What is Raku?
Traditional raku technique was modified by 'western' potters in the mid 20th century with the inclusion of an additional step, sometimes referred to as post-firing reduction, western raku, or smoking. When the red hot pieces are removed from the kiln they are placed into a bin containing combustible materials, such as wood shavings or shredded newspaper.
Unlike other raku artists I use whole oats in my bin, the kind that one feeds to horses. The oats become charred and can be used over and over. The oats also create a soft bed that helps prevent the animal’s delicate legs and antlers from breaking off in the raku process.
As soon as the red hot piece is taken from the kiln and placed in the bin the materials ignite and smolder. The bin is then sealed with a lid to create a highly oxygen-starved reduction atmosphere, which interacts with the glaze chemistry (such as copper). The high-carbon smoke levels in the bin at this time also penetrate any unglazed clay on the artwork, coloring it black.
The crackle glazes make use of the carbon effect by allowing the smoke to penetrate through the crazed glaze and blacken the clay body beneath, highlighting the network of crazing or crackles.
There is a fascinating sense of involvement and immediacy with raku firings. The interaction of smoke, flame etc make for an exciting, spectacular event. For most raku artists firings are typically completed in 45 minutes or so, in gas kilns, compared to many hours for a 'normal' pottery firing. However, I use a custom made electric kiln that is front loading. It takes about 2 hours for the kiln to reach 1850F degrees to 2,000F degrees. By firing a bit slower I have almost no breakage. My small animals are solid clay and this technique works very well.
The massive and rapid temperature changes that are imposed on raku work put incredibly high stresses on the clay body. Combined with the relatively low firing temperatures reached in the raku process the finished artworks are inclined to be somewhat more fragile and porous.
Raku works are therefore intended for decorative art, rather than functional pottery.