Black oxide conversion coatings are widely used in automotive, appliance, machine tool and metal forming industries but can also be utilised to add a different or renewed feeling to any household brass object. It is a conversion coating formed by a chemical reaction with iron in the metal to form an integral protective surface called a patina.
Strip any lacquer or protective coating that may already be on the Brass with either acetone or a lacquer thinner. Goggles, chemical gloves and proper ventilation are necessary throughout the entire process.
Rinse the brass object in distilled water.
Apply the darkening agent to the brass object by either submerging the object in the agent or by painting it on with a brush. Selenium dioxide, or liver of sulphur, is a chemical solution that is typically used by restoration professionals. More commercial products include Birchwood-Casey or Brasso. The Amount of time the chemical is allowed contact with the brass determines the darkness of the patina.
Rinse again in distilled water to stop the chemical reaction.