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Kiln wash curing?
Posted: Thu Oct 09, 2003 3:34 pm
by daffodildeb
Stupid question time--what is the point in "curing" a freshly kiln washed shelf? I can't see why preheating a fully dry shelf before using it at fusing temps is worth doing. What am I missing here?
Re: Kiln wash curing?
Posted: Thu Oct 09, 2003 3:47 pm
by jim simmons
daffodildeb wrote:Stupid question time--what is the point in "curing" a freshly kiln washed shelf? I can't see why preheating a fully dry shelf before using it at fusing temps is worth doing. What am I missing here?
You are not missing anything if the shelf is dry
Jim
Posted: Thu Oct 09, 2003 5:27 pm
by SAReed
Uncured kiln wash can give off gases that will cause big bubbles
Stacey (who has had her share of big bubbles)
Posted: Thu Oct 09, 2003 5:32 pm
by daffodildeb
Ah--never would have guessed!
Posted: Thu Oct 09, 2003 5:35 pm
by charlie
SAReed wrote:Uncured kiln wash can give off gases that will cause big bubbles
Stacey (who has had her share of big bubbles)
i have never prefired my kiln washed boards or molds, never used paper, and have never gotten a bubble under the glass. i have gotten bubbles between the layers of glass, but that isn't attributable to the wash.
Posted: Thu Oct 09, 2003 5:46 pm
by SAReed
I've never cured the kiln wash in a mold since it has air holes.
I was making a platter that because of the design a bubble would form in the center. When using an un-cured kiln wash shelf the bubble was large, when using cured, it was small, more of an indentation.
Posted: Thu Oct 09, 2003 6:05 pm
by Carol
Um, I'm noticing that everyone who doesn't pre fire tends to live in hot, dry parts of the US. In rainier or more humid locations, it is less likely the kiln wash will dry completely in a reasonable period of time.
Posted: Thu Oct 09, 2003 6:23 pm
by daffodildeb
Ok, how about a few minutes at low temp before going to the regular firing schedule, just to make doubly sure it's dry?
Posted: Thu Oct 09, 2003 10:18 pm
by Tim Swann
A kiln shelf improperly dried (even in Arizona) will cause large steam bubbles to form between the bottom layer of glass and the shelf. You can get around the pre-drying by holding the firing at ~500°F for at least 30 minutes. This will not work if the shelf goes in damp. If the piece is very large (bigger than 14” in diameter) you will need to hold for a longer time period or pre-drying the shelf.
Tim
Posted: Fri Oct 10, 2003 8:30 am
by rosanna gusler
i have never pre dried shelves. i do not believe that there is any water left anywhere in the kiln by the time glass softens. i do believe that damp kiln wash makes a really good seal and can trap air. i put damp shelves in all the time . i do a 20 min hold at around 1100F. i have never gotten a bubble under the glass. rosanna
Posted: Fri Oct 10, 2003 1:37 pm
by SAReed
I was getting my bubbles with dried shelves, but not cured. I would put the kiln wash on, let dry a day or two, then fuse. Now I put the kiln wash on, let dry, then pre-fire. I don't know if I have to let it dry before I pre-fire, but I have a good thing going right now and I don't want to mess it up.
Posted: Fri Oct 10, 2003 2:10 pm
by jim simmons
Carol wrote:Um, I'm noticing that everyone who doesn't pre fire tends to live in hot, dry parts of the US. In rainier or more humid locations, it is less likely the kiln wash will dry completely in a reasonable period of time.
I have 2 shelves. I leave one on top of my kiln when I am doing a firing, and only take it off when I am ready to use it. Using BE kiln shalves, I have also never had a bubble under the glass. And I live just outside of Portland Orygun :>)
Jim