Calico Bleaching.

The Textile Mercury, 12.3.1892

There have been many patents taken out for rapid bleaching, such as that of Du Motay, and others, by the use of permanganates of potash and other salts, but the results, although good, and the process rapid, cost very much more than by the older methods. Numerous patents have also been taken out for quick bleaching by steaming cloth saturated with caustic soda and various other materials, but the best results have not been attained at a moderate price. Bleaching, in truth, requires a certain time to do it well, and any saving or hurry is usually at the risk of damaging the material or increasing the expense out of all proportion to the advantage gained. Bleachers who desire to push goods quickly should have relatively smaller kiers, and more of them in preference to large kiers, although large kiers produce the cheapest bleaching. Thus, if one bleacher has four pairs of kiers, each holding 4,000 lb. of cloth, while another has only two pairs of kiers, holding 8,000 lb. of cloth, each of them can produce the same quantity per week; but the former sends up four deliveries of cloth in the same time as the latter sends up two deliveries. Very large kiers sometimes take one day to fill, another to boil, and a third to empty; while a small kier may be filled, boiled and emptied, all within the 12 hours. Calico printers require most of their cloth madder-bleached, which is understood to be the most perfect kind of bleaching. Their cloth requires not only to be white, but clean, and everything to be removed from it that can be, leaving it practically pure cotton or cellulose.

Some kinds of cotton are much harder to bleach than others, Egyptian being the most difficult, and ripe American the easiest. Spinners now generally mix severals brands together in the making of yarn, and frequently the selvedges of some cloths are entirely Egyptian, while the rest of the piece may be American or Indian. Such cloths must, therefore, undergo a process sufficient to bleach the most difficult part, even though it be detrimental to all the other parts of the piece. Selvedges are now made of extra hard-twisted yarn, and are extra finely-woven to give strength, so that it is a difficult matter to bleach correctly low cloths that have what are called tape selvedges.