Copper and brass can be gilded by using the following solution: distilled water, 1 quart; 6 pennyweights of gold converted into chloride, potassium bicarbonate, 16 ounces. To prepare this solution for use, convert the gold into chloride by dissolving it in aqua regia.2 Then dissolve in the distilled water, add the potassium bicarbonate, and allow the solution to simmer over a fire for about one hour. The articles to be gilded are immersed in the warm fluid for a few seconds until the desired color is obtained.
Another good recipe for gilding by boiling is cyanide of potassium, 8 ounces; chloride of gold, 3 pints; sal soda, 8 ounces; water, 1 gallon.
To get a bronze effect on copper, dissolve 3 ounces of nitrate of iron and 1 ounce of sulphocyanide of potassium in 2 quarts of water, and immerse the articles.