White bricks are primarily made using specialized, iron-free clay or a sand-lime mixture to avoid the traditional red color caused by iron oxide. In the clay method, rare white clay is often coated with quartz sand and baked in a kiln at temperatures exceeding 2,000°F to fuse the bright finish. Alternatively, sand-lime bricks blend quartz sand, lime, and water, which are pressed into shapes and chemically hardened using pressurized steam inside an autoclave.