Raku
From Wikinfo
Rakuyaki (楽焼) or Raku (楽) is a form of Japanese pottery characterized by low firing temperatures (resulting in a fairly porous clay body), lead glazes, and the removal of pieces from the kiln while still glowing hot. Raku is the traditional pottery form for creating bowls for the Japanese tea ceremony.
Typically pieces removed from the hot kiln are placed in masses of combustible material (e.g., straw, sawdust, or newspaper) in order to provide a reducing atmosphere for the glaze, and to color the exposed clay surface with carbon. Often glazes which craze (present a cracked appearance) are used, and the crazing lines take on a dark color from the carbon as well.
This last step in the process is unique to the Western form of Raku. In the traditional Japanese process, the pot is removed from the hot kiln and put directly into water or allowed to cool in the open air. The use of a reduction chamber was a American innovation pioneered by american potter Paul Soldner in the 1960s.
The name for this type of firing is taken from the Japanese family that traditionally produces the ware. The name Raku was bestowed on 16th century Japanese potter Chojiro by the great Japanese tea master Sen-No-Rikyu after he began making tea bowls to the tea master's specifications. The name as well as the ceramic style has been passed down through the family to the present.
Raku is typically biscuit fired at 900�C (1650�F) and glaze fired (the final firing) between 800-1000�C (1450-1800�F). It is known for its unpredicability, particularly when reduction fired, and can be returned to the kiln to re-oxidise, if the effects of a reduction firing are not to the potter's satisfaction. The firing times for Rakuware are short, perhaps three hours total, as opposed to up to 16 hours for stoneware. The time take in much shorter, mostly due to the much more rapid temperature changes during the process. As a result of these, clays used for Rakuware must be able to cope with large thermal stresses. The usual way of dealing with this is to incorporate a lot of sand, or 'grog', into the clay, before forming.
External link
References
- Adapted from the Wikipedia article, "Raku" http://en.wikipedia.org/wiki/Raku, used under the GNU Free Documentation License
