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Raku & Transfers

Raku Stoken
Throwing a pot on the wheel The pots are thrown on the wheel with a raku clay body. Thermal shock of the rapid cooling in the raku process is stressful on the pottery. For that reasons an open clay body is used for raku firing. The porosity of the clay body acts like a shock absorber, preventing the body from immediately fracturing when the pot is removed from the kiln. After a day or two of drying, the pot is finished in its final shape. When thoroughly dry, the pot will be fired in an electric kiln for a few hours up to 900 °C. Cooled down, we will start the next phase: glazing.

Glazing A transparent glaze is used that picks up the color of the clay. So a white body will give a white coloured glaze. Typical for raku glazing is to pour the glaze over the pot without too much interfering where the glaze is left on the pot. It will result in white glazed sections and sections with no glaze that blackens in the firing process.

Raku firing The firing proceeds at a rapid pace with the wares reaching a temperature of 975°C in about an hour. Although a thermometer is used for the temperature inside the kiln, glaze maturity is judged by the trained eye. The raku firing process can be followed directly: you fire, the color of the glaze changes, melts, becomes shiny and the pot becomes incandescent. When it's determined that the firing is completed the wares are immediately removed from the kiln. Since at this point the glaze is molten, tongs or other lifting devices are used. The process of raku firing differs from other firing methods because the pots are removed from the kiln at their maximum temperature.

After the firing As mentioned above, the clay body must be able to withstand the huge thermal shock of being removed from an incandescent kiln. The extremely hot pots are placed into containers of sawdust which ignite immediately. The container is then closed with a lid. Inside the container the oxyde is used and there is a thick black smoke. The carbon is wicked into the porous clay body, blackening the clay. Raku glazes are often fractured, which is referred to as crazing. These crackle glazes are enhanced by the post firing smoking of raku pots that embeds carbon into the crackles of the glaze. When the pots have cooled, they are removed from the smoking chamber and doused with water. The soot covered pots are scrubbed clean to expose the crazed surface and unusual patterns created by this firing process.

Transfers
printing is one of the prime methods of decorating ceramics. The advantage over hand-painting is that a print can be accurately and rapidly reproduced. Each artist will be attracted to the aesthetic diversity that print offers. Hand-painting tends to look like just that, whereas a print can take many forms, from the painterly to the photographic. Many of the transfer processes are very similar to methods of printing onto paper. However, in order for prints to be fired onto ceramics there are important differences in the printing mediums and colourants used. The decoration on my objects are from a home-made transfer in cobalt (the coloured triangles) combined with the ready available picture of roses. With some water the images stick to the object. The object is put in the kiln. In 5 hours the temperature of 800°C is reached and kept on that temperature for another hour. The kiln is switched off, and after cooling down the pot is ready. My fascination with the technique lies in the contrast between the stern geometric decoration and the lovely flower on the object.