Art Clay and Gems

[Loriann]

Hello again. I have heard that you can fire gems with a hardness of 7 and over with the Art Clay. I was wondering if that was true and thought to ask you wonderful people if you know? Thanks!

 

[PrecisionGem]

I dont know much about the art clay, but it''s not the hardness that causes problems when heating. Inclusions in the stone can grow, or cause the stone to split. Certain stones are more heat sensative that others. And then I have found that certain colors are more heat sensitive within a stone. For example, the blue tourmalines will crack much quicker with heat than will the nasty olive green ones. I have seen spinels crack from heat, tourmaline, quartz .... the list could go on. Zircons will change color for you if you heat them, they may or may not return to the origianl color.

 

[firebirdgold]

The rio grande gems and findings catalog marks with a symbol all of it''s gems that are safe to cast in place or fire with pmc/artclay.

Hope that''s helpful

 

[Rhapsody]

I've ruined several stones that were supposedly "heat safe" according to the PMC/artclay suppliers. Torch firing seems to do more damage then firing in a kiln and using a fairly long ramp up time to your final temp. The sudden change in temperature during torch firing puts a lot of stress on the stones. Now I only use the synthetic corundum and CZs, theres nothing worse than finding a beautiful stone and making a piece of jewelery for it only to have it explode in my kiln.