Raku is the ancient ceramic Japanese firing method when a piece of pottery is pulled out of a kiln around 1850º F and placed into combustible material, like newspaper. Because of the high temperature the piece is carrying, once it is placed in the newspaper lined chamber, the paper ignites and flames ensue. The reduction firing of flame pulling the little oxygen from the chamber is what encourages the metallic glaze colors to appear. It is an amazing process to behold!