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Tips, Techniques, and Questions -- Technical questions or tips

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  #1  
Old 2007-06-04, 8:18pm
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Default How to use vermiculite?

I went and baught the vermiculite--what do I do with the crock pot and vermiculite. I will be making pendants with Boro and using this system until I can get them in a kiln. Just don't know what to do.
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KnD
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  #2  
Old 2007-06-04, 8:42pm
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You dont really need the crock pot , but if it make you feel better use it.... Its never been proven the heat from the crock post helps in any way...

Anyway once marble or bead or whatever is done, you let heat bleed off piece by slowly removing it form flame, after "bead" loses red heat you gently borrow or plunge it into vermiculite... The vermiculite sort of forms a insulation cocoon around item and drastically slows cooling. This cooling is no alternative to annealing, its allows you to make many items and later batch anneal when you either get access to a kiln buy your own kiln. By the slow cooling you relieve some of the internal stress that can happen if outer shell of bead cools faster than core. The ideal is to allow the bead to cool uniformly, thus allow core heat to dissipate to shell evenly as total temperature drops.

It tales a bit to learn timing on plunge, if bead is to hot you can distort it, if it is allowed to cool to much it may crack before you get it cocooned....

Dale
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  #3  
Old 2007-06-04, 8:56pm
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Dale-
You have been a saviour for me today. Thank you so much.
KnD
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  #4  
Old 2007-06-05, 9:34am
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In my experience, slowing the cooling using a crockpot on high filled with vermiculite truly DOES allow you to make things with the soft glasses that would crack otherwise.

For example, Bullseye (COE 90) and Moretti/Effetre (COE 104) both respond favorably to slower cooling using vermiculite in a hot crockpot. The slower cooling prevents some of the stress cracking that would occur with some shapes, some thicknesses, and even some of the "touchy" colors. I really don't know if it's helpful for boro, because I am speaking from my own experience and haven't ever tried using it for boro.

Remember, the slower cooling only allows a tiny bit less stress to fix in the glass. The most stress accumulates in the glass as you are working it, and that is why flame annealing helps to release the stress a lot -- but attempting to release residual stress is why kiln annealing afterwards is basically an accepted necessity among beadmakers.

P.S. To avoid any distortions from plunging your item into the vermiculite, dig a small hole with a spoon, place your object inside the hole, and cover it with vermiculite.
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Old 2007-06-05, 2:28pm
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Quote:
Originally Posted by scupltorgirl View Post

. The most stress accumulates in the glass as you are working it, and that is why flame annealing helps to release the stress a lot -- but attempting to release residual stress is why kiln annealing afterwards is basically an accepted necessity among beadmakers.
Unfortunately there is no such thing as "flame annealing"..... Only things one can do is heat object in flame so it has a uniform temperature then either garage it into a kiln at proper holding temperature then finish annealing cycle, or slow cool it in vermiculite or fiber blanket and batch anneal later..

Dale
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  #6  
Old 2007-06-05, 5:27pm
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Quote:
Originally Posted by Dale M. View Post
Unfortunately there is no such thing as "flame annealing"..... Only things one can do is heat object in flame so it has a uniform temperature then either garage it into a kiln at proper holding temperature then finish annealing cycle, or slow cool it in vermiculite or fiber blanket and batch anneal later..

Dale
Hi Dale. You are correct in that "flame annealing" is best followed by kiln annealing, but there is such a thing as "flame annealing".

Flame annealing doesn't substitute well for kiln annealing, because most people don't have the patience to take the extended time that proper flame annealing requires (sometimes and usually longer than it took the person to make the object in the first place), and kiln annealing provides a much more uniform distribution of heat.

(Supposedly the lampworkers in Lauscha, Germany only flame anneal the glass pens that they produce -- but I've only read this in one source, so it remains unconfirmed.)

Northstar Glass defines "Flame Annealing" as:
"Flame-annealing
A flameworking technique where the finished piece is reheated in a bushy, relatively cool flame to relax the stresses built up in it during the construction process. This is usually used only on small pieces and is generally regarded as a temporary measure for work that is to be properly annealed later on."

Links to "flame annealing" glass:

http://www.glassalchemyarts.com/supp...ng-Stress.html
8th paragraph down discusses flame annealing

http://www.public.asu.edu/~aomdw/GSI/Glass_Strain.html
In this article, it's referred to as "hand annealing"

http://collegian.ksu.edu/collegian/article.php?a=4435

http://www.public.asu.edu/~aomdw/ampoule/Page_3.html

http://www.guild.com/servlet/Guild/G...?firstLetter=F

There are many more links, too. These links were provided as a small sample to show that "flame annealing" does exist, and that it is a recognized and defined process by (most!) glassworkers. ( Except Dale. I'm just ribbing you because you said it doesn't exist when I'm sure you know it does but you just didn't want to give it as an option because it is totally impractical. )
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  #7  
Old 2007-06-13, 6:10pm
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Quote:
Originally Posted by scupltorgirl View Post
In my experience, slowing the cooling using a crockpot on high filled with vermiculite truly DOES allow you to make things with the soft glasses that would crack otherwise.
I'll agree that vermiculite (and other similar materials) can allow soft glass items to cool slower, reducing (but not necessarily eliminating) the need for true annealing. I have been told that the Japanese glass (Satake, Kinari, etc.) has such a low annealing temperature that they use ash, or what they call annealing bubbles, as a replacement for vermiculite, and many artists do not use kilns to anneal their beads.

But, I'd like to ask the question: why even use a Crockpot? My experience is that a Crockpot cannot achieve temperatures of over 150-180 deg. F. This is so far below the annealing temperature of even the softest glass that I don't see the benefit. Other than psychological, that is.

Malcolm
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  #8  
Old 2007-06-13, 6:56pm
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Again I say what crockpot.... I use a coffee can...

Dale
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  #9  
Old 2007-06-14, 8:43pm
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If I can show you a bunch of links to UFOs.............

Steve
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  #10  
Old 2007-06-14, 9:31pm
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I use a crockpot because it
1 - Holds the vermiculite
2 - Has a lid to cover the vermiculite when not being used.
3 - Looks prettier in my studio than a coffee can would.

As for turning the crock pot on, I don't even have mine plugged in. The only time I've had a bead break when cooling it this way is when I can't stand it and take it out of the vermiculite for one last peek. When I have enough beads, I kiln anneal them. I've had a couple of people want to see how strong these are so they've dropped them from a second story window onto their driveway, and they bounced instead of breaking.
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  #11  
Old 2007-06-15, 3:55pm
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i use a crock pot and i ALWAYS have it on "keep warm" ive never had the pot on high, and my beads have been fine!
just my peneth worth
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