The Raku kiln is often seen as a symbol of experimental involvement with heat and ceramics. Raku is described as a state of mind rather than a technique. The Zen philosophy of self discovery through contemplation, of allowing accidents to happen, is respected. Spontaneity flourishes. Each pot is as individual as the makers themselves.
Raku is a Japanese word freely interpreted as ‘enjoyment’.
It was an ideograph engraved on a gold seal and given by the ruler Hideyoshi to Chojiro in 1598. Raku thereby became his family title.
Chojiro is credited with being the first to produce, in 1580, a low-fired glazed pottery by a direct process which involved putting the pots into and taking them out of the red hot kiln. The Raku process gives the potter control of colourful expression when subjecting pots to oxidations and reductions during cooling.
The openness of the body and the soft nature of the glaze enable subtle variations of colour to be achieved. Originally only oxidation was used following neutral firings. Reduction was introduced in the mid-twentieth century by Paul Soldner of the USA. (The Potters Dictionary by F and J Hamer. A&C Black 2000)
Firing and results
The process of Raku firing differs from other firing methods because the pots are removed from the kiln at their maximum temperature. Thermal shock of this rapid cooling is stressful on the pottery. It is achieved by using an open clay body.
The porosity of the clay body acts like a shock absorber, preventing the body from immediately fracturing when the pot is removed from the kiln.
Raku glazes are often fractured, which are referred to as Crazing. These crackle glazes are enhanced by the post firing smoking of Raku pots that embeds carbon into the crackles of the glaze.
Raku is frequently associated with Zen Buddhism, and the Japanese Tea Ceremony. It was developed in Japan in the 16th century. (An alternative meaning to the word Raku means “joy” or “happiness”.)
Pots are heated to 1800 degrees F, (1000-1200 C) the kiln is opened and each molten glazed pot is removed with a pair of tongs. The extremely hot pots are placed into containers of sawdust, which produces thick black smoke. The carbon is wicked into the porous clay body, blackening the clay and accentuating the crackle pattern of the glaze. (This removes the oxygen from the glaze and clay body of the piece. The result is a blackened clay body and very interesting colours on the piece.)
When the pots have cooled, they are removed from the smoking chamber and doused with water. The soot-covered pots are scrubbed clean to expose the crazed surface and unusual patterns created by this firing process.
Because of the porous aspect of the clay body and crazing of the glazes, Raku pots are not watertight. Their function is in their beauty.