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First firing of new Olympuc kiln. Two large molds. At 1600 I witnessed the breakage of one casting mold. The mold was a negative casting of sculpture weighing qabout 35 lbs. of glassThe other will continue to anneal for 12 days. I have never had a mold break in kiln. What to do. I can not find topic in search or archives. What can I expect? How to deal?The elements!! The clean up!! The new kiln!! The art!!
Judi

Judy

35 lb of glass has quite a bit of static pressure. I will take a guess that maybe your investment wasn't stiff enough. Too much water makes the plaster easy to pour and gets good resolution, but yields a weak mold. Firing too fast can also effect the mold. Driving out moisture is often what breaks the investment. This is one of the reasons that I don't trust straight plaster/silica molds, although there are people who report good results using that formula.

I'd look in to Skamol Vermiculite board for molds. It seems to me to be a great solution, especially for a large mold with lots of glass.

Ha ha
Just kidding. I know it sucks; I've been there. Recently, unfortunately. Clean up- maybe you can coldwork the glass and save the piece, maybe not. 1600 is pretty hot- maybe try a lower temp longer. The colder you can figure out, the easier it is on your mold.
Turn off the kiln- unplug it or shut it of at the breaker- when you are trying to unload it. If there is glass on the element, expect the element to fail soon and get more elements for back up. Glass on the element shouldn't conduct electricity to you while unloading but you never go wrong playing things safe when it comes to electricity.
Glass will find any weakness you have.