Raku Ware - Design Considerations

Design Considerations

Raku is a unique form of pottery making; what makes it so unique is the range of designs that can be created by simply altering certain variables. These variables--which include wax resist, glazes, temperature, and timing--ultimately determine the outcome when firing a piece of clay. Wax resist, which is painted over the bare untainted clay, results in the suspension of wax in water before the raku glaze goes on. This is done so that the glaze does not cover the area where the wax resist was applied, thus creating a design. When in the kiln, the wax melts off and the carbon, that results from oxygen reduction, replaces the wax. This is the result of the combustion reaction. Raku glazes contain alumina, which has a very high melting point. Therefore, carbon will not replace the glaze as it does the melted wax. Raku glazes also contain metallic compounds such as copper, iron, cobalt, which produce different colors. After the glaze has reached its a certain temperature, the metal in the glaze assumes its color. For example, cobalt produces dark-blue, and copper produces green but produces a red when the oxygen in the glaze is completely gone. Any unglazed areas turn black due to the carbon given off from the reduction of oxygen. Next, the clay is moved from the kiln to a container(usually a trashcan), which contains combustible organic materials such as leaves, sawdust, or paper. Once the lid of the container is closed, the reduction oxidation (redox) process begins. The temperature change from the kiln to the container is where the magic of raku occurs. The change in temperature and in the redox sometimes cause cracking or crazing. Crazing is a consistent cracking in the glaze of a piece, as is seen on the white crackle glaze. This either enhance or detract from the design. The timing of removal and placement in water directly affects the shades of each color. Introducing the water to the raku at the right time is incredibly important; if the raku does not cool enough before placement in water, the Raku can crack, break, or even explode!