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Depletion silvering


#1

Several Orchidians have said they repeatedly heat and pickle a
sterling object in order to bring up a layer of fine silver.

I was wondering how hot the sterling needs to get and how many
cycles are typically needed to bring up the silver.

With respect to tarnish, does the finished piece act like fine
silver, or does the copper in the base migrate to the surface and
oxidize?

Salud,
Janet


#2

The easiest way to tell how hot the sterling needs to get is to use
a Sharpie permanent ink marking pen. When the black disappears, the
metal is hot enough. Go through enough rounds that you don’t get
much reaction when you heatit next. Usually takes 8 or so if you are
going to enamel on it.


#3

Hi Janet,

  I was wondering how hot the sterling needs to get and how many
cycles are typically needed to bring up the silver. 

The metal needs to reach annealing temperature; in other words,
short of the temperatures required for soldering. You’ll find that
at a certain point during the heating process the metal will turn
black. That’s what you’re looking for: an even black coating over
the entire surface. You may have to very briefly wave the flame off
the piece to see the black coating develop. The coating is a copper
oxide that will be removed when you pickle, leaving a thin layer of
fine silver behind.

I would say that two cycles are the minimum and more is better
because you’ll build up a thicker layer of fine silver. Three or
four should do it.

  With respect to tarnish, does the finished piece act like fine
silver, or does the copper in the base migrate to the surface and
oxidize? 

The finished surface is fine silver. The catch is that it is
relatively fragile and will rub off in time. Just underneath it is
fire stain and then the base alloy. So, no, the copper in the alloy
will not migrate but the fine silver on the surface will abrade and
expose the base alloy – which will tarnish. In other words,
depletion gilding is inappropriate for a piece that will be highly
subject to friction/abrasion, like a ring. Beth


#4

Belinda, Does this mean the silver needs to reach annealing
temperature? Have you kept any of your pieces long enough to see how
they oxidize?

Thanks,
Janet