RakuRakuyaki (樂焼) or Raku (樂) is a form of 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. The form was created in Japan, and 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 American 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.