Apple Tree Ceramics
by Carolyn Horan

Raku Firing Process

The raku kiln

Raku firing is based on a traditional Japanese firing technique. This process involves rapid heating and cooling of the piece. Therefore it is necessary to use sturdy clay and have uniform thickness throughout the piece.

Ceramic pieces are bisque fired and then glazed. They are placed in a raku kiln and heated up to as high as 1800 degrees Fahrenheit in about 45 minutes. Using metal tongs, they are removed from the kiln while red hot and placed in a metal can with some flammable material, such as paper or sawdust, which burns upon contact with the hot piece. As soon as the paper is burning the can is covered. The flames burn out the oxygen in the can and the glazes work their magic.

Reduction is key to achieving the desired colors for many glazes, so quickly getting the ceramic piece from the hot kiln into the covered container influences the results. For other glazes where the oxygen doesn’t affect the colors that much, taking more time to put the piece in the can will help cool the piece and create a desired crackling effect. Either way the smoke resulting from the burned paper will enhance the design as it permeates the piece inside the closed can.