I’ve been researching the nature of the tarnish on sterling silver
and fine silver. I’m trying to quantify why Sterling Silver tarnishes
(oxidizes maybe) so fast compared to fine silver. When you consider
that silver is stable in clean air and sterling is not… Most if
not all of the non tarnishing or tarnish resistant sterling reduced
or eliminate Copper from the alloy, and substitute whatever seems
appropriate for their product. I’m told that when analysis of the
tarnish or oxide is done, its silver oxide or a sulphur compound.
However, just put fine silver out with copper based sterling along
and watch how much faster the copper containing silver darkens. That
strongly implies the copper is the culprit. I think so. Any one else
sort this out any better? This will be published if I can “prove” the
conclusions in a new precious metallurgy guide we are going to
publish. Thanks! Daniel Ballard
I've been researching the nature of the tarnish on sterling silver and fine silver. I'm trying to quantify why Sterling Silver tarnishes (oxidizes maybe) so fast compared to fine silver.
Daniel, This is pretty well known info, and has been since the
early part of the 20th century. It’s been published in any number
of various sources, including many of our jewelery books, as well as
resources such as Handy and Harmon publications, or various
metalurgy works. Silver oxide isn’t black, so it’s not a factor in
tarnish, and it doesn’t readily form at room temps anyway so tarnish
on fine silver isn’t the oxide. On fine silver, only silver
sulphides normally form, and they tend to do it only slowly. With
sterling silver, you can get silver sulphides, copper sulphides, and
copper oxides. The normal tarnish you see is a mix of the black
sulphides. Copper, being much more reactive than silver, forms it
much quicker and easier than silver. Other variables would be the
presence or absence of fire scale, which affects the nature of
surface copper, other coatings on the silver (such as, for example,
inhibiting films left by some cleaners), and environmental variables.
Atmospheric sulphur compounds are the main culprit, and these can be
variable from place to place. Because of the variability of many of
these factors, it’s difficult to quantify how fast something will or
will not tarnish, and perhaps even a ratio of tarnishing speed from
fine silver to sterling silver…
I've been researching the nature of the tarnish on sterling silver and fine silver. I'm told that when analysis of the tarnish or oxide is done, its silver oxide or a sulphur compound. --
G’day; If you’d like to check you will find that silver oxide is an
off-white shade, certainly not black It is copper oxide which is
black or red - there are two oxides of copper.
Both silver sulphide and copper sulphide are black.
It may be that the presence of copper catalyses the tarnishing of
sterling, so that it tarnishes more quickly than fine silver.
Perhaps your research should be oriented towards that.
Cheers now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ
Be careful! Although copper oxidizes quickly in contact with the air
the tarnish on the silver IS silver sulphide. I’d expect there to be
a complex electrolytic process to be going on rather than a simple
oxidation.
Tony Konrath
www.goldandstone.com
It discusses a tarnish free silver alloy which is sterling with
1.1% germanium added instead of that much of the copper
sterling silver is a composition of fine silver and copper. the
copper creates the oxidation. Fine silver oxidizis at a much slower
and paler rate. It turns a light golden color.
Jennifer in Atlanta