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Old 03-18-2022, 01:41 PM
Brice Turnbull Brice Turnbull is offline
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Can I mix color rod with clear cullet?

I have an order for a lot of opaque black glass. I work from an electric wound-wire element furnace which maxes out around working temp and won't melt batch. I am melting Bomma cullet, in a 55 pound capacity crucible and it works for me.

I bought 15 kilos of Reichenbach black, but it's somewhat slow and wasteful to use a piece of the color bar for each blown piece I make, as the finished pieces are about the size of a grapefruit.

I have an old crucible at the end of it's productive life. It occurred to me that I may be able to melt the black rod into clear glass in that crucible and just make all my black pieces from the furnace.

The method that occurs to me is to cut the rod up into slices, and then 1/4 slices and put in about 6 nuggets of the Bomma cullet with each 1/4 slice of black rod. Total of about 8 pounds per charge, let it melt to liquid state, and stir with a punty like twice for 15 seconds each time.

It sounds really sloppy and like I will probably get strands of black and strands of clear in the final piece. Even if I returned the rod and used frit, I don't have much faith it will yield a smooth black glass body.

Any thoughts on a way to use the color rod and clear cullet? Or should I just order black cullet from Gabbert?

Thanks for any input!
Brice
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Old 03-18-2022, 01:58 PM
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Pete VanderLaan Pete VanderLaan is offline
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Likelyhood of this working is about "0". The color rod is likely a 24% lead and your cullet is a soda lime. Melted together they will resemble oil and water. Cordy, really cordy.. The rod wants to be melted very cold to retain it's color. Once Dale made me do this with Tabac and it turned to absolute shit at about 2100F 1800 might have worked better but still, not a good plan.

I think you'd be better off adding cobalt, manganese, nickel and Pot dichromate at about .01% to the Bomma. Go from there. It will likely need some soda ash to bring the expansion into line.
To get this into perspective, my dense black has 19 pounds of colorants in every 100 lbs of glass and the glass is a lead base 10%. It certainly is black. Frit will look like frit on clear.
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Old 03-18-2022, 09:50 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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Why is it wasteful for you to use the color bar on your pipe? Real dense black (at least) used to be difficult to find as rods
How many pieces?

Last edited by Michael Ahlefeldt-Laurvig; 03-19-2022 at 04:31 AM. Reason: Last question
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Old 03-19-2022, 08:41 AM
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Pete VanderLaan Pete VanderLaan is offline
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well, it's time consuming and takes an assistant that one presumes gets paid.
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Old 03-19-2022, 08:22 PM
Michael Ahlefeldt-Laurvig Michael Ahlefeldt-Laurvig is online now
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If you dont have an assistant, who will you blame when things F up?
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Old 03-19-2022, 11:28 PM
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Quote:
Originally Posted by Brice Turnbull View Post
I bought 15 kilos of Reichenbach black, but it's somewhat slow and wasteful to use a piece of the color bar for each blown piece I make, as the finished pieces are about the size of a grapefruit.
Stick up half a rod at a time and overlay only enough for what you need. It should take your assistant about as long to heat the end of the color rod for an overlay as it will for you to make a starter bubble. The assistant garages the rest of the rod after you take the overlay. Superfast. Alternatively you could also make lots of supios out of a long tube of black and saw them up cold then heat them in the garage, but that still seems slower.
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