Silver Paste Soldering Problems

Jewelry Discussion
1

I’m soldering copper domes to copper disks, with the disk at a bit
of an offset so that a crescent-shaped portion of the disk on bottom
is visible above the upper margin of the dome.

First, I tried applying a paste IT silver solder (calling Beth Katz
!) to the rim of the dome, stuck the dome to the disk, put on my
soldering hat and commenced to soldering. I had the piece on a tripod
and tried heating from underneath first with a butane torch. No go -
what I got was smoke from the flux, but no silver flow. I cleaned off
the detritus and applied paste solder again in the same way, this
time heating from above with a MAPP torch. Same result. Flux burned,
no solder flow. I don’t think I’m overheating as I am gradually
heating the piece all around waiting for it to reach the IT temp.

So, I give up, cut a piece of wire solder (70% - too low for this
piece since it will be enameled, but the only thing I had on hand).
Added a little flux made of 20-Mule Team Borax (remember the old
President, er, um, Ranger ?), applied the blow torch from the top,
and poof - a tight joint. So IT solder wire used in the same way
would work fine.

But what gives with the paste solder ? I kept ending up with globs
of glassy flux and no silver flow. What’s up ?

Brian Corll
Vassar Jewelry

2

So, do you have a vent hole? If you are trying to solder a dome to a
flat piece without any kind of vent hole, you won’t be able to heat
the piece to a high enough temperature, or if you do, you will
explode the piece and injure yourself. You need a small unobtrusive
vent hole at the rim of the dome so that the solder will heat and
flow. A wee filed nick on the edge of the dome will do. Otherwise,
there is nowhere for gasses and expanding air to escape.

Lisa, (just volunteered to run our local annual craft show. I must
have a screw loose!) Topanga, CA USA

3 
So, do you have a vent hole? If you are trying to solder a dome to
a flat piece without any kind of vent hole, you won't be able to
heat the piece to a high enough temperature, or if you do, you
will explode the piece and injure yourself.

Having soldered domes to sheet many times without a vent hole, I
find that it is not necessary to have one. There are no trapped
gasses until it is soldered and cooled. If the sealed dome is
reheated to soldering temp, that is when you need a vent hole as the
air inside expands and can blow up.

I have soldered a bezel to a sheet, and then turned it over and
soldered the top to another sheet so it is sealed many times. If you
reheat this piece without a vent it will explode. I have used a ball
of silver covered in solder, placed on a hole and heated to solder
temp to fill a vent hole that I did not want in the final piece, and
never had an explosion. Solder at temp to flow will let gas escape.

Richard Hart

4

Don’t really know what the problem is, but do know a couple of
things about enclosed space soldering.

You must have at least two holes in an enclosed object that you are
soldering closed. because if anything that is in the flux or solder
that turns to steam will keep the tempature from rising enough for
the solder to flow.

This is the same thing that will happen in water pipes to keep
solder from following and making the joint.

Also if the items are dirty, and not fluxed enough to clean the
metal for the solder to flow, also the temp didn’t reach the correct
temp. The holes will also help when you enamel so any vapor (steam)
that results can escape before reaching a pressure that causes the
the piece break open, rupture.

The borax flux was dry, you probably set it on fire or played the
torch over it till all the liquid in the flux mix was dried up. As to
the difference in torches the type and style of the tip pattern, the
size of the orifice and the pressure of the gas being burned can
play a factor in the BTU’s being put into the piece as to the amount
of BTU’s being taking out of the piece for any number of reasons.

Ottofrei.com They have a torch they make up and sell that uses
propane from either the small tank or the bbq style tank. Comes with
3 different tips for differening heat requirements. and makes it a
lot easier to solder copper and silver. I love this torch. I have a
number of butane, Maap, propane, smiths littletorch, full size
oxy/acty. a hebron 2000 torch and a couple of differing brands of the
prestolite torches that I have aqquried in the last 40 years.

The otto frei torch is the best and very easy to use it is light in
weight. The web is slow this morning almost at a stop loading pages
so I can’t give you the page link for the torch.

Again all the usual legalize and disclaimers apply. just a happy
owner/user of the item described.

glen, been there done that and probably broke it!

5 
You need a small unobtrusive vent hole at the rim of the dome so
that the solder will heat and flow. A wee filed nick on the edge
of the dome will do. Otherwise, there is nowhere for gasses and
expanding air to escape.

Actually, that’s not necessary in all circumstances, and I’m not sure
how it would relate to the solder not flowing in this case.

