[Jewelry making - Article 00473] - Re: [Orchid] Safer pickles

[Kevin]

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    I come from an industrial chemical research background, with a
    strong safety culture.  Making jewellery is a hobby for me. 

    Sodium bisulphate solution can be regarded as chemically equivalent
    to a solution of sodium sulphate in sulphuric acid.  The solution
    contains both sulphate and hydrogen ions, just as sulphuric acid
    does.  As used in jewellery work for pickling it is the equivalent
    of dilute sulphuric acid. 

    I use sodium bisulphate solution for pickling.  I use it cold.  I
    quench metal in plain water before putting it into the pickle. 
    Quenching hot metal in the pickle does produce a little puff of
    vapour, which will contain small droplets of the active pickle
    ingredient.  My reason for quenching in plain tap water first is to
    avoid risking getting these small droplets onto nearby tools and
    other objects in the same room. With the sizes of object I work
    with, and the small number of times I quench, it would not be a
    health hazard.  I have a lid on my pickle pot, mainly to keep dust
    out of it.  In other work situations it (vapours from quenching)
    could easily become a matter of concern though, as for example more
    frequent quenching, or when quenching larger objects.  It is nothing
    like strong mineral acid mist that has been discussed here though. 
    Neither is it being breathed for an eight hour shift. 

    Warm pickle works much faster than cold.  It should be warm though,
    not overhot.  In a hobby situation there is no need for the "boiling
    out" sometimes mentioned in older books. 

    In a professional workshop (by which I mean manufacturing for sale)
    there is likely to be a _much_ higher throughput, and real pressure
    for faster work.  There are also Health and Safety regulations in
    most countries too, and these will address issues such a vapours and
    the possible need for air extraction. 

    Citric acid has been mentioned here, and it certainly is safer than
    dilute sulphuric acid.  There could be a possible concern with
    "nasties" growing in it, if it's cold and unused for some time. 
    Citric acid is nothing to do with vitamin C. 

    Sorry, but all sulphur containing compounds do _not_ attack tooth
    enamel.  The element that sulphur seems to be being confused with is
    phosphorus, and it is true that match workers suffered terribly, the
    condition being known as "phossy jaw".  It was caused really by the
    pure element.  Compounds are a different matter. But, don't imagine
    that there is a problem with all phosphorus compounds.  Many popular
    fizzy drinks contain phosphoric acid.  I don't drink them, but not
    because of the acid.  And please don't start to worry about the
    phosphorus in TSP used to make Prip's flux........ 

    I realise that to folk who haven't had a chemical eduacation it can
    all be a bit confusing, especially with somewhat similar sounding
    names.  I sincerely hope that this may have gone some way to
    clearing up some of the confusion, and perhaps allayed a few fears. 

Kevin  (NW England, UK)


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