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Josh Bernbaum
05-21-2012, 10:49 AM
Hi everyone,

Just got the furnace I built starting in 2010! finally going for the first time a couple weeks ago (photo attached). Charlie Correll design that's been modified significantly by me for my own custom needs and also for minimum fuel usage.
One of Pete's 100# pots in there now.

Been using the Stadelman elec. I bought up until now, but I've wanted to try color melts for a long time now and that's the main reason I built this one.

Here's a basic question for someone who has little experience melting color (hoping to change that next year when some of us will be at Pete's class!)

Is there a nice, bright transparent blue I can make using Black Copper oxide added to SP 87 w/er? I was looking for a light blue a bit different than just the cobalt look and saw somewhere about the copper oxide maybe being an option. If so, anyone have a good measurement for a starting point that I can work off of? I'm just looking for a fairly light saturation.

Thanks,
Josh B

Pete VanderLaan
05-21-2012, 11:03 AM
Sure. I think about 100 grams in about thirty pounds will give you a nice turquoise blue without messing with the expansion significantly. To tone that a little cooler, a gram or two of cobalt oxide will help. It doesn't take much but it is hard to mix it in evenly. Normally to make cobalt go in evenly, take 10 grams of cobalt and add it to ninety grams of crushed batch. Then, mix. When you want to just add two grams of cobalt, instead use 20 grams of the diluted mix and take that mix in turn and put it in about a pound of batch yet again and the mix that. then add that back in to your mixer. It makes it more even in distribution.

It's called making powder blue.

Josh Bernbaum
05-21-2012, 11:12 AM
Thanks Pete, you're quick with these replies!

Do you think stirring with the potato helps any to further mix in color once the batch turns into glass, or does it all really need to happen when dry in the mixer?

David Patchen
05-21-2012, 12:25 PM
Interesting.

Are there many other colors that can be made by simply adding one or two ingredients to SP batch without a lot of specific or complicated melting schedules?

I'd imagine most of these would still need a regular schedule to fine so you couldn't do them w/a small crucible in a gh, right? Are there any easy recipies that would work w/cullet so you could make them in a crucible in the gh?

Hugh Jenkins
05-21-2012, 02:29 PM
If you frit some clear cullet by dumping into water, or take it out of your gather strip bucket, you can mix colors in quite well. Cobalt, copper and nickel as carbonates in small percentages are the easiest to melt. Mix well.

Pete VanderLaan
05-21-2012, 03:39 PM
Thanks Pete, you're quick with these replies!

Do you think stirring with the potato helps any to further mix in color once the batch turns into glass, or does it all really need to happen when dry in the mixer?
*********
You could stir forever and it would just keep getting better and better. The best example, and you'll see it in the class as to how difficult mixing really is, is adding 1 pound of cobalt to 50lbs of an opalescent white fluorine opal. Even mixed for an hour, it's really streaky. This doesn't show up in transparents as much but it jumps right out at you in opaques.

As to David's question, I don't think its practical to pursue. I think if you want decent color in a gloryhole, the way Ed Skeels did it seems to make sense. Ed had a little pot and heated color rod in a color box. About every half hour to hour, he would take a chunk and put it in the gloryhole pot. Because it was hot, it didn't blow up. So it was quite clean as color. Now the warning there is that most color rod only wants to be brought up to about 1900F. In any rods, the lead separates out of the melt easily, leaving you with really cordy stuff.

Experiment. Better yet, take the class!

Peter Bowles
05-21-2012, 06:32 PM
when I was playing around melting transparents, all sorts of blends of copper, cobalt, iron, nickel, chrome, manganese etc. I would cast a piece in a narrow wedge shaped mould, about 10mm at its thinnest to about 50mm at its widest over about 150mm. Its a great way to determine colour density at a known thickness of glass. It made it really useful to find the proportions of colourants needed for very pale melts to get a required colour density at any thickness.

Pete VanderLaan
05-21-2012, 07:12 PM
nice idea Peter.

Josh Bernbaum
05-22-2012, 09:00 AM
Is there anything that happens to oxides after they've been sitting around for 10 or 15 years? I'm asking because the Black Copper oxide in this first melt I just did yesterday just looks like a fairly dense cobalt to me. Granted, I did use about 5g cobalt oxide in the mix with about 120# of SP batch in total. I know cobalt is super-strong, but I would have expected a lighter impact with that little. Makes me think that the Black Copper is just looking cobalt-y also? It's definitely a black powder in the jar instead of the bluish cobalt powder I have, so I don't think the copper was mis-labeled.

Pete VanderLaan
05-22-2012, 09:26 AM
well, all mine runs vary. My cobalt oxide is almost jet black. It's occasionally somewhat blue. It takes one part in ten thousand to show distinct color with cobalt which makes it the strongest soluble colorant out there.

Red copper ( cuprous oxide = Cu2O.)
Black Copper ( Cupric oxide = CuO.)

different animals.

I prefer coloring with red copper but that's only because I've always done it that way. You can use copper carbonate (CuCO3) which will oxidize your glass more than the other two but also means you're paying a lot for oxygen. I think the carbonates are "softer" ways of getting color in to glass but you really may not want the oxygen at all, in which case, actual copper metal or the simple oxide are the best ways to get at it.