As for venting, I have assembled many hollow forms without a vent,
and a friend who has a line made from hollow “pillow” forms never
places a vent in anything she solders. It’s not luck. When you heat
two halves of a hollow form, any gases inside will expand and escape
through the seam as the solder flows. However, I have found that it
is necessary to vent any previously constructed hollow forms on
which to perform any subsequent soldering, but even then you can
solder directly over/into the vent for the same reason described
above, leaving no trace of the vent.

Matthew Crawford
www.MatthewDesigns.com

6

Here is a link to a very book book on soldering for jewelry. It may
be of help. Lapidary Journal - Jewelry Making, Jewelry Arts, Gems, Beads, B&B, Minerals and More It is
called Soldering guide revised costs 9.95 US. or maybe a class at
the local community college in their continuing education program
might be of use. Having been in the art metal/lapidary/jewelry area
of interest for over 40 years. The classes I took last year in the
jewelry making shop skills. Covered a lot of the basic skills and
things you tend to forget if not used regularly.

glen been there done that,probably broke it!

7

My guess is that there is not enough flux present. Copper oxidizes
heavily and needs a good flux. You might try using a fire coat like
prips or cupronil in addition to the paste solder. This is the
problem I seem to have with the paste solder, adding additional flux
and still keeping the paste where you want it. You may also have
better luck if you can heat the part faster to reduce the time that
the flux needs to protect the work.

James Binnion
@James_Binnion
James Binnion Metal Arts

360-756-6550

1 Like
8

Lisa,

So, do you have a vent hole? If you are trying to solder a dome to
a flat piece without any kind of vent hole, you won't be able to
heat

No, I’m trying to solder a dome to a dome and it just ain’t workin’.
I think I might try wrapping some wire solder around the dome joint,
brazing the ends together, and then just solder away. I need to use
IT or eutectic because I plan to enamel. I find the paste solder
difficult to get out of those syringes so that I get a nice bead of
solder all around the dome rim. The solder seems a bit too thick for
easy distribution.

Brian Corll
Vassar Jewelers

9

WOW, can I ever understand where you are coming from! This makes me
crazy when it happens, and sometimes the flame is rather dramatic
when the flux goes poof! BETTER HAVE YOUR HAIR OUT OF THE WAY!

temperature. I live in Tucson, and when I go out and try to solder
with paste in 100 degree plus temperatures, forget it. In fact, the
paste solder seems to work best in temps less than 90 degrees, and
this goes for silver, copper, and silver/copper combo work. And no,
it matters not what kind of torch you use, as far as I can see. You
will notice that the paste is much thinner at the higher
temperatures, and I think that the thinning of the flux chemicals
doesn’t allow for the silver particles to be close enough together
to flow and create a nice solid joint. I’m not a chemist, and these
are just my observations. Good luck and happy soldering.

Linda Palmero
Tucson, Arizona

10

Brian, Paste solder is no different from wire or sheet (cut into
pallions) solder. The difference is that the flux is already in the
paste, thus saving one step (or more) in the soldering process.

One difference is that when using paste solder, you DO NOT BACK OFF
your flame “to see what is happening”, or to dry the flux.

In using a solder (paste or liquid) which requires a flux to be
added before the solder will flow, most people are taught to go “in
and out” with the flame so that the flux can be dried out and to not
disturb the pieces of solder that has been placed so carefully where
it is to be flowed. This is a good practice when using flux that is
liquid or paste (still containing water) at the beginning of the
soldering process. By drying the liquid or paste flux slowly, you
have assured yourself that the chip of solder will not move from its
originally designated placement. If you go in fast and hot, then the
water will boil off the chip and the chip will move, even jump
around, before it flows; landing it in an undesirable spot on the
work.

With paste solder, you go in fast and hot, not backing off the
flame. The same rules apply to paste solder as to
pallions… In the case of silver, bring the whole item
to temperature BEFORE you try to make the solder flow. If you use a
torch flame and go in and out, you will dissipate the flux in the
paste solder and get a crusty black crud on the piece. SO…
technique is prepare your piece properly for soldering, put paste
solder where you want it, bring the piece to temperature but not
directly on the solder and then once you are seeing some activity
from the paste solder, bring the flame closer to the solder, but not
directly on it, and gently coax the solder to flow. Once it has
started to flow, you can direct it with heat to the exact spot, just
like any other solder. If by chance, the paste solder does ball up
and move, you can guide it gently back to your exact spot with a
solder pick, no need to stop and re-flux. A very interesting side
benefit to paste solder is that the join does not have to be as clean
as with the separate flux and pallions. The paste will cut through a
lot more “crud” in the join. Sometimes, when people have pickled and
rinsed a piece, there is still some chemical residue and they have
lots of trouble soldering. Paste solder will flow and make the join
even if the piece is not pristinely clean; a side benefit to the
paste. I do, however, recommend that your piece be prepared and
cleaned correctly.

