Large Kiln Shelves -

Large Kiln Shelves

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Large Kiln Shelves

Postby KellyG » Tue Aug 26, 2003 8:23 pm

Just received my new large kiln :D . Inside dimensions are 28" x 28" sq., but the shelf that came with it was only 21". Naturally, I want to take advantage of all the room available, but having trouble finding (google search) a larger 24" shelf. Do they make shelves larger than 21"?

I'm considering fiber board as an alternative, but wanted to know pros and cons first. I've heard that you always have to fire on thin fire. Should I purchase 1" or 2" thick? Does it warp/trap air? How long should it last? I've read that you get better annealing on fiber board.


Lisa Allen
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Postby Lisa Allen » Tue Aug 26, 2003 10:09 pm

I haven't seen a mullite shelf larger than 21", probably because it would be so dang heavy.

I use a Unifrax HD duraboard that is 1 and 1/2". I have been using the current one for about 8 months now. They do tend to warp slightly and the surface has degraded a bit, but mine is not rigidized or kilnwashed. I just take a little sand paper to it now and again to smooth the surface. And I do always use thinfire with it. I have fired directly on it, which works fine, I'm just not too keen on the texture it leaves on the bottom of the pieces. Overall, I think it serves its purpose well.

Lisa Allen
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Amy Schleif-Mohr
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Postby Amy Schleif-Mohr » Tue Aug 26, 2003 10:32 pm

If you use fiber board it is a good idea to ridgidize it first. Once you fire the board it is like fiber paper and is carconegenic (sp?). By ridgidizing the board you trap the fibers. It is then up to you if you want to use thin fire or kiln wash. In my experience you should use the paper if you are using opal colors with soft glass like BE, but you can get away with thick kiln wash when using transparents.



Re: Large Kiln Shelves

Postby Cynthia » Wed Aug 27, 2003 1:04 am

KAG wrote:...I'm considering fiber board...but wanted to know pros and cons first. I've heard that you always have to fire on thin fire. Should I purchase 1" or 2" thick? Does it warp/trap air? How long should it last? I've read that you get better annealing on fiber board.


I have a 30 x 60 inch kiln and have a 2" fiber shelf called Magnaform. It's an extruded Unifrax fiber product and is rigidized for you. I always use paper as an insurance policy. Most tested compatible opals will stick and when it pulls up the wash, it can tear up the shelf. Some transparent can stick, so I just always use paper unless I'm firing float or window glass. That doesn't seem to no need for paper. I don 't have any experience with any other types of nothing to add there.

It is fiber and therefore pourous, so one really nice advantage is that it never traps air and bubble trubble aint a problem. Again, it's fiber, or specifically RCF (refractory ceramic fiber). My understanding is that RCF's are not carcinogenic, but considered a nusiance dust that cause respiratory irritation, but doesn't lodge in the tissues like asbestos or silica, so isn't currently labeled as a health hazard at certain levels of exposure. :shock: They used to consider asbestos safe I wouldn't take any chances and simply wear a respirator when cutting or sanding, vacuuming the material. Use good vetilation too and clean up with water and use a hepa filtered vacuum.

The thicker the board the less it will warp, but it will warp.

The Magnaform shelf should last indefinitely if you care for it kindly (the thinner softer fiberboards may be more perishable). I carefully sand off the kiln wash with fabricut then vacuum it out before each new application. I try not to sand down to the fiber, but just take off the top layer or so of primer. I wash it with new primer every full fuse firing to make sure that if my paper fails I have a healthy layer of clean wash in place. This is to protect my investment in the shelf. The thinfire I use shrinks and tears under larger pieces, so I want to be sure my shelf is covered with a layer of wash.

Better Annealing? I expect you fire according to the thickness of the glass and the insulating and heating properties of your kiln. I don't think that a fiber shelf will change how well you anneal your glass, but it might require an adjustment to your schedules if you switch.

Happy shelf hunting.
Last edited by Cynthia on Wed Aug 27, 2003 12:54 pm, edited 1 time in total.

Geri Comstock
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Postby Geri Comstock » Wed Aug 27, 2003 12:40 pm

Thorley makes shelves that are 24" x 24". They may be available from a pottery supply place if your glass place doesn't carry them.

The best shelves I've ever had are the 21" square BE bubbles ever!


Rachel K
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Re: Large Kiln Shelves

Postby Rachel K » Thu Jan 08, 2015 10:37 pm

Does Magnaform still exists?
Is unifrax duraboard hd still the universal favorite?

Laurie Spray
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Re: Large Kiln Shelves

Postby Laurie Spray » Fri Jan 09, 2015 2:49 am

I got shelves for my large kilns from Euclid Ceramics in Canada. Expensive but worth every penny!
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twin vision glass
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Re: Large Kiln Shelves

Postby twin vision glass » Sat Jan 10, 2015 12:43 pm

I love my Euclid shelves tooo! for larger shelving and because they are extruded, they are lighter. I can lift my 40" inch shelf my self. AND I am 60 ( tee hee :roll: :D ) ( well 61 in 2 weeks) :cry:

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Re: Large Kiln Shelves

Postby DonMcClennen » Sat Jan 10, 2015 1:46 pm

Another alternative shelf material is Vermiculite. I bought 2 boards fifteen years ago and I'm still using the first one. A 1" well supported shelf will give you years of service. It was initially rigidized and I use shelf paper or dry powder as separator. Never been kilnwashed.
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Stephen Richard
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Re: Large Kiln Shelves

Postby Stephen Richard » Sat Jan 10, 2015 2:20 pm

Once the fiber board has been rigidised, is it still porous/permeable to air?
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