using a crock pot instead of a kiln?

A woman in my jewelry class said a friend of hers uses a crockpot with some (vermiculite? or something??) instead of a kiln. Is this possible? I'm sure you will all tell me why this is a bad idea... or maybe it's ok for beginners???

Thanks :)

Pam

Reply to
Pam
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You can hold small beads and cool them a little slower this way, and many won't crack...BUT it is a temporary thing and not the same as kiln annealing. The stress is still in the glass and will very likely result in cracking some time in the future.

-- KarenK Desert Dreamer Designs

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Reply to
Karen_AZ

On Fri, 3 Oct 2003 15:19:17 -0400, Pam wrote (in message ):

It's a bad idea because it does nothing to relieve the internal stress inherent in glass as it cools. Did you ever hear how some people say that glass is a liquid? It isn't, but it does have a lot of characteristics that are like liquids. The crystalline structure of glass isn't as "rigid" and "lined up" as that of other crystals.

As the lampworker is making a bead, some parts of the glass are heating up more than others, causing the molecules to arrange themselves in ways that stress the structure of the bead. Then as the bead cools, the outside of the glass cools faster than the inside (even with vermiculite), creating even more internal stress. The result is a very fragile bead that could shatter if you look at it wrong. Or not. The problem is that you just can't tell where those stresses might be.

When a bead is annealed in a kiln, all the glass in the bead is brought to the exact same temperature, which ideally is the exact temperature to relieve all the stresses without melting the glass into a sad little puddle. If I understand correctly, it's a fine line between proper annealing and sad little puddle. Once the glass has reached that state, it's all at exactly the same temperature, the molecules do what they're supposed to do, and the stresses are gone. The kiln then cools off so slowly that the glass doesn't form that skin or any internal stress.

Note: This does not apply to enameled beads on copper like Pam East makes. From what I understand, the vermiculite/crockpot thing is just fine.

Oh yes, vermiculite dust is a serious lung irritant. I sure as heck wouldn't want that floating around my house, and I wouldn't work with it unless I had a dust mask on (at least).

Hope this clears it up, and if any of you lampworking ladies want to add to this or make corrections, please jump in!

Kathy N-V

Reply to
Kathy N-V

A woman in my jewelry class said a friend of hers uses a crockpot with some (vermiculite? or something??) instead of a kiln. Is this possible? I'm sure you will all tell me why this is a bad idea... or maybe it's ok for beginners???

send her here

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NOT USE VERMICULITE!Cheryl of DRAGON BEADS Flameworked beads and glass
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Reply to
Cheryl

Thanks for this explanation! I've never had it explained in this detail. Makes perfect sense. Thanks! Gennie

Reply to
Gennie

thanks all, I knew you would tell me why not to do that. Hubby will be disappointed as he would like to see this new venture of mine cost "him" not too much $$, but he is looking forward to some new tools in his garage... so hopefully it will all work out.

:) Pam

Reply to
Pam

Well, that's a hotly debated issue. Some people think it's okay, and some do not. If you do use vermiculite, you cannot say your beads are kiln annealed. And kiln annealing beads really does make a difference in their durability, and in the ability to sell the beads. Many people will not buy beads that haven't been kiln annealed. Plus, vermiculite is dangerous stuff - have to be very careful not to breathe it in. (Same with fiber blankets.) Lots of threads on that subject on the ISGB forum and on WetCanvas. I personally would not recommend the use of vermiculite or fiber blankets, for safety reasons.

Reply to
Kandice Seeber

Vermiculite truly IS "dangerous stuff" and it might be a good idea to spell out the reason: It's been known to contain significant amounts of asbestos fibers. My "significant other" used to work for an asbestos settlement trust and dealt with the heartbreaking stories of dying people on a daily basis, people who had been exposed to asbestos in one way or another. Two of my daughters work for a lawyer who handles mesothelioma cases from asbestos exposure. It's nasty stuff, and I wouldn't even run a small risk of exposure if I could help it. "Nuff said!

- Steve R St Louis MO

Reply to
Steve Richardson

I did a search on vermiculite a while back (2-3 years). There's some contention to a point, because most of the asbestos-contaminated vermiculite came from one particular source in Montana. However, that mine produced a LOT of vermiculite for a very long time.

A lot of my old links are dead, but I was very pleased to find that this one, which is very informative, was recently updated.

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it's difficult to be certain what the source of any store-boughtvermiculite is. Theoretically new stuff shouldn't be contaminated.Personally it's not a risk I'm willing to take, though. Before I had a kiln,I used perlite (sifted to remove dust) instead of vermiculite.-- KarenK Desert Dreamer Designs
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Reply to
Karen_AZ

FWIW, the vermiculite being sold now is not from the same mines that had the asbestos contamination. There was a report on NPR about a year ago about the people who lived near the old vermiculite mines. It said that the vermiculite being sold now is tested for asbestos. Apparently this is a new development that hasn't made it into the glass books. That having been said, I still don't think it is a good idea to mess with it for gardening. And as for cooling beads, the crockpot/ dutch oven/ hot plate/ fiber blanket methods are not going to do you beads any real good. Even if you put them into a kiln after cooling them in vermiculite or fiber blanket, you are not going to remove the micro cracks that may have developed. As far as annealing being a fine line between cooling and making a puddle, the best way to find the annealing temperature of your kiln (to be really technical, this should be done monthly) is to prop a cane of the glass you are going to be using horizontally. Turn the kiln on high and record the temp every 10 minutes or so. When the cane shows the slightest tendency to bend, record the temp on your pyrometer. Subtract 50 degrees F. This should give the correct annealing temp for the glass in your kiln as your pyrometer reads it. So you would have top be quite a bit higher than annealing temp to turn your bead into a puddle, or even seriously distort it..

Reply to
Louis Cage

It's a perfectly suitable alternative to using a fiber-blanket, but it's still just a way to slow-cool your beads, not a way to anneal them. You do need a kiln to anneal them, because they need to be held at annealing temperature (920 or higher, depending on the glass) for a period of time in order to anneal.

Reply to
Kalera Stratton

Please go to vermiculite.com and look at the research there; asbestos is NOT an issue in the end-user product of vermiculite.

Reply to
Kalera Stratton

There's a great thread on Wet Canvas right now about this. You can view it here:

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Reply to
Tink

Great thread! The bottom line for me is that if a bead is not kiln annealed these days, it does not sell well, period. No matter what the science is, no matter what the reasons behind it are, kiln annealing is almost required if you're going to sell beads, because customers are beginning to get the hint that if it's not annealed, it has much more of a chance of breaking. If people plan to sell their handmade beads for a decent price, they should be kiln-annealing them. Especially if they're bigger beads. If a person is just making beads for a hobby, or doesn't mind getting a much cheaper price for them, using vermiculite or fiber blankets is fine, if you don't mind taking a chance with health. (I don't care what the vermiculite site says, I know from personal experience that vermiculite causes chest pain. I've been there.) Of course there are dangers with everything, but one has to weigh the pros and cons. Sure, kilns are expensive, but lampworking is NOT a cheap hobby or career. One has to spend money to make money. Start small, and maybe look for used kilns on eBay or at suppliers. Look for deals. Read the forums, because people sell their equipment all the time when they move up. But don't skip the annealing step just to save money, if you want to sell your beads, unless you want a lot of customers coming back and complaining that your beads are breaking. JMHO, YMMV :)

Reply to
Kandice Seeber

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