Back to Ganoksin | FAQ | Contact

Problem soldering

Having difficult time soldering 3 1/2" x 5" pieces of 24 guage
copper. Taking silversmithing lessons and with the instructor we
sweat soldered the first piece and the solder flowed. Fluxed the
second piece of copper and tried to solder the pieces together. Used
two acetylene/air (not acetylene/oxygen) torches with #3 tips and
thought we had the pieces soldered together. Noticed a small space
between the two pieces of metal and when sticking an xacto blade into
the opening it kept getting larger and larger until the two pieces
came apart. The only thing holding the pieces together.

Then tried Propane/Ogygen with A fittings with the Smith AT615
rosebud orfice tip but again was not able to generate enough heat to
meld the pieces together.

I found that I can solder the eyes and mouth and appendages after
the first two pieces are bonded without affecting the first
soldering. Again my silver solder is extra hard with melt point of
about 1450. Need that as I enamel my pieces with glass in an oven at
1365 degrees and any softer solder would just remelt.

Totally confused with the various I have been trying to
ferret out. Not sure what gasses I should use, what size tips, size
tanks if that makes a difference. Just do not want to buy any more
equipment until I am sure what I am doing. It has been recommended
that I use something like the rosebud tip (3/4" tips with multiple
orfices) and using B type hoses and fittings for the propane/oxygen
which would give me 286,350 BTU’s as opposed to the 39,840 BTU’s I
would get with the A hoses and tips. I don’t know how much heat I can
get with Acetylene/Oxygen but I will look it up. But again I need to
try before buying more stuff. Possibly my cheapest way for the time
being is getting adapters from A to B fittings and getting the larger
tip for the Propane/Oxygen. Or do I need to go to Oxygen Acetylene?

Attached is a jpg of what I am trying to solder together.

Would appreciate any feedback.

Attachment Removed

#3 tips are too small try #5 or #6 tips.

Use lots of clean paste flux, clean metal, and clean solder. Heat
the whole piece with a more attention to the area you wish to solder
but heat the whole piece. Once you get near soldering temperature
then focus more on the area to be soldered. Copper is extremely
thermally conductive and if you only focus on the area you wish to
solder you will take much longer to bring the work up to soldering
temperature and burn out the flux and oxidize the work area. You
should not need to use propane and oxygen solder this size work. You
are more likely to oxidize the work and burn out the flux with the
propane/oxygen and again too much spot heating. If you are going to
use the propane / oxygen rosebud torch use a soft bushy slightly
reducing flame and again heat the whole piece not just the area you
are trying to solder.

Using A-B adaptors will not affect the amount of heat you get
substantially. What they are trying to tell you is the whole torch
system from regulator to torch tip needs to be higher capacity.
Larger hoses larger, fittings, torch body that can handle higher flow
rates, regulators with higher flow rates etc. But again you do not
need this just get a couple of larger air/acetylene tips and
practice, practice, practice.


James Binnion
James Binnion Metal Arts


Copper (100Cu) melts at 1063 C
Hard Silver Solder at about 750 c
Metal firing temps in an enameling kiln:
for Cu 1082 C
.925 Ag 893 C

For copper one must anneal to cherry red first,air cool and water
quench.let it dry 100%. I would suggest nitric Acid for the initial
preperatory pickle at a ratio of about 1:4, then a bit diluted for
dissoving scale ( if you have not put a firecoat on to protect the
non-joint parts of the metal) after soldering.).Ordinarily a gap is
the sign of incomplete or poor fitting, so double check your joins
for perfect fits.It is better to take the time to get it right in the
beginning than having to re-do it.

Not having the slightest clue as to whether you are using transparent
or opaque enamels,or are using the wet or dry technique -if not both-
and presuming you have prepared the glass well in distilled water
until clear, you may consider torch melting the enamel onto the
copper using a tripod to allow heat to encase the piece,but not melt
it as a kiln would do if above 816 C. thoroughly stone the glass
working coarse to fine, then refire to bring up a glossy finish ( if
that’s what you’re after)…For a matte finish try dilute hydrochloric
acid instead of refiring.

Copper paste solder may be the answer in your case. as opposed to
silver solder…due to the sheer size of your pieces that your are
attempting to connect…regular silver solder strikes me as
incorrect.,not to mention the flux is already in the copper paste
type solder so the flux you are using for Ag may bear on the problem
too! ( alternatively make your own enamelling solder ( 6 g fine
silver to 1.5 g copper- no zinc, no anything else.roll out thin or
draw into a wire and mark clearly the grade and purpose)

Make sure you clean the joins in between the attempts as well as you
can (sand them perhaps with a very fine grit paper or film in
addition to a nitric acid dip).I’m not sure why acetylene and O2 have
not worked…check your regulator pressure(?) if it’s correct, try
MAPP brand gas and oxygen as it achieves a slightly higher temp than
acetylene… with propane you would best have a second person holding
an additional torch on the piece- even then it probably will not
give you the results you need…the main consideration is a Reducing
flame - or about half of the length from the tip of the torch to the
end of the flame,oxidising flames are of no value n soldering
enameled pieces together.

hope at least there is a grain of something usable here…if not
there are a number of excellent enamelling books out there, one that
might be specific to your needs is"Enameling onCopper and other
Metals" by Thomas e.Thompson,c.1950’s or “Enamels and Enameling” by
Randau, both are probablyout of print but available on or