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I have a Skutt GM 1414 kiln (13" deep model).

This kiln uses three shelves 2 that are 10.5"x22'x5/8" (half 10 sided) and one that is 18"x22"x5/8".

I have an piece that I want to fuse that is 35" x 18" and don't want the lines that seperate selves would leave.

I had my supplier order me a piece or Duraboard Fiber board that is 24"x48"x1/2" and plan to trim the board to the inside dimensions of my kiln floor (minus an inch all the way around) and use this as my seamless kiln shelf.

The catalog description for the Duraboard said that both sides of the board should be coated with alumina rigidizer hardener also available through the supplier of the Duraboard but which happens to be backordered for at least 2 weeks.

So I came here to look for other possible suppliers and started searching through the archives and came across at least one posting that the said the alumina rigidizer had a tendancy towards "Extreme hazing of glass for weeks even after the first burn-out" and colloidal silica based rigidizer works better.

For those that are using the alumina rigidizer, are you seeing this hazing.

I had at one time tried a cheaper fiber paper that caused this extreme hazing and I don't want to coat the Duraboard with a product that is going to do the same. Yet it's what is suggested as the rigidizer to use in the suppliers catalog for the Duraboard so I am a bit confused on what to use at this point.

Also not sure how much of either product to order to properly rigidize the Duraboard. The Alumina Rigidizer Hardener that I currently have on back order is a 32 oz container that says "a sprayed thing coat covers approximatel 25sq ft up to 1/16" thick. This board will be approximately 7 sq feet when trimmed down and 1/2 in thick.

Links to the supplier web sights for any products suggested would be greatly appreciated!!

On a related note, again after reading the archives I saw that I probably should have ordered the 1" thick board to cut down on the potential warpage. But since I already have the 1/2 in board in hand, can this be placed directly on the kiln floor and fired without any kiln posts under it (kiln floor and walls are 2" fire brick). Can it be placed on top of the normal mullite shelfs (which are supported by 1" kiln posts) for support or is that a bad idea....I am thinking it is because of possible thermal problems that could be caused with the fiber shelf on top of the mullite shelves.

The Skutt kiln I am using has both top and side firing elements if that makes a difference.

I have only been fusing for less than a year and this is my first look at using fiber shelves for seamless fusing of a large pice so any input would be appreciated.

And I apologize in advance this requested information seem a bit redundant for some.

- Al

Phil got us Collodial Silica which I believe Doug Randall recommended. It worked well for us. I've used my shelves a lot and don't have a problem.

A few pointers:

After soaking, let dry outside for a few days. It really cuts down on the fumes when you fire and I think it may help it stay level.

I did have some warpage in some of my shelves. I think I didn't apply the silica evenly, so you might want to watch that.

I have a 1414 and was trying to get the most length, but I now barely have room to grab the shelf. You can have the extra inch but your shelf pays the price.

Phil also got us Kaowool Ceramice Fiber filler for holes. It worked very well and is quite durable.

We have 2" fiber board. With 1/2" I'd make sure you assemble your pieces in the kiln.

And, Jackie also discovered if you use 1/8" fiber paper, the seams don't show.

Hope that helps.

Cindy next door

Al, I can't answer your rigidizer question, other than why bother with it. We use bunches of fiber board here, mostly low density; and we don't rigidize. (I believe the duraboard is harder than the LD.) You didn't mention if you were looking for a smooth surface and wanted to rigidize in order to kilnwash. If texture is not a problem, I suggest simply sprinkling dry kilnwash over your board as a separator (after you've fired the organics out of your board). Also, putting that size board on your mullite shelves could result in breaking the shelves, as the fiberboard is an insulator. If the floor of your kiln is flat, I don't see a problem putting the board directly on the floor. We do that here, but I take the precaution of preheating the kiln first, without the board, in order to warm up the floor brick. Hope that helps. You'll have a lot of good responses from others on the Board, tho, who have a lot of experience with rigidizing. - Barbara

Barb and Cindy,

Thank you very much for your replies. They were very helpful.

While a slight texture on the back of the iniitial pieces I am going to fuse really would not be a problem for this project. Future projects might require a more smooth surface so I planned on rigidizing the board to give it strength/stability and so that I could kilnwash the board for a more smooth surface for those unknown future projects.

I was having a heck of a time locating local supplier of the Colloidal Silica or Alumina because the Stained/fused Glass suppliers in the area had the products backorderd or sold it in quantities much less that what I needed. So I decided to do what was suggested in one of the other archive messages and to look up dealers of refractory products in the phone book.

I finally got in contact with guy that said I would be better off with the Colloidal Silica as it is much cheaper that the Alumina and more appropriate for the intended use. He also let me know that the prices I was paying for the products (both the duraboard and the colloial silica) were severly inflated.

I thought I was getting a deal on the 1/2 inch board because I paid about 50.00 for the 2x4 foot one I ordered. He said his price for the 1" board was not much more than that.

So I might just set the 1/2" board aside for making dams and small slumpinig/casting molds and pick up a 2" board for a shelf.

He's suppose to give me a call back with the price for a 1/5 gallons of the colloidal silica and a 2" board.

Anyway...I thank you again for you help and insight.

- Al

Barbara Cashman wrote:... If texture is not a problem, I suggest simply sprinkling dry kilnwash over your board as a separator (after you've fired the organics out of your board). - Barbara

Barbara,
You can also use cchildren's play sand as a seperator.