Several years back, I was in an enameling class where we were doing
soldering prior to doing champleve enameling on a piece. Many people
who were in that class did have problems with the black crustiness
happening. Once I was able to observe their technique of their
soldering, I saw that they were backing off as they soldered, not
bringing everything to a hot enough temperature for the solder to
flow. This backing off of the flame allowed the flux to dissipate and
not activate the solder itself. That is what causes the crusty black
residue. The flux had been dissipated (in the paste) and there is no
where to go but form the crust…

Sometimes, the paste flux will still form a little bit of black, but
if the metal temperature is correct, this will quickly disappear and
the solder will flow.

Soldering is an acquired skill. Many excellent solderers still need
to adjust to the learning curve of a paste solder. As with any
technique, it is practice. Once you master it, you are well on your
way to enjoy using the paste solder.

If you are not happy with the product(s), after you try the method
described above, please feel free to contact me off list and I will
make arrangements to give you a refund.

The IT formula may have too high a melt for the copper you are
trying to solder, you might want to try the Eutectic formula since
you can enamel directly over that solder. It contains no zinc, so you
will not get any bubbles in the enamel when/if you enamel over that
solder. It is a perfect product if you are making pod forms that you
want to cover with enamel or dome shapes, put onto a disk. When
enameling on copper, you must be very careful to have the copper very
clean so as not to contaminate the enamel. The Eutectic paste solder
flows at F 1435 and contains both copper and silver, no zinc. The IT
flows at a higher temperature of F 1490.

I do hope I have found the problem and you will soon be on your way
to being proficient with the paste solder.

Beth Katz,
Unique Solutions, Inc.
www.myuniquesolutions.com
Paste and Powder Solder for Jewelers and Metalsmiths

11

Hi Linda,

Your post caught my attention.

From my observations, the problem in my neck of the woods is air
temperature. I live in Tucson, and when I go out and try to solder
with paste in 100 degree plus temperatures, forget it.

I just spent a month and a half soldering with paste flux while on
my patio in Phoenix in 112 to 118 degree temperatures. Never had a
problem. Been doing that for years in the summer.

I use a very limited amount of paste flux as it will wash away any
anti fire scale flux and leave purple cuprous oxide around the
joint.

Lee Epperson

12

Beth,

Thanks very much for your informative post. Yes, I was indeed backing
off at the wrong moment. I just need some practice it seems. I have
several copper domes I want to solder together so I’ll let you know
how it goes. No, I don’t want to return it - I want to learn it !

Brian Corll
Vassar Jewelers

13

I want to thank Beth for the info on paste solder. I have not had
too much success with it, and this may help. I still find it
disconcerting that paste solder produces smoke…

For those who want the benefit of paste solder without the smoke,
Beth also sells powdered solder. I bought a complete set of the ones
she offered a couple of years ago at SNAG, and I really love them. I
use them this way: I dip the whole piece in borax and alcohol, then
dip the tip of my soldering pick in paste flux, then just touch it
to the paste solder. I scrape off this combination onto the spot I
want to solder-- it will stick like paste solder. Then heat as
usual. The only caveat is that if heated too fast, the powder can
splatter a bit because of the water-base paste flux. There is no
smoke or black crud, so it is great in closed forms like beads or
domes, or sweat soldering. I have eutectic, which I have not used,
as well as hard, medium+, medium-, and easy. Now that eutectic has
been explained here, maybe I’ll start to use that, too.

Noel

14

Hi Brian,

I find the paste solder difficult to get out of those syringes so
that I get a nice bead of solder all around the dome rim. The
solder seems a bit too thick for easy distribution.

Most paste solder has a shelf life. The older it gets the harder it
is to extrude.

One way to make the paste solder easier to extrude from the syringe
is by warming the syringe. This can be done a number of ways, Here
are two that I’ve used successfully:

  1. Wrap the solder containing portion of the syringe in a cloth
    soaked in hot water.

  2. Place the syringe on the bench & put a 60 watt light bulb close
    to it for a while. The old flexible neck lamps work well. Don’t
    leave the syringe there too long or the lamp may melt a hole in it.

