Sewing silk is made by winding and doubling the raw product, then twisting into tram, giving it a slack twist, doubling and twisting in the reverse direction under tension. Machine twist is similar, but three ply.
The principal fabrics made of silk are: silk, satin, plush, chenille, crepe, crepon, gauze, damask, brocade, pongee, and ribbons. Silk thread and cord are also extensively used. The United States is among the leaders in the manufacture of silk fabrics.
=Silk Waste.= When the cocoons are softened for reeling a certain portion of the silk is found to consist of waste and broken threads.
The tangled silk on the outside of the cocoon is called floss. The residue after reeling, and other wastes in reeling, are known as frisonnets. Floss silk is not used for weaving. It is a slack twisted tram, generally composed of a large number of threads of singles.
=Spun Silk.= There is another class of threads made from waste silk by spinning and known as spun silk. Waste silks include the pierced cocoons, that is, those from which the moth has come out by making the hole and breaking the fibers in one end of the cocoon; the waste made in the filatures in producing raw or reeled silk, chiefly the outside fiber of the cocoon and the inside next the chrysalis; and also the waste made in manufacture. The waste silk is ungummed; that is, the gum is removed from the fibers by boiling with soap, by macerating or retting, or by chemical reagents.
After the gum is removed from the cocoons, they are opened and combed, most of the chrysalis shell being removed. The remainder, with other foreign matter, is picked out by hand from the combed silk. The silk is put through a number of drawing frames to get the fibers even on the roving frames, where it first takes the form of thread, then on the spinning frames, where it is twisted. If it is to be used as singles, the manufacture ends here. In two- or three-ply yarns, the singles are doubled, twisted again, singed by running through a gas flame, cleaned by friction, controlled, that is, the knots and lumps taken out, and then reeled into skeins for dyeing or put on spools.
=Spun Numbers.= There are two methods in general use for numbering spun silk. In the French system, the number is based on the singles, by the meters per kilogram; two and three cord yarns have one-half, one-third, etc., the length the numbers indicate. Thus--
No. 100 singles has 100,000 meters per kilogram.
No. 2-100 has 50,000 meters per kilogram.
No. 3-100 has 33,333 meters per kilogram.
The other system which is more generally used in this country, is the English system. The hank is 840 yards, and the number of hanks in one pound avoirdupois is the count of the yarn. It is based on the finished yarn, and singles, two or three cord yarns of the same number all have the same yards per pound. Thus--
No. 50 singles has 42,000 yards per pound.
No. 50-2 has 42,000 yards per pound.
No. 50-3 has 42,000 yards per pound.
=Dyeing Yarns.= Generally speaking there are two large classes into which silk goods may be divided, those in which the threads are colored before weaving and called yarn-dyed goods, and those dyed or printed after weaving and called piece-dyed or printed goods. In dyeing yarns, the silk is first ungummed and cleaned by boiling in soap and water, then washed in cold water. If the thread is to be weighted, as is frequently done, tin salts, iron, or other heavy material is deposited on the fiber. If carried far, this is injurious, making the silk tender and weak. Sometimes there is more weighting than silk. Yarns are usually dyed in hot liquors, aniline colors being the ones in most common use to-day, though other dyes are used for special purposes. Some yarns are dyed in the gum, and some with a part of the gum left in. After dyeing, they are washed in cold water, dried, and wound on spools.
=Silk Dyeing.= Silk occupies in several respects an intermediate position between the animal and vegetable fibers. Like wool, it is a highly nitrogenous body, but contains no sulphur. It readily takes up many of the colors which can be worked upon vegetable fiber by the aid of the mordants. This is particularly the case with reference to a large number of aniline colors, which require merely to be dissolved and mixed with perfectly clear water in the dye vessel. The great attraction of silk for these colors simplifies silk dyeing exceedingly. The sad colors, on the other hand, and especially black, are in many cases exceedingly complex, the main object of the dyer being not so much to color the silk as to increase its weight.
Dyeing black on silk is unquestionably the most important branch of silk dyeing, and it has probably received more attention than any other branch, in consequence of which it has been brought to a high degree of perfection. Blacks on silks are produced both from natural and artificial coloring matters, the former having, so far, retained their pre-eminence despite the recent discoveries of chemists. For various reasons coal-tar colors have never proved successful in dyeing black on silk. Since the discovery of America, logwood blacks have formed the staple of the black-silk dyer, who has carried their production to a high degree of excellence. But unfortunately, besides aiming at a high state of perfection in the actual dyeing operation, the black-silk dyer has also aimed at increasing the weight of the dyed silk, so that nowadays it is possible for him to receive ten pounds of raw silk and to send out fifty pounds of black silk, the extra forty pounds being additions made in the process of dyeing.
