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Unusual soldering condition

Jewelry Discussion
#1

When we solder a brass domed/stamped object to a flat sterling
pendant using Stay Brite solder and flux we are getting a rough,
very deep, approximately 1mm wide line all around the object in the
sterling.

I cannot emphasize enough how very deep into the silver this line
is. It is almost impossible to polish out without removing allot of
silver. There must be a very aggressive chemical reaction between
the components.

I would appreciate if anyone could tell me what I’m doing wrong and
what I could do to correct the problem. I have spoken to the Stay
Brite Company without success. I must use a low temp solder.

Not related… how or what can I use to keep solder chips close to
the solder line so they don’t move away from the intended joint
during the soldering process?

Thanks for all your help,
Jon

#2

Good Morning,

The first question I would ask is… Is there lead in your low temp
solder?

I was always taught that if you solder sterling silver with low temp
solder that contains lead, the silver around the joint will melt
away just as you describe.

I did a demonstration with my students once, where I burnished
filings of lead on to a sterling silver surface. When heated, there
is a chemical reaction and lead eats into the silver.

Hope that helps,
Corrie
Corrie Silvia
Manufacturing Jewelers & Suppliers of America

#3

Hi Jon,

You can try a couple things…First try melting a tiny amount of
solder on the smaller piece and then place it on the larger piece
and let the larger piece take the solder from the smaller
one…or…Try flattening the stay bright with a hammer and make a
sandwich before applying the heat. Just smacking it with a hammer it
will thin out very easily. You don’t need a lot of solder.

Mark

#4

i suspect that its something to do with the zinc in the solder and
brass. i guess the zinc and silver are forming a low melting
(eutectic) alloy which is boiling off, leave a large hole. i’ve had
this when soldering brass to copper. if this is the case, you’d have
to be over heating the brass. try soldering a copper object to
silver using to same method and see if there’s still pits, if there
are then i’m stumped…

try melting the solder to the base or the heavyer part first,
cleaning up, refluxing and soldering the to parts together. that way
the solder cant budge and there’s less cleaing after.

#5 
i suspect that its something to do with the zinc in the solder and
brass. i guess the zinc and silver are forming a low melting
(eutectic) alloy which is boiling off, leave a large hole.

Stay Brite is a soft solder that contains Tin 96% and Silver 4% it
melts at 430 F. So no zinc. The problem is due to overheating the
work. The tin is alloying with the silver base sheet and the liquid
is being drawn into the joint leaving the depression

James Binnion
James Binnion Metal Arts

#6

Jon,

When we solder a brass domed/stamped object to a flat sterling
pendant using Stay Brite solder and flux we are getting a rough,
very deep, approximately 1mm wide line all around the object in
the sterling.

Stay Brite and other soft solders aren’t intended for jewelry use.
They only contain 5-15% silver and are considered "silver bearing"
solders. This amount of silver has conductive properties for
industrial and construction uses, but won’t provide polishable
surfaces. Soft solders contain tin and/or lead. When you heat your
silver jewelry and tin-based soft solders, the tin and silver combine
to become a very low temperature alloy with all of the metal
properties that you describe. Also, this type of solder is very weak.
It is not intended to be filed flush, and in so doing causes a join
that you can often break with the pressure of your fingers. Repair
ing this join with hard solder now is highly problematic since the
join-are a has become a low temp alloy.

For future reference, keep in mind that what jewelers refer to as
soldering, everyone else refers to as brazing. Non-jewelry industry
soldering experts can inadvertently provide bad advice when we ask
about soldering (but mean brazing) and they answer about soldering.

Good luck on your project
Jamie

#7 
When we solder a brass domed/stamped object to a flat sterling
pendant using Stay Brite solder and flux we are getting a rough,
very deep, approximately 1mm wide line all around the object in
the sterling.

The first thing I would try is to use a mechanical means of keeping
the solder from spreading. In Alan Revere’s book “Professional
Goldsmithing”, he creates a groove just inside the applique to keep
solder from leaking out and spoiling the base to which he is
soldering initials.

An alternative would be to try a different soft solder, perhaps even
one with lead. Since you are not doing any other soldering or
heating, you have more options for the connection.

Another suggestion is to greatly reduce the heat you are using with
Sta-brite. It needs very little heat to work.

Another idea is to coat the silver with yellow ochre or some other
stop to keep solder from flowing.

When I did a production run of sterling and brass images for award
belt buckles, I used conventional easy solder, a good anti-firescale
agent and careful heating. It took a peroxide pickle to remove the
pink stuff on the brass after soldering. I then tumbled the pieces in
two stages of abrasive media and finished with stainless steel in my
big rotary tumbler. They are nice looking buckles. I didn’t groove
the brass and had absolutely no solder leakage.

Judy Hoch