Janet H Walker on fri 16 may 97
vdow@muse.sfusd.k12.ca.us asked:
We have a fairly new Skutt KM 1027 electric kiln with automatic
controller. We've only fired maybe 6 times, and we're having some
problems....
Protect yourself against overfiring with the kiln sitter? Or does this
model not come with a kiln sitter?
Are you using an Environvent or other bottom-pulling vent system? Doing
so helps to even out the temperature.
It took me awhile before I got successful firing my Skutt evenly. I'm
not sure what the main differences are!! Mostly I do fire very slowly.
But I fire slowly AT THE END of the cycle whereas the standard programs,
if I am understanding them correctly, fire quickly at the end, even for
a "slow" firing. With a small kiln and light load, this usually gives
you an uneven firing.
Do you soak? Better to use a slightly lower end temperature and a longish
soak at your top temperature. Then the bottom has a chance to catch up
to the top, if not the middle.
Be careful how you load the kiln -- evenly is good. But you also have
to be sure not to have any shelves or posts close to the pyrometer for
the controller.
Jonathan Kaplan (I think it was) told me that he always fires using half
shelves, even if both are at the same level so that air can circulate
freely throughout the kiln. I haven't done this yet but I have tried to
be more aware of whether the loading will facilitate evenness. He also
recommends a very long soak (he does 2 hours!) AND also changing the end
point of the firing depending on the loading. For example, if there is a
very heavy load (lots of furniture and pots), he changes the end temperature
for the firing to be 50C less than usual. (This would be a full cone.)
For a light load, you would go up to 20 degrees C below the usual. And
then soak until the witness cones say you are done.
Fire by the witness cones on the shelves, not by what the controller does.
At least until you are pretty confident that you know what kinds of results
you get for what kinds of load. It is the cones that tell you what goes on
in there, not the pyrometer. Furthermore, the cones can tell you an
ambiguous story (e.g. when BOTH cones 6 and 7 bend by the same amount
which is what I sometimes end up with). (See Tony Hansen's fascinating
web page on how to read cones at www.ceramicsoftware.com.)
I guess that's it. Good luck with gettin' even!
Jan Walker
Cambridge MA USA
| |
|