[Illustration: WINDING SILK ON SWIFTS]
Logwood black-silk dyeing consists essentially of alternate dippings in separate baths with the mordant and dyestuffs suitable for producing the required color and weight. The number of dippings and the length of time taken in each operation depend on the intensity of the black wanted and the amount of weighting which is desired. The chief substances used for weighting are lead salts, catechu, iron, and nut-galls, with soap and oil to soften in some degree the harshness of the fabric which these minerals cause. As the details of the operations are practically the same for all kinds of logwood blacks (raven, jet, crape, dead black, etc.), the method for producing one will suffice for all. The process involves several distinct operations, as follows:
1. =The Boiling Off.= This is the removal of the gum and natural coloring matter in the silk. It is accomplished by boiling the skeins of silk in water and good olive oil soap for about one hour. This dissolves the gum and leaves the fiber clean and glossy.
2. =Mordanting.= This is done in a bath of nitrate of iron, in which the skeins of silk are allowed to remain one hour. The silk gains some in weight in this operation by absorbing a quantity of the iron in the bath. After having been dipped in the first bath three or four times, it is ready for the soap and iron bath, in which it is repeatedly immersed, the operation causing a deposit of iron-soap on the fiber which adds to its weight, but at the same time does not lessen its flexibility and softness. Eight dippings in the iron and soap bath increase the weight of the silk about 100 per cent.
3. =Blue Bottoming.= The next operation is to dye the silk blue, which is done by immersing it in a solution of potash. In this it is worked for half an hour, when it acquires a deep blue color. It is then taken out, and after rinsing is ready for the "weighting" operations.
4. ="Weighting" Bath.= A catechu bath is now prepared, in which the silk is entered and worked for an hour, and then allowed to steep over night. The result is that the blue on the silk is decomposed, and the goods by absorbing the tannin in the catechu increase in weight from 35 to 40 per cent. This bath is the most important one in the dyeing of "weighted" black silks, as the dyer can regulate the strength of the bath by the addition of tin crystals so as to increase the weight of the silk to an astonishing degree. The proportion of tin crystals used is regulated by the number of iron baths that have previously been given the silk; if two baths of iron have been given, 5 per cent of tin crystals are used; if four baths, 10 per cent, and so on. The action of these chemicals is somewhat complex. All that is known is that by reason of some peculiar quality possessed by silk it is enabled to combine with iron and tin, and that exposure to the air after the baths fixes these chemicals permanently upon the fibers, thus increasing their weight to almost any desired extent. Silk, according to its quality and weight, will take up of these substances from 50 to 200 per cent without creating much suspicion. Instances have been known in which silk has been increased nine times its own weight. All the operations thus far have had for their object the weighting of the silk, although the blueing and the catechu baths have some influence on the finished result. After these come the dyeing operations proper, two in number, mordanting and dyeing.
5. =Mordanting.= A bath of iron liquor heated to 130 degrees F. is provided. The silk is entered, worked well for one hour, then wrung out and hung up to "age" for two hours, after which it is ready for the logwood dye.
6. =Dyeing.= A bath of logwood liquor is prepared to which is added 10 per cent of fustic, and the solution is brought to a temperature of 150 degrees F. In this the silk is entered and worked for an hour, then taken out and wrung dry. Sometimes the black does not come up full enough, and in such cases the bath is repeated.
7. The final operation has for its object the restoration of the luster and suppleness of the silk, which has to some extent deteriorated from the many operations through which it has passed. The brightening and softening of the fiber are effected by immersing the silk in a bath of olive oil in the form of an emulsion. In this the silk is worked until it is thoroughly impregnated with the oil, when it is taken out and wrung dry, after which it is ready for the loom.
Practically the same process is followed in piece dyeing, though only inferior grades of silk are dyed in the web.
=Colored Silks.= This class of silks is generally purer than black and sad-colored silks. It is not nearly so easy to weight the former as the latter, for the reason that there are but few substances capable of giving weight which do not interfere with the effect of light colored dyes. The weighting agents most generally used are sugar and acetate of lead. The weighting by sugar is done after the silk is dyed. A solution is made of pure lump sugar by placing it in a large copper pan with water and heating until dissolved. In this bath the silk is thoroughly saturated, and then dried and finished; or, the dipping process may be repeated several times if desired. One dipping will weight the silk about 12 per cent, two about 20 per cent, and three about 30 per cent. In a solution of acetate of lead, each dipping will weight the silk about 8 per cent, and these may be repeated as often as it is wished. In this case the weighting is generally done on the undyed, boiled-off silk, although it may be done on the dyed silk if the color is such as will stand the acid.
=Mixed Silk Fabrics.= Until lately silk was invariably dyed in the state of yarn. When the silk was to be woven into mixed fabrics, such as satin, gloria, etc., it was impossible to dye both fibers exactly the same shade. Formerly such fabrics were woven with the cotton and silk yarns dyed separately, care being taken to match them as closely as possible. The weaving of dyed yarns of different fibers is open to the objection that when the fabric comes to be finished there is a wide difference in the color, no matter how closely they may have matched in the beginning.
=Ribbons.= Ribbons are woven several pieces in one loom, with a separate shuttle for each piece. The shuttle is carried through the shed or warp by a rack and pinion, instead of being thrown through as in broad goods; otherwise the weaving is the same.
