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Paco
2007-09-17, 1:26pm
Hi All,
I am setting up a "hobby" studio. I cannot afford a kiln at this time so I wonder what the popular opinion is on using vermiculite in a crock pot versus using a fiber blanket. Also, what are common procedures for both techniques? ie: timing, fine/med or coarse vermiculite,temp of crock pot etc. I do plan to batch anneal my beads at a studio after the fact, but, do not want to lose beads to shock.
Thank you in advance for any tips and suggestions.
Dinah

wendbill
2007-09-17, 1:35pm
I used/use vermiculite in a flower pot and I have never worried about heating it in a crockpot. I had very few break.

Sculptural beads are the exception. Those I find need to go straight into a kiln to avoid cracking. Based on survival rates, I suspect beads heavy in silver are better off going straight into a warm kiln as well.

Basically you wait until the glass is "set", wave it a few times through the flame to even out the heat in the bead, then pop it into your vermiculite. Leave it a minimum of 20 minutes to cool down.

Just Nancy
2007-09-17, 1:39pm
I've read that there is no need to heat the vermiculite. I used a fiber blanket when I first had my hot head. Then I worked for quite a while with vemiculite eventually batch annealling beads worth keeping.

Your goal is controlled cooling. I think either works. For me, I think I opened up the blanket too far, too much. So if I was going the blanket route, I might get two. If you go with the vermiculite, I just had a bag from a garden center. Basically when the bulk of the glow was gone from the bead (the outside firm enough to not dent in the vermiculite or get fuzzy from the blanket) you put it in. I ran mine in one of those crock pots that has a pan on top of a hot plate. I ran it on high until I was ready to quit. Then I turned it off and let them cool for as long as I could stand. As I recall probably several hours. You want them to go from the 900-1000 degree range to most say under 4-500 degrees before you take them out.

Paco
2007-09-17, 1:59pm
Thank you both so much. I love this forum!! Everyone is so helpful.
Dinah

ArtcoInc
2007-09-17, 3:22pm
This subject has been a pet peeve of mine for some time.

1) I've measured the temperature of several crock pots. The hottest one I have might hit 180F. This is sooooo far under the annealing temperature of glass as to be a "why bother?" I've used vermiculite, but I have never bothered heating it in a crock pot.

2) You will hear that neither vermiculite nor fiber blanket truly anneal the beads, and you should never sell beads that have not been kiln annealed. Yet, there are glass beads that have survived hundreds (thousands?) of years, made long before computer controlled kilns were invented.

3) People talk about the annealing temperature for a specific glass as if it is a single temperature. Hold you beads at this temperature, and they will be annealed. Not true! I can hold my beads at this temperature for an hour, a day, a week, or even a year, but if I pull them out of the kiln (still at that temperature), they will crack. They need to cool down slowly *through* that temperature.

If we remember from high school physics; when things get hot, they expand. When they cool off, they contract. Glass is a good insulator. This means that it does not conduct heat well. This also means that a piece of glass (such as your bead) can have parts of it that are much hotter (such as the inside) than other parts (such as the outside), and that the heat will not easily 'even out' all by itself.

When you finish making your bead, the outside of the bead is in contact with the cool air. The outside will want to cool down. The inside is sheltered, and has no reason to cool down. Since the outside is cooling off faster than the inside, it will want to contract (shrink) more than the inside. This sets up stresses, which can cause the bead to crack.

If your beads are large or thick, this temperature difference can cause problems. If your beads are small and/or thin, there won't be much temperature difference, and there won't be much internal stresses. This is why you can pull stringers and not have to anneal them. This is why furnace workers can blow very thin pieces, and not worry about annealing them.

Even if your large bead survives cooling down without cracking, these stresses are still in the bead, and the bead may crack (or worse) at a later date.

So, what you want to do is slow down the cooling of the outside of your bead, so that the inside and the outside cool at just about the same rate. All the vermiculite or fiber blanket does is insulate the outside of the bead, making it cool down slower, thus evening out the overall cooling process. Computer controlled kilns do the same thing, just in a much more controlled way.

Vermiculite, fiber blanket, ash, or the Japanese annealing bubbles can all work *for the most part* for small beads made out of soft glass. For larger pieces, these materials do not slow the cooling process of the glass enough, which means that you now need the more controlled environment of a kiln.

Now remember, beads also crack for reasons besides annealing (or the lack there of). Mixing incompatible glasses will also cause cracks. Trapped air, trapped bead release, improperly attached dots, etc. can all lead to cracks (or worse).

So, if you can't afford a kiln, you can still make glass beads. Vermiculite, fiber blanket, ash, or Japanese annealing bubbles can all be used to slow the cooling of smaller pieces in soft glass.

Two closing thoughts:

1) If you are trying to build a business selling your glass beads, do you want to risk your reputation, and your business, on having of one of your beads crack (or worse)?

2) The use of vermiculite has its own health issues. With inexpensive alternatives available, how much is your own health worth?

