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cone 6 porcelain issues


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#1 pam sinclair

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Posted 09 April 2013 - 12:13 PM

I am having problems off and on with a fine textural bubbling just under the surface of fired pieces. Using a Grolleg cone 4-6 porcelain fired with the schedule from Mastering Cone 6 Glazes. Ideas????

#2 neilestrick

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Posted 09 April 2013 - 02:01 PM

Same glaze, different glazes, new batch, etc?
Neil Estrick
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#3 pam sinclair

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Posted 10 April 2013 - 10:56 AM

Same glaze, different glazes, new batch, etc?


It is the clay body itself just under the surface - under the glaze. The glaze is the majolica cone 6 from mastering cone 6 glazes. I fire to 2170 with a 20 minute soak and then fire down.

#4 neilestrick

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Posted 10 April 2013 - 11:56 AM

Sounds like bloating. The clay is over fired. Have you used cones to verify the heat work? 2170 may or may not be accurate with your thermocouple. The 20 minute hold adds about 1 cone.
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#5 Marcia Selsor

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Posted 10 April 2013 - 05:05 PM

I agree with Neil, use some witness cones. It could also be over firing the glaze.
I have used that glaze without any problem on a raku clay body fired to ^6 in electric.

See what a witness cone tells you.

Marcia




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