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12AX7
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It'll be fine in the oven. If you want to be even more cautious you can even put a towel between the beaker and the metal grate. Both oven, towel
and beaker will be safe up to 300F (cotton or wool towel).
Tim
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prole
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Thanks, Tim. If it does crack, I won't blame you . I like your towel idea. I
have some welder's cloth that won't even blink in the oven at these temps. I'll give it a whirl and post back with my results.
It worked like a charm. No cracks or nuttin'. Smells are gone. It took about 5 hours at 150 F to drive off the smell of ammonia. I didn't have the
stones to run it hotter. Maybe next time, I've got several more bottles to de-aromatize. And thanks again for the towel idea, I'm gonna use that
from now on.
[Edited on 10/11/2008 by prole]
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jarynth
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Temperature itself is not the problem. Glass is still glass up to 1000K and more. You only have to pay attention to the temperature change rate. Pyrex
expands little, quartz even less, that's why it's more resistant to rapid heating. Insulating your bottle from the metal parts by means of a bad heat
conductor (cloth, fiber wool etc) ensures slower, smoother heating.
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prole
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That clears it up, jarynth. You can soften glass without cracking it if it's heated slowly and evenly, and as long as you don't quench it in water or
otherwise rapidly cool it, it won't crack. In the past, I've dried pyrex glass in the oven directly on the metal grates or a cookie sheet. Nothing
happened to the glass, but now that I am less ignorant on the subject, I'll be using the welder's towel for those purposes. The towel wasn't even
warm after I heated the above bottle for 5 hours at 150F. Next time, the oven will be a bit hotter, because five hours is too long.
On a distantly related note, I once attempted to heat a solid mixture in a porcelain crucible, which is made for heating (right?) and as soon as I put
the flame to it, it popped into several pieces. I replaced that piece of crap with a stainless steel one, which had damn well better not 'pop' when I
put flame to it!
Thanks for your replies, guys.
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12AX7
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Porcelain has a high glass content, you have to be careful with it as well. More porous, refractory ceramics tend to perform better.
Tim
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