Malcolm

beadmama
2007-09-17, 3:57pm
Hi

I am a newbie. Could some explain the health issue using the vermiculite. Thanks Becky

Listenup
2007-09-17, 4:05pm
I use vermiculite to cool the beads till I'm ready to batch anneal them. I keep mine in a crock pot, but I don't ever turn the crock pot on. When I dip my mandrels, I just flip them over and stick them in the vermiculite to dry. I have less thermal cracks with the vermiculite than with the fiber blanket, but I think that's because I resist the urge to peak better with the vermiculite.

I also bristle whenever I hear that you can only properly anneal beads in a kiln. I would venture that not very many (if any) of the beads in "The History of Beads" ever saw the inside of a kiln, and as Malcolm mentioned, have survived through the years - I've seen them in the Bead Museum in Washington, DC.

I do know that a large campfire does get hot enough to melt glass and that the embers are still hot enough to slump a glass rod the next day so I would contend that it is possible to anneal beads "poperly" in the ashes of a campfire.

When you have enough beads to do a batch annealing of them, just post a message here. I bet you'll get loads of folks who will volunteer to do it for you. In fact, I'll offer to do so right here, right now.

Welcome to the addiction!

-Kay

ArtcoInc
2007-09-17, 4:24pm
I am a newbie. Could some explain the health issue using the vermiculite.

A quick Google search can turn up a lot of information. I just used "Vermiculite health issues", and the first several hits all were useful.

Working with hot glass has never been completely free of health risks, and never will be. Only through education can *you* make an informed choice as to which risks you wish to take, and which ones you don't.

So, to address the health issues with vermiculite, *some* vermiculite *may* contain free silica and/or asbestos, neither of which is good to breath. This is not to say that any vermiculite you buy *will* have these, only that it *may*.

If you do choose to use vermiculite, use some common sense: try not to "stir it up", so as not to raise any unnecessary dust. Make sure you have adequate ventilation. And don't stick your face down in the crock pot when adding or removing your beads.

I have also heard of people rinsing their vermiculite in water to get rid of any loose dust. I've never tried it. Obviously, you need to dry it completely before using it for your beads.

Mind you, you don't want to breathe the fibers from fiber blanket either.

Malcolm

Dale M.
2007-09-17, 4:36pm
Oh no, not the Vermiculite contains asbestos scare again.........

http://www.vermiculite.org/hse.htm

http://www.cdc.gov/niosh/topics/vermiculite/

YES there is a dust hazard using vermiculite but it can be rinsed and dust removed and most of the hazard is abated....

There is also hazards using fiber blankets as it break`s down it releases fiber elements as dust and they also can be inhaled and lodged in lungs.....

Dale

prairieson
2007-09-17, 5:12pm
Malcolm - Absolutely spot-on about the crock pot thing, a couple hundred degrees won't make any difference at the bottom of the scale.

However, don't confuse annealing with thermal shock, they're two different critters entirely and not really related in any way. Reference point 3 in your initial post:

People talk about the annealing temperature for a specific glass as if it is a single temperature. Hold you beads at this temperature, and they will be annealed. Not true! I can hold my beads at this temperature for an hour, a day, a week, or even a year, but if I pull them out of the kiln (still at that temperature), they will crack. They need to cool down slowly *through* that temperature.

Absolutely true that it's the annealing "range" and not temp... it's the temp range between the strain point at the low end and the softening point at the high end. Proper annealing is soaking somewhere within that range long enough to relieve the stress and then slowly lowering the temp such that the entire object is the same temp throughout untill the strain point is reached. Below the strain point no appreciable annealing will take place. But work can thermal shock well below the strain point. Put a properly annealed bowl in the freezer for a couple of hours, take it out and pour boiling water into it, and you've got thermal shock breakage. And it happened about 600 degrees below the strain point of the glass.

Properly annealed glass can thermal shock, and unannealed glass won't necessarily do so. There's no relationship between annealing and thermal shock.

While part of the job of the kiln is to prevent thermal shock, it's main purpose is to ease the work through that annealing range and relieve the stresses, something a blanket or torch just cannot do.

The reason glassblowers and flameworkers alike are able to get away with unannealed work is all about controlled cooling, by means of torches, glory holes, blankets or what have you. it's easier and quicker to do so with thinner pieces of glass, but with patience and control can be done with thicker work as well.

evilglass
2007-09-17, 5:17pm
and....one could always use perlite :)

Works the same way, LOL!

I use perlite.

ewdb
2007-09-17, 5:18pm
i make big (1-2"+) beads and switched over to a crockpot as my beads kept cracking with the fibre blanket. i bought a $10 ceramic insert crockpot and a $3 bag of vermiculite from walmart. i preheat the crockpot (cranked to high) for about 15mins before i start beadingmaking then i put the lid on and leave it on for about 30-60mins after i'm done. since i started doing it this way, i've had no more cracking or breakage, so i'm happy.

i finally have a kiln (AF138 ) so once i figure out how to use it i'll be batch annealing my bead collection.

