Reversability of Boron Nitride on ceramic moulds.

[Stephen Richard]

I have used boron nitirde on stainless steel moulds and moved back to kiln wash as I found it just as effective and cheaper. It now appears that the current formulations perform better than the one I used long ago. This leaves me with come questions.

Some people are applying it to ceramic moulds for the "smoother" surface. They are beginning to wonder if they can go back to kiln wash after having used the boron nitride. Some say you cannot unless you sand off the BN.
My understanding is that the BN fills the porosity of the ceramic. But I don't see why that would inhibit the kilnwash from being applied. It would seem good practice to me to remove the old, worn out separator before applying the new, but is it necessary? It does not seem to me that the ceramic mould needs to be porous to accept the kiln wash. Am I wrong?

I am looking for others' experience, as at £50 per tin, and apparently needing to be re-applied before each firing, I don't feel up to the expense of experimenting. So, I am asking for help from you all who already have done the experimenting. Thanks for your help

[Brad Walker]

My experience has been that I can't apply kiln wash on top of the boron nitride. It just washes off. Given that the BN creates a non-wetting surface that makes sense, the water in the kiln wash mixture just beads up or washes away.

I get rid of the BN by sandblasting, then just apply kiln wash as normal. The sandblasted ceramic mold accepts kiln wash no problem.

And like you, I greatly prefer kiln wash over boron nitride. The only real advantage I have found from BN is that if you spray a very small amount on a fiber strip for damming you will get less needles.

[Dani K]

never used BN but using stainless for slumping many years and loving it... I'm using aluminum spray for under $ 5 a can. check well in the ingredients , you don't want silvery tin or other metallic paint. Rust-Oleum number 7515, never failed up to 1350 degrees, burn above, good luck

[Terry Crider]

Rust-Oleum number 7515 --- Fumes/Health ????

[Brad Walker]

Rust-Oleum number 7515 --- Fumes/Health ????

http://www.rustoleum.com/MSDS/ENGLISH/7515838.pdf

[Bert Weiss]

Rust-Oleum number 7515 --- Fumes/Health ????

http://www.rustoleum.com/MSDS/ENGLISH/7515838.pdf

I looked up the melting point of aluminum and it says 1221ºF. Interesting report that it works to 1350. I wonder if there are any paints where the solid ingredient is some colored mica. I bet that would work better.

[Brad Walker]

Rust-Oleum number 7515 --- Fumes/Health ????

http://www.rustoleum.com/MSDS/ENGLISH/7515838.pdf

I looked up the melting point of aluminum and it says 1221ºF. Interesting report that it works to 1350. I wonder if there are any paints where the solid ingredient is some colored mica. I bet that would work better.

I suspect that aluminum refers to color, not the actual metal. According to the MSDS the boiling point is 752C, which works out to 1385F.

But you're right, mica should work. I've used a mica solution as a kiln wash on the shelf, don't know why it wouldn't work on a mold, too.

[Bert Weiss]

http://www.rustoleum.com/MSDS/ENGLISH/7515838.pdf I looked up the melting point of aluminum and it says 1221ºF. Interesting report that it works to 1350. I wonder if there are any paints where the solid ingredient is some colored mica. I bet that would work better.
I suspect that aluminum refers to color, not the actual metal. According to the MSDS the boiling point is 752C, which works out to 1385F.

But you're right, mica should work. I've used a mica solution as a kiln wash on the shelf, don't know why it wouldn't work on a mold, too.

Didn't it say in the MSDS that the ingredients are a series of solvents, binder, and aluminum powder? I'm willing to believe that molten aluminum might not wet to glass, and that boiling it is too far. Any metallurgists out there?

[Dani K]

sorry for the delay but I'm doing glass in delhi lately so some time zones...a few things to clarify . used the spray version 7515 for years on ss all kind. spray dry a few minutes and slump. depend on the shape,size and depth between 1200-1350 beautiful smooth finish, no residue stick to the glass. wash the mold, spray and try again. above 1350 the glass be soft enough so the burned aluminum will stick to the glass and leave ugly brown stains. for the fumes, vent your kiln. by the way in india i was unable to find the right spray so i brought in form the states the same paint in a can(spray not allow to fly) and just using a sponge brush , pain but work the same...

[JestersBaubles]

On ceramic (typically texture tiles or casting molds), I lightly brush with a paint brush and reapply. You don't need a lot of spray on subsequent coats.

With stainless, if the separator is not "scratched" I will refire without recoating the mold. If I need too, I'll lightly reapply, but often I don't brush off the BN. After several firings, the BN will begin to look a little grainy, so I'll brush it all off.

Seems to work for me, YMMV.

Dana W.