The next two steps of investment casting are knockout and finishing. After the castings have cooled, the ceramic shells are broken off using powerful, jackhammer-like tools. It is a very loud and violent part of the process. The castings then go to the finishing department, where any excess metal is removed, the surfaces are polished and finished as specified, and then are heat-treated to ensure the parts have the right properties. Heat-treating can strengthen the parts, improve their elasticity and more.