ArtcoInc
2007-09-17, 6:35pm
However, don't confuse annealing with thermal shock, they're two different critters entirely and not really related in any way. Reference point 3 in your initial post:

People talk about the annealing temperature for a specific glass as if it is a single temperature. Hold you beads at this temperature, and they will be annealed. Not true! I can hold my beads at this temperature for an hour, a day, a week, or even a year, but if I pull them out of the kiln (still at that temperature), they will crack. They need to cool down slowly *through* that temperature.

Absolutely true that it's the annealing "range" and not temp... it's the temp range between the strain point at the low end and the softening point at the high end. Proper annealing is soaking somewhere within that range long enough to relieve the stress and then slowly lowering the temp such that the entire object is the same temp throughout until the strain point is reached. Below the strain point no appreciable annealing will take place. But work can thermal shock well below the strain point. Put a properly annealed bowl in the freezer for a couple of hours, take it out and pour boiling water into it, and you've got thermal shock breakage. And it happened about 600 degrees below the strain point of the glass.

Quite correct. If my glass has soaked at "annealing temperature", it shouldn't have any internal stresses. But, if I cool it quickly *from* that temperature, it will develop internal stresses, due to thermal shock. Most people wouldn't know why their beads cracked, and would probably blame it on annealing.

The point I was trying to make is that I hear so much talk about a single "annealing temperature". Like you said, it should be more accurately described as the range between the strain point and the softening point. It is through this range that the glass must be cooled slowly, so as not to develop internal stresses, or strain. And like you said, below the strain point, no appreciable stresses will be added or relieved.

Properly annealed glass can thermal shock, and unannealed glass won't necessarily do so. There's no relationship between annealing and thermal shock.

While part of the job of the kiln is to prevent thermal shock, it's main purpose is to ease the work through that annealing range and relieve the stresses, something a blanket or torch just cannot do.

Again true ... but if a piece is small or thin enough, the amount of stress developed while cooling can be low enough to not be a problem. This is where the vermiculite, fiber blankets, and/or torch "annealing" works. Not true annealing, I'll agree. But, the internal stresses are low enough to not be a problem.

The reason glassblowers and flameworkers alike are able to get away with unannealed work is all about controlled cooling, by means of torches, glory holes, blankets or what have you. it's easier and quicker to do so with thinner pieces of glass, but with patience and control can be done with thicker work as well.

But how many of us have the time and patience (let alone skill) to flame anneal a large piece? :)

Thank you very much for your contribution. Like I said, this has been a pet peeve with me for some time. Hopefully, this will clear things up for some.

Malcolm

Lorraine Chandler
2007-09-17, 7:03pm
As far as saying that hundreds of year old beads never saw the inside of a kiln ( maybe not a digitally controlled kiln) how do you know?

You did not live way back then and if you look at some of the ingenious things people in history created maybe those beads were annealed and annealed better than we do it today but in an entirely different way...??? :-s\\:D/

I say this because it is so easy to mislead newbies. I know because I was one not too very long ago.

We now have all kinds of tools and equipment to ensure proper annealing so why not do what we know works now in the 21st century?

Why take chances, why take a chance on lawsuits and injuries even if it is only a small chance?

Cooling mediums such as vermiculite work by containing the heat immediately around the hot bead.

I use a crock pot, no heat and have NEVER had a bead fracture or crack. There is a certain 'touch' to using a cooling medium and it all comes down to just the three PPP's, and using the search button here to read all you can and then decide what is right for you.

I cool my beads in the outter flame edges before they go into the crock pot. I never take one that I just finished working on and put it right into the cooling medium. It seems to help to take it slowly farther and farther out of my flame and then into the vermiculite. Have a great time setting up your studio.:waving:

Hugs
Lorraine

Listenup
2007-09-17, 7:17pm
>> You did not live way back then and if you look at some of the ingenious things people in history created maybe those beads were annealed and annealed better than we do it today but in an entirely different way...??? <<

I did not say they were not annealed, but that they were not annealed in a kiln - at least one that you plug into the wall and can control the precise temperature with. I did go on to say that it can be done in the ashes of a campfire so I'm sure that however they melted the glass, there was some way to utilize a part of that technology to anneal them.

>>We now have all kinds of tools and equipment to ensure proper annealing so why not do what we know works now in the 21st century? <<

Because some of us enjoy recreating, as much as is possible, how it could have been done in the past.

>> I use a crock pot, no heat and have NEVER had a bead fracture or crack. There is a certain 'touch' to using a cooling medium and it all comes down to just the three PPP's, and using the search button here to read all you can and then decide what is right for you. <<

I couldn't agree with you more.

:wave:

beadmama
2007-09-18, 9:35am
Thank everyone for the clarification!

Becky

Paco
2007-09-18, 10:12am
Thank you all so much for the great info. Thank you Kay for your offer, I do have a source for batch annealing here locally.
Dinah