=Velvets.= Velvets and other pile fabrics are woven in two pieces, one over the other, with the pile threads woven back and forth between them. A knife travels between the two pieces cutting the pile threads so as to leave the ends standing up straight. Velvets used to be woven over wires and cut by hand, but this method is practically obsolete.
=Piece Dyeing.= If the goods are woven with the gum still in the silk, it must be taken out afterward, and the goods either dyed in the piece or prepared for printing.
=Printing.= The most primitive method of printing is by the use of stencils. It is the method employed by the Japanese and Chinese. Next came block printing, which is still extensively used in Europe. The pattern is raised in felt on wooden blocks, the color taken up from pads, one block for each color. The results are good, but the work is very slow. Most silk goods are to-day machine printed. The design is engraved or etched on copper cylinders, one cylinder for each color; the color thickened with gum is supplied by rolls running against the cylinders, and the surplus is scraped off by a knife blade, leaving only that in the engraving which is taken up by the cloth. After printing, the cloth is steamed to set the colors, and then washed in order to remove the gum used to thicken the colors for printing.
[Illustration: JACQUARD SILK LOOM]
=Finishing.= All silk goods, whether yarn dyed or piece dyed or printed, are given some kind of finish; sometimes it is no more than is necessary to smooth out the wrinkles. There are many finishing processes by which goods may be treated. They are run through gas flames to singe off loose fiber, and over steam cylinders to dry and straighten them, over a great variety of sizing machines to stiffen them with starch or glue. There are calenders or heavy rolls to smooth and iron them, steam presses of great power to press them out, breaking and rubbing machines to soften them, and tentering machines to stretch them to uniform width. There are also moireing or watering, embossing, and various other machines for special purposes.
=Waterproofing.= One of the worst difficulties with which the manufacturer of piece-dyed and printed silk goods has to contend is the ease with which they become spotted with water, and for a number of years many people have tried to prevent this by various processes.
There are no less than two hundred such processes patented. None of them have met with much success, as they injured the feel or strength of the goods. After goods are finished they are carefully inspected for imperfections, measured, and wrapped in paper and packed in cases for shipment. The complexity and number of processes for treating silk goods may be realized when we know that a piece-dyed or printed fabric is handled its entire length between fifty and one hundred times after it comes from the loom, sometimes even more.
CHAPTER XVIII
PRINCIPAL SILK FABRICS
=Alma.= Cloth, double twilled from left to right diagonally, first made in black only as a mourning fabric. The name is from the Egyptian, as applied to a mourner or a singer at a funeral.
=Barege.= Sheer stuff of silk and wool for veiling, named from the town of Bareges, in France.
=Bengaline.= An imitation of an old silk fabric made for many centuries in Bengal, India, whence the name. The weave is similar to that of ordinary rep or poplin, being a simple round-corded effect.
The cord is produced by using a heavy soft-spun woolen weft which is so closely covered by the silk warp threads that it is not exposed when examined from the wrong side. The same weave is also found in all-silk goods, under the designation of all-silk bengaline. When cheapened by the use of a cotton weft in place of wool the fabric is known as cotton bengaline, although the cotton is in the filling only.
=Berber.= Satin-faced fabric of light-weight cloth. It came into favor about the time of the defeat of the Berbers by General Gordon in his campaign against the Mahdi in North Africa.
=Brocade.= Raised figures on a plain ground.
=Brocatel.= A kind of brocade used for draperies and upholstery; usually raised wool figures on a silk ground.
=Bombazine.= Silk warp, wool weft, fine twilled cloth; originally made in black only for mourning. It is used largely for mourning hat bands.
The root of the name is _bombyx_, the Latin for silkworm.
=Chenille.= Cloth of a fuzzy or fluffy face; woven of cotton, silk, or wool; used sometimes for dress goods; more generally for curtains and table covers. _Chenille_ is the French word for caterpillar, which the single thread of the cloth resembles.
=Chiffon.= A thin, transparent silk muslin. Although one of the thinnest and gauziest of modern silk fabrics, it is relatively strong considering its lightness. To convey an idea of the fineness of the thread used in its manufacture, it is stated that one pound of it will extend a distance of eight miles. In the process of finishing the fabric receives a dressing of pure "size." There are two styles of finish, called respectively the demi- or half size and the full size.
Chiffon finished by full sizing is comparatively stiff; while the demi-finish produces a softer and lighter texture. It is dyed in a great variety of colors, and sometimes is printed in delicate patterns. It is especially adapted for home and evening wear, and is used for neck and sleeve trimming, drapery over silk foundations, fancy work, and millinery.
=China Silk.= A term applied to plain woven silks manufactured in China. The term China silk has been adopted in the United States in recent years for a class of machine-woven silks made in imitation of the hand-loom product. These imitations are narrow in width and lack the soft, lustrous quality of Eastern fabrics, and are also free from the uneven threads. China silks are distinguished by their irregular threads, caused by some of the threads being heavier than others, and their extreme softness.
The warp and filling are identical in size and color, and being woven evenly produce a beautiful natural luster. It is generally plain color, although the figured goods are printed in much the same manner as calico. It is used for gowns, waists, underclothing, etc. It launders as well as white cotton.