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December 11, 2018, 05:54:03 pm
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new crucible

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Charles
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« on: August 11, 2014, 09:09:39 am »

I getting ready to do some centrifugal lost wax casting and I have new, as in never used, crucible. I have heard that you need to "break them in" before you use them for casting. My best guess is that you use Borax to do this. But how much and how to finish the process I have no Idea. Can anyone give a clue or something on how it is done?   saved3

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gemfeller
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« Reply #1 on: August 11, 2014, 09:51:37 am »

Yes, borax is the stuff.  It seals the pores and blocks oxygen entry from beneath the metal.  Set the crucible on a fireproof surface and heat it with a torch until it's glowing red.  While still torching from one side, sprinkle borax into the bowl as evenly as possible and melt it.  Repeat several times until the bowl has a glass-like appearance.  Allow the crucible to air cool away from drafts that might cause it to crack. 
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Charles
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« Reply #2 on: August 11, 2014, 10:00:37 am »

Thanks, that is just the information that I was looking for.

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bobby1
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« Reply #3 on: August 11, 2014, 10:25:19 am »

I seal them by placing borax in the crucible, melting it and using metal tongs to tip the crucible and spread the molten borax around the surface. You have to have the torch directed on the crucible all the time during the process. Just another method that accomplishes the goal of sealing the inner surface of the crucible.
Bob
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