, and light bleaching, much the same as in the regular mordant dye process.
PRINTING COLORS.-The dye materials used in printing are largely the same as those used in regular dyeing, except that they are applied in printing in the form of a thick paste instead of in the form of a liquid. Various substances such as starch, dextrin, tragacanth, and gum arabic are used as thickeners. In the case of the mordant dyes, both mordant and dyestuff are sometimes imprinted at the same time, but the results are usually less satisfactory than when they are separately applied. In some cases the mordant is applied in vats to the whole cloth as if it were all to be dyed, although the actual printing colors only the portion covered by the design.
STYLES OF PRINTING.-There are, then, as many methods of printing, "styles" of printing as they are called, as there are classes of dyes commonly used. Direct printing utilizes the direct dyes. The combined dyeing and printing method utilizes the mordant dyes. In addition to these styles, there are also what are known as the "discharge," the "resist" or "reserve," and the "topping" printing methods.
Discharge style.-The discharge style of printing consists in printing chemicals upon dyed fabrics in designs, the chemicals causing the dye to come out wherever applied, leaving the designs either white or in a different color from that of the dyed ground.
Resist style.-The resist or reserve style of printing obtains white figures on a colored ground by means of printing, before dyeing, with substances that are impervious to the dye liquids. When these substances are thoroughly dried into the cloth, the cloth is dyed, but all portions covered with the resist paste or substances remain white. Countless variations are possible through the means of these different styles of printing and dyeing and through the use of various chemicals, printing pastes, dyes, and mordants.
Topping.-Topping printing is simply reprinting a fabric a second time after the colors from the first printing process have been fixed and dried. The first or ground colors applied are usually light in tint, while the topping colors are heavy, dark, or brilliant according to the demands of the dyer.
USES OF PRINTING.-The printing process is used most extensively in coloring cotton fabrics. Cotton prints such as calicoes occupy an important place in the textile world. Wool and silk are also sometimes printed. In silks especially many beautiful patterns are obtained by means of printing. Yarns are sometimes printed before they are woven, particularly the warp. This gives the effect of an indistinct design in the finished fabric. The fiber is also printed sometimes before it is made into yarn, while in the combed sliver stage in worsted manufacturing. Printing on combed sliver is called "vigoureux printing."
Factors affecting success of dyeing.-Several factors affect the success of the dyeing industry. The necessity for technical and chemical knowledge has already been empha sized. But there are also certain requirements as to environment, such as pure water, air free from factory smoke, blast-furnace smoke, or sulphur fumes, and so on.
PURE WATER.-The importance of pure water is very great, since any lurking chemical dissolved in the waterlime, for instance-would upset all of the chemist's calculations, would cause the same dyestuffs to give different results or fast dyes to become fleeting, and, in some cases, would prevent absorption of the dye at all. Hence dye houses are usually located in regions where the water is very pure and soft, and, besides this, pains are taken still further to purify the water by removing any lime, sulphur, iron, or other minute mineral matters which may be found dissolved therein. It is noteworthy that much home dyeing fails, even when the dye recipes are closely followed, simply because of some chemical impurity in the water used to dissolve the dye substance.
DIFFERENCES IN FIBERS.-Another thing the dyer must consider is the particular variety of cotton, of wool, or of silk that he is to color. No two varieties absorb the colors in the same way or to the same extent. For example, India cottons take a deeper shade, under the same conditions, than American cottons. A stronger solution, or a longer soaking, is necessary for the American cottons than for the India cottons. In addition, there are minor differences in the fibers from different localities, perhaps because of differences in soil, rainfall, temperature, and care received during the growing season. Similar differences are also to be noted in wool and silk, especially in the latter. Silk dyers in Europe always desire to know the source of the silk before they prepare to dye it.