As some of you may know I’ve attempted to obtain some as
to the content of this alloy in the belief that what’s in it has a
huge effect on what one can expect from it in the shop.
It has been suggested that this type of is of
"scientific" interest only and that one might happily work the stuff
in ignorance of it. While I suppose that is technically true I’m
unconvinced that ignorance is bliss when it comes to spending hours
working a metal in the shop and then selling the products to the
public, never mind basing ones livelihood on it.
Like it or not an alloy’s composition goes a long way to determining
it’s mechanical characteristics and reactivity to heat and
atmosphere. In other words knowing it’s composition and knowing how
alloys like it behave gives one a head-start on knowing how it will
react and behave under torch, hammer and tongs.
With that in mind, and lacking from the S88 producers
directly, I would like to share some patent info which an orchid
reader forwarded me, specifically US P/N 5039479 awarded to United
Precious Metal Refining Co., Inc.
The patent describes several master alloys and two silver (sterling)
alloys. For the sake of our discussions here I quote the silver
"5. A silver alloy composition consisting essentially of the
following parts by weight: about 89-93.5% silver, about 0.02-2%
silicon, about 0.001-2% boron, about 0.5-5% zinc, about 0.5-6%
copper, about 0.25-6% tin, and about 0.01-1.25% indium.
6. A silver alloy composition consisting essentially of the
following parts by weight: about 92.6% silver, about 1.85%
zinc, about 0.05% indium, about 4% tin, about 1.44% copper,
about 0.01% boron, and about 0.05% silicon."
There’s no quarantee that S88 is in fact described by this patent
but I’m told it is one of the patent numbers cited in the literature
that accompanies the alloy so it’s not a bad assumption.
The thing that I see in the alloy descriptions is that they are
basically zinc and tin based which makes them quite similar to a
number of other de-ox sterling alloys out there. In fact alloys like
this have been around for over 50 years. I’ve tested a few of these
and noticed a marked tendency for such alloys to form a tough zinc
oxide layer when heated with a torch. See the “Other alloy tests -
results” post on my blog
In particular note that this layer is a “skin” on the metal, that it
is very resistant to the mild acids that we normally use for pickling
(in other words it doesn’t pickle off), and that it is relatively
easy to cut or abrade through (in other words it will wear off). Once
you do so you can clearly see that the surface layer, although
silvery, is noticably darker and duller than the host metal beneath
This dark layer forms much more readily when the heated metal is
exposed to the atmosphere, typical of torch heating procedures such
as annealing and soldering, and much less so during casting where the
hot metal is largely protected from the atmosphere. The oxide layer
does not appear to reform on it’s own: it appears to require torch
Another feature of these alloys is that they tend to be rather soft,
and do not precipitation harden easily, certainly not to the degree
that Argentium Sterling will harden under moderate temperatures (a
domestic oven for instance).
So my point is this: all metals and their alloys have their quirks.
Rare indeed is the alloy that does not. I think we all know this and
it is, in fact, part of our decision making process in that we choose
our alloys based on “the quirks” that we’re willing to accept and
work with, after price and other considerations of course. As such
it’s well worth knowing what you’re working with to better predict,
understand, and accomodate the results you’ll get with it.
And of course it’s one step better to get your hands on some of the
stuff and try these things for yourself, which I freely confess I
have not yet done with S88 specifically.
in The City of Light
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