Bronzing.

Scientific American 47, 12.8.1848

When bronze is exposed for some time to the atmosphere, it becomes a peculiar looking greenish color. To make this artificially 2 parts verdigris and 1 part sal ammoniac are dissolved in vinegar, boiled, filtered and much diluted, and articles to be bronzed are immersed in this solution till they acquire the peculiar color, when they are carefully washed. - Different tints may be given to bronze from a reddish to a light yellow, by muriatic acid, or by a mixture of saltpetre, common salt and sulphuric acid. Bronze powders are made from Dutch foil, gold leaf, mosaic gold, or powdered tin or precipitated copper. Precipitated copper is made by putting clean iron plates in a solution of nitrate of copper - the sulphuric acid leaves the copper and attacks the iron. These powders are generally mixed with dry pulverized bone dust. A mixture of these powders with mucillage of gum arabic is used to give paper or wood a bronze appearance. All the bronze powders are made from mixtures of tin foil and brass and copper finely triturated. Copper will appear nearly red when dipped in a solution of nitric acid diluted with water. The copper must be quickly washed from the acid and dried in hot saw dust.