Back to Ganoksin | FAQ | Contact

Trouble sweat soldering


#1

Hello group.

Long time lurker, first time poster here. I’m relatively new to
jewelry making as far as hours of experience, just a few hours a week
over the last year. Enough rambling, now the issue. I am having a
heck of a time sweat soldering an overlay. I have searched the forum
for ideas on how to solder an overlay before I atempted it, and now I
have a question. Here is a link of some pictures of the bracelet
coming apart after a solder atempt,

http://tinyurl.com/5vb2wj

I was able to pull top off without any damage, it was apparently not
soldered, not even close. Here is what I did:

I created filings of hard solder.

Sprinkled them on the surface that was covered in Handy Flux. This
was the top piece.

Heated the SS until I saw the solder flash. Actually, I never saw it
flash, I just saw molten metal as I was heating the ends. Couldn’t
tell what was happening in the middle, but it seemed to melt there as
well.

I then pickled the pieces and setup for the join by fluxing the top
and bottom.

I placed the top piece face down. I wasn’t convinced that I had
enough solder, so I added some more filings.

I placed the bottom (uncut) piece on top of the upside down top
piece. I heated and heated and heated…

I am using generic smith little torch with a number 6 tip and
propane/oxy fuel. The piece is roughly 1 inch by 6 inches. I cranked
up the fuel pretty high and proceded to heat. I spent a good minute
getting it to temperature. When it looked like it was at the right
tempurature, I used the side of my solder pick to press the back
plate down onto the top plate. I spent a good three minutes going
back and forth over the piece, pressing with the side of the solder
pick (not the point). Correct me if I’m wrong, but I think this is
too much time. Does it matter that I was heating on top of a
magnesium block? The pieces weren’t perfectly flat and 100% in
contact, but I think close enough. Even if they are perfectly flat
before adding solder, they won’t be in perfect contact after one
side gets solder, since the solder would produce high/low spots. So,
how do you create a good solid contact surface for soldering a fairly
large overlay? I was thinking of sandwiching the bracelet between
two steel plates and heating it in the kiln, but I haven’t read about
that in the forum, so I think it’s overkill. Any help is
appreciated. I live in Houston, TX and would be interested in finding
a mentor.

Thank you
Kelly


#2

The joint failed because the solder didn’t melt. The torch supplied
heat at a temperature high enough to melt the surface, but it leaked
away before the solder got hot enough to melt. The major problem was
in using a magnesium block and heating from the top - the resulting
temperature gradient from the molten top surface down to the block
was just too steep and the solder remained solid.

You can’t rely on gravity to keep the strips together - use binding
wire. If you use a torch, make sure to conserve as much heat as
possible and heat the work from below as much as you can. A soldering
wig can help. (In case you don’t know, a soldering wig is a mass of
old binding wire squashed together to make a highly porous block that
can support the item to be soldered and allow the flame to penetrate
beneath it.) Use fire bricks to reflect the heat back into the work
rather than allowing it to escape. If it takes more than 30-40
seconds before the solder melts, the flux will deteriorate and become
ineffective - it basically means that you are losing too much heat.

You mentioned you have a kiln. Bind the items together and use the
kiln - get it to temperature before placing the fluxed work in it.

IHTH.
Regards, Gary Wooding


#3

Kelly,

Not enough solder
Not enough heat
Base should be down with overlay on top
"heating the ends" sounds very strange to me

I’d use lots of pallions of solder and not pre-melt. Every time you
melt hard solder the melting point goes up. With the overlay on top
with a solder sandwich heat BOTH pieces over their full length,
remember everything has to get to the solder flow temperature at the
same time. Don’t be gentle, you are really pushing the limits of the
little torch. Adding a hardware store plumbers propane torch might be
handy although one does need 3 hands. Ok to get the overlay a little
hotter (and hard to avoid) this will make it slump onto the base,
poke and prod to help if needed.

I have found that most soldering problems involve heat; not enough
and not quickly enough. Sure I’ll ultrasonic if covered with oil from
the mill and emery if black but the only rocket science usually
involved is using the right sized rocket :slight_smile:

Jeff

Demand Designs
Analog/Digital Modelling & Goldsmithing
http://www.gmavt.net/~jdemand


#4

Hi, Kelly

In my classes, we do this kind of soldering everyday, numerous
times, and I can give you some tips.

