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underglaze pastels and glaze crawling

updated tue 10 jun 03


Zoe Paddy Johnson on mon 9 jun 03

Please excuse me if this is a silly question, but I have just returned to
clay after a very long absence and I am a list newby. I spent many years
working with kiln-fired glass (fused or "warm" glass) in the meantime,
until the liability issues scared me out of the medium.

I have been playing with amaco underglaze pastels/chalks on lightly carved
forms. I have been having problems with the glaze crawling when I follow
the instructions on the box of applying the chalks to a bisqued form and
then daubing on glaze. I am having problems with the glaze crawling. I
assume this is due to the very dusty surface left by the chalks. I have
been using Duncan glazes because I haven't found the Amaco glazes locally.
Could this be the problem?

If this were glass, I would blast it with borax or a very low fire glaze to
make the surface runny. Would this work? Would getting the kiln hotter
work? Would switching to a non-food safe glaze help? I assume this means
it contains lead, and in glass, lead=runny, which might help. These pieces
are not intended to be functional and lead is still used sometimes in
non-functional glass.