I've been working with sterling, brass, copper and other metals for
years, and for some reason, I've never encountered this before. I've
done some research and reading, including searching these forums,
and can't find an answer to why this mysterious reaction is
Recently, while I was teaching a soldering class, I demonstrated
sweat soldering a copper wire spiral and some small brass disks (Rich
Low Brass, melts at 1877, 85% copper, 15% zinc, from Metalliferous in
New York, 1/16" and 3/32" in diameter, cut with a tiny disk
cutter/punch) onto a sterling 1" disk. The demo was for beginners, so
we used easy solder and I set up everything as usual. I applied
solder first to the underside of the brass disks and copper wire,
placed them on the sterling disk and heated the whole piece from
underneath until soldered. For this demo, I held the sterling disk in
air with a third hand. Because this class is meant for people to
practice at home, I used a micro-butane torch.
The copper soldered down fine and the brass dots started too as
well. But suddenly the brass dots just started for lack of a better
word, disintegrating. The sterling was fine. The copper spiral was
fine. They weren't even glowing, since I was holding the temp at
around the flow point of the easy solder. The brass dots never even
showed any color. And the brass dots are floating in their own molten
blobs, melting out from below, leaving thin skins of brass on the
surface. I haven't seen this before, so I held the temperature a
little longer. Eventually, even though the sterling never even came
close to a visible red or orange heat, one of the dots ate right
through the sterling below it.
I tried another piece of the same brass on a piece of sterling, no
copper, set it up again and got the same results. I've done the same
demonstration with exactly the same dots in copper, and that strange
melty metal thing never happens.
In another class, one of my students used dots of 24 ga. patterned
brass, also from Metalliferous to solder a texture onto a sterling
blank for a ring. The dots sank into the sterling and disappeared,
leaving round craters as if they had etched into the silver.
Any ideas? Even after 17 years of jewelry, there's always something
new to learn. This one is bizarre and doesn't seem like a normal
reaction to a simple soldering. Maybe I've just never encountered
something that other jewelers like you guys have experienced before.
Unless the rich low brass is not the alloy they claim? So far, I've
only seen the reaction with the Metalliferous brass. I'm looking
around for a piece of brass from another source to try.
Anyway, I'd love to have some sort of explanation to offer for this
little mystery. Your help is appreciated.