Gavin Stairs on sun 9 aug 98
At 01:59 PM 8/7/98 EDT, Kris Busch wrote:
....
>hours or sometimes days later I will hear a loud crack and the plate or
>bowl is history. ...
I replied:
....
>I note that you see dunting only with the open forms, plates and bowls.
This >leads me to suppose that your problem is one of lack of
"compression". That is, >your forms have been thrown or formed in such a
way as to cause them to dry with >residual tension, probably in the centre
of the form. ...
Well, I guess yesterday I was just not quite with it. This non-compression
fault would normally lead to s-cracking on drying, not to dunting on
firing. Mea culpa. The only way this could be the real cause of the
problem would be if the body were way underfired, and probably quick fired
as well.
So I guess the problem is likely to be either a body composition fault
leading to unresolved stresses, or a glaze problem: crazing leading to very
weak ware that simply cracks. Maybe not enough pugging or wedging? Maybe
some contaminant? I give up.
Gavin
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