Monday, July 20, 2009

More Detailed Raku Info...

Raku is a process for firing pottery, developed in 16th century Japan. The Japanese tea masters for its unique and timeless beauty prized Raku pottery. In the ancient Raku tradition, the Gwinups's fire their pots in a small kiln one at a time. With a practiced eye, they determine when the pots have reached the desired temperature and the glazes have melted. The Raku pots are then removed from the kiln while still red hot and placed in a pit of sawdust and covered so that the combustibles cannot burn freely. The chemical reaction between the burning sawdust and the molten glaze creates beautiful and unpredictable effects on the surface of the pottery. Metallic luster’s and dark crackle effects are the hallmarks of Raku. Each piece, born of earth, water, and fire is a unique creation, never to be duplicated.

In order to complete the firing process, the Raku pottery must remain in the kiln till the temperature reaches approximately 1800°F (about 982°C). At this point the glaze will be molten. The pottery is then removed from the kiln using specially designed Raku tongs. While the piece is still hot and glowing, it is placed inside a metal can full of combustible materials. I use organic materials, leaves, sawdust, straw, dried wet land grasses. etc. The heat emitted from the pottery causes these materials to catch on fire.

After the materials inside the metal can catch on fire, a lid is placed over the can and the pottery is sealed inside. The Raku pottery is capable of withstanding these high temperatures and the fire within the can because it is made from a special type of clay that is capable of withstanding thermal shock. Traditional pottery clays, on the other hand, would crack from the drastic temperature changes Raku pottery undergoes.

As the fire consumes the oxygen within the can, it also draws the oxygen out of the pottery and its glaze. This process is called post fire reduction. It is the post fire reduction stage that creates the unique look of Raku pottery. The resulting patterns and colors are unpredictable, as they are created through the natural process of oxygen removal.

After the pots remains in the sealed metal can for about 20 minutes, they are removed and placed in a can of water or cooled with a hose. This stops the reduction process and freezes the patterns that were created during the post fire reduction stage. The amount of time a piece should remain in the cooling water largely depends on the piece and its size.

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