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Old 06-06-2018, 04:53 PM
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Pete VanderLaan Pete VanderLaan is offline
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How big a batch do you actually mix and melt at a time?
Phosphates shouldn't be confused with typical opals. Opals grow crystals. They grow and collapse and grow again. They rely on Alumina or calcium Fluoride to grow them. Phosphates still need some calcium to work but not to the point of making a bunch of apatite snot. Phosphates have two glasses in solution at the same time which go through an actually separation going from cooled to heated. It's a billion tiny bubbles causing the opalescence, not crystals.

I would have to think for some time about Dave's assertion about mismatch in the cooling process. I don't think I agree with it at all. Your goal is to have two glasses showing no mismatch at room temp after annealing. The pull test is usually a confirmation that neither glass is tugging on each other at that time. That's true of the Ring and the Hagy as well. I can see wanting to attempt the strike on the opal when drawn as a clear as well as after the phase separation occurs. I would find that info useful.
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