Like other metals, brass has a reflective surface that shines when the metal is new, but tarnishes over time and becomes dull and spotted. Tarnishing is a natural process for many metals that occurs due to exposure to sunlight and other elements. If you want to stop brass from tarnishing, keep the brass out of the elements or coat the brass. Coating brass creates a protective barrier that keeps the elements from tarnishing the metal.
Coat only exterior brass. In most circumstances, interior brass, which is not exposed to the elements the way that exterior brass is, does not need coating to prevent tarnishing. Keep interior brass in good condition by dusting regularly and washing with soapy water when necessary.
Provide exterior brass with a regular coating of wax. Before applying the wax, dust and wipe down the brass fixture that you want to coat to remove old wax from the brass. Then apply a new wax coat according to the directions on the wax packaging. According to Bernards, applying new wax to brass fixtures once a week protects them from the elements.
Cover brass fixtures in lacquer if your want a more permanent solution to prevent brass from tarnishing. Test a spray lacquer on a piece of scrap metal to make sure it sprays clear, and then spray it on exterior brass fixtures. Ask the Builder recommends 3 to 5 coats of lacquer on each fixture. Once lacquered, brass fixtures do not require regular waxing.