Create a blackish-brown copper patina by mixing 2 ounces ferric nitrate, 2 pints distilled water and 1/4 ounce sulfurated potash. Heat the solution and pour it over heated metal, or mix the solution cold and pour it over cold metal. Repeat until reaching the desired color.
Alternatively, create an antique green copper patina by mixing 1/3 ounce of ammonium chloride, 3 ounces of cupric sulfate and 1 quart of distilled water. Heat the solution to 180 degrees Fahrenheit and pour over metal heated to 200 degrees F. Wash the metal in cold water after it has cooled to about 100 degrees F. Let the metal dry and repeat until the desired color is achieved.