grey tinted glass from color scrap

[Marc Carmen]

I saved up a few hundred lbs of scrap glass, moils, trimmings etc. Melting a pot of this stuff of course yields that nice blue tinted glass. Adding 10% batch to this and stirring while melting makes the color consistent and bubble free. Now, I’d like to try shifting this pale blue towards a neutral grey while still maintaining a light tint. Does anyone have any experience or input they can share?

I suspect using a pinch of nickel would just make a green/grey the way it does in combination with cobalt.

Maybe the right manganese/chrome combo could oppose the blue nicely but manganese is so unreliable in low concentrations.

Selenium or Iron/selenium? I don’t have much experience with selenium but as I understand it, Iron and selenium make a red/brown? What percentage of selenium do I add before it begins to show color? My glass is sodium based.

[Pete VanderLaan]

manganese and iron.

[Josh Bernbaum]

I'd guess selenium will steer you more towards brown if you're base is mostly sodium for your alkali. Manganese and iron added to SP (all sodium) gets me a light amber or tea type result which I've preferred to having to do a typical amber and then have to deal with the sulphur odor. But maybe if you have the blue tint already, then adding those two will have it go more light grey for you with Pete's recommendation. There seem to be lots of ways to get to a grey when looking through the old factory formulas. One of the things John and I had emailed about was minute changes in proportions of nickel, cobalt, and copper for getting a light grey shade that's to your liking. I did get to a light grey I really liked, but there was at least some potassium in that mix for whatever that is worth.

[Pete VanderLaan]

I was assuming the base cullet was already a washed out blue. You can only add so much crap to cullet before it goes cordy on you.

[Ed Pennebaker]

I've made grays from Spruce Pine 87 plain several times. 100 pounds of batch. .25 gm cobalt oxide to 8 gm nickel carbonate was greenish gray
.5 gm cobalt to 8 gm nickel was good
1 gm cobalt to 8 gm nickel was bluish gray
It is pretty touchy. I was also using some cullet from previous batches in each batch. It is pretty light gray. I was using it to blow single color transparent pieces.

[Marc Carmen]

Ohhh yeaaa, manganese and iron. Thanks, I’ll try that today.

Yesterday I tried a small addition of manganese/chrome. The ratio was one that would normally make a reddish brown in higher concentrations. It did turn the glass greyer, but also greener. I guess I could just keep adding manganese.

Josh, I’m interested in the grey from cobalt, nickel, and copper because those are pretty reliable colorants. For me, any combination of nickel and cobalt will get the whole range of smokey blue-greens but never quite go neutral grey. It doesn’t seem like copper could help. Maybe the potassium in your batch is shifting the nickel towards a warmer tone. I always had to add manganese/chrome in my grey color bar melts.

Cords never seem to be a problem. All the crap cullet was quenched in water and turned into relatively fine frit and small chunks. I also stir the melt with a punty in a drill with a cold gather on the end.

[Pete VanderLaan]

Originally Posted by Marc Carmen

Ohhh yeaaa, manganese and iron. Thanks, I’ll try that today.

Yesterday I tried a small addition of manganese/chrome. The ratio was one that would normally make a reddish brown in higher concentrations. It did turn the glass greyer, but also greener. I guess I could just keep adding manganese.

Josh, I’m interested in the grey from cobalt, nickel, and copper because those are pretty reliable colorants. For me, any combination of nickel and cobalt will get the whole range of smokey blue-greens but never quite go neutral grey. It doesn’t seem like copper could help. Maybe the potassium in your batch is shifting the nickel towards a warmer tone. I always had to add manganese/chrome in my grey color bar melts.

Cords never seem to be a problem. All the crap cullet was quenched in water and turned into relatively fine frit and small chunks. I also stir the melt with a punty in a drill with a cold gather on the end.

****
Try the potato. It mixes really well.

[Marc Carmen]

Planning on trying the potato soon since I recently moved up from a wire melter to a gas furnace.

Manganese and Iron looked very promising while melting in. A nice neutral grey. After fining that changed back to a dull blue. I guess it's the same deal as manganese/chrome, I could just keep adding manganese til it greys out the blue.

What ended up working was adding tiny bit of nickel for a green grey and then neutralizing the green cast with erbium. Very stable color and its not a prohibitively expensive amount of erbium either.

[Pete VanderLaan]

Any reduction in the flame burns out manganese if it is actually gas.