Kiln Shelf Material

[Joe Wokovich]

I need a replacement shelf for my GF8. It’s 22 x 46 inches. Currently I have been using a fiberboard shelf that has now seen better days.

I’ve been looking at Corelight or Dyson (now made by Euclid) and worry about the cracking due to unbalanced heat loads.

Fiberboard is too flexible without a lot of bracing and I am trying to learn more about using a sand bed. I’m still searching for info on sand beds.

I found a place that offers a silicon carbide shelf. My only experience with sic is sand carving and etching glass. Has anyone any info on using this for a shelf? It is supposed to be good to 2300f.

Any ideas will be greatly appreciated and a special thanks to Brad for all the help he has given me.


Joe

[Bert Weiss]

You can use a fiber board on the floor of your kiln if you like. Those heavy boards will cost you more money to heat up and more time to cool down. And they will thermal shock on a fast heatup. Get a new fiber board. Unifrax makes an HD board 24"x 48".

I line by big kiln with Unifrax 1/4" blanket, I make a sandbed on it 10mm thick. I like to use a mix of 75% sand and 25% alumina hydrate. When I am done with the sand, I sift it back in to a trash barrel with a lid. Then I sift it again in to the kiln. Little bits of fiber are killer when you are screeding the sand smooth. I maintain several different sand beds, utilizing different particle size mixes and different kinds of sand.

[Babette (Shawn)]

I have a 25 inch by 42 inch Dyson shelf in my Denver kiln, this kiln has fiber sides and a fiber lid. Yes it does take forever to cool down, but the shelf is smooth and stable and practically indestructible. I never heat it up AFAP, at the most I go 400*F an hour. Another negative is that this shelf is very very heavy, hard to pull out and clean. The bottom line is there are advantages and disadvantages to the Dyson (Corelight, Euclid) shelf.

[Joe Wokovich]

You can use a fiber board on the floor of your kiln if you like. Those heavy boards will cost you more money to heat up and more time to cool down. And they will thermal shock on a fast heatup. Get a new fiber board. Unifrax makes an HD board 24"x 48".

I line by big kiln with Unifrax 1/4" blanket, I make a sandbed on it 10mm thick. I like to use a mix of 75% sand and 25% alumina hydrate. When I am done with the sand, I sift it back in to a trash barrel with a lid. Then I sift it again in to the kiln. Little bits of fiber are killer when you are screeding the sand smooth. I maintain several different sand beds, utilizing different particle size mixes and different kinds of sand.

Bert, for some reason I have problems visualizing the idea of a sand bed. Do you put down blanket material and then the sand? When firing a large sheet (20x44”) how do I keep the sand level. Will it not shift if one end of the project contacts before the other end? Can you point me to a reference book that shows this type of arrangement? Does it take a longer time to cool down than on a shelf with air circulating around and under the shelf? I’m open to trying anything and maybe to get a better handle on this idea I’ll try it out in a smaller kiln to see how it works.
Thanks.

Just tonight I found someone here that has some 15x15 silicon carbide (sic) shelves for sale and am trying to set up a time tomorrow to pick up a few. They are supposed to be in great condition and have only been fired twice in a gas reduction kiln. $30 apiece so it is too hard to pass this deal up.

[Marty]

Dyson shelves are wonderfully smooth and flat. They are also wonderfully heavy and expensive. Both of mine (30"x 72" and 24" x 48") eventually cracked and I will not be getting them again. I'm headed in the HD fiberboard direction.

[Brad Walker]

Both of mine (30"x 72" and 24" x 48") eventually cracked and I will not be getting them again.

I think this is the key. For the price, they don't last as long as they should. I took really, really good care of my shelf, but eventually it cracked anyway.

[Bert Weiss]

You can use a fiber board on the floor of your kiln if you like. Those heavy boards will cost you more money to heat up and more time to cool down. And they will thermal shock on a fast heatup. Get a new fiber board. Unifrax makes an HD board 24"x 48".

I line by big kiln with Unifrax 1/4" blanket, I make a sandbed on it 10mm thick. I like to use a mix of 75% sand and 25% alumina hydrate. When I am done with the sand, I sift it back in to a trash barrel with a lid. Then I sift it again in to the kiln. Little bits of fiber are killer when you are screeding the sand smooth. I maintain several different sand beds, utilizing different particle size mixes and different kinds of sand.

Bert, for some reason I have problems visualizing the idea of a sand bed. Do you put down blanket material and then the sand? When firing a large sheet (20x44”) how do I keep the sand level. Will it not shift if one end of the project contacts before the other end? Can you point me to a reference book that shows this type of arrangement? Does it take a longer time to cool down than on a shelf with air circulating around and under the shelf? I’m open to trying anything and maybe to get a better handle on this idea I’ll try it out in a smaller kiln to see how it works.
Thanks.

Just tonight I found someone here that has some 15x15 silicon carbide (sic) shelves for sale and am trying to set up a time tomorrow to pick up a few. They are supposed to be in great condition and have only been fired twice in a gas reduction kiln. $30 apiece so it is too hard to pass this deal up.

My everyday glass is 10mm float glass, so I have plenty around to work with. I have some 2" wide strips that I place on top of my blanket layer, at the outer edges. Then I fill the area between them with the sand mix. I use another piece of glass as my screed. I screed back and forth until I have a smooth bed exactly 10mm deep. Then I am free to press shapes in to the sand to make patterns. If I were to want just a smooth surface, I'd figure out how thin a layer I could get away with. I never do that. I often fire directly on blanket that has been powdered with alumina hydrate. That is quick and easy.