What Is Raku Ceramics?
Raku ceramics are highly individualized pieces of pottery due to the distinct way in which they are fired. Raku ceramics is both a style of pottery and a firing technique which has its origins in 16th-century Japan. Raku ceramics are made by many potters, but it is still a technique that is hard to master.
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History
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The founder of Raku ceramics is a potter born in Japan in the 16th century, named Chojiro. Chojiro adopted the name "Raku" after he was presented with a plaque containing the raku character by Japanese leader Toyotomi Hideyoshi. Raku became Chojiro's family name, and the name of the unique style of pottery he developed. Chojiro adhered to the Japanese philosophy of "wabi," which sought to see the beauty in things imperfect, and the essence of life in things transient. His pottery style reflects that in the way it is fired---no two Raku ceramic pieces will ever be the same, because the firing technique introduces an element of unpredictability. Chojiro's family is still making Raku ceramics to this day, in a 400-year-old unbroken line of ceramicists.
Firing
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Unlike other ceramic firing techniques, Raku firing requires glazed ceramic pieces to go into an already hot kiln. Raku firing is typically done at around 1,800 degrees Fahrenheit. Because the ceramic pieces are placed in an already hot kiln, the firing process is much quicker, but it also requires that ceramic pieces be pre-fired to a stoneware level (around 2,500 F) in order to withstand the thermal shock that Raku firing involves. The ceramic pieces are left in the kiln only long enough for the glaze to melt---master Raku ceramicist know when a glaze is ready by looking at it, but less-practiced ceramicists usually use a timing device.
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Post-Firing Reduction
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The wabi element of Raku ceramics comes into play in a process called post-firing reduction, or oxidation. As shown on Raku ceramicist Gary Ferguson's website, pottery pieces are taken out of the kiln when fire hot and placed into a reduction chamber, normally a metal drum or tub filled with combustible material (newspaper, sawdust, dried vegetation). The combustible material spontaneously ignites upon contact with the fire-hot ceramic piece. A lid is placed over the reduction chamber and this creates an environment where oxygen rapidly depletes---eventually the oxygen in the ceramics itself is drawn out and this creates the unpredictable, individualized glaze formations that make Raku so highly prized. After about 10 or 15 minutes the ceramic piece is sprayed with water to freeze the glaze pattern.
Uses
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Raku is often used for decoration because of its beauty. Raku ceramics are also less water-tight than other ceramic ware, so this limits uses somewhat. While green tea cups are commonly made with Raku firing, vases that have water sitting in them for a prolonged period of time are very rarely made of Raku, because they eventually leak.
Dangers
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Raku ceramics are far more dangerous to produce than ordinary ceramics. The exposure to heat and fire is much more pronounced, and there is also the danger of ceramic pieces popping or exploding due to the thermal shock of both the placement in a hot kiln and the washing with water in the final stage.
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