[Jewelry making - Article 00614] - Re: [Orchid] Silver Bubbles

[Ala]

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Hi Jim,

    The bubbles that appear each time you anneal are the remains of
    actual bubbles in the metal when it was cast. They may have been
    rolled flat afterwards, but they are still there and those at the
    surface will rise up when annealing. 

    Bubbles or porosity occurs because silver will absorb oxygen when in
    the molten state. I would re-melt the silver using an oxy/acetylene
    (or other) torch with a reducing flame (a bit more fuel, or less
    oxygen in the gas mix), and just before pouring throw a few match
    heads onto the molten silver. The phosphorous in the burning match
    heads will "suck" any oxygen out of the melt. There are proprietary
    fluxes that will de-oxidise silver very well. Also do not overheat
    the molten silver, just get it liquid enough for a quick pour into
    the mould or trough. 

Alastair
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