calcedonio glass

[Pete VanderLaan]

and just when you think you have the color nailed, it will stop working entirely.

I have colors I simply don't try to melt if the barometric pressure falls below 30.

[Dave Bross]

Thanks, that's great to have a number for exactly where that problems begin.

I wonder if I'm maybe avoiding that somewhat by running my glory bottled up so tight that there's "sting out" (flame coming out under pressure) at any openings? There's certainly plenty of atmospheric pressure within the glory in that situation....or is it one of those wonderful things that glass does that aren't quite explainable? I've heard the silver glass horror stories over the years.

Other things I forgot to mention... I run 1/2% phosphorus in all my base batch and that probably has some effect on getting the nucleation going too.
I use cast iron blocks for shaping/chilling and when you roll this glass in one of those you can watch the silver go insane, I presume from the fast chill down.

Dave,
Where does one purchase cast iron blocks? Thanks.
Mark

[Eben Horton]

Originally Posted by Pete VanderLaan

and just when you think you have the color nailed, it will stop working entirely.

I have colors I simply don't try to melt if the barometric pressure falls below 30.

Welcome to New England..

[Franklin Sankar]

Dave do you get flames coming back out of the burner port also?
Does it heat up the tip of your pipe burner more than if it was not coming out?
Franklin

[Dave Bross]

The iron blocks are no more for the moment. Tom Fuhrman's friend did a homemade iron cupola for a vocational class and they made a bunch of blocks for Tom with the iron. They've all been sold. There's an iron foundry in my little town here and eventually I'll check with them to see if they could make some more blocks for a reasonable price. Someone here was working in a foundry and looking into that and some other stuff like optic molds at one time?

Franklin, yeah, flames coming out everywhere, looks like the fourth level of hell running at night. Burner tip running at yellow heat with flame blowing out past it. I should mention that my burner tip is a 3/4 to 1" reducer (pipe fitting) on a 3/4 " pipe burner, which conveniently allows just the right expansion of gas to get all the things done that a burner tip needs to do. Regular iron fittings last a few months, stainless ones up to a year, and the price is right. It even has pretty good turn down.

Yesterday I melted a batch of this glass with the copper in it. End result was even more spectacular color swirls, with lots more different shades of blue, green and purple, and lots more of those colors. Turned the dark browns a really pretty mahogany shade too. Sweet!

[Jon Myers]

hey Dave et al, glad to hear you tried the Ti. It has to be put away before you see it going nuts if you want the more subtle version. If you have any left try cooling then writing with a clear bit (say, a name) or a red hot rod (gotta drag it slow enough to reheat the surface) then cool and treat as normal. I love these colors, so sciencey.

Dave, any pictures?

The guy that you're thinking of who was (or is) working in a cast iron foundry is Ray Laubs.

[Dave Bross]

Jon, hell yeah, more fun than a barrel of monkeys and high science too. What more could inquiring minds want?
Thanks again for the info on that. Something else I want to try is mixing some ground up cullet of this same glass in with the batch and see if I can take the madness to a new level. I'm thinking the partially struck cullet might nucleate even more colors.

Drew, no promises, but I'll see if I can get some pics. Both furnaces have popped their elements (timing is everything) and I'm finishing up c-balls via glory melt so things are a wee bit hectic at the moment.

[Jon Myers]

No prob, thank Pete. I think adding to the zinc % of the batch will do more than grinding and adding as I believe (without expermentation I might add) that remelting will 'reset' the crystal structure. While keeping the zinc up will make it more liquidy (scientifically speaking ) at the crystal growing temp. (Also spoken without actual knowledge, but with years of ruining my kilns with crystalline glazes)

[Dave Bross]

I think viscosity is critical too. I used two different batches with these melts, one with lots of Borax that makes a very sloppy and long glass at work temps. That one strikes faster and harder than the one done in my usual batch designed for quick set-up and higher viscosity at work temp.


What got me thinking about adding cullet to the batch was re-using some of the cullet from these melts as a shard pickup and watching the strike on the shards go way farther into the blue/purple/opaque yellow/tan range. Only one way to know for sure, and I'll try it post-holiday madness.

Under intense light you can see that the mahogany brown color is the copper striking red along with the amber/brown from the silver.

I'm also gradually backing off on everything one ingredient at a time. The base glass under the strike is still quite brown. That pic in the beginning of this thread shows the color striations on a mostly clear base. I suspect the Phosphorus in all my batch may be the cause of this (more nuclei, more striking) but if I can get this glass to go with way less silver and tin that would be a plus in the economy department. Readymade silver nitrate is up to almost a dollar a gram these days. My glory is also a touch reducing in atmosphere and that could be the browner strike too.

Drew, send me your address again, my email is at the bottom of my posts. I'll send you some shards that would theoretically (test them against what you're using) fit most "96" coe glass to play with. That would be easier to do than organize the pic thing at the moment.

[Jon Myers]

when you pick up shards you don't get them to that hot-like-the-sun-temp you get when you batch so I would expect the shards to keep thier goodie. maybe you put reground stiff glass into the sloppy melt. I really enjoy reading your experiments.

