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I can hear the groans now (especially from all my teachers - Hi guys!) - "not another thermal shock question"! I've spent hours in the archives and couldn't find a situation similar to what I am going to ask.

I have successfully slumped over 12 items with the same schedule, kiln, BE compatible glass and stainless mold I used yesterday. It looked beautiful until I took it out of the mold - there was a sharp crack from side to side 1/3 the way down. I know it has to be thermal shock, right? The only difference from other firings - the heat in my studio went off and the room temp was probably around 40 (yes, it does get cold in Atlanta)when I opened the kiln and the internal temp on the kiln was 51. Possibly the room got down to 33+/- last night. Would this cause the shock?

And the really BIG QUESTION - Can this piece be saved? It's been fused twice and slumped once - oh, and it's 3/4" thick. Help!

Hey Bebe, sorry to hear that. I'm afraid that a slumped, cracked, 3/4" thick bowl is really beyond repair. From your description, it's thermal shock on the way down, so lenghten the cooling portion of your schedule. Brock

Thanks, Brock! I was afraid that was it, and not that the temp got so cold!
Will slow it down EVEN MORE!

Bebe- slump it flat and cut it up to use in other pieces. Marty

I can't imagine that the temperature of your kiln went down fast enough to thermal shock a successfully slumped piece unless the lid was opened and it was hit with a blast of cold air. Thermal shock usually blows a piece apart -- there is some seperation between the pieces. If you looked in and couldn't see the crack, I'm willing to bet it's an annealing problem. The crack ran through slowly after the piece was totally slumped.

Did the power go out, or just the heat? Check the schedule actually in the computer. I've anneal soaked for one minute when I thought I was plugging in one hour.

ch

Thanks, Marty, for the good advice - I'll probably just hit it with a hammer!!!

And thanks, Charlie, I'll check the computer - and with my neighbors to see if they know if the power went out!