Fred Hagen on fri 7 nov 08
Yesterday I ran a bisque load to my usual cone 07 but made a mistake in the program and entered a hold at the peqk temp for 9 hours instead of 9 minutes per usual. I caught the mistake about 2.5 hours intoi the peak temperature hold Most of the ware was porcelain cone 10 and I need to know if there is a major problem in glaze application and melt as a result.
I have an answer from a respected authority who I trust but want to know if there are any other thoughts on this problem. My authority said to wet one of the pieces a little to see if it would still absorb moisture. It appears that it will but I'm not certain about the risk of having the glazes just run off the pots. I will use a common studio gas kiln for the glaze work and don't want the shelves to be ruined by my mistake.
Thanks Fred Hagen
Steve Mills on sat 8 nov 08
Fred,
For me, the most accurate way of testing porosity of bisque is to touch it with your tongue; you can feel how absorbent it is better that way than any other. High absorbency will "pull" Low will not.
Bisque just fired is absolutely sterile.
Steve
Bath
UK
--- On Sat, 11/8/08, Fred Hagen wrote:
From: Fred Hagen
Subject: Over Cooked Bisque
To: CLAYART@LSV.CERAMICS.ORG
Date: Saturday, November 8, 2008, 1:53 AM
Yesterday I ran a bisque load to my usual cone 07 but made a mistake in the
program and entered a hold at the peqk temp for 9 hours instead of 9 minutes per
usual. I caught the mistake about 2.5 hours intoi the peak temperature hold
Most of the ware was porcelain cone 10 and I need to know if there is a major
problem in glaze application and melt as a result.
I have an answer from a respected authority who I trust but want to know if
there are any other thoughts on this problem. My authority said to wet one of
the pieces a little to see if it would still absorb moisture. It appears that it
will but I'm not certain about the risk of having the glazes just run off
the pots. I will use a common studio gas kiln for the glaze work and don't
want the shelves to be ruined by my mistake.
Thanks Fred Hagen
Snail Scott on sun 9 nov 08
On Nov 7, 2008, at 7:53 PM, Fred Hagen wrote:
> Yesterday I ran a bisque load to my usual cone 07 but made a mistake
> in the program and entered a hold at the peqk temp for 9 hours instead
> of 9 minutes per usual. I caught the mistake about 2.5 hours in...
It should be fine. It may be slightly less absorbent
than usual, but even a multi-hour soak at ^07 is likely
to have raised the actual cone to no more than ^05 or
so. If you have work that needs an exact match with
prior glazed work, you may need to dip it just a little
longer or warm it very slightly. If you normally brush
or spray your glaze, you are unlikely to notice any
change.
While time can indeed substitute for temperature (the
whole point behind the concept of heat-work), it's
not infinitely interchangeable. Holding at ^07 is not
going to vitrify a ^10 clay, or even get it more than a few
cones more mature, even if it had gone for the full nine
hours.
Even if it was much more vitrified (extremely unlikely),
it would not affect the firing of the glaze, but only its
application, and only then if the application relies on
an exact level of absorbency.
It'll be OK.
-Snail
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