Dyestuffs

substances used for dyeing. Any dyestuff in solution is called a dye. Dyestuffs are known as natural or artificial. The natural dyestuffs are mostly of animal or vegetable origin, and are prepared by purely mechanical processes, such as grinding, crushing, or simply steeping, as in the case of certain chips and barks. Artificial dyes are prepared by chemical processes from coal-tar products.

The larger number of natural dyestuffs are of vegetable origin. They are from various parts of certain trees, plants, and shrubs. Logwood, used for red dyes, and, in combination with other substances, for purples, violets, and blues, is obtained from the chips of a Central American tree. Yellow fustic, from the Brazilian wood of that name; young fustic, from an Italian shrub, a variety of sumac; quercitron, from the inner bark of the dyer's oak of eastern North America; Persian berries, from the Levant; and turmeric, from the East Indies,--all yield yellow dyes. The shell of the pomegranate yields thirty shades of yellow dye. The roots of madder cultivated in the East Indies, the Levant, France, and Holland yield the dye that produces, not only the turkey reds, but madder, purple, orange, and brown. The Cape Verde Islands and the northwestern coasts of Europe produce a seaweed that yields a rich dye. Indigo, obtained from the leaves and herbaceous parts of the indigo plant, is one of the most important dyes. Fifty shades of blue are produced from it. Sumac is raised in the Mediterranean countries for dyestuff, Sicily producing the best. It is gathered also in Virginia. Gall nuts, produced on the leaves and twigs of oaks and other trees by the punctures of various egg-laying insects, yield a valuable dyestuff.

Among animal dyes cochineal stands easily first in importance. The famous Tyrian purple is produced by a fluid secreted by a shellfish. Sepia is obtained from the common cuttlefish.

Until about fifty years ago the dyer depended entirely upon these natural products for his dyes, mixing and preparing them according to certain recipes; knowing, perhaps, under what conditions he was most successful, but not knowing why. In other words, his knowledge was wholly unscientific. The development of applied chemistry has opened up a new source of dyestuffs and has revolutionized dyeing processes. The dyer no longer works in the dark, but is guided by scientific principles. While the natural dyestuffs are still in use to some extent, they have been largely superseded by artificial colors, produced indirectly from coal-tar. Coal-tar is a thick, black, opaque liquid, which condenses in the pipes when gas is distilled from coal. Coal-tar was considered formerly a waste product; but the chemist has succeeded in obtaining from it many useful substances. It is the most abundant source of many beautiful dyes. These are classed frequently as aniline dyes, because aniline was the first substance discovered from which these dyestuffs were produced. There are, however, other groups of coal-tar colors besides those belonging to the aniline group. Coaltar colors are more brilliant and give a greater variety of tint and shade than natural dyes. For some time after their discovery they were regarded as more transitory, especially if fabrics dyed with these colors were exposed to sunlight. This objection has been overcome to a large extent. At the present time the primary colors, as well as tints and shades produced by combinations of the primary colors, are extracted from coal-tar products. Some of these artificial colors have the same chemical constituents as the natural dye. A French chemist estimates that fourteen thousand shades and tints can be produced from coal-tar colors.

The dyer may purchase his dyestuffs prepared by the chemical manufacturer. From these the dyes or solutions are prepared at the dye works. The larger dye works have chemical laboratories in connection, and prepare their own dyestuffs. According to the last United States census, 37,000 people are employed in the manufacture of dyes, and in dyeing and finishing cloth and its materials. The demand for dyes has become so great that $20,000,000 worth of madder is made from chemicals yearly.

See Calico; Madder; Indigo; Aniline; Saffron; Sepia; Ink; Purple; Paint; Painting; Logwood