Boric Acid 4 ozBoric acid is mixed with denatured alcohol to create a solution called fire coat. This boric acid/denatured alcohol mixture protects sterling silver from fire scale during heating and soldering. a fire coating to protect silver, copper and gold from forming fire scale during heating.
To mix a fire coat to protect copper-bearing alloys from firestain and firescale during heating, place about 1/2" of boric acid in the bottom of a container. Add enough denatured alcohol (make sure it's denatured and not rubbing alcohol) to bring the jar to half full. (The ratio can be anything from half boric acid and half denatured alcohol to 1/3 boric acid to 2/3 denatured alcohol...the measurements are not critical. There just needs to be enough liquid to get the boric acid into solution when it is stirred so the metal being treated can be completely coated in the boric acid. Bring back to your work surface and ignite the piece so the denatured alcohol burns away leaving a protective coating of boric acid over the surface. When the article is heated, the boric acid melts and creates a flux coating that protects the piece from fire scale and fire stain for a limited amount of time. After heating, be sure to soak the article in a pickle solution to dissolve away the flux and the oxides that have been created during heating.
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