Your torch: That “Little Torch” is NOT my favorite, especially for
heating large areas evenly, and that is your goal with the 1 x 6 in.
piece you are making. A Presto-lite, or acetylene torch, with a
fairly
large tip is what you need. High regulator pressure. It generates
some serious heat, which silver of that size will need, but with a
softer, bushier flame. You want to heat evenly, by fanning that flame
back and forth quickly. Silver is a great heat conductor, and it will
"steal" your heat. Don’t be stingy with the heat!

For overlay work, soldering 2 plates of silver (or gold) together, I
would recommend getting both of them DEAD FLAT, having the bottom
sheet being slightly wider than the top sheet on all sides, which
will serve as a “shelf” for your solder. I don’t recommend putting
solder between the layers.

Flux: Handy flux is just fine, but I’d recommend NOT putting it in
beween the layers, but flux the sheets together, as a unit, not
getting the grainy flux between the flat sheets. You need to have
them close fitting.

Solder: Use a MEDIUM solder for this. Hard solder will require way
too much heat to melt, and you may see your silver sheets melt before
the solder does. After drying the flux with a soft flame, place small
solder pallions ( I like to cut small rectangles of sheet solder)
around the edge of your “sandwich”, on the lip of the bottom sheet,
touching the top sheet’s edges.

Heat: I’d also recommend using a large, heavy steel screen, and
heating from underneath, if possible. Also, try to keep your
soldering set-up perfectly level, or you will find that as the solder
becomes a liquid, your pieces may just slide apart, toward the
down-hill side.

I think that with perfectly flat sheets, clean and well fluxed, with
plenty of medium solder pieces around the edges, and providing a
robust, even heating should do the trick. Watch for solder flow
around the edges, and inspect the seam closely before sawing off the
"solder lip" on the bottom sheet.

Jay Whaley


#5

Hi Jay:

For overlay work, soldering 2 plates of silver (or gold) together,
I would recommend getting both of them DEAD FLAT, having the
bottom sheet being slightly wider than the top sheet on all sides,
which will serve as a "shelf" for your solder. I don't recommend
putting solder between the layers. 

I’ve done a lot of sweat soldering over the years but I’ve never
heard of not putting solder between the layers.

I do slightly bevel the edge of the metal on the top layer so the
solder stays underneath the layer, but I can’t perceive just putting
solder around the edge - does it flow all the way throughout? or does
it just “seal” the layers tightly?

I was taught that placing thinly cut and small solder pallions
between the layers was the way to do it and was told that you could
tell when the solder melted when you saw the top layer “slump” onto
the bottom layer. It would seem if the bottom layer was larger than
the top layer that you would have “trimming” to do when you finished.
And I’ve always dipped both pieces in the boric acid/alcohol mixture
and flamed them off before assembling with the solder pallions
between the layers. And I’ve heated from bottom or from top with the
same results.

What do you do when you only wish to sweat solder a free form shape
on top of another piece?

Always happy to learn new methods but would like to know how
important it is for the solder to flow totally between the two pieces
as opposed to “sealing” off the border. Otherwise it seems you’d have
to use one heap of solder to be sure the top layer was totally
soldered to the bottom layer.

Kay


#6

Kelly,

Good suggestion from Jay. Here’s another way. I suggest you try both
to see which works for you.

  1. make sure the pieces are flat

  2. rough up the overlay piece by sanding on 120 grit for a few
    seconds on a flat surface. Note: the granite counter craze is
    everywhere these days. Find a scrap piece of marble or granite which
    you can get free. These make excellent flat sanding surfaces.

  3. I snip micro chips of solder and pre-flow onto the overlay piece.
    You don’t need much, but enough so the piece is mostly covered.

  4. Medium solder is fine, but check the melting temperature of
    solder against your other solders. Use a tiny amount of flux for the
    pre-flow. Rough your flat piece one more time. This allows maximum
    flat contact with the parent metal.

  5. heat with #1 or Smith acetelyene either underneath your piece or
    around. Underneath is best, as the melting solder will flow towards
    your heat source. If it is coming from the sides, it can flow outside
    your piece.

This process works very well if you have textured metal that you
want to put an overlay of gold and don’t want the solder to spread
outward. You get maximum coverage and minimum spread.

There are many ways to solder. That’s why I like this group. You get
a varied number of opinions and ways to try out what is best for you.

Karen Christians
Waltham, MA
http://www.cleverwerx.com


#7
but I can't perceive just putting solder around the edge - does it
flow all the way throughout? or does it just "seal" the layers
tightly? 

