A kiln is an important piece of equipment in the making of pottery. It is an oven where the clay pieces are dried by subjecting them to very high temperatures. Kilns and firing techniques range from the homemade to the highly sophisticated.
This technique uses smoke for firing pottery. It is simple but it may take days to finish because this process uses only low temperatures. The clay pots are first burnished before being fired to a pinkish brown color.
The pots are packed in a bed of sawdust. 6 inches of sawdust is usually enough to make the bed. The sawdust is also sprinkled around the pots and it is allowed to slowly burn for a few days or until the pots are ready to be taken out. The pots are polished and then waxed after smoke firing.
Wood firing uses wood as a source of fuel for firing the clay pieces. This process requires a lot of time and labor to accomplish. It takes a lot of work to prepare the wood as well as firing and making sure the fire is maintained. There are two styles of wood firing, namely the noborigama and the anagama style.
As a rule, soft woods produce a hotter fire quicker than the hard woods. Hard woods are best used as coal on the bottom of the oven to add to the heat. A temperature of 2400 degrees Fahrenheit is ideal for firing pottery. To maintain this temperature, the fire must be constantly stoked. The temperature of a wood fire is also dependent on the type of wood used as well as its moisture content.
Raku firing was first used in Japan during the 16th century. During this process the clay pots are removed from the kiln when the temperature is at its highest. The shock from the sudden change in temperature causes cracks to appear on the pots' surface.
Before the raku firing, the pots are glazed in a mineral bath and dried before being loaded into the kiln. The pots are heated until the temperature reaches 1800 degrees Fahrenheit. This is the point where the pots are removed from the kiln. The hot clay pots are placed in beds of sawdust. The sawdust produces a thick black smoke as it comes in contact with the hot pots. The burnt sawdust sticks to the pot's body, which enhances the crackle on its surface. The pots are cleaned after they have cooled to reveal the unique patterns created by the raku firing.