Raku is a Japanese method of firing pots in a wood burning or gas kiln (oven). The kiln is constructed so the potter can look inside during the firing process. When the pots look shiny, the oxygen supply to the kiln is closed off and the pots are reduced. At this point, the kiln has reached cone 06 (1800 degrees). Each pot is removed with tongs, placed in a nest of sawdust and shredded paper, then immersed in water to cool, and scrubbed with an abrasive.
Each raku glaze is unique, but most contain metallic compounds (copper, cobalt, silver). Some glazes, like Seth's Luster, contain bone ash for an interesting finish. In crackle glazes, the drastic temperature change causes the glaze to crack; smoke goes into the cracks; and an interesting crackle pattern emerges.
The potter has some control over the finished product. For example, glazes that contain copper and cobalt will be red if the pot is taken out of the kiln quickly; copper turns green if the pot is taken out slowly and oxidizes, while cobalt turns blue.
Raku pots are not food safe, but they will hold water if you put a small glass jar or plastic tube inside the pot.
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