This bothered me also. The other thing I’m a bit confused about is to
do with the fact that the two sheets of silver were being soldered
together before making into a cuff bracelet. Will such a
sheet/solder/ sheet sandwich bend into a cuff bracelet successfully,
taking into account that the outer sheet has to stretch
considerably, while the inner sheet has to compress? I guess it
depends largely on what gauge of silver we’re talking about - but
does it generally work okay?

Helen
UK
http://www.hillsgems.co.uk


#8

This was how I was taught to sweat solder. Placing the chips around
the perimeter and drawing through. The solder does, in fact, flow to
the interior. Capillary action draws it in wonderfully. The analogy
that I use when teaching is two panes of glass stacked. A drop or two
of water “shoots” across the interface between the two sheets. Very
strong bond. The advantage to perimeter sweat soldering is that
nothing shifts.

Battern’s flux-which I rarely use-- is a good choice to apply after
the pieces are fit. Being so liquid, it too will flow capillarily
between the two sheets. Nowadays, I use paste flux and simply wait
for the liquid phase and position the sheets accordingly while
heating with a torch.

As always, solder follows the heat…

Sometimes I pre-coat one sheet and sweat solder that way; sometimes
I perimeter sweat solder; sometimes I work out another solution. Not
every strategy works every time…

Don’t sweat it!
Andy


#9

I also use a Smith Little torch for everything and rarely have a
problem. However I would recommend using the larger #7 tip. Also
there is an even larger tip available that I am about to purchase
for my Smith Little called a melting or annealing tip to cover larger
surface areas.

Good Luck!


#10
Been reading this thread but up until now it's been the standard
answer - more heat! 

As far as the new twist… There is a point at which you can feed
solder in the sides, and a point where you cannot. Soldering a 4mm
sheet onto a 5mm sheet is sweat soldering, but it’s so narrow that
you can solder it down like wire, if you want to. Obviously, when
soldering a 2" (5cm) piece onto a slightly larger base, there is no
way on God’s green earth you’re going to pull solder all the way
through. You can solder the edges only and let it go, but if anybody
ever heats it again you’ll get a huge bubble and maybe it will
explode. Even if you could manage to do it, it’s shoddy work and
needlessly difficult. Also if you take a 2"/50cm square, pierce it
like lace, and solder it to a base, it’s technically an overlay but
you can treat like soldering down wires, again if you want to. There
are some really obvious things, like soldering vast expanses of metal
will require presoldering one surface, but it’s also a matter of
skill and experience as to where the line is that solder can be fed
from the edge. In a nutshell - “True” overlay soldering (of any
quality) of two larger pieces of sheet REQUIRES presoldering and
saying otherwise is bone-headed. I’ll say here that this is where
paste solder is ideal - I used to do a lot of silver overlay with
pierced tops and things, and paste will give a perfect job, once you
get the hang of it.

And yes, Helen, if two pieces are “perfectly” soldered together,
they will behave as one piece of metal, at least up to any
reasonable point of stress. That is, for all practical purposes
there is no longer a “top” and a “bottom”, it becomes one. Since we
are all of us imperfect, sometimes a seam might pop, but usually it
can be cleaned, pounded back and repaired…

http://www.donivanandmaggiora.com


#11

For a good sweat solder, especially if you are forming the metal
with a soldered top applique, it is vitally important to pre-flow all
the solder on the applique first. Once this has flowed and is
complete covered in a very thin layer of solder, then apply the top
part to the parent metal. When you see the solder flow around the
exterior of the applique, then you know you have two pieces
completely joined.

After soldering, before forming, run the two halves into the rolling
mill (if there are no patterns to worry about) and do what is called
a “dead pass”. A dead pass is one where the metal slips through mill
without any pressure. The next pass, apply the smallest amount of
pressure. Any unsoldered pieces will buckle and you will find the
part to apply some solder to, or reheat while hold the piece down.
Not to toot my own horn here, but that soldering pick I sell is
perfect for these applications because sometimes you need just the
extra pressure in one spot to create a solid contact.

Once the two pieces are sweat soldered together, you should have no
problem in forming a cuff bracelet. Heavier gauge metal works better
than smaller for forming, and personally, I would go with hard solder
than medium. Yes, Medium would flow easier, but an easier and less
temperature flow point als= o means it can spill out of the seam onto
your parent piece.

