How to antique brass with acid:
Proprietary antiquing solutions are commercially sold locally and over the internet. Several brands are available. These solutions are a mixture of acids. Typically they contain copper sulfate, ferric nitrate, ferric sulfate or other chemicals. See the list below for a complete list. The process is the same for any acid used. A word of caution. The acid is caustic and you need to wear rubber gloves for protection. Work in a well ventilated area. The material to be antiqued should be clean and the protective lacquer coating should be have been removed in preparation.
Brass item to be antiqued
Wax or lacquer
Abrasive pad (Scotch-brite or similar)
Put on the gloves. Prepare the acid solution per manufacturer’s instructions in the plastic container. Place the brass item into the acid solution, carefully as to not splash the acid and such that the piece is fully covered. Agitate the solution to remove any bubbles from the surface of the item. Surface bubbles will prevent the solution from oxidizing the surface. Carefully monitor the surface for color change. It will only take a few seconds to minutes. When the desired patina is reached, remove the item and rinse in hot water. Polish any white reside off. If you want a darker patina, return to the acid solution for a few more seconds. It the color is too dark, use the abrasive pad to bring back some luster.
Here is a list of chemical available for antiquing brass. Those marked with * are caustic and hazardous. Handle with extreme care.
Acetic Acid or Vinegar
Ammonium Hydroxide *
Glacial Acetic Acid *
Nitric Acid *
Sulfuric Acid *
These chemicals alone or in combination can be used to achieve a particular color. This site lists numerous recipes.
Protect the antique brass patina with a coating of wax or clear lacquer.