[Jewelry making - Article 00111] - Re: [Orchid] Boric Acid vs. Borax

[Juerg P Muff]

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    Boric Acid  changes into Bortrioxide (B2 O3) at a temp. of 500 C.
    Borax splits into Natriummetaborate (NaBO2) and Bortrioxide at 878
    degrees C. 

    Bortrioxide is the active anti-oxidation part and dissolves
    metaloxides into Borates, commonly seen as brownish/reddish slurry
    on silverwork. Borax has already good oxidation-diffusing qualities
    at temps from around 700 degrees C, before it is actually split into
    the above. For the goldsmith all that counts is that Boric Acid is a
    antioxidation agent (protective coating) and Borax is a flux (with
    some antioxidation abilities). 

    Traditionally have mixtures of the two been used (3 parts Borax to 1
    part Boric in methylated spirit and some water) to maximise the
    effects and create a protective flux whith a meltingpoint of 620
    degrees C. A word of warning: do not use this flux as a protective
    coating on stones. Particularly corundums as the Borax tends to etch
    the surface of these stones under heat. Straight Boric Acid and
    methylated spirits mixed to a paste, will provide good protection on
    diamonds, corundums and whitegold (especially Nickel-Whitegold). 

    At my bench I use a commercial flux like Fluoron or Auflux for all
    goldwork and use the straight Boric Acid to protect the stones and
    the prepolished work. For silver I now use Dandix, a non-fluoride low
    temparature flux paste which works fine. 

    Hope this is not all too Bor-ing. 

Juerg  P. Muff  t/a O R B I T Contemporary JEWELLERY
Award Winnign Designs
Q U E E N S T O W N   
NZ 



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