ENAMEL. A shining vitrified substance, employed as an indestructible coating to pictures, and various articles of taste and utility. The basis of all kinds of enamel is a perfectly transparent and fusible glass, which is subsequently rendered either semi-transparent or opaque by the admixture of metallic oxides. White enamels are composed by melting oxide of tin with the glass, and adding a small quantity of manganese to increase the brilliancy of the colour. The addition of the oxide of lead or antimony produces a yellow enamel. Reds are formed by an admixture of the oxides of gold and iron. Greens, violets, and blues, are procured from the oxides of copper, cobalt, and iron ; and these, when intermixed in different proportions, afford a variety of intermediate colours. The proportion in which these ingredients are used, as well as the degree and continuance of the heat necessary to their perfection, constitute the secrets of the art. The best enamel was formerly imported from Venice ; but during the restrictions on commerce imposed by the late war, the importation had almost wholly ceased. The high price of the article, therefore, induced British artisans to attempt its manufacture, and they succeeded in producing a hard enamel, superior to the best Venetian in whiteness, and much more valuable to the dial-plate makers. In 1817 Mr. Wynn communicated to the Society of Arts a series of receipts for the preparation of enamel colours, and for which a premium was awarded by the Society. The fluxes are those em
ployed by Mr. Wynn." After the fluxes have been melted they should be poured on a wetted flag-stone, or into a large pan of clean water, then dried, and finely powdered in a biscuit ware mortar for use.
To make yellow enamel : take red lead 8 parts, oxide of antimony 1, and white oxide of tin 1. Mix the ingredients well in a biscuit-ware mortar, and having put them on a piece of Dutch tile in the muffle, make it gradually red hot, and suffer it to cool. Take ofthis mixture 1 part, of flux, No. 4, 14, and grind them in water for use. By varying the proportions of red lead and anti mony, different shades of colour may be obtained.
To make orange enamel : take red lead 12 parts, red sulphate of iron 1, oxide of antimony 4, and flint powder 3. After calcining these without melting, fuse 1 part of the compound with 24 of flux.
To make dark red enamel : take sulphate of iron, calcined dark, 1 part, flux, No. 4, 6 parts, and of colcother 1 part; of the two latter mixed, add 3 parts.
To make light red enamel : take red sulphate of iron 1 part, flux, No. 1, 3, and white lead 14.
To make brown enamel : take maganese 21 parts, red lead 8i, flint powder 4.