We have covered in the preceding chapters the culture of raw silk, its reeling, and finally its marketing in the countries where it is to be manufactured into the finished textile. We now come to the mechanical phases of the industry, by which raw silk is made first into yarn and then into fabric. Whereas, in the case of cotton and wool, we have seen that yarn is manufactured by various modifications of the spinning process, this is not true in the case of silk. The spinning process is here supplanted by an operation known as “throwing,” and is resorted to only in the manufacture of yarn from the various kinds of silk waste. 1. THROWN SILK [Sidenote: _Necessity for Throwing_] The ordinary raw silk, as it comes from the filature and is sold in the market, is composed of from two to eight filaments adhering together by virtue of the natural gum secreted by the worm. This thread is too thin and delicate for many uses and so must be submitted to further twisting and doubling—a process called “throwing.” It must be borne in mind, however, that there are several types of fabrics in which raw silk is used without going through the throwing operation. This is usually the case, for example, with the warp threads for crepes, charmeuse, and messaline. [Sidenote: “_Throwsters_”] Although some of the larger silk mills have their own departments for this process, as a general rule it is done by independent concerns known as “throwsters”—who specialize in this particular operation. Machinery of a very complicated and accurate type is necessary, capable of operating at very high speed. It has been found that the investment called for to equip such a mill is too large in most cases to allow the manufacturers to incorporate this operation in their factories, particularly if it happens that the spindles are not fully employed during the whole of the year. [Illustration: _Throwing Machines_] [Sidenote: _Organzine and Tram_] There are two main classes of thrown silk—organzine and tram—the former has a heavy twist and is used for the warp; while the latter is given only a light twist and is used for filling. Within these two general types there are many special grades, according to the type of material for which they are to be used, such as crepe, chiffon, sewing thread, floss silk, embroidery silk, etc. [Sidenote: _Soaking the Raw Silk_] The raw silk as it comes to the throwing mill is done up in books of skeins and packed in bales, as described in a previous chapter. The skeins, after being weighed and examined, are first soaked for about twelve hours in warm soapy water, which softens the natural gum, after which they are thoroughly dried. This, of course, reduces the moisture content below the customary 11 per cent, which is later restored by natural absorption. [Sidenote: _Winding_]