perhaps more specific experience with this unknown
plating will clarify somewhat. First, the color is very, very
close to that of raw sterling although with a slightly "harder"
I’ll trust your statement, and that of others, that fine silver is
now a common such plating. The mere fact that it’s likely a
"brightened" plating might well explain the “harder” look all by
itself. Eletroplates often have a somewhat different look than the
same metal when prepared by usual means.
In many cases, as with curb chains, the chains are not
finely finished in the first place and the plating is extremely
difficult to recognize with the eye. Therein is the problem. The
effects of heat to the plate are discovered after it is too late
and the blisters have formed.
since the bubbles are most likely a function of the copper and
nickle underplates, rather than the outer silverplate, this would
account for my experiences with rhodium doing the same thing, as it’s
also applied over copper and nickel underplates when on sterling.
(Possibly I will simply reserve some used pickle for a quick
dip to see if a copper deposit forms as a warning indication!)
That would only work, I’d expect, if the nickle is chemically
available at the surface, meaning the silver layer is either too thin
or worn. If it was thicker, your pickle test might not detect it.
You might also want to experiment with some liver of sulphur or
similar silver oxidizer. These, while they may affect fine silver
some, do it markedly less than sterling, if even at all. And since a
bit of “tarnex” will take the mark back off, it would be easier to
remove your test than would a copper flashing. Just a thought…
My recourse to being the item to consistent color is abrasives
such as medium Cratex or the new and wonderful silicon rubber based
wheels(so called medium grit) on the polishing lathe spindle. From
here, the sterling is exposed and all can be finished to similar
color. Of course, tarnish will occur there and the customer is
You may also find the 3M radial bristle disc products to be of
considerable use in this type of situation. They get into details
well, yet also are good at maintaining surface contours, meaning they
don’t buff off high spots as aggressively as do normal buffs or
rubber wheels. And the metal removal rate is very uniform and easily
controlled. Try them. You’ll like them.