Boron Nitride spray is used to coat steel and ceramic glass fusing molds instead of kiln wash, sold in an aerosol can it is now being made by a number of manufacturers.
The higher the boron nitride content the more effective the spray seems to be.
Stainless steel fusing molds do not need to be heated when using boron as is customary with kiln wash.
Once this primer is applied to a fusing mold, you cannot go back to normal kiln wash for future kiln firings; the surface is sealed and won't fully accept kiln primer.
As a fine powder is sprayed on the mold, it is advisable to either work outside or in a well-ventilated area, a face mask is highly recommended.
If the mold has been previously coated with kiln wash, it should be completely removed by careful brushing.
Once the it is cleaned, even coats of spray will need to be applied, allowing each coat to dry before applying the next coat.
Allow the last coat to dry for about fifteen minutes before adding glass.
Do not saturate the mold; just apply light even coats to the surface.
Always follow the suppliers instructions carefully.
As the coating is very thin, care needs to be taken when placing fusing glass in the mold.
Where possible it is better to work with powder or fine to medium frit.
Large pieces may scratch the surface and cause the pieces to stick to the mold.
After removal from the fusing kiln, the mold should be gently brushed to remove any left over spray.
The surface should look shiny; re-spray with one coat until the surface appears matte, touch up any shiny spots with another coat.
Fused Glass Cleaning
Fused glass should be cleaned with gentle dish wash liquid or a mild abrasive to remove any remaining boron.
It is important to remove any spray, as it will prevent complete fusing if it needs to be fired again.
Before purchasing Boron Nitride, a careful examination of the sprays available is most important, from not only a pricing difference, but also whether a particular brand suits your needs.
Improper use, or faulty product, may result in glass sticking to the mold or breakage.
This spray should be used for mold protection and release only.
A search of the Internet will produce more detailed information on the use of these sprays.