Most fabrics produced by weaving or knitting have to undergo further processing before they are ready for sale. In finishing, the fabric is subjected to mechanical and chemical treatment in which its quality and appearance are improved and its commercial value enhanced. Each type of fabric has its own particular finishing operations. Textiles produced from vegetable fibers require different treatment than textiles produced from animal fibers or synthetic fibers.
Woven cloth is usually boiled with dilute caustic soda to remove natural oils and other impurities. It is then rinsed, scoured in an acid bath, further processed, and bleached with sodium chlorite. Singeing may be done to remove any fibers on cotton or rayon materials, especially if they have to be printed.
In the course of spinning, weaving, and finishing, the fabric is subjected to much pull and stretch. When the material gets wet, the material reverts to its original shape. Sanforizing mechanically shortens the fibers, so that they will not shrink in the wash.
Raising (or napping) is a process in which small steel hooks tear some of the fibers or ends of fibers out of the weft yarn, so the fibers acquire a wooly surface (called the "nap"). This improves heat retention and absorptive properties (as in flannel fabrics), making them softer to the touch. Raising is chiefly used for cotton, rayon, or woolen fabrics. It can be applied to one or both sides.
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