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Posted by Rick Crockett on May 5, 2000 17:59:35 UTC

I too have considered casting borosilicate. I am searching for a kiln and recently passed one up that was capable of the temperature and control but was smaller than stated.

I am not sure about the Boron oxidizing out, I don`t believe it does. There are other less stable compounds that will oxidize out and it was my understanding the the melt temp. would go down with a radical increase in co-efficeint of expansion. If your assumption is correct then the glass would oxidize to quartz solidify and anneal all at 2200F and under. Many refractories use gas heating rather than electric to stablize the oxidation process.

This leaves the question of starting material. I believe if one uses the raw materials it will require a batch reactor that is stirred to obtain a homogenous mix and then poured. If one used broken PYREX then expect many bubbles and inclusions. PYREX frit is probably the method of choice but I am not sure you could save anything in the way of costs.

I am eager to hear what you figure out and can probably come up with the annealing formula once you get that far.

Good Luck,
-Rick

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