One tip here. You don’t have to make everything flow at once. Say
you are making an edging for 16 ga cuff bracelet. I would use a 14 or
12 ga for the edging. If you have round wire, form it in an oval and
sand the whole thing as flat as possible. Preflow the solder on the
oval and sand again. Trying to solder the oval edging in one shot is
difficult. You have a lot of mass going there and a lot of heat which
is buckling the flat stock. So, tack it in pieces. Start with the
opposite ends, north and south and then hit east and west. Keep
moving around until everything is tacked down.

You can make little clips out of binding wire, or if you are lazy
like me, pile a bunch of pumice in your pan on the part you aren’t
soldering and throw a scrap piece of heavy steel or anything to
weight the other side down. Let the whole thing cool and then keep
moving along.

I like Superior Six flux for this operation. If you start clean and
don’t overheat, you will get great results and your flux will be
quite sturdy.

http://www.ccis.com/home/hn

I would stop, rinse pickle at this point and then flux the hell out
of your piece and go with a #2 Smith tip and your solder will flow
like an unobstructed river. Rinse and pickle again, do your dead
passes (if you need to, with edging not necessary). A loop is a good
thing to have hanging around your neck. Give it a full examination.
Anything not solder will jump out at you like giant crevasse.

You should be doing all of this with your sketch book open and
documenting everything while building.


#12

Properly fluxed and close together capillary action will suck the
molten solder in without a problem. Plumbers use the technique when
soldering copper pipe joints.

Bending laminated bracelets takes a bit more muscle and hammering.
You are indeed stretching the top layer and shrinking the bottom
layer. There is a tendency for the bracelet to bend at the weakest
point i.e. where the inlay portions are the largest.

There is also a tendency for the bottom sheet to bump up through the
open inlay channel. This can be hammered down using a punch and a
steel bracelet mandril. In fact I use a couple old leatherwork
punches so that I texture the inside of the inlay channel giving the
adhesive a better bound.

Rick Copeland
Silversmith and Lapidary Artisan
Rocky Mountain Wonders
Colorado Springs, Colorado
rockymountainwonders.com


#13

John,

I have been following this thread very carefully, because it is a
common type of soldering done in my classes, and a technique I have
been using since the early 70’s. Andy Cooperman also uses this
technique quite successfully, according to his post.

I got my start in silversmithing in Phoenix in the late 60’s. Indian
jewelry was what was popular, and that is what I learned how to
make. I worked my way through college making and selling Indian
jewelry, selling nearly all my work to an upscale Indian-jewelry
gallery on Scottsdale’s Fifth Ave. One of my specialties was
Hopi-style overlay. I would modify basketry designs I found in books
and pierce them by hand out of 18 ga. sterling sheet, soldering them
to a 22 ga. sterling sheet. My particular style was an intricate,
lacy pattern of cut-outs, carefully hand filed before being soldering
down.

I must have done hundreds of rings, cuff bracelets, bolo ties, and
squash blossom necklaces in silver and set turquoise stones.

Over these years of doing overlay silver work, my soldering was done
with a Prestolite (acetylene and air) torch, and all my overlay
soldering was done over a heavy steel screen suspended between two
fire bricks. Both the pierced-out overlay sheet in 18 ga. and 22 ga.
backsheet were perfectly flat, fluxed together as a unit, and solder
chips were placed around the outside edge of the slightly larger
backsheet. A large bushy flame was used, heating the sheets evenly
from beneath the screen, and the solder could be seen melting and
being sucked between both sheets.

When soldering was completed, and the work was pickled, I could
loupe my overlay and see solder under every single bit of overlay,
even on 3 inch wide bracelets. These wide overlay bracelets were
"sunk" in tree-stump dapping impressions with oversized ball bearings
and hand formed over oval bracelet mandrils, and rarely did any piece
of soldered overlay come loose from the backplate. The soldered bond
was quite strong between top and bottom sheets.

So PLEASE don’t tell me that solder doesn’t have the ability to flow
great distances between sheets. My years of experience doing just
that proves that it does it quite well. You DO NOT have to pre-melt
solder between sheets to solder them together unless you prefer to do
it this way. This capillary action of solder is quite an efficient
way to solder, provided you have perfectly flat sheets, you have
adequate flux, and your heating is even and sufficient.

Jay Whaley


#14

I just remembered a Native American technique I believe it is Hopi.
To sweat solder overlay pieces they would file solder into a pile of
shavings. Then pass a magnet through the shavings to be sure to
remove any ferrous metals. Then spread the solder on the base piece.
I can’t remember what they used for flux. Some old NA silversmiths
didn’t use flux. They just made sure they filed or sanded each
joint.

