Is there any kind of glassblowing one can do without using flame? E.g. (but only an example) suppose I just want to be able to insert an electrode into a test tube but don't want to use flame, even though that is probably the most convenient way to do it. I don't care whether the alternative is prohibitively expensive, I just want to know in principle how whether it can be done and how. If someone (e.g. a manufacturer) actually does it that way on some items, by way of automation, that would also be good to know.
I've never tried this for glass, so in that context it's completely theoretical:
Back decades ago when I had an AC buzzbox (arc welder), I had an accessory known as a carbon arc torch; basically a hand-held fixture for holding a copper-covered carbon electrode a fixed distance from a ground electrode. Pull the handle (squeeze the trigger) to bring the two together and strike the arc, then release to create a 3/8" or so gap. You now have a blue hot arc in front of you.
The amount of heat could be controlled by adjusting the amperage on the welder. Also, there were 1/4" and
3/8" (and larger?) carbons you could use. The size of the gap also controlled, to some extent, how focused the arc would be.
I may actually still have this piece of hardware hidden away in a box somewhere, and if I run across it, I'll see how well it works on my current DC ARC / TIG / Plasma unit.
In principal, I see no reason a carbon arc couldn't be used in a limited way for glasswork, but am not aware of anyone actually doing so. There is a *LOT* of UV produced, so that'd certainly be a drawback.
What part of "CRAFTS" didn't you understand? This is not a theoretical scientific community. We look for the "easy" way to do things, not try to reinvent the wheel.
Aren't you the same guy who posted (and cross-posted) a nonsensical bunch of bullshit about a telescope mirror a couple of years ago? We like to NEVER got rid of that thread and all of the pocket protector bunch. Go find somewhere else to play.
Thanks very much for your comments. One advantage I can see for flame is that you can easily move it around on the glass to keep one part from expanding faster than other parts and maybe breaking the glass. That doesn't seem to be a feature of the carbon arc apparatus you describe. I was thinking in terms of some well insulated container with lots of little heating elements all around the glass, elements which can be controlled independently, so that the glass heats up as a whole in a controlled way but the particular part you want to soften gets more heat. I have no idea whether something like that could work or whether it is actually used. If the insulation is good enough, the amount of heat produced by the heating elements might not need to be that great, since the heat insulation would cause the heat to accumulate. It just might take a long time to get to the right temperature and a long time to cool.
Is Moonraker the local judgemental heckler for rec.crafts.glass or is he right about this question being off topic for this group? If so, I apologize, since it wasn't intentional on my part.
There are several bench torches in use. I'd use the carbon arc in place of the bench torch. You might even set up a parabolic reflector to direct more of the heat to the glass instead of toward the artisan. Alternatively, you could set up a glory hole with multiple arcs inside.
If that's the way you want to go, it wouldn't take much to just buy a kiln or glory hole and modify it.
The only way to find out if something will work is to try it.
Dunno what his problem is.
The charter would seem to include glassblowing as an acceptable topic of discourse.
I think your big problem is going to be gravity. When you're working in the flame, you're constantly moving the glass so it doesn't sag, and you have the option of removing it from the flame if it's getting a little too hot. In a kiln, you're going to have to do something else to keep it from slumping.
It sounds like you're asking about scientific glassblowing, which isn't entirely on-topic here. But the general principles are at least roughly the same, so it's not as off-topic as grinding telescope mirrors.
No, Moonraker needs his tubes and fingers tied to prevent procreation and rudeness. You can block his messages just like e-mail on your brower if you wish. The real problems with using an arc for working glass are the very high temperature in a very small space and the interesting problem that most glass becomes conductive when melted. (And yes people have thought of using a carbon arc to melt a pool of glass, but you need a safety cutoff when you dip the pipe in the glass and because you need to melt the glass with something else like gas, what is the point of two electrical systems.) It is possible to work glass with an electric glory hole built like the bottle melting rig I built
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but it doesn't scale up very well, I am told. People melt glass with electricity all the time, but it is done with silicon carbide elements in a highly insulated box that is opened only briefly to get the melted glass out. The actual working of the glass is done with a gas glory hole.
Of course, what is missing (he realized after sending the long message) is the duty cycle of the glory hole. If the hole somehow manages to stay hot and have the elements on only 25% of the time, which seems low, you get up to 40 hours a week.
I ran across it today. Main problem is that it really is designed for AC, and the arc tends to walk around the gap more with DC. IOW, even if the carbons are stationary, the "flame" isn't. I surmise it may due to the copper migrating too much with DC.
That said, I did manage to melt some glass with it.
1/4" electrodes; machine set at 30 amps. In order to get a stable arc, I had to go with something less than
1/4" gap. It was really too much of a pinpoint heat source at that setting, so the glass bubbled/boiled. All other considerations aside, you'd need more current across a wider gap to get a "softer" arc with more heat so you could work the glass farther out.
What amazed me was that the rod (standard COE 104) didn't crackle and spit as it tends to do when you heat it too aggressively. Since I don't have an AC welder any more, that's as far as I took the experiment.
From what I saw today, I'd have to say that with the right setup and a little while dialing in, it certainly would be possible to do some beadmaking and light glassblowing with a carbon arc.
I would hastily add that I wouldn't personally go to the bother of figuring it all out since oxy-propane is a tried and true method, and I already have that setup... albeit not set up at the moment.
How much did they each cost? Where did you get them?
I'm a little confused. Why were you running it on DC current and how did you arrange for the current to be DC? Later on, you say you don't have the AC welder any more, so maybe it has something to do with the way it is used with the welder. Are you saying that: (1) the hand torch runs on DC; (2) it works ok on DC provided by the the AC welder; (3) it doesn't work ok on DC you provided by some other means?
Neat!
implications for house wiring... and higher for better conditions, as you describe later.
To compensate for effects of using DC current?
The arc is an electric discharge, rather than just a source of heat. Do you think that maybe the electromagnetic field of the discharge exerts some control over the molten glass?
The welder was from Montgomery Wards. Seems like it was about $225. The carbon arc attachment... I really have no idea. Maybe someplace like JC Whitney... for like $25.
This "torch" is really just a fixture that holds the electrodes. Has leads you attach to the welder. They don't seem to be as common today as they were, oh 25 years ago, but they're really simple to cobble together. Google is your friend.
Normally the sub-$1000 welders put out AC or DC; not both. When I bought the carbon arc torch, I had an AC welder. That went away many years ago, and the welder I have now (which does stick welding, plasma cutting, and TIG welding) is DC only.
Welders used to use honking big transformers to convert 240 VAC to something in the neighborhood of ~30 VAC or so (and for DC, add a big ol' heat sinked rectifier). As your voltage decreases by a factor of about 8, your amperage increases by about a factor of about 7 (due to heat losses, etc), so a 30 amp 240V circuit would get you up to about 210 amps at the electrode.
Having an arc current of 30 amps, means something like 4 amps on the house wiring. Kicking the arc up to 100 amps would mean maybe 13 amps on your 240V circuit.
No, to compensate for the fact that I was just playing around, and had the welder set for 30 amps.
Nope. Then again, I only played for 5 minutes or so, and only at 30 amps. I believe MF said that at higher temps, glass does exhibit some sort of EM reaction.
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