Stainless Steel Molds

[tgotch]

I just got some stainless steel bowls to use a molds. I am trying to get Primo Primer to stick. I sanded the bowls, cleaned, heated to 500, and applied primo.

Couple questions.
1. I assume I put 3-5 coats on. Do I need to heat every time to 500? I kept applying coats while it was cooling, It appears I am getting coverage, but I have not fired yet.
2. I get some pooling in the base. The pooling crusts up, and looks a bit unappealing. Any way to resolve this?
3. Is there an alternative method/primer?

Thanks.

[Valerie Adams]

I use Boron Nitride to coat my stainless. I'm only doing the outsides for draping.

[Bert Weiss]

I suggest using a regular shelf primer like Bullseye. Primo is designed for a one time use when firing hotter than 1400ºF. A generous coating of an alumina/EPK primer will last for many slump firings without needing any additional anything.

If you have access to a sandblaster, you can abrade the surface. If you don't, I suggest heating the bowl to 1200ºF. This will burn off the oils used in production of the bowl. Cool to below 500ºF and then spray on kiln wash. If the steel is too hot, it will all bounce off. If the steel is too cool, it will drip and run. When the steel is the right temp and the wash is the right thickness, it will stick and not run. With practice, you can get a perfect no bump coating. You can spray with a variety of tools from a mouth atomizer on up. I like the paasche 62, which is an automated atomizer.

I have many ss bowl molds that work fine for slumping in to. Not all are ideal for this.