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Raku, is an oriental technic from the 16th century, it is believed to have been originated in Coria but it prospered in Japan and has extended throughout the world, apparently thanks to the tea ceremony. The word Raku means “happiness”. It is a method of creating effects with colors and textures with enamels or simply with smoke, rapidly fired and cooled while still in the oven. The clay used for Raku must be prepared with a high percentage of sand or grog to resist rapid changes at the extreme temperatures. A good choice of the clay to be used will avoid the risk of breakage.`
The firing of the enamels is done in gas or wood fired kilns. The enamels and colors are fired between 800 º and 1000 º C with rapid firing, reaching the right temperature in 15 to 30 minutes, then the kiln is opened and the pieces that are red with heat are taken out.
When a piece is taken out of the kiln and it is exposed to the air, it is put, for a short while, into a metal bucket, half full of sand or dry leaves, sufficient for the reduction of heat and smoke to penetrate into the piece and transform the colors, enhancing the crackled enamel due to the heat crash, which is quite common in this enamel technic. Next it is rapidly cooled down, for a short time in another bucket with water, washing out at the same time the smoke stuck to the enamel.
Besides the work done with classic enamel, brilliant and crackled, we also have the naked or lost enamel Raku technic, on which the engobe will not adapt itself to the holder making the enamel loose at the end of the process, and only the drawings produced by the smoke will remain, which can be induced by chance (crackled) or by the work of the ceramist.
There is also the technic known as “matt copper”, thanks to which with an over loaded copper enamel we manage to get a matt finish thanks to the wide color variety which copper develops in a reducing atmosphere.
The oven can be loaded from the top or at the front, although the most recommended is the one by which the body of the oven lifts, thanks to pulleys, and the pieces are left at the top easily workable. This procedure produces smoke, so it must be done in the open air. To get the pieces out of the oven you must use long pincers and protect yourself with spectacles and heat gloves.
Link to Author – Ramón Fort