Blak-Ox DRY produces the darkest smooth deep black patina on silver and gold. Add 3oz of hydrochloric acid to the powdered contents. (Hydrochloric acid can be purchased as muriatic acid at hardware and pool supply stores). Dilute with water for shades of gray. Works on silver, gold, copper, brass, and bronze. Do not use on Aluminum. If not sealed properly Blak-Ox will oxidize the closest metals. We recommend that you double bag the bottle and store away from all metal materials. Handle with Care .