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Old 03-06-2006, 01:07 PM
Dave Bross Dave Bross is offline
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Location: Archer FL(near Gainesville)
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Extremely good chance you will get to experience many, many, of Pete's condolences if you go after the red, but, then again, if you get it, you've accomplished something major.

I sound like a used car salesman.

Anyway....

I'll give you some suggestions and then you get to late night experiment until MAYBE you get something that will work.

First problem....gotta have tin with the copper for it to go red gracefully. It can be white tin but then you need something else to take care of reducing the oxygen. Pull out your copy of Weyl, read page 343, read pages 420 thru 432. Rough rule of thumb, start with equal amounts of tin and copper.

The problem is that the tin doesn't want to melt. Hence the streaks Pete mentions. Other than mixing it up with lithium or some other alkalai, which will move the expansion up radically, your best way around this may be high temps for melting. Note: you can always bump up the expansion of your clear cullet with a bit of alkalai to match expansions if you absolutely have to have the lithium to melt the tin in the ruby.I've also thought about using stannous chloride for the tin, but the chlorine would cut back on the "pretty" in the glass and we're talking expensive chemicals again with stannous chloride.

Second problem.....Reducing the oxygen. Black tin really cuts down on problem one and two, but let's see if we can get around having to use it because it's VERY expensive and hard to find.

Sugar used as a reduction agent in copper ruby batch without oxidisers is used around 5 grams to 20 pounds of batch. Thank Dudley Gibberson for that number. Using cullet, you will be fighting oxygen already present in the glass so you will need more reduction.
To give you a speculative maximum number, you can theoretically make an amber glass from cullet by reduction only, using 18 grams of sugar per pound of cullet. Thanks to Rollin Karg for this amber recipe. This will be a "test and tune" situation. If you reduce the glass too far you get livery colored glass, not enough reduction and you get no red.

Another possibility for reduction is antimony. ANTIMONY IS POISONOUS AS HELL!!!!!DO NOT ALLOW IT TO DUST KEEP IT OFF YOUR SKIN! DO NOT THROW POWDER ANTIMONY IN A HOT FURNACE WHERE YOU COULD HAVE A DUST BLOW-BACK OR FUMES! RESPIRATOR AND RUBBER GLOVES MANDATORY!
Ok, I'm done yelling now.
The way antimony is usually used is as a fining agent. It changes valance as you come down from cooking temp and sucks up large quantities of oxygen, which were put in there originally by the nitrates and other oxidisers in the batch.I'm sure you see where this is going. Putting more antimony in with the already melted and fined cullet sucks even more oxygen out of the glass, making for reduction. Thanks to Rollin Karg, I actually have an antimony reduced cullet recipe:

20# cullet
1# soda ash
17 grams antimony
45 grams tin oxide (white tin)
45 grams zinc oxide
45 grams red copper oxide

Antimony in this quantity in a clear glass would discolor it yellow-grey, but that could actually help the red color a bit in this application. The grey may detract a bit from the "pretty".


Problem number three is to get it to fine out. High temps to reduce the glass viscosity so the bubbles can rise is probably your best bet. You can't use the traditional nitrate/antimony combo in reduction glasses because of all the oxygen in the nitrate, and antimony by itself doesn't do much towards fining.
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