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The Technique

The clay that is used is mixed with grog, which is hard fired fireproof clay, ground ad meshed to a particular size. It “opens” the clay, and absorbs the thermal expansion and contraction of heating and cooling. Nearly all kinds of clay can be used for RAKU, when mixed with 25-50% grog.

The glazes used earlier where made by lead and clay, but today boron and lithium are mostly used. The glazes on my pots are absolutely lead free.

The different colours are made by metallic oxides and-nitrates, mixed in the glaze, or brushed on the clay or glaze.

The firing process is the most exiting part of making RAKU, and it gives the pot the special RAKU look.

When the pot is fired the first time, by 900 degrees Celsius, it is glazed, dried and put in the hot RAKU kiln, 600-700 dgr.C. then heated to 950 dgr. C.. The glaze is melted  after 10-15 min., the pot is removed red hot from the kiln, and put in a bucket with straw, paper or dry leaves and covered with a lid.

The heat from the pot sets fire to the material. A fire needs oxygen, but as the oxygen is shut out, the fire takes the oxygen from the clay and the glaze. If there is cooper oxide in the glaze, will the combustion take the oxide away, and leave the pure cooper in the glaze.  This is called reduction. The carbon from the smoke will burn into the clay, where it is not covered with glaze, and create a grey or black surface.

The pot is taken op after about 10 min. and put in a bucket with water to cool down in a few minutes.

This is a very rough way to treat the clay. It creates very strong tensions in the pot, and makes both clay and glaze craze, so RAKU pottery is not quite waterproof. You can drink tea from it, but you can’t use it as a vase, and you can’t use it for acid things like juice or marmalade.