Kiln
My 70+ cubic foot propane-fueled soda/wood soda kiln is designed to be converted to use bio-diesel in the near future. During the firing, I throw small amounts of wood into the kiln for body reduction, a critical time when the clay body is beginning to transform to the hard pot. Then towards the end of the 24-hour firing, I introduce a solution of soda ash and water into several ports (small openings) built into the kiln. The kiln cools for about 48 hours before it is unloaded.
The process of firing is magical and alchemical. It transforms the soft earth material of clay into a formed, stone-like pot. I use a flameproof clay body for cookware and woodstove pots, and a light stoneware clay body for table and kitchen pots, fired to cone 10 (approximately 2350° Fahrenheit).
Soda Firing
Loading the kiln
Firing
Unloading
Soda Firing Process
I add small pieces of wood through ports above the burners for about two hours from cone 010 to 04, (approximately 1650 to 1930° Fahrenheit). The introduction of wood provides a very light sprinkling of ash on the surface of the pots and produces a smoky atmosphere for carbon trap shino glazes. I have been working with wood in gas-fueled soda kilns for about 15 years and have found that in combination with the use of soda ash, I get a desirable subtle and softening characteristic on the surface of my pots.
I use a solution of soda ash and hot water (approx. 2#'s soda to one gallon of hot water). I apply a light application of soda to my firings usually about 1 ½ - 2 #’s soda.
The soda solution is introduced into the kiln via a garden sprayer. I begin spraying the soda solution into the kiln as cone 8 is going down (approximately 2250° Fahrenheit). I slowly circle the kiln and give a few short sprays in each of eight ports—four in back, two in front, and one on each side. Then I let the kiln breathe and begin again. I am not interested in carbon trapping at that temperature with the soda. For my pots, I do not like the glossy graying surface that produces. So, I let the kiln breathe in between rounds. Depending on weather conditions, the spraying process usually takes about an hour. If I have not reached a soft cone 10 by then I will continue to fire in a neutral atmosphere until I do. If I find cone 10 getting soft before I have used my desired amount of soda, I will turn the burners down while I finish spraying the soda solution. In either case, I clear and lightly oxidize the kiln for 10–20 minutes before shutting down at cone 10. Whether bare clay, slips, or glazes, what I'm looking for is a soft and subtle, but clear and clean surface.
Private Firings
A quarter, a half or the full kiln space may be rented to experienced clay workers. For further information, please call or email.
