Raw silk is shipped to the throwing mill in the original bales from the country of raw silk production. The bales are opened and the skeins enclosed are first checked as to weight and quality and tagged with the name of the owner. The first step is the soaking. The skeins are given an overnight bath in warm, oily soapsuds, usually of olive oil, to soften the natural gum. After the necessary length of time, the skeins are removed, dried and placed on reels or swifts. Then comes the winding process; that is, the silk wound off from the reels onto small spools or bobbins about foul or five inches long. The bobbins are wound with a rapid re ciprocating motion, so as to lay the fibre in diagonal lines. These bobbins are then in general taken to the first spinning and there the single strands receive their first twist, which rounds them, and prevents the compound fibre from splitting up and separating when, by the subsequent scouring operations, the gum . is removed which presently binds them into one. The spinning of silk differs from cotton or wool spinning. In the lat ter, spinning is the drawing out of the fibre or floss into a thread. In silk spinning, the process is that of twisting only. The method used is that of twisting from the vertical bobbin on which the silk has been wound from the swift on a horizontal bobbin. Next fol lows the operation of cleaning, in which the silk is simply reeled from one bobbin to another, but on its way it passes through a slit which is sufficiently wide to pass the filament but stops the mo tion when a thick lump or nib is presented. At this point the throwing of organzine and tram differs. In the doubling, which distinguishes organzine from tram, two or more filaments are wound together side by side on the same reel, preparatory to their being twisted or thrown into one yarn. The twist this time is placed in the opposite direction to that in the original single thread. Bobbins to the number of strands which are to be twisted into one are mounted in a creel on the doubling frame, and the strands are passed over smooth rods of glass or metal through a reciprocating guide to the bobbin on which they are wound. Each separate strand passes through the eye of a faller, which, should the fibre break, falls down and instantly stops the machine, thus effectually calling attention to the fact that a thread has failed. The spinning or throwing which follows is done on a frame with upright spindles and flyers, the yarn as it is twisted being drawn forward through guides and wound on revolving bobbins with a reciprocating motion. In crepe weaves, the filling is made from alternating twists of hard-twist tram. The crepe effect is achieved by the contrary pull of the two tightly twisted threads. The weaver must know the direction in which the threads have been twisted—left or right. For easier identification, the throwstef tints the threads a colour designated by his customer for the left and the right. These colours are known as "fugitive tints" as they must completely disappear in the boiling off of the woven fabric before dyeing. The final spinning brings the thrown silk ready for shipment to the weaving or knitting mill. If skeins have been ordered, each must be carefully divided into small sections by the interlacing of cotton threads. This prevents tangling of the yarn in further handling. If not shipped as skeins, the bobbins or cones are packed carefully into boxes or cases and shipped to the origi nal owner.
Most thrown silk is shipped in bobbins and cones.
Weaving.—The type of looms used in weaving silk are the same as those for other textiles: plain, box and Jacquard. In gen eral, the plain looms weave the flat fabrics such as taffetas, linings, etc. ; the box looms take care of the crepes, novelties ; and the Jacquard loom is the intricate mechanism that weaves elaborate designs for damasks, brocades and lame. For silk, the loom manufacturers have developed many contrivances to give smooth ness to the weaving and regulate the tension on the fine threads. Ends and rough spots that would be relatively unimportant in cotton or wool weaving had to be eliminated in the silk weaving. For many years, the use of the hand loom in silk weaving was considered necessary and as recently as 1932 a writer in the Brit ish publication, Textile Exporter, stated that the "impression exists even now in some of the great silk manufacturing centres in France and England . . . that the personal touch of the weaver of the hand-woven product was a valuable asset to the cloth. That its wearing qualities, looks and handle were improved."
This prejudice for the hand-made article, however, was parallel to that in many other fislds but machine-made silks, that is, woven on power-looms, show a greater degree of real perfection than hand-made silks, and the low-cost production of machine made silks has brought to women throughout the world silk cloth ing that was formerly the privilege of the few.
Silk fabrics are woven either as skein-dyed or piece-dyed mate rials. The first are those woven from the dyed yarn such as neck wear or cravat silks for men's wear or for the fine taffetas. A multi-coloured figured fabric, woven on the Jacquard loom, can be made only from skein-dyed yarns. By far the greater proportion of silk fabrics since 1917 is piece-dyed. The weaving is done from the ungummed thrown silk and the dyeing or finishing is applied after the weaving is completed.
The development of crepe fabrics marked the change. from the skein-dyed to piece-dyed fabrics. The standard staple colours of the silk dresses or hosiery of the i9th and early loth centuries gave way to the multi-coloured and bright shades in prints and solid colours. Colour became the fashion indicator in women's ap parel and the manufacturers of the materials had to supply the popular colours when they were in demand. A supply of undyed fabric or hosiery ready for dyeing or printing within a few days took the place of the products made only on order long in advance of sale to the consumer.
The weaves most closely identified with silk are taffeta, satin, chiffon and crepe. In the United States, public acceptance of these weaves as synonymous with silk resulted in rulings by the Federal Trade Commission that, regardless of the fact that orig inally the words were descriptive of a method of weaving, or con struction of weave, their use on anything but silk content prod ucts must be accompanied by a qualifying description of the fibres substituted for silk. Technically, the words are applied to any fabric made in the method designated as taffeta, satin, etc., whether of cotton, silk, wool, rayon or any combination of them.
Variations of the weaves are found in such popular fabrics as the Canton crepe, crepe de Chine, flat crepe, georgette of the Crepe family ; in the crepe satins, lingerie satins, satin Duchesse, char meuse of the satin family; the triple sheers, marquisettes among the chiffon weaves; and the gros de Londres, faille and plain taf fetas.
Taffetas are the basic plain weaves. Most of the silks of past generations were made in that fashion. Satins were next popular, because the high lustre of silk was especially adaptable to the method of weaving that brings the filling thread on the surface of the material rather than the simple in-and-out movement of the taffeta. Crepes are woven either as the taffeta plain weave or in the satin effect. In many cases, the weaves are combined. Chif fons are the transparent type, thin, ephemeral; the origin of the name is a description—the French for "rag." Silk when woven from the undyed thread is referred to as "raw goods" or "grey goods." The latter term comes from the term gres meaning gum and refers to the natural gum or coating of albuminous matter which is part of the filament spun from the cocoon and ivhich is still a part of the thread before dyeing. The woven fabric has a lustreless, stiff and harsh appearance which would be unacceptable for any practical use—with one exception. That exception is bolting cloth, a unique type of silk fabric with out which flour and grain millers could not produce the type of products now in demand. It can be made only of silk and of un gummed silk. The smoothness of the silk thread and its strength meet the rigid requirements of an even filter of fine texture. No treatment or sizing is used as that would affect the flour in the sifting process. The fabric is very carefully made and for the most part in Switzerland on hand looms. The looms are located in the cellars of mountain homes in the St. Gall and Appenzell sections where the humid air helps to keep the fine threads in place during the intricate weaving operation. Some bolting cloth is made on power looms in France but the best and largest sup ply is made in Switzerland. Bolting cloth is so special a type of silk fabric that in a country of protective tariffs for all other silk goods, as in the United States, it comes in duty free if marked as required by customs regulations. In addition to its use by millers, it has also developed a demand among manufacturers of wom en's cosmetic boxes where it provides a satisfactory filter for face powder.