vermiculite boards

[SusanHyatt]

Hi All,

I purchased two vermiculite boards from a company that sells refractory materials. I was told this is the board he most often sells to glass hobbist. I know this is not much information but do any of you know if I should possibly pre-fire? If so hot long and to what temp? I suppose I will need to still use fiber paper?

I am a newbie and trying save money. This supplier can get most things like fiber paper and boards for me at a lesser price than large glass supply stores, plus I can drive to pick it up (no shipping fees).

I have searched sites trying to find what is sold for the purpose of glass kiln work but I am still not experienced enough to know exactly what to ask.

Thanks for any assistance you can offer.

Susan

[AndyT]

Hi All,

I purchased two vermiculite boards from a company that sells refractory materials. I was told this is the board he most often sells to glass hobbist. I know this is not much information but do any of you know if I should possibly pre-fire? If so hot long and to what temp? I suppose I will need to still use fiber paper?

I am a newbie and trying save money. This supplier can get most things like fiber paper and boards for me at a lesser price than large glass supply stores, plus I can drive to pick it up (no shipping fees).

I have searched sites trying to find what is sold for the purpose of glass kiln work but I am still not experienced enough to know exactly what to ask.

Thanks for any assistance you can offer.

Susan

Perhaps this BE thread will help.
http://www.bullseyeglass.com/index.php? ... =14&t=3465

[Marty]

VB does not need pre-firing.
Handle gently, it is sort of fragile.
Cut to shape with hand woodworking tools.
You can get enough kiln wash on it for slumping but you will need fiber paper of some sort for fusing temps.
It does not need to be elevated on kiln furniture- it can go directly on the floor of your kiln.
There are different densities available; my experience is with medium density, 2" thick.

[Stephen Richard]

My experience is that it *does* need pre firing. Blew a big hole in a large piece following the advice of the supplier that it did not need pre-firing. There are binders or something in vermiculite boards that generates gasses.
I now fire kiln furniture before using it after this experience. This is a precaution against the refractory materials containing something unexpected.

Vermiculite will stick to glass, so separators are required (as for ceramic shelves). I'm not sure why it is indicated that only fibre paper separators will work at fusing temperatures.

I agree the board can be placed directly on the floor of the kiln. One recommendation though is to turn the board every 25 or so firings to avoid warping. The board will gradually bow upwards to become noticeable after 100 or so firings. So you should make sure both sides are smooth before using. You can sand the board smooth with about 120 grit sand paper on a large block. Do this outdoors and with a respirator on the dust is unhealthy for your lungs.

Of course my experience is with 25 mm board and so may differ with thicker boards.

[Marty]

My experience is that it *does* need pre firing. Blew a big hole in a large piece following the advice of the supplier that it did not need pre-firing. There are binders or something in vermiculite boards that generates gasses.
I now fire kiln furniture before using it after this experience. This is a precaution against the refractory materials containing something unexpected.

Vermiculite will stick to glass, so separators are required (as for ceramic shelves). I'm not sure why it is indicated that only fibre paper separators will work at fusing temperatures.

I agree the board can be placed directly on the floor of the kiln. One recommendation though is to turn the board every 25 or so firings to avoid warping. The board will gradually bow upwards to become noticeable after 100 or so firings. So you should make sure both sides are smooth before using. You can sand the board smooth with about 120 grit sand paper on a large block. Do this outdoors and with a respirator on the dust is unhealthy for your lungs.

Of course my experience is with 25 mm board and so may differ with thicker boards.

The 2" stuff does warp slightly, perhaps 6 to 9mm over a 1 meter span. The first time I had the stuff cut down to various kiln shelf sizes, the woodworker said it cleaned off all the resin accumulated on his blades- no dullness noted- but it did make a terrible mess. I've since cut them with a hand saw with a vacuum cleaner close by. Outside with the wind behind you is better.

No matter how much kiln wash I got on the boards, the glass found its way down to the vermiculite- not every time but often enough to discourage the practice, hence the fiber paper.

I've been using Skamol's stuff without prefiring for more than 15 years. They've repeatedly said no burnout was necessary and I never had a problem with it. I was told that Skamol uses a silicate to bind the stuff, not organics (as used in fiber-board or -paper).

However- it's my studio, my work practices etc. and others' mileage may vary. There are several manufacturers of VB and that might contribute to the confusion. Also, Skamol makes a variety of VB products- http://www.skamol.com/Insulating+boards.87.aspx - and some may work better (for one's purposes) than others.

[jolly]

I use kiln wash on vermiculite and it is fine but I am using stiff window glass (float glass mostly). The one inch thick boards that fit my kiln (2 foot x 3 foot) warp the first firing and if I flip it, it warps up the first firing on that side. So I don't use it for a large flat shelf. It is great for making odd shapes as it it cheap and I can reach in and take it out of a hot kiln without the Vboard breaking from rapid heat change. However, I have broken a couple of pieces because it is a bit delicate so never lift it by a corner.

[Nikki ONeill]

Bullseye markets a box casting kit made from the higher density Skamol vermiculite(600 compression..the 450 is too crumbly), and a set of instructions for making one from a 1" thick sheet of vermiculite. They suggest pre-firing the components. No reason given.

Nikki

[G's]

Vermiculite will stick to glass, so separators are required (as for ceramic shelves). I'm not sure why it is indicated that only fibre paper separators will work at fusing temperatures.

I used a prefired and kiln - washed, 2 inch vermiculite board to fully fuse a 14 inch by 15 inch glass panel. I did not use a fiber paper separator. My target temperature was 1440 degrees F. The result was that I was unable to remove the glass panel from the board! To save the panel, I had to chip the VBoard off of the back and then completely sand the back of the glass panel. Needless to say, my VBoard is in a hundred, unusable pieces and shavings...

Use a fiber paper separator....
Ginny

[SusanHyatt]

Thank you all so much.