Raku is a sixteenth century Japanese firing process originally intended to produce ceremonial tea ware. It involves firing a piece to around 1850 degrees F., pulling it out of the kiln with tongs, then placing it in combustibles such as straw or sawdust. A cover is placed over the glowing piece, forcing the fire to smolder and engulf it with smoke. This smoke changes the chemical composition of the glazes by creating a "reducing" environment. This "reduction" changes copper glazes from green to metallic red, while turning any bare clay jet black. On non metallic glazes, a crackle effect is created when a piece is pulled from the hot kiln into the cold air, causing the glaze to shiver and crackle. As smoke penetrates the piece it enters the tiny array of cracks turning them black. Because of the unique Raku process, no two pieces will ever be the same.
Sagger firing is a cousin to the Raku process. It involves coating the piece with a thin layer of clay known as Terra Sigillata which is burnished and then coated with a layers of ferric chloride. Various elements such as horse hair, sugar, coffee grinds are placed on top of the piece. The pot is then covered in layers of aluminum foil and fired in a kiln at a relatively low temperature where the aluminum burns off and the resulting pot gets all the various colors and patterns. Once fired the pots are coated with wax and then polished.