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Trouble soldering to copper


#1

I’ve run into this problem a couple of years ago when I was just
starting out. To my dismay, I am still experiencing difficulty when I
attempt to solder silver to copper. I am in the process of making a
30mmX40mm oval copper pendant with a small (3/4 inch or so) fine
silver bezel centered on top of the copper. I am using the Smith
Little Torch, using the largest oxidizing flame I can possibly make.
I also tried using a large bushy flame. The copper becomes heavily
coated with what I assume to be oxide, even though I am using a large
amount of flux, and the intended joint becomes so dirty that the tiny
solder pallions will not flow. I’m using a mesh screen, have tried
heating from below and above and even directly inside the bezel. It’s
as if the copper will not come up to temperature. Right now the bezel
is stuck to the copper, with a tiny bit of solder that did partially
flow. I’ve tried pickling and re-attempted the join, to no avail. I
was going to attach a decorative sterling frame (like a wall) around
the copper, but if I cannot solder the tiny bezel onto the copper,
the frame (a much larger and heavier piece of silver) will never
join.


#2

In a class I attended, the instructor suggested to keep adding flux
on the copper as you heat it. She did use a second person to do the
fluxing. The little torch just may be too little to bring the copper
up to temperature fast enough, as in another class, a different
instructor used two torches for heating. For your difficulty, perhaps
the extra flux and larger torch will solve the problem.

Alana Clearlake


#3

You don’t have enough torch, and you’re using the wrong flame. Silver
is the #1 conductor of heat of all metals, copper is #2. Once you get
black oxide on copper, there’s no point going on, solder will never
flow - that’s the wrong flame part. As I’ve said here before, if you
get a piece hot enough, solder will flow, or a least melt. If your
solder is not melting, you’re not hot enough, and it’s just that
simple. There are issues about flowing it relating to flux and torch
control, but if it’s just sitting there not melting, you just don’t
have enough heat. I used to use the mini torch (I went Swiss), and I
made a tip out of the fittings that is a straight through pipe. For a
bigger piece like yours, you might find a propane torch useful, just
to get a boost. But copper oxides and also zinc oxides (brass) are
impermeable to solder, just don’t try…

http://www.donivanandmaggiora.com


#4

The Little Torch is a wonderful tool for little tiny work but cannot
provide enough heat (amount of heat (BTU’s) not magnitude of
temperature (degrees)) to do this kind of job effectively if at all.
You need a larger flame than the little torch can produce. Do you
have a different type of torch? A prest-o-lite or even a bernz-o-
matic type plumbers torch with a large tip will work much better for
this type of work. The copper is just too large, too thermally
conductive and too easy to oxidize for a tiny little oxidizing flame
to be able to raise the whole piece to soldering temperature before
the flux is exhausted. The one possibility with a little torch is
the “rosebud” or heating tip that is availble for it. This is a multi
orifice tip that is sold to allow for using the little torch for
casting. It is still too small for any but the smallest of castings
but should provide a lot more BTU’s and with it you should be able
to solder your piece. If you do us this type of tip do not adjust it
for an oxidizing flame but a neutral or even a very slightly reducing
flame will be your best choice for soldering anything but platinum.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#5

I’ve done a lot of copper-silver soldering-successfully 8-)…so let
me have a go at this.

First, this is a fairly large bezel & many of us would have problems
with it. I think somewhere on Orchid are hints for soldering on
large bezels.

Second, I hate using mesh screens. I find them to be a huge heat
sink. From what you describe you aren’t able to get the mass of the
bezel plate up to heat fast enough b4 your flux is done and the
copper starts to oxidize.

Instead of the mesh, I have made little platforms w/ flat flooring
nails (soldered 2 together) and I set my bezel plate up on it. Then I
heat from the bottom,(as you did, good idea) directly on the bezel
plate until I see my flux coming up to temperature. I use a paste
(non-fluoride) flux from Rio. I think it lasts longer then Batterns.

You may also have too small a torch for this job. Can you get a
cheap propane/air torch? You need to bring it all up to temp quicker
so your flux will last and your solder run b4 the copper gets dirty.
I think that is your main problem, aside from your bezel size.

hth
Carla
www.carlamfox.com


#6

Cathy,

From your input, I would say you have two problems. The first is
your little torch. Copper LOVES heat and you have to pump in a lot of
it to bring the copper plate to critical temp. Because you are using
a small torch (read small heat input) you are simply pumping more and
more O2 into the surface of the copper. The longer you do that, the
more oxidation occurs to interfer with the solder. The little torch
is actually too small to even do silver on silver when it is 30x40mm.

