Several months ago I attended a one on one class with master Raku ceramicists Lynn Dee. My initial motivation for the session was to hone my sculpting skills. The first project I tackled was a surprisingly intricate antler. From there I took the clay and ran with it. Lips, and horseshoes, and hashtags, oh, my!
"Raku is a process of taking pots, while they are still glowing red from the kiln, and placing them immediately into containers filled with combustible materials such as sawdust, dried leaves, newspaper, etc. A reduction or carbonization process begins once the red hot pots ignite the combustible materials. Lids are then put on the containers to create a totally smoke filled atmosphere. The result is that any unglazed areas on the pots will absorb and turn black from the smoke. During this extreme temperature change of cooling down, cracking occurs on many of the glazed areas on the pots." Bill Herb
Further explanation of the metallic end result via Wikipedia, "[Raku] gets its color from deprivation of oxygen. The reduction agent is a substance from which electrons are being taken by another substance.The reaction uses oxygen from the atmosphere within the reduction tube, and, to continue, it receives the rest of the oxygen from the glazes.This leaves ions and iridescent luster behind. This creates a metallic effect. Pieces with no glaze have nowhere to get the oxygen from, so they take it from clay minerals. This atmosphere will turn clay black, making a matte color."
On Sunday after an initial firing, came the exciting task of glazing and firing. Lynn is a masterful instructor and the process was captivating.