Black dyes
The substances employed to give a black colour to cloth, are red oxide of iron, and tan. These two substances have a strong affinity for each other, and when combiued, assume a deep black colour, not liable to be destroyed by the action of air or light.
Logwood is usually employed as an auxiliary, because it communicates lustre, and adds considerably to the fulness of the black. It is the wood of a tree which is a native of several of the West-India islands, and of that part of Mexico which surrounds the bay of Honduras. It yields its colouring matter to water. The decoction is at first a fine red, bordering on violet: but if left to itself, it gradually assumes a black colour. Acids give it a deep red colour; alkalies, a deep violet, inclining to brown: sulphate of iron renders it as black as ink, and occasions a precipitate of the same color. Cloth, before it receives a black colour, is usually dyed blue: this renders the colour much fuller and finer than it would otherwise be. If the cloth is coarse, the blue dye may be too expensive; in that case, a brown colour is given, by means of walnut-peels.