[Jewelry making - Article 00117] - Re: [Orchid] Silver tarnishing fast

[Peter W . Rowe]

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>     What exactly does the sulfur do? 

    the answer to that is in part to explain that we use incorrect terms
    to casually describe the black "antique" finish we often put on
    silver. We call it oxidized or antiqued. But this is not a silver
    oxide (which is not black, among other things). The black color on
    silver that's been treated with liver of sulphur is a mix of silver
    and copper sulphides. Silver simply reacts with sulphur compounds
    (like in eggs, in your pool water, or in liver of sulphur solution)
    to form black sulphide compounds of silver and copper. It's that
    simple. The sulphur is the active agent in turning the silver black
    because the black color is sulphur compounds, rather than, as might
    be assumed by what we call it, oxides. You can demonstrate that
    these are not simple oxides by putting silver like this in your
    pickle solution. If you heat sterling silver, such as in annealing or
    soldering, without flux, it turns black. The black color there is
    copper oxides. It's also forming silver oxides, but much less so, as
    as I noted, they're not black. All those oxides are soluble in the
    acid pickle solution, so after pickling the silver is then nice and
    white again. But after "oxidizing" with liver of sulphur, pickling
    doesn't take off that black color. The reason is because it's
    sulphides, not soluble in sulphuric acid based pickle... The easiest
    way, by the ways, by the way, to remove that black chemically, are
    thiourea based silver cleaners like "Tarnex", or with cyanide
    solutions, or simplest of all, electrolytically with a solution of
    washing soda in an aluminum container, with your silver in contact
    with the aluminum. 

Peter Rowe
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