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Old 11-05-2003, 07:48 PM
Dave Bross Dave Bross is offline
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Pete,

Not to worry about the nepheline syenite...

After seeing this glass I believe that I too will invoke the "no spars" rule in my glass making. Much like my "no guts" rule for eating meat. You only go around once so you might as well try for the best you can get. I will melt some other glasses just for the knowledge but I am just blown away by this particular one.

I hear you on the silica adjustment. That's straightforward if I'm going down in expansion, once I figure out exactly how much it takes to move it.

I'll adjust for the 1% moisture in the sand on the next one. I think you're right about bumping it one point with the 63 grams of soda. In my rough guestimates of expansion via thread pulls it comes closer to some older gaffer clear canes that I have than anything else, and I think those are supposedly around 95.3 COE. I suppose I may be retaining a bit more soda/potash in the melt due to the lower melt temp. too. I definitely haven't quite hit 96 COE yet though.

I'm thinking I might be good at my current COE, close enough to 96 to put 96 color on the outside of the clear, and I'll have a bit of compression in the clear from the slightly lower COE if I use it to encase 96 color.

If I want to go up in COE would it be wiser to maintain the ratio between the potash and soda but increase quantities of soda/potash, or just back off on the sand?

Any suggestions on annealing temps?

And....particular thanks for pointing out the idea of mixing the color base as stock and adding the nitrates and antimony when needed.

Jay,

I'm sure you've noticed all the turmoil, sudden surprises and trouble surrounding batch and cullet supply lately, or should I say always? How about batch or cullet that is not quite on spec. like the chinese stuff? At least if I screw up on the scale or something it's a quick fix. Speaking of screwing up...I'm writing each measurement down as soon as I finish it. I know just how easily I could forget or be distracted.
I find it very exciting to have this level of freedom in having control and adjustability on what I'm using. Particularly having a "one fits all" for becoming oxidising or reducing batch on one mix.

Bob Boyd,

For me, the best general and most easily digested info when I was beginning to think about color, and actual percentage suggestions, was a copy of the book "Modern Glass Practice" by Scholes. It's out of print and hard to find but not impossible. Try Whitehouse books in Corning NY or abebooks.com
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