[Jewelry making - Article 00509] - Re: [Orchid] Dip Plating

[Peter W . Rowe]

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>             Hi Have any of you tried, or heard of,  gold plating a
>     metal object by dipping it in molten gold then burnishing etc the
>     surface? 

    In gold, I've not heard of this.  But it does vaguely resemble the
    "wave soldering" technology used in electronics.  In that method, a
    circuit board can be held just above the surface of a molten
    container of tin/lead solder, which of course melts MUCH lower than
    golds, around 400 to 600 degrees F.  A wave traveling across  the
    solder tank  traverses the underside of the circuit board,
    simultaneously soldering all the prepared connections.   But I'm not
    aware of anything like this being done in golds, perhaps simply
    because the temperatures of molten gold alloys usually equal or
    exceed the melting points of most of the things you might wish to
    cover with gold. 

    However, I wonder if your term for "dip plating" has not been
    misinterpreted. When I read that term, I normally associate it with
    what's often also called electroless plating.  This is a type of
    electroplating which does not use a direct source of voltage to cause
    an electroplated layer.  instead, the jewelry (or whatever) item to
    be plated is connected to a wire of other "electrode" of a more
    chemically reactive metal, such as zinc.  This combination is then
    dipped into a specialized type of gold plating solution.  The
    connection between the reactive electrode and the less reactive metal
    to be plated sets up a weak galvanic cell, which generates enough
    voltage to cause gold to be electroplated onto the surface of your
    work item.  It proceeds only until the surface has been covered
    enough to be chemically and electrically isolated from the solution
    by the built up gold,  at which point chemical equilibrium is
    reached, and the plating stops.  For some items, made of already
    reactive enough metals, even the wire isn't needed, as the item
    serves as it's own electrode.  The method thus produces very uniform 
    in thickness deposits, which are typically considerably thinner than
    those produced by normal plating methods with an external power
    supply.   But the method does not have the problems with "throwing
    power", that in normal plating lead to thicker deposits on edges, and
    less, or even no, plating in highly recessed or interior surfaces. 
    The deposits are generally intended for cosmetic advantages, where
    long term durability is not needed. Often, these solutions are
    directly marketed to the public, since it allows folks to renew the
    gold plated look on their costume jewelry without needing anything
    other than the solution and the specialized wire to hang the item
    into the solution with. The basic operation of this method is about
    the same as what occurs if you put your silver or gold jewelry item
    in your pickle pot while it's in contact with steel or iron.  If the
    pickle has been used for a while and has dissolved copper in it, then
    with iron contacting your work, copper will plate out on your work.
    The electroless gold plating solutions (also available to plate
    other metals, including tin, for electronics use, or silver or
    copper, I think, for various uses.) are a bit more costly than
    comparable normal solutions made with the same gold concentrations,
    in order to allow the deposits produced this way to be properly
    adherent.   Of course, as with any plating, the items have to be
    properly cleaned first. 

Hope that helps.
Peter Rowe


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