This striking example with blue and green hues and uneven edge has a volcanic feel.
From a Private collection.
One of the main characteristics of raku firing is a second firing at temperatures between 900 and 1,000 degrees C. After about an hour, the object is extracted from the oven when still hot with a pair of long iron tongs and placed in a container filled with different materials – such as wood shavings, saw dust and shredded paper. When in contact with these materials the ceramic triggers a combustion that causes chemical and physical changes in the fired object, which is then removed from the container and dunked in water. The combustion process eliminates the air particles within the ceramic, which results in a shrinking of the object and a change of color. Unglazed, if all the oxygen has been removed, the ceramic becomes black; otherwise it turns into varying shades of grey, depending on the oxygen left. In order to obtain the right color, therefore, the master potter must take into consideration several factors: The kind of fuel used, combustion times and desired final oxygen levels.”