This section is from the "A Complete Dictionary of Dry Goods" book, by George S. Cole. Also available from Amazon: A complete dictionary of dry goods and history of silk, cotton, linen, wool and other fibrous substances,: Including a full explanation of the modern processes ... together with various useful tables.
Logwood. A valuable dye, the product of the logwood tree, native to Central America, and grown also in the West Indies. The best qualities come from Campeachy, but is only obtained in small quantities. The wood deprived of its bark is sent to market in the form of large blocks or billets. It is of a dark, brownish-red color, of firm texture and so heavy as to sink in water. The wood was introduced into Europe as a dyeing substance soon after the discovery of America, but for many years (from 1581 to 1662) its use in England was prohibited by law, on account of the inferior dyes which at first were produced from it. Logwood is prepared for use by dyers in the form of small chips. The chips are moistened in hot water and spread in thin layers till a gentle fermentation sets up. These gradually become coated with brilliant metallic green crystals which are at once accumulated and molded into cakes, when it assumes a dark purplish color. The principal use of logwood is for dyeing woolen goods, on which it produces, with various mordants, shades of blue from a light lavender to a dense blue-black, according to the amount of logwood used and the number of dippings. Logwood blacks are a standard product of print factories. They assume a bright red tint by the action of dilute acids, a test by which they can readily be distinguished from aniline and other fast blacks. Log-wood blue is a color produced on woolen flannels and yarns, mordanted with alum and cream of tartar. It is similar in tone to indigo blue. The same color is sometimes produced on cotton, but is seldom used on account of its loose, fugitive character.