Alisa and Claus Clausen on wed 28 jul 99
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Thank you Earl for your input.
I realize now I was not clear about the glazes I am using.
I have transparents (both Matt and gloss) that are suited for 04 and 2
transparents (Matt and Gloss) that are for cone 6. One wide range clay =
body,
separate glazes for both earthernware range and medium stoneware range.
The crazing appears when I glaze fire this wide range body to only 04.
I have the understanding (correct?) that stoneware can be bisqued lower and
still be fired up to stoneware glaze temperatures with a good glaze fit.
However, earthernwares must be fired to a properly high bisque temp. to =
later
avoid such glaze faults as blistering, pinholing, etc.
What should that bisque temp. be?
I have always bisqued both earthernware and med. range stoneware to the same
bisque temp. despite my supplier catalogue says I should bisque earthernware
between cone 09 and 04 (920 - 1060c)
and stoneware to cone 06 (1000c).
I bisque everything together to only 920c.
Do you think that bisquing to a hirer temp. for the pots that will come in =
the
04 glaze kiln could resolve the crazing problem I have?
What is a =22normal=22 bisque temp. for earthernware?
What is a =22normal=22 bisque temp. for cone 6 stoneware?
IS there a bisque temp. I can use to fire all greenware together? (in the =
quest
to save energy.)
Thank you for your reply in advance,
Alisa in Denmark.
Dave Finkelnburg on fri 30 jul 99
Alisa,
I'd venture to say the problem isn't in your bisque temperature. If I
understand this correctly, your glaze on your clay body doesn't craze when
glaze fired to cone 6, but does craze when glaze fired to cone 04. Is that
correct?
If that is true, then the problem is, your cone 04 glaze just doesn't
fit your particular clay body glaze fired to cone 04. I doubt changing the
bisque temperature will fix the problem. I rather suspect you need to
modify the cone 04 glaze, or go to a different glaze at cone 04.
Are you using a commercial glaze, or one you mix yourself? Are you
willing to take time to modify your low-fire glaze?
Since your glaze crazes, it obviously has too much expansion compared to
the clay body at cone 04. I have no idea what the correct expansion should
be, but if you want to e-mail the low-fire glaze recipe, if it's not a
commercial product for which you have no recipe, I can run it through
Insight and recommend some changes to lower the expansion. You could test
fire that to see if it would eliminate the crazing.
Please don't expect an immediate reply, I'll be out until Sunday.
Dave Finkelnburg half a world away in Idaho
dfinkeln@cyberhighway.net
-----Original Message-----
From: Alisa and Claus Clausen
To: CLAYART@LSV.UKY.EDU
Date: Wednesday, July 28, 1999 12:34 PM
Subject: Sv: Re: Clear glaze crazing.
----------------------------Original message----------------------------
------------------
--
Thank you Earl for your input.
I realize now I was not clear about the glazes I am using.
I have transparents (both Matt and gloss) that are suited for 04 and 2
transparents (Matt and Gloss) that are for cone 6. One wide range clay
body,
separate glazes for both earthernware range and medium stoneware range.
The crazing appears when I glaze fire this wide range body to only 04.
I have the understanding (correct?) that stoneware can be bisqued lower and
still be fired up to stoneware glaze temperatures with a good glaze fit.
However, earthernwares must be fired to a properly high bisque temp. to
later
avoid such glaze faults as blistering, pinholing, etc.
What should that bisque temp. be?
I have always bisqued both earthernware and med. range stoneware to the same
bisque temp. despite my supplier catalogue says I should bisque earthernware
between cone 09 and 04 (920 - 1060c)
and stoneware to cone 06 (1000c).
I bisque everything together to only 920c.
Do you think that bisquing to a hirer temp. for the pots that will come in
the
04 glaze kiln could resolve the crazing problem I have?
What is a "normal" bisque temp. for earthernware?
What is a "normal" bisque temp. for cone 6 stoneware?
IS there a bisque temp. I can use to fire all greenware together? (in the
quest
to save energy.)
Thank you for your reply in advance,
Alisa in Denmark.
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