Like most ceramic firing techniques, Raku ware undergoes two firings: the bisque and the glaze fires. For both processes, Raku is fired at lower temperatures than western high-fire ceramics, resulting in a more porous and somewhat fragile vessel. Neither the Raku bisque fire nor the glaze fire is fueled hotter than 1940 degrees F. Western stoneware, on the other hand, is bisque fired to 2350 degrees F.
The Japanese potter Chôjirô developed Raku to create monochromatic hand-built (not wheel thrown) tea bowls in opposition to the colorful, highly decorated pieces that were then in use. Chôjirô's aesthetic idea was to eliminate movement, decoration and variation of form to more closely align with the philosophy of "nothingness" derived from Zen Buddhism, according to the Raku Museum.
The origin of western pottery is prehistoric. Shards of pottery have been found on every continent and from practically every period in time. Its roots lie in the utilitarian clay-lined baskets and vessels used for storing foods, oils and wine. In contrast, the Raku process developed later in history for a specific ceremonial purpose.
The Raku glaze fire is quick and process oriented. Contemporary Raku potters end the firing with a heavy reduction, which creates the unusual luster colors and smoked areas. Experts learn to predict and control Raku results, but novices enjoy the unpredictable results and the dramatic process.
Regular high-fire ceramics, such as stoneware, require a longer firing process with more gradual temperature changes. Times and temperatures are determined by the ingredients in the clay body and the glazes.
Raku pieces are removed from the kiln with tongs as soon as the glaze melts and are placed immediately in a metal can filled with a combustible material, such as sawdust, paper or leaves. The ware is cooled quickly, and the carbon from the combustible material is brushed away, revealing glaze effects determined as much by the fire and smoke and as by the glaze itself.
The temperature of the glaze fire kiln in the traditional western high-fire ceramic technique is carefully controlled to achieve predictable results. Western glazes behave differently at specific temperatures so that the ceramicist controls the process from start to finish. While a reduction phase in the glaze fire is a normal part of a ceramicist's practice, it is only in Raku that the reduction takes place rapidly and outside the kiln with combustible materials.
Raku is not suitable for use in food preparation or service. Use high-fire ceramics instead.