To obtain a black colour, dip the brass in a strong solution of copper nitrate or copper sulphate, and then heat on a hot plate or hold the article in a Bunsen flame. To bronze the metal, dissolve 1 1/2 oz. of copper sulphate in 1 pint of water, and pour in a solution of 1 part carbonate of soda in 2 parts water until the precipitate ceases to form. Decant, well wash the precipitate with water and dissolve it in ammonia until the latter is saturated. This solution is warmed and the article dipped in it as before.