Raku is a Japanese firing technique that utilises post-firing oxidation to create limitless variations on glazes, as each piece of pottery comes out totally different from the next. Raku firing can be done in any kiln, but the post-firing oxidation is usually done in a metal drum, when the pottery pieces are still fire-hot from the kiln, according to Idaho raku artist Gary R. Ferguson. Making a raku kiln is relatively easy, using firebricks and a metal drum for the final stage of firing.
Find a suitable location for the kiln, well away from buildings or combustible material like trees and grasses. Lay a square of bricks for the base, around 2 or 3 feet for a small kiln.
Build the walls of the kiln, laying the bricks with 1/4-inch space between them for letting oxygen into the kiln. Make the walls around 2 feet high, so the kiln is a cube shape.
Lay sawdust on the bottom of the brick part of the kiln, then add the pottery pieces, the largest at the bottom. Layer sawdust and pottery until all the pottery is loaded, or there is around 5 inches of space from the top of the brick walls.
Fill the metal drum with newspaper and sawdust to about half way, and set beside the brick part of the kiln.
Light the sawdust in the brick kiln section, and cover the top of the bricks with the metal sheet--leave burning for around 12 hours.
While the pottery is still hot (982 degrees C),use the tongs to take one piece out, while wearing the heatproof gloves and goggles.
Place the pottery piece into the metal drum part of the kiln, shutting the lid quickly after you put the pottery piece inside. The sawdust and newspaper will spontaneously ignite, causing the post-firing oxidation indicative of the raku technique. Once the fire has burnt itself out (around five minutes or so), remove the pottery using tongs and gloves.
Refill the metal drum with new sawdust and newspaper, and repeat the oxidation process with each piece of pottery from the kiln.
If there are numerous pottery pieces to be fired in the raku metal drum, it may help to have several metal drums filled with combustible material on hand, to speed up the process.
Never fire a kiln, raku or otherwise, outdoors on a windy day. Always check that local authorities permit the use of an outdoor kiln in your area.