[Jewelry making - Article 00687] - Re: [Orchid] Use of Hydrofluoric Acid in jewelry shops

[Mike Kersley]

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    There has been a lot of discussion regarding the dangers of using
    Hydrofluoric acid in the jewellery workshop and it could be that
    there is no alternative to this very dangerous acid when working
    with titanium.  However for enamellers who wish to remove the glass
    enamel from the metal base without damaging the metal base, there is
    another method originally published in article by Woodrow Carpenter 
    in Glass-on-Metal vol 16 no 3, August 1997 using molten sodium
    hydroxide[anhydrous] which seems to be relatively much safer than
    HF. 

    The method uses standard commercial grade sodium hydroxide [e.g. red
    devil lye] heated in a moisture free environment, such as an
    thermostatically controlled electric kiln, to 350 degrees
    centigrade [650F] for approximately one hour. It certainly works
    but as yet I have not found any other enamellers using this process,
    they all seem to use HF or just use the piece as scrap metal.. 

    I have discussed this process with a number of chemists who agree
    that it is a relatively safe procedure providing you keep all
    moisture away from the hot caustic but caution that fumes may be
    produced and that the kiln might be damaged in the longer term. The
    article published in GOM said that they were not aware of any
    vapours [at the specified temperatures] and that no damage appeared
    to be caused to the kiln. GOM states that they have been using the
    procedure for many years so they should be the best source of
    information. In addition disposal of the waste does not cause a
    major environmental problem. 

    You need to read the full article GOM in detail before trying this
    yourself and back issues are available from the GOM website at
    relatively low cost . Maybe GOM would make the article free for
    publication on the Orchid site in the interests of safety 

    I make no claim to the safety or effectiveness of this process other
    than that stated in the GOM article but I would be interested in
    hearing from other enamellers who have had success with this process
    or have found any disadvantages/safety issues in its use. 

regards
mike kersley [UK]

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