TECHNIQUE

Raku is a fast firing process which began in 16th century Japan, where it was associated with the traditional tea ceremony. It involves working with a preheated kiln, in my case a small gas fired kiln. The warmed pieces, previously bisque fired to 1900 degrees F., and sometimes with glaze of a colorant (copper carbonate) added to the surface, are placed in the hot kiln and quickly fired up to a temperature sufficient to melt the glaze or fuse the copper to the clay body. At this point the kiln is shut off, the lid removed, and the very hot pieces are immediately removed using long steel tongs, and while wearing asbestos gloves and a long sleeved shirt of cotton or wool (no synthetics; the intense heat could melt the fabric, fusing it to your skin).

In Japan, the hot pieces were placed on a brick to cool and that was the finished product. Western potters generally carry out another step by placing the hot pieces in a metal container into which has been put some combustible material, in my case sawdust and/or straw. After the initial flame up, the lid is placed on the container, cutting off the oxygen supply and creating a reduction atmosphere around the pieces. The still hot clay body absorbs carbon and turns a gray to black color except where it is glazed. My white glaze is actually a clear glaze; it is white because my clay body is porcelain, a white firing clay. If I used a red clay, the glazed areas would be pink or salmon colored. The black and white pieces are then left in the container to cool while the next load is placed in the still hot kiln and fired to temperature, which takes 20 to 30 minutes.

The pieces with copper are treated somewhat differently. After the initial reduction, which develops red/orange/yellow colors as the copper attempts to return to its metallic state, the lid is removed, oxygen enters, and another flame up occurs, which begins to oxidize the copper, developing blues and greens (like an old weathered copper penny). The lid is immediately replaced and more reduction occurs. Sometimes this is done several times, attempting to get a range of colors from the oxidation/reduction combination before the piece cools to the point where it no longer reacts. The piece is then allowed to cool in the container.

After the pieces have been removed from the container they are cleaned with water and a nylon scrubber to remove ash, soot, and oil residue. Post firing additions (copper, horsehair, feathers, leather, beads, etc.) complete the piece.

The raku process is very exciting. Results are rather unpredictable and I feel that it is mostly magic.

Pit firing, as the name implies, involves digging a pit in the ground, lighting the fuel, and letting it burn or smolder until all of the fuel is consumed. The process takes about 24 hours.

The original primitive method starts with unfired clay (greenware), gradually warming the clay and then adding more fuel; and later covering the pit and letting it smolder until consumed. My pit firing is somewhat different: I do a bisque firing first, after which I often put copper carbonate on the piece (but no glazes). This allows me to eliminate the slow warming step and also get more heat in the pit. This fuses the copper to the clay and develops some colors, not as intense as the colors that I get in a raku firing using the same copper carbonate, but mostly oranges and yellows. I sometimes cover the pit with sheet metal or potshards, and sometimes leave it open for more oxidation.

For fuel I use a mixture of cow dung, sawdust, straw, leaves, and sometimes twigs and branches. As in raku firing, the results are relatively unpredictable depending on hot spots, oxidation and reduction. A piece without copper or any other surface treatment will come out black/white/gray in a random pattern, while a piece with copper will have random flashes of subtle color.

As in raku, after the pieces have cooled they are scrubbed and later decorated with additions of natural materials.