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exploding pie plates

updated thu 15 apr 04


muddauber@INTERLINC.NET on tue 13 apr 04

I have had a few people come back to me complaining that their pie plates
have exploded in their ovens. I fire to cone 10 in reduction. I have
also had problems trying to refire pots made with this clay. The clay
bloats and shatters. (no carbon in bloats) The recipe is:

Plastic vitrox 20
Foundry hills creme 25
Diamond kaolin 20
Epk 10
XX Saggar 15
Kona F-4 8
Silica 2

What can I do to make this clay safer?

Bryan Keeland

Ivor and Olive Lewis on wed 14 apr 04

Dear Bryan Keeland,
There may be folk who would disagree with me on this but it sounds
more like thermal shock rather than a phase change.
One question. Does this happen when the dishes are put into a cold
oven and slowly preheated or are the incidents associated with putting
the uncooked pies into a hot oven.
To rule out silica inversions, total up the free silica content of
each of the minerals you are using in your clay recipe, being
suspicious especially of your Fire Clay.
Best regards,
Ivor Lewis. Redhill, South Australia