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Old 04-13-2019, 01:51 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 22,276
Pete VanderLaan is on a distinguished road
Shawn points out that the mass is going to change the kiln performance which if you go slow with SP87, voluntarily or not, you're going to see devit. While I know SP's formula, I'm not at liberty to divulge that at Tom's request. I di not write the gaffer formula at all but I do know that John made it to match Gaffer colors and there were no other considerations.

I have slumped large rings of my formula which I blew out , cut on a saw and then slumped and they slumped beautifully with no sign of devit at all. Slumps are handy because they push the glass to places where it may not want to go. It will tell you a lot about your glass. (Just nice high luster and it went down at about 1450F. I like it as my best work in formulation. SP does sell it but I think by the ton until there is sufficient demand that they could have some premixed.

The alumina flux ratio has been around a fair length of time. It was the creation of of Nick Labino, one of the early pioneers in studio formulas. It works very well as a ratio. Alumina is really important in avoiding devit but keeping the material out of the happy devit range keeps Buddha happy

I would council you to stay away from boric acid as an additive. I would say pretty much the same thing about borax. I'm not a fan. I do think the calcium fluoride (CaF) would be the place I would start. You can buy that from Universal Pigment. Not good if you're running electric. I'd go to lithium if that was the case and it's far more squirrely to deal with.

Try to solve one problem at a time with one change in process at a time. Too many and you will start to get really conflicted.
Where are we going and why am I in this basket?
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