The Conductivity Ring is the classic device to demonstrate the different heat conductivity of different metals. A strong cast ring holds a strip of brass, copper, iron and aluminium such that they meet at the central point. This central point is heated over a flame and a small piece of wax is placed in the depression provided at the tips of each strip. The melting of the wax indicates the ability of each strip to conduct heat. Each strip is stamped with the initial of the metal used.