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making raku clay, thermal shock

updated tue 11 apr 00


Jon Pettyjohn on mon 10 apr 00


A few of us here in Manila are experimenting with raku.
Since there are no commercial clays available we
must mix our own. So far we have tried using our usual
stoneware and a specially mixed version that has an
addition of 20% talc. We are getting maybe 50% cracked
pots, not sure when the cracks occur but it seems to be
in the quenching.

We'd appreciate any advice on how to formulate a clay
that can stand the process better. I have read that
the additions of Mullite or Kyanite are a big help but
we might not be able to get these here, I'm checking.

Could anyone suggest other materials that might improve
shock resistance?

Would grog be a major factor also? Is coarse much better
than fine? We see so much raku work in books and magazines
that seems very smooth and thin, and large too and we wonder
how this is possible.

Apreciate any info, clayart is where we turn when there's
no place else to go.


Jon Pettyjohn
Mt. Makiling, Philippines