[Pete VanderLaan]

large Shards work quite well whereas small frit size ones don't. I would not be surprised to find that rapidity of melt had a lot to do ith that.

[Dave Bross]

Pete, Jon,

I think I know what you mean. In the past I could never get the silver glasses to do their thing in an oxy propane torch at that higher flame temp.. When I used a handheld propane torch or one of those hothead propane torches on the silver glass the fun would commence.

Glad you're enjoying my tinkering...sort of like "wake Willy up, he ain't never seen a wreck like this"

[Franklin Sankar]

Dave do you have any idea on what is the approx COE of the long working time sloupy glass? It seems that the quest to be lazy with long working time leads to higher COE that is not compatible with anything.
Franklin

[Dave Bross]

I'm targeting everything for 96 coe these days.

Borax at 4% will make it sloppy, long and drop the expansion a little, which you can compensate for by adding a bit of something that raises expansion. Not sloppy like a high lead glass now, mind you, but pretty loose. Don't forget using higher working temp for more time and lower viscosity too. This is right on the borderline for fit problems due to viscosity mismatch with stiffer glass. Test, test, test

[Franklin Sankar]

Thanks I thought you were the 104 COE guy. Glad you came back down.

[Dave Bross]

Franklin,

I haven't come down since the sixties......just kidding, I quit the "heavily medicated for your protection" long ago but the ol' brain will never be the same for having been let so far off the chain way back when.

OK, back on topic....(novel concept) if you try this stuff, do take the time to hot/cold strike it 3 or 4 times at least. Big upgrade in psychedelia. The thicker the piece is the better I like the effect too.I love this stuff! I've been melting it all weekend again. C-balls from this stuff are leaving as fast as I can make them. Neighbors are lurking around the annealer in the morning, watching and waiting....

I've sort of settled on the "everything but the kitchen sink" version:

10 # of neutral batch (no oxidisers, no reducers)
5 silver nitrate
25 black tin
25 zinc
2 iron
2 copper
5 salt

I would lose the salt if I melted it in the wire melters, halogens and wire elements are not good.

I tried melting it very cold and it does stay lighter longer but multiple strikes still darken the base glass a good bit. Eventually I'll mix some up without the phosphorous and see if my suspicions about that accelerating striking are correct.

Pete, If you catch this, any idea how those lampwork glass suppliers are getting a glass like this with a green or blue base glass color instead of the amber/brown?

I also remembered what got me wondering about putting cullet back in the melt, the last ones out of the pot, which were combined with the leftover glass from the last melt, had the most/best color variations. I'll try it eventually.

[Jordan Kube]

This type of stuff Dave?

http://www.doublehelixglassworks.com/glassrods-1.aspx

[Dave Bross]

Yes, that's it.

I'm thinking that's all a variation of what we're discussing here.

If I had to guess, I would think the expensive purple one might be a gold purple schmaltz/calcedonia and the others look like schmaltz/calcedonia glass with cobalt or more copper. Maybe enough phosphorous in there to strike a little and lighten them up. Probably variations in oxygen content/reduction too.

More notes from this weekends melts:

Storm front (low pressure) rolled in while melting, glass changed. Still striking fine, just different colors/strike times, and lighter base glass strike.

putting clear (oxidised) over it does a nice job of slowing the striking.

[Jon Myers]

I'll bet that the purple is high cobalt carb (maybe 6-7%)/ silver with a little barium carb for flavor (look up barium blue glazes)

[Dave Bross]

OK Jon, I'll do that. Thanks.

I probably wouldn't use barium though, trying to mimimise the toxins. I usually use strontium in its place but that doesn't work color-wise. I actually got a nice blue out of manganese with a high strontium glass, sort of the reverse of what we're talking about here.

More thoughts from the weekend melts:

When I pulled everything out of the annealer there was a color variation in the base glass from mahogany to the light amber that they were when they went in. The lightbulb goes on! The copper is continuing to strike in the annealer, just like the low copper percentage copper rubies I was doing. The color gradation changing from the first ones put in (mahogany) to the last (amber)was the clue.
I want to try backing the copper way down and see if I can hit something towards red in the base glass. Some of what I pulled out this AM were close. The trick will be hitting the right tone in the given time spent in the annealer. The copper rubies I did were interesting in that they varied from a pink fade out to overstruck (brown tones) depending on how long sitting in the annealer striking. That's what I love about glass, the challenges are endless.

Interesting how well the copper is striking, considering that it's only .04%

[Pete VanderLaan]

I am moving my formulas at this point by one tenth of a gram in 20 lb batches which should tell you something about the importance of accuracy at the scales. I sell DoubleHelix their crucibles and have watched them for some time. Again, they are better glasses from the pot than from a rod. It isn't gold, it is cobalt. Gold really has to have lead and selenium at the same time or it ain't gonna strike. Copper and silver in the same glass would turn it to a motor oil mush.

[Eben Horton]

what COE is double helix's glass? Furthermore, what kind of operation would sell glass to glass makers and not tell you anything about compatability or how they test it??

Their colors are beautiful however..

[Dan Ellis]

double helix is 104coe