Raku pottery is made by placing glazed pottery pieces into a hot kiln and heating them until the glaze melts into a glossy, molten state. The pieces are pulled out and immediately placed into a container filled with combustible materials like sawdust or dry leaves. The container is sealed tightly, starving the fire of oxygen. This forces the carbon smoke to penetrate the unglazed clay (turning it deep black) and triggers crackled effects in the glazes.