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Old 04-30-2018, 11:40 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Brossphate v. Cristalica

I melted my first batch of Dave's phosphate opal this weekend. It was the straight formula:

(http://talk.craftweb.com/showthread....ight=phosphate)

The compatibility tests did not make it out of the annealer...except for a couple and they blew apart right at the saw. First pic has some all-brossphate pieces to show the color at the top. At the bottom, the broken pieces are inside or outside color-clear...no difference. Last 2 pics show the color intensity achieved for a couple all brossphate pieces.

I've got my work cut out but I'm hoping for a little direction. My only clue is the E&T measurement which for Dave's 2.5% is only 92.6 while Pete's silver opal is 94.1. The silver opal has fit perfectly for me to Cristalica with ring tests for final proof. I have no idea what the Cristalica E&T would be so I have to make a guess that it's closer to Pete's than the Brossphate.

I'd like to intensify the phosphate similar to Jordan's results. Coincidentally, I can raise the E&T to 95.1 by increasing the phosphate 3.6%, but is this really a good way to modify the expansion? Pete usually points to soda ash and sand for moving the expansion. Should I use soda/sand to find a compatible 2.5% glass or just modify the phosphate and see if I can kill 2 birds with 1 stone?

Thanks for any input and to Dave for sharing this formula. My results need work but that was really fun to work with!
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Old 05-01-2018, 07:41 AM
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Pete VanderLaan Pete VanderLaan is offline
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cristalica is currently about a 97.
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Old 05-01-2018, 12:57 PM
Dan Vanantwerp Dan Vanantwerp is offline
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OK...that gives me a direction. Thanks.
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Old 05-01-2018, 03:25 PM
Jordan Kube Jordan Kube is offline
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Using Dave's calculator I would shoot for 91 LEC for something compatible with Cristalica. My notes indicate the more phosphate you add the lower your target number will be. I melted a 5% that showed 1 point high in a trident seal but no stress showed in the product under the polarimeter. The calculator shows a theoretical 87.75 LEC. Melting a phosphate opal will yield different results than a straight soda lime calcedonia. You can really only rely on your previous phosphate tests as a guide.
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Old 05-01-2018, 04:29 PM
Dan Vanantwerp Dan Vanantwerp is offline
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Wow...thanks Jordan! I had a hunch that making LEC adjustments with the phosphate was a bad idea. I am awaiting a package of a la carte ingredients from Jim at East Bay including his sand. I'll be able to tune this in a bit on my next batch.

I'd be interested to know if you got the fit worked out for the 5% with 1/2 borax and if it needs 2300 to melt.
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Old 05-01-2018, 05:11 PM
Jordan Kube Jordan Kube is offline
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I considered the 5% recipe compatible due to the product showing no stress. I melted at 2300 and I would recommend higher if possible. Go ahead and make LEC adjustments, just don't rely on your non phosphate batches as a guide.
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