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Old 07-10-2018, 11:01 AM
Dan Vanantwerp Dan Vanantwerp is offline
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I think that a reduced phosphate opal would be good if it could be done with some modification of the existing formula...maybe low PO4 % with moderate black tin. At least start there and see if it's feasible. Getting too far away from that would suggest to me that it doesn't want to be done.

It's impressive that black tin can overcome a cullet oxidation. At my elevation I only use 5g black tin in cullet...30g is way too much. I may actually have a better shot then those at sea level to get this to happen.

Question then becomes...when have you "hit" a reduced glass?
I might try to run silver bromide over the surface, use tramp iron as a color changer or copper (blue versus red). Iron would be a nice addition if the goal was a opal-phos chalcedony.
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