The operation of extracting the coloring matter from the wood itself, of which it forms only some three per cent. by weight, is a troublesome and delicate one. The logs are chipped or rasped into fine pieces, then moistened and piled in heaps and the color developed by a process of fermentation. Accordingly, extracts of logwood have been put on the market by various large firms, especially of late years, and, while the use of the wood itself by dyers has for the most part been abandoned, these extracts are widely used for dyeing blacks upon silk, in spite of there now being many excellent acid blacks.
The dyeing process, too, is rather complicated, for the goods must be carefully mordanted before dyeing, with salts of iron, chromium, or tin. For this reason wool is rarely dyed with logwood. It is, however, still used for silk dyeing, partly because it gives very full, deep, permanent shades of black, but principally because, by using one mordant after another before dyeing, it is possible to increase enormously the weight of the dyed silk, at very moderate expense.
Turkey Red.—The use of madder which, as before mentioned, was probably known to the ancients, was greatly developed during the sixteenth and seventeenth centuries, owing to the introduction from the near East of the so-called Turkey red process for obtaining, upon cotton and wool, very fast and very brilliant shades of scarlet.
The process took some three months, and consisted of an elaborate series of mordanting operations, before the dyeing proper began. The goods were first soaked in a bath of some fatty material, such as milk or, later, rancid olive oil, and then dried carefully. After this they were soaked in a bath of alum and then in limewater, or a chalk bath—and these operations were repeated over and over, with various manipulations in between.
Finally, the mordanted material was dyed by boiling it in a bath containing the finely-ground madder root, and then “brightened” by washing out, in a boiling soap bath, all the loose color and the unfixed mordant. This process was repeated until the proper shade was reached.
During the early part of the nineteenth century, various extracts of madder were made, by treating the ground root with strong sulphuric acid and other agents, which destroyed the woody tissues and other inert matter, without injuring the coloring matter. The dyeing process also was greatly simplified and shortened. Later the real active principles of the madder root were investigated, and found to be two crystalline bodies named alizarine and purpurine, respectively. And finally, several years after aniline dyestuffs had been discovered and manufactured, two German chemists, Graebe and Liebermann, discovered a method for making these very identical substances out of coal tar.
Since that time the cultivation and use of madder has disappeared almost entirely. But real Turkey red is manufactured to-day, and in very large quantities—and, though freely imitated by inferior products, the modern Turkey red is just as fast to light and to washing as it ever was in the past, and possesses a brilliance and a lustre which never could have been obtained formerly. The process, however, is completed now in hours, not days, and instead of yielding a few shades of red and purple, the alizarine colors have been added to until they cover a large range of blues, purples, reds, oranges, yellows, and browns, all of them as fast as the original Eastern products, and all of them made from coal tar.
The dyes already mentioned were the ones which, after hundreds of years of experiment, proved to be of distinct value. Many of them were expensive in themselves and, in almost every case, the process of dyeing with them was a quite complicated one, worked out by generations of practical dyers, and passed down from father to son as a precious trade secret.
Besides these there were, in almost every community, certain special formulæ and recipes for obtaining, by comparatively simple methods, dyes of varying degrees of value from more or less common vegetable materials. Some of these are occasionally met with to this day. Thus, in the province of Quebec, well down on the St. Lawrence, the French Canadian women still dye their homespun worsteds an orange shade of yellow, of very moderate fastness to light, by boiling them with the skins of the yellow or brown onions. And they get a pretty, but fugitive, shade of golden yellow by using the dried flowers of the goldenrod.
Some recipes from the mountain districts of North Carolina, where the sheep are raised and sheared, and the wool carded, spun, dyed, and woven into homespun, are unique, and wool dyed with them shows extremely good color. Thus, for green, we are told to “Git blackjack or black oak bark, and bile it right good, and put in a li’l piece of alum. This makes the pur’tiest green, mighty nigh, that ever was.” And for purple and black the instructions are to “git maple bark and bile it. Throw in a grain of copperas and put in your wool. Bile it just so long if you want purple, and longer if you want black. The longer you bile it the darker it gits.”