Mercerizing

in the manufacture of textiles, a process of treating cotton yarn or fabrics with chemicals by which they are made stronger and are given a luster or gloss. The chemicals employed in the mercerizing process are usually caustic soda and sulphuric acid. John Mercer, by whom the original method of caustic soda treatment for cotton was invented, was an English calico printer. He was seeking for a method which would produce upon cotton goods an effect similar to that produced on woolen goods by fulling. He hoped he had discovered what he wanted when he found that strong caustic soda had a decided shrinking effect upon cotton goods, increasing the weight thereof. Mercer patented his process and named it mercerizing, but it proved of little value, the loss in shrinkage not being counterbalanced, in the opinion of manufacturers, by the gain in strength and weight. Moreover, the caustic soda was expensive.

The next step in the story of mercerizing is a peculiar one. About 1885 worsted crepons and other goods showing crinkly effects were very fashionable. They were woven with two warps, the back warp being of cotton and held at greater tension than the face warp. While the popularity of these goods was at its height, a novelty goods was brought to this country from France, which completely eclipsed the home product. In this French fabric the crape effect was greatly exaggerated, the crinkles having become veritable puffs. American manufacturers tried in vain to reproduce this material. Not until the fabric was long out of fashion was it discovered that the French had taken advantage of the decrease in price of caustic soda and mercerized this fabric. The goods had been woven in a manner similar to that used for the American crepons. The mercerizing caused the cotton backing to shrink greatly, leaving the worsted warp threads of the face in great puffs. In 1897 a firm of German dyers wished to dye a fabric of cotton and silk. Finding that the cotton did not take the dye as did the silk, they concluded to try the mercerizing process, and, lest too much be lost by shrinkage, to stretch the goods and mercerize it while stretched. Their success was astonishing, for they not only accomplished the end aimed at, but found that their cotton had acquired a luster equal to that of silk.

Since that time mercerizing under tension has become very common, and in its effect has been almost equal to the discovery of a new fiber. The mercerizing is done usually in the yarn. With a moderate increase in expense the beauty and variety of cotton goods has been extended. The mercerizing of yarns under tension results in a change in the structure of the fiber. Cotton fiber under the microscope appears as a flat, twisted ribbon. Mercerized, it instantly swells, untwists, becomes firm and round, and loses its cuticula or outer skin, becoming thereby more glossy. The rounded form of the fiber after mercerizing causes the rays of light to be reflected from the surface of the fabric, increasing the luster. Only the better grades of cotton, as the Sea Island and Egyptian, can be mercerized to advantage. A genuine mercerized fabric can be distinguished readily from one in which the glossy appearance has been produced by calendering. If a sample be subjected to a hot water bath and dried, gloss produced by calendering will disappear; but the luster of genuine mercerized goods is permanent.