Snail Scott on mon 20 aug 01
At 12:34 AM 8/20/01 -0400, you wrote:
..I suspect that the lower level is probably a cone lower.
Marianne
That's also true in mine, if I don't watch and
control it. For bisque, I don't bother, but for
glaze firings, I put a cone pack at each level.
I start watching when the first guide cone drops
(usually 2-3 cones lower than I am aiming for).
Once the top gets close to temperature, and the
firing cone starts tipping, I cut the top ring
back to medium and let the bottom catch up. (If
it's really uneven, I'll do an 'even-it-up'
earlier than that, too.) I can usually shut
it down dead even if I'm careful. Sometimes,
though, I'll use the discrepancy to my advantage,
and fire glazes that are a few cones apart by
putting (for example) the ^4 glazes on the bottom
and the ^6 glazes on top.
(Talking about top-loading electrics, here.)
When firing single pieces that fill the whole
kiln, I figure the temperature gradient is
probably more even, but it's tricky to put
cone packs at multiple levels without shelves,
so I boost the firing pack up to around the
level of the sitter, and leave a witness pack
down on the bottom to check after the firing
is over.
I put the work as high in the kiln as I can
for its height. Sometimes I have to put the
piece directly on the kiln floor, but if there's
room, I'll raise the bottom shelf as high as
I can for each piece, on 3", 4" or even 6"
posts. I seem to get more even results that way.
I put a higher cone in the sitter, so that the
sitter doesn't shut down before I'm ready. (If
it does, I just tape it back up into position
and push the 'on' button again.) For a ^6 with
a soak, I often use a ^8 in the sitter. My work
is large and thick, and I feel that the work
stays cooler a lot longer than those little
sitter cones do. Even the witness cones are
probably more sensitive than my actual objects,
but I don't especially care. Whether that
temperature condition calls itself ^6 or ^7
or ^5, the only thing that matters is whether
the clay responds the way I want it to. As
long as I know which cone will give me the
information I want, I don't care if it's
technically not the proper one. When the ^6
shelf cone tips, my clay is probably only ^5
or so at most, but I know that that cone reading,
combined with a 3 hour soak on 'low', will
give me results that I like.
What temperature was the clay, actually? I
don't know, and it doesn't matter.
-Snail
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