I’ve been getting lots of emails asking me if my clay can be fired with the SpeedFire Cone system. My answer was always “Unfortunately not,” because the SpeedFire system has no digital controller, and there is no way of knowing how much gas is left in the tank. “Unfortunately,” because not everyone can afford a digital kiln.
I’ve just come back from teaching a 4-day workshop at The Greater Philadelphia Metal Clay Guild, hosted by Holly Gage. Holly had the SpeedFire Cone system and thought it might work for firing base metal clay. It was totally her idea. I thought: what is there to lose? And we tried. Before I go on, please bear in mind that I am not recommending anything, at least not yet; I am just telling what happened.
While I was teaching, Holly was reading the instructions and setting up the system. I prepared 3 test pieces. Two of them I made according to the suggestion for test-firing in my Instruction Manual, and the third was a cane-slices piece, about 10 cards thick.
We did not use the cone system as instructed. We removed the screens, and fired inside the cone rather than on top of it, with the bowl sitting directly on the burner. We used a little stainless steel bowl (typically used for cat food), filled with carbon. The pieces were positioned vertically in the bowl.
We put the cone on top of the bowl and turned the system on.
We tried to set the temperature for the first phase. After the pyrometer reached 1000°F/538°C it suddenly went back to zero, and we realized that the metal wire that connects the thermocouple to the pyrometer had melted. So, we removed the pyrometer and the thermocouple altogether.
After 30 minutes we turned it off and let it cool down. That didn’t take long. Then we proceeded to the second phase, and fired for 2 hours. There’s no telling what the temperature was. The valve of the gas tank was open all the way. Since this tank is supposed to last 3 hours, it seemed the appropriate amount of time for a full firing cycle.
Here are the results:
Full sintering, no under- or over-firing. What a surprise!
There is a lot to be tested yet. I am wondering whether this kind of firing can be done in just one phase. I also don’t know whether the temperature can go high enough for firing steel clay on its own, or how to regulate the temperature to fire White Bronze. If you have the cone system, it will help a lot if you do some experimentation. The more information I have, the better I will be able to report reliable schedules. By the way, this system fits the blue propane tank as well. I just don’t know yet how long it will last. To reach higher temperatures, we can try Mapp gas; this tank fits as well.
Now for a pre-announcement of a future class. Holly Gage will be coming to my studio to teach two different 2-day workshops. Between our schedules, one possible date is in February. Valentines Day is on February 14. What I am asking now is: Who would like to take a class but