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Old 03-18-2021, 12:29 PM
Josh Bernbaum Josh Bernbaum is offline
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Finicky iron sulphide blacks

Why are iron sulphide blacks so prone to being brittle and having a low tolerance to thermal shock? I'm curious what's going on chemically. Both Gaffer's and Reichenbach's formulas which I've used need a LOT of pre-heating and the cane I pull with them sometimes cracks during re-heating from room temp (small cane too, not just large diameter stuff). And that's in my pre-heat oven, placed in there at room temp, and before it even gets to the GH. Forget about putting cold cane into an already hot pre-heat oven like I can get away with on almost every other type of cane that's thin enough. I've noticed this often with the iron sulphide blacks cased with clear for cane. I tried annealing some cane yesterday just after pulling it and I think I thermally shocked it just by moving the still warm lengths into my annealer, which seems to be just where I touched it with the kevlar gloves. Finicky stuff.
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Old 03-18-2021, 05:59 PM
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Pete VanderLaan Pete VanderLaan is offline
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Hi there,
First off: It's telling you to not make things for sale out of it.

I went and spent time on this during the afternoon when it was obvious that I was going to accomplish nothing doing anything else. I will be right up front admitting that I don't make black that way It turns out there are good reasons some of which I will share here after really looking to a lot of texts and coming up wanting.

I started off with Volf and it essentially brought nothing to the table. Volf does not deal in colors much, Volf is far more interested in the interstitial spaces in molecules and he does great at that. But Iron Sulfide blacks? Nope. He does indeed go into the utter insolubility of the foams made by such melts but they aren't going to help you.
So then, I went to Thuringen of which you might have a copy, I'm just not sure. Even by 2013 it was a rare book and Joe had the remaining copies which I'm certain are gone. Thuringen did not help , coming only close with a gray. Find that book on the net and buy it. Ignore the price.

Then Hellmer and that showed formulation for blacks but no revelations about density.

Finally, I went to Weyl and there was your complaint. Weyl says to paraphrase " Iron sulphide glasses are unfortunately really brittle. ( you knew that) .He goes on to say, and this was 1952 mind you, that making these glasses is futile particularly when you consider the more modern approaches to making black using Chrome, Cobalt, manganese for doing it .

What's the big difference? Lead Lead Lead. Lead opens up such matrices to allow what I use to say in the classes allows "packing a glass with metals" and it does. It's a way of achieving supersaturation. My basic lead formula ( which you should still have if you didn't throw it out) needs substantially more lead in it to make the black.

I've not tried it but Dave does suggest that Volf suggests it might be the case that substituting Strontium for lead might work out. When I melt it these days, I change nothing.

Scott Benefield and I have gone around on what happens as the chromophores thin out. Scott told me recently that using my black ultimately led to cane where one could see actual separation between black chromophores actually when the cane was examined closely. As I thought about that, it made good sense. Think about how when one makes a cane that the black gets cased in clear and then pulled. Then, do it again, and again. We can see clearly what 1/10,000th looks like. That's not particularly big but if the color holds up, and it does, we can keep dividing it yet again. Eventually, that black has to get down to molecular size and Scott got to see it splitting up. I suggested it well could be devitrifying but I'm not sure.

Now how Croucher makes things is really excellent and I think the world of him but as time has gone on, I realize that he puts his pants on one leg at a time and some of the gaffer materials cause conniption fits. So do some of mine but I'm not trying to sell color to the masses.

So, it seems to me that what you are experiencing has been well known to be brittle and troublesome for well over half a century. Why? Who knows? You I believe know how to make mine from the class. It's really better stuff. Takes Lead. I'm 70, it hasn't hurt me yet and hasn't hurt my kids who grew up with it.

What did I stay away from ? Hydrofluoric acid.
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Old 03-18-2021, 08:51 PM
Josh Bernbaum Josh Bernbaum is offline
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Pete, your black is denser than most, and I use it for certain things. But it ain't nearly as dense as this "Nero Durissimo" that John formulated. It's so stiff it'll make a seasoned cane-puller feel like a newbie at first. The viscosity is sooo high. I had to come up with some tricks so it doesn't pull right off the pipe. Only thing that I think will stretch farther is Mark's stiffest white final iteration. John wouldn't elaborate on it much when we spoke in the Penland class about it some, but he said something about there being multiple "systems" (his word if I recall correctly) at work in this dense black. I'm guessing at least both the iron sulphide and his duro base as well maybe.

As to your first sentence though, I've put this shit through the ringer and I'm confident of the fit. Multiple heat cycles and cutting through it with a saw later, it's been fine. (knock on wood) But I understand why you're thinking it shouldn't be based on what I'm describing about the cane, but it seems stable after annealing the cane, which it seems even is needed with thin sections.

I have to preheat it to 1250F or it cracks going to the GH. Oh, and it smells a bit like sulphur sometimes it's being worked.

I do have a copy of Thuringen. I think I've gleaned more from Hellmer's so far though. I'll check that section in my Weyl copy that you mentioned.
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Old 03-18-2021, 09:31 PM
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Melt that formula I gave out but just until it's melted, then gather it out into rod. Don't let it sit overnight. Might have a little black bleb in it here and there but it melts pretty fast. My experience with it has been that it loses density the longer it sits in the pot.
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Old 03-19-2021, 10:04 AM
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Pete VanderLaan Pete VanderLaan is offline
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I think the observation that you had best draw it right away suggests to me that it isn't very stable, which would support the notion of brittleness ( sort of kind of glassy) .
I was only attempting to respond to Josh's query and what I came up with is all I've got. I know that beer bottles are made in an iron sulphide glass and they have always struck me as really easy to break compared to clear bottles.

In making the more modern dense blacks, the balance always seems to be solubility of the metals. Mine has nineteen pounds of oxides in 100 lbs of the leaded batch which is way up there. Initially, it was touted as a glass that would not run on the surface and I find that to fundamentally be true but what John did with the durissimo I suspect has an additive of more than a little alumina. Mark got to the Blanco somewhere up around 11% alumina. Probably bathing it in Lithium before putting it in the mixer. Funny material, it sits right next to silicon and just below Boron in the periodic table but where you might want to classify it as a light metal, it is not in that column. Boron is a metalloid as they call it. Aluminum is in the row but separated to the right.

The more I look hard at the periodic table, the more I understand and the more confused at the same time.
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Old 03-19-2021, 11:52 AM
Kenny Pieper Kenny Pieper is offline
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Josh I have a recipe for a duro black that is an iron sulfide. Its not as stiff as the gaffer but holds up quite well and is not hard to use. Give me a shout if you want.
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Old 03-19-2021, 05:02 PM
Josh Bernbaum Josh Bernbaum is offline
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Thanks Kenny I'll shoot ya an email.
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Old 03-27-2021, 01:12 PM
Marc Carmen Marc Carmen is offline
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Does everyones iron sulphide black have that gritty opaque character to it like gaffers does? Most people complain that is doesn't appear black enough but I actually like that earthy warm grey/black look as an overlay color. My iron sulfide melts just looks like a very dense transparent black that will show a transparent brownish color when blown very thin.

I've tried adding more reducing agents but then I just end up with molten iron blobs at the bottom of the pot. I've never made it into bar, though. Maybe that would get that colloidal look to strike out of the melt.
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Old 04-06-2021, 02:12 PM
Art Freas Art Freas is offline
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I put gaffer 50 over reichenbach 54sp and that is very opaque and doesn't reduce if you torch it.
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