Coloring Gold.

Manufacturer and Builder 1, 1872

Gold is colored by two processes, called the dry and wet color; but the materials used in both cases are the same. They are as follows : one part salt, one part alum, and two parts saltpetre; each material to be pounded separately in a mortar, taking care they are perfectly clean—this is the dry process. After being well pounded, they are put into an iron color-pot and slowly heated over a fire. The color must boil gradually, and must be stirred with an iron rod. It will then rise, and then it is ready for the reception of the articles to be colored, which must not be less than 18-carat. They are suspended in the color by 18-carat wire, and kept in motion till the liquid begins to sink; then they are taken out and dipped in aquafortis pickle. The color will rise again, and then another dip, and sometimes two, is necessary to give the proper color. The wet color process is a much inferior method, except for gold of lower standard, and then not below 15-carat, as the alloy would suffer so seriously from the coloring. The fact is, coloring is no more than taking from the surface the inferior metals, leaving a thin coating of pure gold.

—Ex.