Rick Copeland
Silversmith and Lapidary Artisan
Rocky Mountain Wonders
Colorado Springs, Colorado
rockymountainwonders.com


#15
file solder into a pile of shavings. Then pass a magnet through
the shavings to be sure to remove any ferrous metals. 

Here’s a better idea-- if you want powdered solder, buy it from our
own Beth Katz at Unique Solutions (uniquesolutions.com, I think). I
have 5 or 6 grades, and I bought it for just that purpose. Paint on
some paste flux, sprinkle the solder, assemble and heat.

The downside, in my experience, of using paste flux and powder is
that as you heat it, the water-based flux may boil and spatter,
spreading solder a bit where you don’t want it. This isn’t generally
an issue with sweat soldering, however, as the solder is all “in the
sandwich”. It happens more if you use it like paste solder-- I dip
my pick in flux, then just the tip into the solder, then apply it
where I want it. I know exactly how much solder I’m applying (less
clear with paste solder, at least until you get used to it). It just
has to be heated a bit slowly and carefully until dry so it won’t
spatter.

Noel


#16

There are just so many techniques that will work for sweat
soldering, you have to find what will be the best road for you. Many
of the suggestions on the list are just fantastic.

Another approach is to use paste solder. Paste solder already
contains flux in the paste, so there is no need to add any more flux
before you are ready to flow the solder. To begin, make sure the two
pieces that are to be joined are completely flat and will not have
any air between the layers. There were many suggestions of how to
accomplish this part of the task, please review those to find the
one that suits your application.

Once you have determined the top and bottom of the piece and they
match with no gaps, apply paste solder to the bottom of the top
piece using an amount that will coat the entire piece with no areas
void of solder once it is flowed. Keep in mind, you do not want to
use too much paste solder as it can flow out of the seams, but just
enough to coat the bottom of the piece to be joined with a smooth
coating of solder. Flow the solder. Do not pickle. Place top piece on
top of bottom part with flowed solder side down, using a tripod with
a screen and heat from below. You can also put a very, very small
amount of fresh paste solder (not flowed yet) inside of the edge of
the part that already has the solder, (about 1 mm in from the edge)
this will just make the join on the edges even more tightly joined.
Once the bottom part is the proper temperature, the top piece will
also reach the correct temperature (since silver is such a great
conductor of heat), and the solder will again begin to flow
connecting both pieces. Make sure that you heat from the bottom,
using the torch, over the entire piece making the solder flow toward
the heat. This will help seal your edges. Please keep in mind, as
with “regular” (wire or sheet) solder, you need to remember the
flowed solder needs to be brought to a higher temperature than when
it was originally flowed, in order to flow again. It might be best
to select a solder for the “sandwich” that is one temperature grade
below the solder that you would normally use, thinking ahead. Once
you master the learning curve with the paste solder, it is possible
for you to do the soldering of the sandwich in one operation and not
flow once and then again. If you do want to try this, simply make a
sandwich, with the paste solder in the middle and go for it. You can
balance on screen on a tripod, making sure that all the solder has
flowed and that your edges are fully soldered.

Another technique of “sweat soldering” is to use powder solder.
Powder solder has no flux, so a heavy duty paste flux is recommended.
Mix the powder with the paste flux to any saturation. In essence, you
are making your own paste solder; it can be made very saturated (more
solder) or less saturated as needed by the project. This mixture is
then put between the layers and heated on a tripod with screen. The
operation is a one time heating situation, making sure that the
powder solder and flux have reached the proper flow temperature to
make a completed project. Make sure the edges are soldered together
as with any other sweat soldering.

Beth Katz
http://www.myuniquesolutions.com
Paste and Powder Solder for Jewelers and Metalsmiths.


#17

For many years I worked with a very experienced silversmith. Not a
generic silversmith but one who focused on flatware and holloware.
I’m sure the way he would approach this is by tinning with
silversolder.

After fluxing and flowing solder onto the piece he would quickly wipe
excess solder off, I can’t recall if he used a rag with some
goop (tallow maybe?) on it or steel wool or something. The piece
was now completely and evenly coated with solder. Then place two
halves together, flux and heat. You would see the top piece dance
ever so slightly and then settle down and it was done. No worries
about gaps or oozing.


#18

I posted a wrong URL yesterday-- Beth Katz (whom I recommended for
powdered solder) is actually at www.myuniquesolutions.com.

Sorry to anyone who tried and couldn’t find it!

Noel