Bradford on tue 21 jul 98
Hello fellow claypeople,
Many thanks for all the help last week on jiggering. I think I have it
on the run now and I owe it all to Clayarters.
Now I'm posting a problem for my friends who are not on Clayart(eek
gad!). They have been casting with a custom made slip for a number of
years now. Just recently they've been getting serious bloating
problems. I also fire this same slip with no problems whatsoever. The
only difference is that they have manganese added to their slip to give
a speckled appearrance. They bisque to ^06 in an electric kiln and fire
to ^4 in a gas updraft. They do not intentionally reduce. Does anyone
have any thoughts on the matter? My only idea is to slow the bisque
down considerably and go to ^04. Thanks for reading this.
Tracy in Boothbay Harbor Maine
tbradford@wiscasset.net
Tony Hansen on wed 22 jul 98
>Now I'm posting a problem for my friends who are not on Clayart(eek
>gad!). They have been casting with a custom made slip for a number of
>years now. Just recently they've been getting serious bloating
>problems. I also fire this same slip with no problems whatsoever. The
>only difference is that they have manganese added to their slip to give
>a speckled appearrance. They bisque to ^06 in an electric kiln and fire
>to ^4 in a gas updraft.
It's the manganese. Vitreous bodies containing manganese bloat suddenly.
If its maximum stable temperature is cone 4 and they fire to cone 4.5 it
will bloat.
How do you know they are firing cone 4? Do they have big cones in the
kiln set at the proper angle and throughout? Is there a cone 5 big cone
that is not bent? or a cone 4 that is at 3 oclock?
--
T o n y H a n s e n thansen@digitalfire.com
Don't fight the dragon alone http://digitalfire.com
Calculation/Database Software for Ceramic Industry
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