problems with local low fire clay

updated wed 22 apr 98

Odette Binder on tue 21 apr 98

I have been using some local marine clay from the Boston harbor tunnel
project for some time. It's great to throw with, but occaisonally after
firing I get horizontal cracks, not all the way through the walls, but they
are pretty unsightly.

I brush on glaze when the pots are bone dry and fire in an electric kiln to
05 or 06. Has anyone had a similar experience and know what can be done?

Thanks, Odette

Cambridge, MA
USA