Modern bleaching is a highly technical science, conceived and planned by engineers, and carried out with elaborate machinery by skilled workers.
Gray cloth, as it comes from the loom, is of an unattractive color, a dirty grayish yellow, and contains not only those impurities which it has picked up on its journey through the mill but those inherent in its natural state as well, all totalling some five per cent. more or less, of the total weight. In addition there may be numerous bits of leaf from the boll which have clung to the fibers through all the processing, and which appear finally in the cloth as little brownish specks, known to the trade as motes. Finally, there is the sizing which was put into the warp.
Warping—The creel in the rear
Bleaching an Intricate
Chemical Process
In the bleaching of cotton, there is a series of operations which have for their object the elimination of the waxy, fatty matters embodied in the fiber, as well as any dirt which it may have acquired. Then, there is the actual whitening and the bleaching of the cloth which destroys any coloring matter which it may contain and finally there are treatments designed to neutralize the effect of the chemicals used in the bleaching. Thus, the sequence of treatments might be: first, boiling in plain water, which removes certain soluble substances; next, an extended boiling in a strong alkaline solution, which saponifies the waxy, fatty matters in the fiber, and thus removes them from the cloth or yarn. Third, a steeping in a bleaching solution—a solution of chloride of lime being largely employed for this purpose, and which treatment is known as the chemic. Next, after another thorough washing there is a treatment in diluted sulphuric acid to neutralize the effects of the chemic, and finally this is followed again by another thorough washing with possibly an additional mild alkaline treatment. The nature and the method of all these treatments varies considerably, and depends upon the character of the 58 goods being treated, but, at the conclusion, if all has gone well, the cloth should be a good white and should not be impaired in strength.
Singeing Necessary
in Some Finishes
For a certain class of goods, where a clean, smooth surface is required, it is desirable to singe the goods before the bleaching. This is accomplished by passing the cloth, stretched out at full width, very rapidly over heated plates, or through gas flames, so that the fine hairs or fuzz are singed off, but the fabric itself has not had time to take fire. Both sides may be singed and the goods may be passed more than once through the flame. When yarns are singed, the threads are passed through the flame very rapidly, being unwound from one set of bobbins and wound up on another.