I’ve ‘resurrected’ some really old stiff paste by removing the
plunger from the syringe & mixing 3 or 4 drops of mineral spirits
with it. Mineral spirits are sold in hardware & paint stores as
‘paint thinner’. Be sure to check the label, you don’t want the
paint thinner that’s sold as lacquer thinner.

It helps getting the plunger out if you ‘break the vacuum’ in the
syringe. To do this, remove the needle & insert a blunt ended wire
until it touches the plunger, then remove the wire. Don’t use a
pointed object or you may poke a hole in the rubber plunger.

Beth Katz (myuniquesolutions.com) sells some paste solder that
doesn’t age as fast as most.

Usual disclaimers, just a very satisfied customer.

Dave

15

I find the paste solder difficult to get out of those syringes so
that I get a nice bead of solder all around the dome rim. The solder
seems a bit too thick for easy distribution.

If the paste solder is difficult to get out of the syringe it may be
old and dried up. Having tried several different brands, I would
recommend the one Beth Katz sells. (I have no connection to her,
just like the product). Even after several months of not using it,
it still flows easily out of the syringe. If possibe, you might also
try soldering your domes on a fire brick instead of a trivet and
grid system. The latter is a heat sink and might be allowing the
flux in the paste to burn out before flow temp is reached.

Donna in VA

16

i too am having problems specifically with solders from Unique
Solutions…perhaps there’s something in her formulaes that isn’t
quite right. I suggest using a paillion of solder and giving up on
the pastes…or trying a different brand. I have tried three different
formulations of B.Katz’s paste silver solders ( #'s 65, 68 and
perhaps it is 70…i can’t remeber without going to the studio and
looking at the tube!) but it was another variant of her "hard"
formula. It just fluxes- rather incompletely at that no matter what
gas, or gas and O2 combination i use, and the silver has never flowed
in months of trying. I recenntly wrote her about the five tubes i
bought, but am waiting to see her make it flow with my own eyes, in
august…i’ll let you know, using my solder, not some she has brought
with her, if the process works at all…But for now, i’kk bet you’d
have better luck with a paillion of good hard solder and clean joints
and a self-pickling flux ( perhaps try cupronil to prevent the
inevitable firescale that will come with copper, or Prip’s because
the TSP in the formula works with the copper to keep the flux from
burning off before the metal ( which has a higher flowing point than
silver) reaches solderable temperature…Cupronil is perhaps the best
product on the market to solder with but much overlooked… and as for
the air space between the domes that is a good thing… though i
rarely recommend a low or easy flow solder, there is one specifically
for copper available at any home depot or lowe’s and some plumbing
supplies, also in a syringe/paste form…but unlike unique solutions,
works every time…and is copper in colour, and has a very high
tensile strength…it runs about 3 bucks a tube…

17

R.E.,

Well, I seriously doubt that Beth is selling something that just
doesn’t work. There’s something we’re both missing. I must admit that
having tried paste, sheet and wire solder, the wire works best for
me. Flows every time.

Brian Corll
Vassar Jewelers

18

Lisa,

You can solder a dome to a flat piece without a vent hole if you are
only going to make one solder join (or a half sphere to another half
sphere, etc.). The problem comes in when you go to put on another
part and bring it to the temperature needed for the melting point of
the solder… that is when you have the problem of explosion. It will
also happen if you let the piece cool down just the slightest bit and
then go back in to make the solder flow, in essence bringing back up
the heat. The “one shot” soldering will work fine for spheres. Just
make sure you do not let the object get cool in any one place and
always keep the temperature steady and hot over the entire object.
It is always safest, of course to have a very small opening in the
seam. “A wee filed nick on the edge of the dome will do” as you
stated in your post. It is a dandy solution to putting a small hole
in the construction.

