Gilding may be broadly understood to mean the application of metals in thin leaf form to decorative purposes, by the use of mordants and vehicles. Originally limited in scope to the application of gold leaf, it has now become a general practice to substitute many kinds of metal, both in imitation of gold, and in order to produce other metallic color effects. This is not altogether to be regretted, as the use of the more precious metal in such a form that it is ultimately totally lost to the community is a deplorable waste, which is not entirely defensible, especially as it draws a large quantity of the metal away from its more legitimate use in ' the arts of the goldsmith and metal worker. The small proportion used for really high-class decorative work, as in illuminating and permanent decorative schemes and pictures, is in proportion less than one per cent of the enormous amount used for commercial advertising, and the overlaying of plaster and composition picture frames.
The various metals in common use for gilding in the leaf form are:
Gold, in many degrees of fineness and tint.
Alloys of gold and copper.
Alloys of gold and silver.
Alloys of copper and silver.
Alloys of copper and tin.
The alloys are known as metal d'or, Dutch metal, gold metal, etc. The commonest and cheapest forms are thick and brittle in quality, while the better degrees of gold leaf are beaten to extreme thinness, the malleability and ductility of the metal allowing as many as 2,500 leaves, 3 inches by 3 1/4 inches, to be obtained from 1 ounce of fine gold, or to put it in another way, the total thickness of 300,-000 leaves is less than 1 inch. Gold leaf is usually put up in books of 25 leaves, each leaf being 3 1/4 inches square. It is sold by the 1,000 leaves - viz., 40 books. Silver leaf is usually 4 inches by 4 inches, and metals are made in both sizes, and larger.
Gold leaf is termed white, pale, medium, deep, extra deep, citron, red, etc., according to its color. Gold is readily damaged in the book by handling, damp, and shaking, for this reason good gold leaf of recent make should be selected. The best work cannot be produced by any other. It should be kept in a dry. place, and may, with advantage, be placed upon a hot plate, or in the oven prior to using. The red powder on gold books is put on to prevent the gold sticking to the leaves of the book, it is bole, a red earth from Armenia, of peculiarly flaky, smooth, and soft texture. A red French clay is sometimes used for the same purpose.