Q: What is Raku, and how do you do it?
A: Invented in ancient Japan as a party game, in which guests could decorate a small pot and take it home with them as a keepsake; the Raku technique has enjoyed a revival in modern times.
Characterized by a dark body color, a pattern of blackened cracks, and splashes of metallic color, Raku ware can exceed (or fall short of) expectations as to its appearance. Ware intended for raku is best made from a heavily grogged body high in fireclay, to deal with heat shock. Porcelain works poorly in this application, but stoneware bodies may be used as well as earthenware clay. The pots are dried and bisque-fired in the normal manner, then are (optionally) decorated with underglazes and a low-fire glaze (not exceeding cone 01, and usually around cone 07) is applied. Often this will contain metallic oxides such as copper carbonate, which will reduce to a pure metal in the process. Once the glaze is dry, the pieces are placed in a kiln, which may be cold or already up to temperature. A front-loading kiln is much better than a top-loader for raku, as the ware must be removed from the kiln when the glaze is observed to melt, and the rush of superheated air that comes out from the opened top of a kiln results in a rapid loss of heat, and can be dangerous as well. This process is also much more suitable for outdoor than indoor potteries, due to the toxic fumes generated.
The pot is removed from the kiln with long tongs (wear heat-resistant gloves and eye protection when opening hot kilns) while the glaze is observed to melt, is put on a small pile of leaves, sawdust, or newspaper lying on the ground (these will burst into flame when the red-hot pot touches them; the ground should be cleared of other nearby combustibles), and is covered with a fireproof container so as to seal the pot in a smokey and oxygen-poor environment. Steel drums with their tops cut off, sized proportionately to the ware, work well for this. It is of utmost importance that the ware be transferred and sealed up quickly, one piece at a time, as the reduction effects only take place while the glaze remains molten. Although some sources advise a water quench, this is not necessary, and will only weaken the ware, which does best if allowed to cool off in a warm place.
Due to the crackling of the glaze and the marks of the tongs, the raku technique is not very well suited for producing tableware, although the Japanese traditionally have used it for tea-bowls. But it is capable of producing decorative effects that cannot be achieved any other way, and introduces a measure of spontaneity into the potter’s otherwise methodical craft.