The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Coloring Finishing And Painting Wood
Some of these new colors have been found to be fugitive, while others are usually light-proof and permanent. In fact, many of the coal-tar dyes are known to be clearer, more brilliant, and far more permanent than were the much-prized, and greatly-extolled vegetable dyes that have been known and used for hundreds of years.
At the present time coal-tar dyes almost entirely dominate the dyestuff field. They furnish probably more than 95 per cent of the material used in wood-stains, and seem to be driving nearly all of the highly-prized colors of our ancestors from the market. Several very important industries of 75 years ago, such as the production of madder and indigo, have proved unprofitable, and are gradually disappearing from the world's business.
70. Definition of Dyestuff.—A substance which when in solution is capable of changing the hue and imparting a new and permanent color to a fiber, especially a textile fiber, is commonly called a dyestuff. Coloring-matter that will change a color for a brief time only, or that can be washed out, is not classed as a dye.
The chemist thinks of dyes, both artificial and natural, as complex compounds consisting of carbon associated with other elements, particularly nitrogen, hydrogen, oxygen, and sulphur. Such materials or substances are sometimes known as aromatic compounds.
71. Theories of Dyeing.—Chemists have for a long time debated the question as to just what dyeing really is. The puzzle does not yet seem to be settled. Three theories have been advanced to explain the phenomenon of dyeing: (1) the chemical theory, (2) the mechanical theory, and (3) the solid-solution theory.
(1) The chemical theory is based on the possibility that a definite chemical compound called a color-lake is formed between the fibers of the material being dyed and the coloring-matter of the dye. Supporters of this theory say that animal fibers, such as silk and wool, contain animal acids and have the power to react with acid and basic substances, and that they do react and change in color with acid and basic dyestuffs. In the case of cotton fibers, which are inert chemically, an extra treatment with an acid or basic mordant is necessary in order to secure a change of color with dyes; the acid mordant going with the basic dyestuff, and the basic mordants (such as various metallic oxides) being used with acid dyes. There is very little direct evidence to prove the chemical theory. The fact that alcohol and some other solvents may remove the coloring-matter, and leave the fibers unchanged, seems to break down the strength of the arguments for the chemical theory to some extent.
(2) The mechanical theory is supported by possibility that the coloring-matter may be composed of fine particles, which are invisible even with a microscope, that lodge between the tiny imaginary molecules that are supposed to be component parts of the fibers themselves.
