The Art of Dyeing. The art of fixing coloring matters uniformly and permanently in the fibres of wool, silk, linen, cotton, and other substances. Dyeing is a chemical process, and the mode of its performance depends upon the substance operated on. Thus it is found that the process by which wool is dyed black, would only impart a rusty brown to linen. Wool unites with almost all coloring matters with great facility, silk in the next degree, cotton less easily than silk, and linen with even more difficulty. Preparatory to the operation of dyeing, each of these substances undergoes a species of preparation to free the fibres from adhering foreign matter, as dirt, grease, etc., which would prevent the absorption of the aqueous fluid to be afterwards applied, as well as impair the brilliancy of the dye. Wool is cleaned or scoured by means of a weak alkaline lye, soap and water, or putrid urine; the latter being very generally used for this purpose. Silk is cleaned from the natural varnish that covers it, by boiling with white soap and water. Cotton and linen are cleaned with alkaline lyes of more or less density. The substances so prepared are ready to undergo the various operations of dyeing. Among the various coloring materials employed by dyers, some impart their tints to different substances by simple immersion in their infusions or decoctions, and have hence been called " substantive colors;" but by far the greater number only impart a fugitive dye, unless the fibres of the stuff have been previously filled with some substance which has a strong affinity for the latter on the one hand, and the coloring material on the other. The substances applied with this intention are called "Mordants," and generally exercise the double property of "fixing" and "striking" the color. Thus, if cotton goods be dyed with a decoction of madder, it will only receive a fugitive and dirty red tinge, but if it be first run through a solution of acetate of alumina, dried at a high temperature, washed, and then run through a madder bath, it will come out a permanent and lively red. The principal mordants are the acetates of iron and alumina, sulphate of iron, alum, and some other chemical salts. A perfect knowledge of the effect of mordants on different coloring substances is of paramount importance to the dyer. After having received the proper mordants, the goods are dried and rinsed, after which they are passed for a shorter or longer time through an infusion, decoction, or solution of the dyeing materials, which constitute the " dye-bath"; they are again dried and rinsed. In many cases, the immersion in the dye-bath is repeated, either with the same materials or with others to vary or modify the color. After the substances have been properly dyed, they are subjected to a thorough rinsing or washing in soft water, until the latter runs off uncolored.

94. Dye Woods

94. Dye Woods. Decoctions of the different woods are prepared for general use in the dye house as they are required. If the wood be in the chipped state, it must be boiled for an hour, in the proportion of 1 pound of wood to 1 gallon of water; a second boiling is generally given with new water, and the liquor obtained used instead of water with more new wood. This second liquor is not good for dyeing alone, but when employed instead of water for new wood, 3/4 pound of new wood is sufficient. The second liquor may, however, be used as an auxiliary in the dyeing of compound colors, such as browns, drabs and fawns. If the wood be ground the same quantity is taken - namely, 1 pound for each gallon of the decoction required, and is prepared as follows:- on a piece of coarse cloth stretched upon a frame, or laid into a basket, put the ground wood, and place it over a vessel, then pour boiling water over the wood until the liquor that runs through is nearly colorless. Barwood and Camwood are always used in the ground state, the wood being put into the boiler along with the goods; no dec actions of these woods are made. Decoctions of bark and weld are often formed by putting them into a coarse canvas bag, and then suspending it in boiling water.

The coloring principle of archil is highly soluble in hot water, and is useful in combination with other dyeing materials; but used alone, does not impart a permanent color.