Brass is a metallic alloy with the majority of the composition being copper. Alloying elements can include zinc, tin, lead, silicon, or manganese depending on the application. Brass can be broken into two categories â€“ red and yellow. Red brass is usually used in plumbing fixtures, gears, and valves and is about 85% copper, 5% zinc, 5% lead, and 5% tin. Yellow brass is usually used in faucets, plumbing fixtures, and household decorations and is about 60-65% copper and 30% zinc.