CerroSafe® is a special alloy of Bismuth, Tin, Lead and other metals, that shrinks slightly during the first 30 minutes, to allow easy removal, then expands to exact original size in one hour. We recommend CerroSafe® for making a chamber cast. CerroSafe® melts easily between 158° to 190° F, the temperature of hot water. Melt it in a clean iron ladle. Remove heat as soon as it is completely melted and ready to pour. Clean and degrease your chamber. Remove the casting as soon as the metal cools to room temperature. Sold in 1/2 pound ingots, infinitely reusable, it never wears out. Cast it into holes for missing screws, to learn thread size. Use it to grip small fragile parts while machining them. Case head separation? Use CerroSafe® to grasp and remove it. It has hundreds of uses, if you are clever.