[Jewelry making - Article 00078] - Re: [Orchid] Technique to prevent firescale?

[Peter W . Rowe]

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>     Make a mix of boric acid and borax (50/50) and add alcohol. Add
>     extra Alcohol so the whole mixture can be shaken to mix. Then the
>     item is dipped in the mixed up solution, taken out and the alcohol
>     if burned to "stick" the boric acid and borax onto the piece.
>     Solder away with no fire scale.... 

    That works well with gold. In fact, on gold, the standard method of
    preventing undue oxidation is exactly that method, or most commonly,
    that method using only boric acid, without the borax mixed in. On
    sterling silver, the boric/borax mix does not adequately cover the
    silver because surface tension effects will have the coating trying
    to bead up in areas. it's better than nothing, but not in general as
    effective as one would wish, especially if the soldering operation
    is more prolonged, or you're using a higher melting grade of solder.
    In Prips flux, one of the best ways I know to prevent fire stain and
    fire scale, the purpose of the sodium phosphate is to act as a
    surfactant, lowering the surface tension of the metal surface, so the
    flux coating can evenly spread out and coat it without beading up or
    pulling away in areas. 

Peter
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