A great way to leave the very tiniest of holes when doing a closed
or decked form is to put a small amount of antiflux on a very small
spot between the two objects. I do this application with a piece of
26 or 28 gauge wire used as an applicator, don’t get the wire
soaking, but just to hold enough to put on a very, very small amount
of the anti flux. I prefer to use a product called Stop Flow. It is a
wonderful product that keeps the solder off any place you apply the
anti flux. This anti flux is a bit pricey, but worth every penny to
me as it keeps the solder off of any area you do not wish to have
solder finds its way. I use it on patterned metals that are at a seam
so the solder does not flow into the crevasses of the patterned
metal. I generally let is dry before soldering, but that is not a
must do situation. After soldering, this will wash off clean with
just a touch of a soft toothbrush and water, not like the scrubbing
and work when you use yellow ochre powder mixed into a paste. If you
do love yellow ochre, then I suggest mixing it with a bit of olive
oil instead of water as that does come off the metal slightly easier
than when mixed with the water. I still never use yellow ochre at
all, if I can help it; just a personal opinion. I am into easy for
getting off the anti flux. The Mine Shaft in Pompano Beach, Florida
(no affiliation-just happy customer) is where I buy the Stop Flow.
They ship 800-654-3934. The brand they sell is Pro Craft. When you
are soldering two domes together, you can also use a burr to create
the slightest unevenness in a small “u” shape so the solder will not
flow into that space. BUT… if using the hard paste solder, it does
tend to fill in the smallest holes when flowing… that can be
an added benefit in other situations, but not when trying to keep a
small, small opening in a seam.

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

19

David,

1. Wrap the solder containing portion of the syringe in a cloth
soaked in hot water. 

2. Place the syringe on the bench & put a 60 watt light bulb close
to it for a while. The old flexible neck lamps work well. Don't
leave the syringe there too long or the lamp may melt a hole in it.

Great ideas for keeping the paste solder soft and easy to get out of
the syringe.

An idea that works really well for me is to use a coffee mug heater
on the lowest temperature. It keeps a steady low heat source. I do
not keep the solder on there all day, just a short time seems to give
it a warming that lasts a good amount of time. If I am having trouble
getting the paste out of the syringe, I pop the syringe on the
“heater” for a few minutes while I file or fit pieces and then I am
ready to rock and roll. The best part of this suggestion is that the
coffee mug heater is very inexpensive. Sometimes you can find these
at a thrift shop, or when on sale at a local super store or a large
pharmacy chain, they are only a few dollars; works like a charm.

Noel says:

use them this way: I dip the whole piece in borax and alcohol,
then dip the tip of my soldering pick in paste flux, then just
touch it to the paste solder. I scrape off this combination onto
the spot I want to solder-- it will stick like paste solder. Then
heat as usual. The only caveat is that if heated too fast, the
powder can splatter a bit because of the water-base paste flux.

I must credit Noel for letting us know how she uses the powder
solder (quote above). It is a great solution for her applications and
anyone else who needs to use a very, very small amount of solder in
an area that is to be joined with solder. When you are using the
powder with this application, it is prudent to heat the items very
slowly (all over) so that you do not splatter as Noel has described.
Of course, you can use any amount of solder that will be needed to
fill seam, just adjust the amount of the paste flux. I recommend
Handy Flux as it seems to hold up very well with the powder solder
and heat application.

The binder in the paste solder from Unique Solutions is organic and
tends not to dry out as much as other brands. I have one small jar of

65 (medium) and one small jar of #56 (extra easy) on bench. I put

the #56 in the jar from a syringe so that the paste was exposed to
more air on the unprotected surface area in the jar. The #65 was in
the jar already. I have left them on my bench now for 6 1/2 years. I
do have the cap on each, but have done nothing special to the paste
other than putting back on the cap after I had finished using it. I
have left the cap off for extended periods of time, so do not think
it is open grab and cover. BOTH are still as workable as the day they
were manufactured. I test every few months, using a clean toothpick
to get it out of the jar, it is getting to be a smaller amount in
each jar, so I tend not to use this solder except for testing. Still
works the same as the day it was put into the jars. I think that is a
great shelf life. It is now almost a mission to see how long these
will last and still be viable. Will keep you all posted on this
experiment.

Beth Katz
Unique Solutions, Inc.
www.myuniquesolutions.com
Paste and Powder Solder for Jewelers and Metalsmiths

20

Richard,

In the past I have reached that point in soldering a piece where I
know it is not perfect but am scared the whole thing might fall
apart if I try and go for perfection.

Using successively lower melt temperature solders as you build your
piece will of course keep you from too much heat with each successive
solder join. You start with highest temperature melt and flow and go
down in melting temperatures. Some metalsmiths swear by hard, using
that for every join… One of the ways that I prevent a piece form
falling apart is to use the Stop Flow product that I described in a
previous post. It will prevent the solder from flowing… Of
course, if you overheat the piece, you will have it fall apart, but
using the Stop Flow will help to keep the solder joins intact. I put
it on both sides of the solder join I wish not to melt and go from
there. Good luck in your fabrication.

Beth Katz Unique Solutions, Inc.
www.myuniquesolutions.com
Paste Solder and Powder Solder for Jewelers and Metalsmiths