The final spinning into yarn consists of drawing out the roving strand finer and giving it a twist. Two-ply yarn is made by twisting together two yarns, three-ply, three yarns, etc. The air in spinning rooms should be moist and heated to 70° to 900 F. Cotton may be spun on a frame or on a mule, which differ as follows:
In the ring and fly frames, series of rollers, each set revolving faster than the one before, draw out the cotton strand. The twist is then given by a "flier," or a ring which revolves around the bobbin and also feeds the thread to the bobbin. The mule is much more complicated. The spools of roving to be spun and the drawing rollers are on an immovable part of the machine, while the spindles are on a carriage. The carriage moves away from the main machine as the thread is drawn out and twisted, then moves back as the thread is wound on the bobbins.
The mule produces a yarn of greater elasticity, more uniform twist, and is used for best grades of fine yarn, although the frames are partially replacing the mule because they are cheaper to operate. The mule requires more space and more skilled labor to operate it. The yarn from the spinning machines is wound on cops and is ready to be sent to the dyer or to the weaver. Some kinds of goods, as ginghams, have the yarn bleached and dyed before weaving, others not until after weaving. Fancy yarns are made by combinations of different colored yarns, by irregular twisting, and by various other methods.
In order that warp yarns may hold together well, be more compact, and not rub fuzzy in weaving, they are sized. This sizing is the immersion of the yarns in a solution of gums, starches, etc. Light sizing, ten to twenty-five per cent of the weight of the yarn, is put on warps which are to be bleached and dyed afterwards. Medium sizing, twenty-five to fifty per cent, is put on to the warp of light cloth which is to be sent out in an unfinished state. Heavy sizing, fifty to one hundred per cent, is used on the warp of coarse fabrics, as linings and paddings; while extra heavy, one hundred per cent or more, is rarely used. The materials used in sizing may be classed under four heads.
Adhesive bodies are flour, starch, farina, sago, and dextrine. These also are weighting bodies.
Softening bodies are palm oil, castor oil, cocoa oil, olive oil, soaps, etc.
Weighting bodies are china clay, magnesium or zinc chloride, and the adhesive bodies given above.
Antiseptics, zinc chloride, both prevents mildew and is a weighting body.
Not all of these materials are used in one sizing mixture, but all four classes may be found in a size which is to be left on the cloth. If the softening body is omitted in a heavy size, the yarn is too harsh for weaving; if the magnesium chloride is omitted, the fiber is too dry, as this is a deliquescent salt and is necessary. If the zinc chloride is left out, the fabric may mildew or decay entirely.
Warping is the series of processes by which the warp is put into the warp beam which goes into the loom. It consists in rewinding threads from the cops. If the material is to be striped, the threads must be put onto the warp beam in stripes in the order they are to appear in the cloth. Drawing in is the process of threading the warp through the harnesses and the reed of the loom. Up to the present time, drawing in is done almost entirely by hand, although a machine has been invented which ties a new warp onto an old one before the old one is drawn out of the loom, thus pulling the new in as the old is drawn out. There is also now a machine to draw the threads through the harnesses, by which the work may be done in one-third the time required by hand.
The designing and setting up a warp for a figured design is the largest part of the work, for, once the loom is ready, the shuttles fly back and forth, changing from one color to another automatically. The reed beats up the cloth, and if a warp thread breaks a ring drops and stops the machinery. The weaver in a modern factory tends from six to ten looms, and only needs watch them to see that they are running properly and to tie a thread when it breaks.
There are dozens of effects produced by weave, but all combinations may be traced to three simple foundation weaves. In the plain weave, there is a regular interlacing of warp and weft as in darning. In the twill weave, the weft may go under two warp threads, then over two, and so on, the next weft taking up different threads, so that the effect produced will be a diagonal stripe. In the sateen weave, the threads are so arranged that only one series, either warp or weft, appears on the surface, the other series being entirely concealed.
The rib weave is a modification of the plain weave, in which a heavy stripe is produced by combining two or more warp threads. The basket weave is produced by weaving both warp and filling with two threads together.