When I solder copper, I go directly to a Smith single gas
(acetylene) torch with the appropriate tip for the size of job I’m
doing. This gets the heat in quick and the job is done before you
know it.

Secondly, you mentioned a mesh screen. How heavy is the screen? Is
it on a tripod or a bridge of charcol blocks or soldering bricks? The
screen will sink much of your heat…especially if it is on a tripod.
I never use a tripod. If I do use a screen, it will be light and held
up by either charcol or soldering (magnesia) blocks. You are correct
to heat from the bottom. That will protect your thin silver bezel.

Hope this will help you. Cheers from Don at The Charles Belle Studio
in SOFL where simple elegance IS fine jewelry!


#7

Cathy:

I class that I am taking is in the middle of this very issue.
Soldering Silver to copper. We have to make very sure that the silver
and copper are both clean. No oxides or firescale and no
FINGERPRINTS.We are using Presto-lite tourches and working on heavy
stainless steel screen. Gently brush the piece with the flame until
you see that the flux is dried. Then move the tourch to the bottom
and again constantly moving the tourch around heat until you see the
flux go glossy and liquid looking. Immediately move the tourch to
the top of the piece again moving constantly. You should be able to
see the solder sheen around the edges of the bezel. Immediately
remove the flame. Let cool for about a minute and then quench in
water then pickle or if you prefer straight into the pickle.The
tourch flame needs to be pretty good sized so it can bring all the
metal to temperature and keep it there. I have both tourches at home,
the little smith in oxy-a= cet and a presto-lite type on acetelyn.
For the kind of work you are talking about I always use the
Presto-lite. Save the little smith for finer spot jobs.

Hope it helps and good luck.
John (Jack) Sexton


#8
making a 30mmX40mm oval copper pendant with a small (3/4 inch or
so) fine silver bezel centered on top of the copper. 

Part of the problem may be that you are soldering a small thing
(silver) onto a large thing. I suspect that another part of the
problem is that copper radiates heat like crazy. I recommend trying
three things:

(1) sink your whole arrangement into your annealing pan and build a
little “wall” around the copper, so that some of the heat it
radiates will come back on itself.

(2) heat the copper only; let the heat travel to the silver solder
and bezel. The melting points of the silver are well below that of
copper, so you shouldn’t have the problem of melting the copper.

I've tried pickling and re-attempted the join, to no avail.

Before you try this again, bright-dip the whole thing. Pickling will
not remove the red cuprous oxide from the previously-heated
copper,and that may be what prevents the solder from flowing.
Bright-dip can be dilute nitric acid (fast) or the mixture of PhMinus
and hydrogen peroxide (slower). Rinse very well and re-re-attempt the
join.

Let us know if this works out!

Judy Bjorkman


#9

Mesh screens are OK if you use a big enough torch. I use a prestolite
acetylene-air torch with a number 4 tip or larger for soldering large
pieces. Sometimes ya just gotta use a bigger hammer. The advantage to
using a mesh screen is twofold- first, the screen provides support
for the whole piece and decreases the likelihood of warping. Second,
you can come from underneath with a huge bushy flame that envelops
the piece and should inhibit the development of firescale.

Lee


#10

Cathy, I also had problems with soldering copper with the smith
torch. the small tips don’t heat fast enough to melt your solder
before the copper oxidizes.

are you using lots of flux on the entire piece? fire scale on copper
will travel from an unfluxed spot (even the back!),over to where you
are working so flux the entire piece!

also at a minimum I suggest the rosebud (casting tip) for the little
torch. so it heats quickly and uniformly.

I have a air acetylene torch with very large tips that I use for most
of my copper soldering. I also solder on a stainless screen on a
tripod or on some small bits of firebrick.

you can pick one of the torch’s up from a jewelry tool catalog or go
to the plumbing aisle of your local hardware store, it the same thing
plumbers use to sweat solder copper pipe.

