Thread: Phosphate Opal
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Old 12-05-2006, 01:50 PM
Hugh Jenkins Hugh Jenkins is offline
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When I was teaching and any time I have been at Penland, we used Spruce Pine. The color base for SPB is a good match but holds out the decolorizers, fining agents and oxidizers. We were able to make better phosphate opals with that than we did mixing our own batch. I think Labino covered a lot of things with the formula that SPB is based on. It has small amounts of many things that just seem to help. The zinc, boron, flourine and barium are not enough to really change the glass much but they are just right for selenium-cad colors, phosphate opals, fairly saturated transparents, holding silver and gold in reasonable amounts, etc. I have actually come to like other clear formulas better for working properties, but I think that for most color making, this is a great basic glass.

I'll dig around and see if I can find the notes on that mix. In order to compensate for the sodium in the STP we had to make almost complete glass with the STP and add it in proportions to the color base.
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