Brass Ingots are created by smelting one Tin Ingot and three Copper Ingots in an Alloy Furnace. They are not to be confused with Bronze Ingots, which are made from copper and tin dusts in a crafting grid, but serve completely different purposes. The primary use of Brass is for crafting Pneumatic Tubes and other RedPower2 Machines. Brass is similar to Gold Ingots, but the texture is slightly brighter.
In real life, brass is made by combining copper and zinc.