I hope this helps, Jerry (freezing in Wisconsin)


#11

Hi:

I think your problem may be using an oxidizing flame. Copper
oxidizes so easily that you really have to everything you can to
reduce it. Try a carbonizing or reduction flame. I’m not familar
with the torch that you’re using, but the advise about torch size
sounds good to me. Its that six of one half a dozen of the other.
Use a small flame that lessens the chances of mistakes or use a
larger flame that could do the job but you run that risk of things
going badly very quickly. Flame techniques take awhile to learn. If
you go to a larger flame you could lessen the risk by using a heat
sink, By putting the work in a metal vise or something that will
take some of the heat away.

Chris Gravenor


#12

Also Re: Brass Pendants and Melted Bezel

A few things I would like to contribute here.

Regarding tips for the littletorch…I have hogged out a number 7
tip so that I am able to solder cuff bracelets of some size, several
ounces. Its not the prettiest flame but it works.

Screens…If you have a tricky soldering task, heating through a
screen from the underside is working blind to some degree. The
backside will become hotter than the front because it stands between
your heat source and the area you wish to solder… you may overheat
your back surface because you can’t see when its at that dangerous
point. Soldering upside down is totally blind

What has worked for me is a compressed charcoal block (they don’t
break the way soft blocks do when heated a lot) and from the top,
circling the flame around the piece, spiraling in as the temperature
of the object rises. Watch the flux carefully, as this is the
indicator of temperature. You will see it bubble and then settle in
shortly before the flowpoint of solder is reached. If you need to,
put a heat shield such as a coin on the top edge of the bezel. The
bezel would tend to melt from the edge downward usually. The heat
shield will both deflect the flame and draw heat away from the
’nervous’ edge. Solder flows toward the heat so try to keep the bezel
cooler than the base until proper temp is reached, then play the
flame directly at the join.

If the bezel did partially stick, before you try soldering more,
remove the bezel completely and file the mating surfaces. You need to
physically remove the oxidation that has accumulated on the mating
edge.

Flux…Batterns and similar thin liquid fluxes will burn away. Try
Handi-flux (paste) for those jobs requiring a lot of prolonged heat.
On a tangent…Handi-flux is pretty good at cleaning diamonds (but
ONLY diamonds) you have accidentally started to burn. If they have
turned black from not being completely clean but not yet frosted,
pack the stone with Handi-flux, heat to liquefy and pickle. May have
to repeat.

If your bezel melted when you were doing the JRs, you were just too
hot. Working from the front you will be able to keep an eye on your
previous joints.

Hope you find this useful.


#13

Firstly, I’d like to thank all of you that responded with suggestions
on my soldering problem. The general consensus was that I needed more
heat (bigger torch), and I was inclined to agree. I could actually
see the heat radiating around the copper plate as I drew my torch
around the bottom and it seemed that it would not come up to temp to
melt the silver pallions inside the tiny silver bezel. However, I am
happy to report MISSION ACCOMPLISHED. I learned that if I cleaned the
copper really well (pickling) and then dishsoap, water and a soft
fingernail brush, I could remove all of the oxide. The small silver
bezel was partially soldered and not misshaped or burned from all the
heating, so I left it where it was. I then coated the copper
completely and generously with paste flux (StaSilv, a brazing flux,
which is all I ever use). StaSilv takes a ton of heat before it
expires. I heated from below, as before, with a large neutral flame
(not oxidizing flame as before), and as soon as I saw the flux go
glassy, I quickly brought my flame to the join. Amazingly, the
solder flashed and my bezel was attached. I forgot to mention that I
also decided to use medium solder instead of hard this time. The next
step was more foreboding, but I managed to attach a heavy outer
sterling bezel (actually a frame) to the circumference of the copper.
Expecting problems joining the two, I intended to just “spot” solder
in a few places to secure the frame to the copper. Surprisingly,
using the method above, I was able to solder one great big heat sink
to a bigger heat sink with my little torch! So the answer was: clean
metal, tons of high-heat flux, a big neutral flame, heat from below,
and heat the join when the flux goes glassy, all hopefully before
oxide forms. The copper is now beautifully patinated blue with
ammonia/salt, and the druzy and ceylon sapphire mounted. Too bad I
don’t really like the look of the finished product, but it was a
great lesson. Thanks a bunch for all of your responses and
suggestions!

Cathy