BERNARD J WILLIAMS on thu 22 jan 98
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Have been firing a 7 cu. ft. updraft gas kiln using propane. Able to reach
cone 10 well into the upper regions of the kiln BUT am experiencing really
bad warpage of kordurite (sp) half circle shelving at the bottom of the
kiln. The center of a 21=22 diameter shelf of 3/4=22 thickness was slumped =
a
good 3=22 off level. Bottom of kiln well above cone 10 but don't know how
hot it was. What's the cure? A thicker kordurite shelf or must I get into
silicon carbide? Will I find silicon carbide in most catalogs or is this a
real specialty item? Any suggestions will be appreciated.
Bernie
Bernard Williams
Chigger City Pottery
13065 Pine Grove Road
P.O. Box 99
Cobb Island, MD 20625
BernardWilliams=40compuserve.com
(301) 259-2349
KLeSueur on fri 23 jan 98
In a message dated 1/22/98 7:44:07 AM, you wrote:
<
cone 10 well into the upper regions of the kiln BUT am experiencing really
bad warpage of kordurite (sp) half circle shelving at the bottom of the
kiln. The center of a 21" diameter shelf of 3/4" thickness was slumped a
good 3" off level. Bottom of kiln well above cone 10 but don't know how
hot it was.>>
First you really need to know how hot the bottom is. Then, how are you posting
them. And then, how fast is the firing. All of these factors wilI affect
warping corderite or silicon carbide. I use corderite shelves as high as cone
11. They are 14x24x3/4". It takes me 10 hours to cone 10. Very slow at the
end (Three hours between cone 8 tipping and shut down.). These shelves should
perform well. But you can't abuse them. Fast firing is one of the fastest ways
to warp them. If are firing beyond cone 11 you'll probably loose them.
Kathi LeSueur
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