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I am trying to make a series of concrentric circles on an existing mold. I want to then slump a bowl over it to get the ridges in the glass. I have tried several things, a paste of kiln wash (crumbled), clay rings (shrunk and cracked) any ideas? Would calcium hydroxate work? I would like to be able to scrape these ridges off the mold after I am done. Is this possible with the lime?
Thank you,
Andrea

why not try plater of paris, or its high temp cousins, hyroperm or hydrocal. They should sand right off.

Liam

I'd use plaster/silica. Mix it soft (i.e., 1 part plaster, 2 parts silica), apply it to the mold wet, carve it after it dries, then scrape it off after you've fired.