The Chau Gong, otherwise known as a tam-tam, is one of the most familiar looking Chinese gongs. The Chau Gong differs in shape from the wind gong in that it has a rim around the outside edge. It also has a very distinctive "target" appearance. It is made of a bronze alloy which is roughly 80% copper and 20% tin, and the crafting process is a mixture of hand hammering and working the bronze on a lathe while carefully heating and cooling the metal. On the Chau Gong, the center spot and outside rim retain the black copper oxide that forms when the gong is made. On the rest of the gong this coating is removed and the surface is polished. Chau gongs are available in a range of sizes, with each size having its own distinct full sound. Smaller sizes have a rich but higher sound while the larger sizes are deeper and ring with more power and sustain.