Painting on Glass and Porcelain. II.

Manufacturer and builder 8, 1876

One of the most important materials used for painting on glass and porcelain is manganese, a substance rarely seen in its metallic state; but its oxid are largely employed in the arts, especially for decorating porcelain and staining glass. At Sèvres it is used in the composition of violets and blacks, and replaces advantageously the oxid of cobalt, and with the oxid of iron it is used for obtaining fine browns. This oxid is now more extensively used in pottery than before. The native oxid of manganese is sometimes combined with the oxid of lead as a glaze for the purpose of imparting a peculiar brown to many descriptions of porcelain. It is advisable to employ the oxid of manganese prepared as recently as possible from its solution in hydrochloric acid by precipitation with ammonia or potash dissolved in a large quantity of water. The precipitate, which is the dentoxid of manganese, is well swished, and being dried, carefully calcined. The salts of manganese appears not to be available to the artist in oil or water colors. In glass manufacture the peroxid of manganese forms a very important substance, it is largely used in the making of flint, crown, and plate glass, the principal use being to prevent the peroxidation of the iron which enters into the composition, and thus to preserve the whiteness of the glass. If the quantity employed slightly exceeds that which is necessary to prevent the peroxidation of the iron, or if the glass has been exposed to long-continued or too great a heat, it assumes a fine pink or rose-color. Indeed where glass contains an excess of manganese, although it may preserve its desired whiteness, it will, under the influence of sunshine, slowly ebonize, and become gradually more and more pinky. This is often observed In the windows of old mansions; and it is not an uncommon occurrence that a ship proceeding to a tropical climate with white glass in her cabin windows, returns home with glass of a tine rose tint. Common cast flint glass is often distinguished by this peculiar color, produced by excess of oxid of monganese.

The colors used for painting glass, porcelain, and earthenware are all metallic preparations; they do not afford any shades for the palette of the artist, unless under some peculiar circumstance; still the enamel-painter uses all those colors as well as the potter. It should be remembered that all these metallic oxide, used either for glass or porcelain, or for the higher art of the enamel-painter, are mixed with silicious matter, with which, in the heat of the furnace, they combine and form a hard glass.

We will now give some formula, for the composition of colors with several metals:

Ruby Red. - 6 cwt. of batch (the technical name for the mixture used for making flint-glass) with about 1 ounces of oxid of gold.

Amethyst, or Purple.- 6 cwt. of batch with 20 pounds of manganese.

Common Orange. - 6 cwt. of batch with 12 pounds of iron ore and 4 pounds of manganese.

Gold Topaz Color. - 6 cwt. of batch with 3 pounds of oxid of uranium.

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