Copper & Brass cleaning by Vinegar

Copper is a metallic element; brass is an alloy or mixture of the metallic elements copper and zinc. The surfaces of copper and brass items tamish with prolonged exposure to air, particularly in moist environments with high carbon dioxide (CO2) or sulfur dioxide (SO2) concentrations. The compounds that form on the surface, ranging in color from black to blue to dark green, dissolve readily in acidic solutions. Vinegar contains acetic acid, ketchup contains tomatoes rich in ascorbic acid (Vitamin C), and onions contain malic acid and citric acid. All of these foods provide variable amounts of acid to dissolve the tamish on copper surfaces.