I noticed there was firescale on the back of thependant. I thought
you didn't need toworry about firescale with Argentium.
There are two forms of oxide that form on silver. One is firescale
and the other is firestain.
The two terms are often somewhat confused, with firescale being
misused for both types.
Firescale is the usually black or gray oxide and discoloration that
forms on the surface of the silver when heated. It's primarily a
copper oxide. It comes off in the pickle leaving a matte white
Firstain, on the other hand is more subtle, being also a copper
oxide, but imbedded within the surface layer of silver, to a variable
depth depending on how hot you got the metal and for how long, and
under what level of oxidizing atmosphere. So you pickle off the
firescale, the silver looks clean and white, and you then go to
polish the piece, only to discover that the metal is still slightly
discolored, with a faintly reddish or creamy white tone. You don't
normally see it except for where you polish through it to the clear
clean silver underneath. Unlike firescale, which being a surface
oxide, is easily cleaned off in the pickle, firestain penetrates,
forming part of the surface layer of the silver, and generally has to
be removed along with that thin surface thickness it's reached. That
can be more than a little annoying. It can be damaging to the piece
if you have to take off too much metal, or the appearance can be
damaged if you cannot get it all off.
Historically, it was dealt with by using a number of types of flux,
such as Prips flux, to protect the metal from that oxidation
(ordinary boric acid in alcohol, as is used for gold, won't quite do
it for silver). Another way is to simply accept that as the final
surface. The famous Scandinavian silver firm of Georg Jenseon was
well known for their firestain finish. After their pieces were
totally finished and polished and very clean (no flux or anything),
the pieces would again be annealed carefully, so as to be sure the
fire stain layer reached everything. Then pickling and minimal
polishing saw to it that the layer, and thus the surface color,
With Aregnetium and similar alloys, the biggest worry that these
alloys prevent is that deep penetrating oxidation, the firestain. You
won't get any of this on such alloys.
However, although they prevent most of the firescale too, they won't
prevent all surface discoloration on heating, especially in those
areas that are not protected by a reducing flame. Thus you got some
oxidation on the back.
But you should have found that it comes off quickly and easily in
the pickle (more easily than the firescale comes off of standard
sterling) Even fine silver, which has no copper in it at all, can
sometimes discolor a little on heating, especially if there is
anything containing sulphur around. Silver does form an oxide, though
it's not strongly bound, and is essentially colorless. But sulphur
and a few other things can also bind to the silver, causing some
discoloration. And Argentium or Sterlium alloys are more than just
silver. You avoid or minimize the problems from copper oxides, but
the metal still benefits from being protected during heating.