Bruce Girrell on wed 20 dec 00
Seasons Greetings to all.
Though you normally hear me piping up about raku, there are times when Lynne
and I would like to make more functional objects. We both like porcelain and
have been keeping our eyes open for a high fire kiln for some time. One has
finally popped up, but now that we're looking at actually shelling out the
money, we realized that we have some questions. The archives have a few
posts on "buying the right kiln" but nothing that I found discussed how to
decide what to buy. We hope that others here can help.
We know that we want a cone 10 gas-fired kiln. The biggest problem is how to
decide how large it needs to be. The one that we are looking at is an
Olympic 2831G, which looks like a cylindrical electric kiln that has been
converted to gas. It has a usable volume of 11.7 cu. ft.
It's that volume that scares me. With an internal dimension of 28 inches
diameter by 31 inches high, it sounds like I can glaze fire about two or
three pots per shelf with three to four shelves. That makes anywhere from
half a dozen to a dozen pots per kiln load, which doesn't sound like much
for all the fuel that it will take to get to cone 10.
What makes an economical kiln size for high fire? Even if I made only a
small number of pots, it would seem that firing them two at a time would not
be economical. Nor would it make sense to wait until I had enough pots to
fill a kiln the size of the ones you see in the Tom Coleman Geil
advertisements. How does one determine an appropriate volume?
What about down-draft vs. updraft? I've kind of been thinking that a
down-draft will give me more even heating and have been contomplating
building an MFT, but this little Olympic updraft is here, assembled, and
ready to go. I've managed to tune our updraft 35 cu. ft. Stack O' Bricks
(TM) bisque kiln so that I have about 1/2 cone between bottom and top, so
I'm not afraid to tinker with the thing, but I still have some misgivings
about an updraft. For example, I don't quite see how you're supposed to put
a stack on this thing.
Finally, if anyone has experiences, good or bad, with this model of kiln,
I'd appreciate it if you would share those.
Thanks,
Bruce "damn, I've exceeded Clennel's attention span again" Girrell
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