Refractory materials have allowed people to use fire and extreme heat to make products for centuries. The unique ability to withstand extremely high temperatures and retain form and chemical properties make refractory materials such as aluminum and bricks suitable for lining furnaces, kilns, and other equipment. All manufacturing industries that require heat, especially steel industries, use refractory products in some form or another. Many kinds of raw material are used to make refractory products. One important raw material is clay.