[Clayart] Bloating problem at cone 6

Joe Brecha via Clayart clayart at lists.clayartworld.com
Fri Aug 29 15:24:09 EDT 2014


Unless your clays are mixed incorrectly, you are simply over firing. If you
have a controller kiln your thermocouples are probably worn out. As
thermocouples age they read a lower temperature than it actually is. So
instead of firing to cone 6, you are actually firing to cone 7 or higher. Do
you use witness cones? They are the only true guide as to how hot your kiln
is getting. In addition to this possibility you may have added a longer hold
period to the end of your firing. That can easily drive your firing up to
cone 7 or higher. Get witness cones and see what you are really firing to.
Then you can either change your firing schedule and/or replace your
thermocouples. The clays we mix don't like going much above cone 6. Joe
Brecha

-----Original Message-----
From: Clayart [mailto:clayart-bounces at lists.clayartworld.com] On Behalf Of
Ellizabeth Gamelin via Clayart
Sent: Friday, August 29, 2014 7:27 AM
To: clayart at lists.clayartworld.com
Subject: [Clayart] Bloating problem at cone 6

I'm having trouble with cone 6 clay bloating. It's not limited to one type
of clay, I fire six different types and it happens in two different kilns.
I bisque to cone 06. This has just started happening
in the last six months.

Do you think that I should slow down the bisque firing? Maybe do a
ramp/hold schedule instead of a straight on 06 firing? If so does anyone
have a schedule recommendation?

I would really appreciate any help anyone has to offer, this is driving me
crazy!

Thanks,
Liz
Mountain Home Pottery
MAILMAN_MIMEDEFANG WRAP
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