This is a frame built with forty or more spindles. Two or three slubbing rovings are put up behind the machine opposite each spindle ; each end is guided separately into back rollers and thence between smaller rollers, known as carrier rollers, to the front rollers. The back rollers revolve slowly, the front rollers quickly, thus drawing the rovings out into a thinner size or count. The product is wound onto the bobbin by means of flyer and spindle, and is known as dandied or fine roving, and is then ready for the spinning frame.
The spinning is done by exactly the same methods as cotton or worsted, viz., either mules, ring frames, cap or flyer frames, the choice of machine being determined by the size or count of yarn intended to be produced.
Twisting and Doubling.—If a 2-fold or 3-fold yarn is needed, then two or more ends of the spun thread are wound together and afterwards conveyed to the twisting frame for the purpose of putting the needed twist in the yarn necessary for weaving or other requirements. This process is exactly the same as in the cotton or worsted industry, ring or flyer frames being used as desired.
Weft Yarns.—These are taken straight from the spinning frame, wound onto a long paper tube and so delivered to the manu facturer ready to place in the loom shuttle.
Folded Yarns are hairy after being spun and folded, and in addition sometimes contain nibs and rough places. The fibre and nibs have to be cleaned off by means of a gassing machine so constructed that the end of silk (silk yarn) is frictioned to throw off the nibs, and at the same time is run very rapidly through a gas flame a sufficient number of times to burn off the hairy and fibrous matter without injuring the main thread. The yarn is
now ready for reeling into skeins or for warping, both of which operations are common to all the textile yarns. It may be washed or dyed just as required, either in hank or in warp.
As will have been gathered, spun silk is pure silk just as much as that used by the throwster. The yarn is used widely for sewing thread, elastic webbing, lace, plush and for novelty yarns in combination with wool and rayon for use in men's clothing fabrics, upholstery materials, etc. Spun silk is also part of national defence. In the World War, millions of yards of cartridge bag cloth were woven of spun silk. The cloth is made into bags to hold the charges of powder for the guns. Only pure silk proved satisfactory as it was necessary to have complete destruction occur when the gun was fired to avoid a back-fire when the next charge was in serted. Of all the fibres, only silk burned completely without leaving a dangerous ash. To a large extent, the introduction of rayon and spun rayon supplanted spun silk yarns especially in the making of plushes and velvets but there is still a substantial market for the yarn, especially for military purposes.