Dave Finkelnburg on wed 29 oct 03
Gigia,
There are two possible explanations for what you observe.
Most likely is the plates crack in the drying or trimming, you just
don't detect the tiny cracks until the bisque firing. You may want to
really look over the greenware before loading it into the kiln, maybe even
use a magnifying glass, just to check for this possibility.
The second possibility is the plates are heating and cooling faster at
the rim than on the foot. Depending on how the plate is made, say if the
thickness is significantly different between the center and rim, or if the
foot is flat on a shelf so the center heats slower than the rim, this can be
an issue. Firing with the foot on a few coils layed out like wheel spokes
can let the center heat up faster and help it keep up with the rim. In all
cases I think uniform thickness across the plate, except for a foot ring, is
helpful.
Good potting!
Dave Finkelnburg, who's finally got his garlic planted and mulched
and is now smugly watching the snow fall in southern Idaho...
----- Original Message -----
From: "Gigia Oman"
I have such a hard time with plates. Of all of the things I make, the
plates are most likely to crack in the firing process. It is
strange....they dry without a flaw, but I'd say 5 out of 10 plates break
during the bisque firing. Does anyone have any pointers for me? I fire
using a gas updraft kiln fueled by propane.
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