Firecoat is used to protect copper-bearing alloys (such as sterling silver etc) during heating.
The ingredients you require are:
- Boric Acid (I bought my supply easily enough on Ebay, but it proved impossible to buy it on the High Street)
- Denatured Alcohol (which is Methylated Spirits)
- Screw top jar that is airtight to store it in
Place about 1/2" of Boric Acid (not Borax Powder) into the bottom of a screw top jar. Add enough Methylated Spirits (which is denatured and not rubbing alcohol) to bring the container to about half full.
It's important to note that the ratio is not super crucial, I am aim for 1/3 Boric Acid to 2/3 Methylated Spirits, or even 50:50. The important thing is that there is enough liquid to get the Boric Acid into solution form when stirred, so that the metal being treated can be completely coated.
PLEASE BE RESPONSIBLE: Once your solution is made store in a safe area clearly labelled and well away from animals and pets etc.
To use Firecoat:
Drop the piece you are firing into the solution, the ignite the wet piece in your torching area (obviously taking the appropriate workroom precautions people!!). The Meths burns away leaving a protective coating of Boric Acid over the surface.
Thus when you are working the piece in the heat the Boric Acid coating Meths and creates a flux coating that protects the piece from fire scale and fire stain for a limited amount time. After heating/working your piece it is important to then quench and go on to soak in a pickle solution to dissolve away the flux and the oxides that have been created during heating.