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Old 12-20-2016, 07:52 PM
Dave Bross Dave Bross is offline
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Lists of Color Additives for Cullet

The whole thread is here and it's worth going through to catch the discussion on fine tuning some of the colors via oxygen levels:

http://talk.craftweb.com/showthread.php?t=4382

Most of the coloring chemicals can be had from US pigments:

https://uspigment.com/product-category/chemicals/


Here's the part about Pete's take on how much of what.

Go get the clear furnace nice and hot and ladle a lot of the clear into very cold water allowing the glass to enter the water as a fine stream. If the water warms up, get more cold water. You are going to need a fine frit to do the things I will suggest. Make a bunch of it. Bug lumpy chunks of cullet make for hard coloring.

I am going to think in seven pound quantities heres since most of my old cullet formulas were based on a Tamax crucible that held... 7 lbs.

Most colors do pretty well in the one tenth of one percent amount there certainly are exception If I wanted to make a turquoise blue in cullet I would add about 25 grams of red copper to the frit. I think you could go up to 32 grams with no expansion shift at all. Fire in a neutral atmosphere.

The same would apply to Nickel oxide. It will make a purpley brown glass depending on the alkaline flux. I would bet that the 4c is cheap and the flux is soda so expect the brown tones. Again 32 grams.

Iron glasses. Ick... Some people like them. Add 20 grams red iron to the frit. it's coke bottle green. Try variants with a bit of cobalt or copper or both.

Try one gram cobalt and 30 grams copper. that should yield a periwinkel. You can mess with this combo endlessly.

Three grams cobalt is a dark blue for the absolutely uninitiated. Go to thirty grams and you will have a threading color as well as a trashed pot. Being in the crucible biz, I think that's just great.

Try 4 grams silver nitrate and 20 grams black tin and ten grams red iron. Reduce this stuff heavily. Beautiful opal swirls

try 20 grams copper oxide, 20 grams of black tin and reduce while melting. IF YOU ARE LUCKY this will make a red glass. I don't know enough about c4 to know for sure.

Chrome... it's hard to get potassium dichromate these days. No one wants to ship it. If you can get it, grind it finely and add 30 grams to the 7 lbs of cullet. Think 7 up bottles. Add cobalt or copper to change the blue tones. You can do some very nice and some very ugly things with this stuff. Aviod chrome oxide. It's very hard to melt. It's also carcinogenic. Think rat poison. That's it's claim to fame.

Neodymium oxide. It takes a lot. About 50 grams in seven pounds for a color that is violet in ultra violet light and ice blue in fluorescent light. This is not a casing glass.

Manganese dioxide add about 65 grams of this to the 7 lbs of cullet and see what it does. If it's too light, add more- maybe another 20 grams. It will kick into a strong purple. Tends to be messed up by high sodium base glasses and is gorgeous in potash glasses. You could add silver to this stuff too.

In general, ty to add the colorants to a slightly damp frit and shake it or whatever to get the cullet coated. Try to avoid dumping the chemicals onto the top of the cullet. This tends to sink to the bottom when the melt gets going.


For now, that should do it. You can't make opaque glasses with cullet. Forget cryolite and phosphates. Also don't add selenium to cullet or zinc. They won't work This however should keep you off the streets and amazing your friends for a while.

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Silver Nitrate at 1/10th of a percent up to one percent in cullet makes some nice stuff. It require less silver if Black tin gets added ( stannous oxide). Hard to find though and it is not to be confused with Stannic oxide, an opacifier. You can add cobalt to the silver for some really beautiful stuff. It does drill pots if the silver is allowed to sink to the bottom. Pete V
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Last edited by Dave Bross; 12-21-2016 at 02:26 PM.
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