If you are getting a blue that is not distinctly turquoise, then it wasn't copper oxide. five grams in 120# is not a lot . How much copper did you add? Cobalt as a color is hard to mistake.

Josh Bernbaum
05-22-2012, 10:13 AM
I added 140g black copper oxide in total to that 120# batch, along with the 5g of the cobalt.

Josh Bernbaum
05-22-2012, 10:16 AM
And not seeing any turquoise, which I was hoping. Maybe I need to try the red copper oxide instead? I don't think I'm ready to try carbonates yet, I'm hoping to start off 'easy' with not having to worry about furnace atmosphere too much.

Pete VanderLaan
05-22-2012, 01:09 PM
If you don't see any turquoise tones, I don't think you are using copper. Copper glasses look like the caribbean waters. If it was cobalt that you used inadvertently, that would be a very dark blue glass, like phillips milk of magnesia bottles if you know what they looked like.

Atmosphere is not an issue with copper carbonate blues but the carbonate is significantly more expensive than the oxide.

And on a really early question you asked, No, the oxides don't change, or go bad over time.

Jon Myers
05-22-2012, 04:34 PM
when I was playing around melting transparents, all sorts of blends of copper, cobalt, iron, nickel, chrome, manganese etc. I would cast a piece in a narrow wedge shaped mould, about 10mm at its thinnest to about 50mm at its widest over about 150mm. Its a great way to determine colour density at a known thickness of glass. It made it really useful to find the proportions of colourants needed for very pale melts to get a required colour density at any thickness.

So Peter, I am curious about the wedges... Do you just pick a thickness (say 75mm) and a best guess as to the colorants then use the wedge as a calculator? Is it normal for a piece of glass 150mm thick to have the same tone as a 75mm piece with 2x the colorants? Do you have a scale built into the mold or is it measure as you go?

Josh Bernbaum
05-22-2012, 10:39 PM
If you don't see any turquoise tones, I don't think you are using copper. Copper glasses look like the caribbean waters. If it was cobalt that you used inadvertently, that would be a very dark blue glass, like phillips milk of magnesia bottles if you know what they looked like.


Don't remember, too young I guess ;)
But yes, that's the color and density I got on this melt. Definitely cobalt. But whatever black powder I thought was copper does look different than the bluish powder that does look cobalt-y. Can cobalt be that black?

Today I ordered some red copper oxide, copper carbonate (actually a bit cheaper), yellow iron oxide (not sure what that'll do yet but sounded cool), and some potassium dichromate (sounded like OSHA will be hand delivering that one personally from how the woman on the phone made it sound) from this place:
http://www.standardceramic.com/Materials.html

Gonna keep experimenting!

Pete VanderLaan
05-23-2012, 01:29 AM
My cobalt is usually black. Make sure you grind the Potassium dichromate or it will not melt in. It will give you trouble regardless. It makes these little corundum stones. Keep in mind it's the main ingredient in rat poison.

Rollin Karg
05-23-2012, 10:18 PM
and some potassium dichromate (sounded like OSHA will be hand delivering that one personally from how the woman on the phone made it sound)

You'll be getting a visit for sure and they are there to collect the dough. Safety for you and your helpers is a remote second place, very remote.

Potassium Dichromate is a great colorant, by itself you get a really great green and can be used with copper and/or cobalt for some neat colors. A small dash will help your Manganese disperse in the melt.

Peter Bowles
05-23-2012, 11:43 PM
So Peter, I am curious about the wedges... Do you just pick a thickness (say 75mm) and a best guess as to the colorants then use the wedge as a calculator? Is it normal for a piece of glass 150mm thick to have the same tone as a 75mm piece with 2x the colorants? Do you have a scale built into the mold or is it measure as you go?

Hi Jon,

Thatís pretty much it. I was using colourants anywhere between 0.025% and 0.1% of batch weight and doing all sorts of triaxial blends for some great mid tones. At these low quantities its fairly okay to assume that twice the colourants will give twice the saturation at the same thickness - or inversely, half the thickness with twice the colourants will give the same saturation.

They were also great for layering up colours together too. With a bit of juggling you could get an idea of the range of hues available between say a chrome green and a copper blue with the thick and thin edges of the wedges stacked together (or not). They were a kind of ready reckoner to get into the ballpark before committing to a melt. Think of two door wedges, one red and one blue that can be slid on top of each other to give a whole spectrum of purples. I could find a colour I liked at a point along the wedges and have a pretty good estimation of how much colourant of each colour there was at that point.

There was no scale on the edges - an interesting improvement -thanks. I just zapped up a steel mold and would ladle some glass in. It was all a bit crude I have to say, but I did find it useful.

Peter Bowles
05-23-2012, 11:52 PM
And not seeing any turquoise, which I was hoping. Maybe I need to try the red copper oxide instead? I don't think I'm ready to try carbonates yet, I'm hoping to start off 'easy' with not having to worry about furnace atmosphere too much.

I found that adding even the smallest amount of Co would swing a copper blue into more of a cobalt blue. If you have any residual cobalt in the pot from a previous melt that would be enough to taint a pure copper melt to a cobalt tint. Copper carbonate by itself should give a good aqua colour.

Paul Hayworth
05-24-2012, 02:50 AM
put brass water tap in your glass ,nice light blue / stir the melting

lovely blue in lead glass