Hi Trevor and Michael,
Hopefully some knowledgeable person (Beth Katz?) will offer up
the secrets of using Hard paste solder with the torch and put us
out of our misery.
Thanks for the vote of confidence.
Unfortunately, over the years, many have bought paste solder that
had a tendency to dry out. Yes, … this is a disaster when it
does dry. It did not work due to the components of the product. The
shelf life was also very short.
f the paste dries out, even for as little as an hour before you
apply the torch the soldering will fail. Based on what I've read
elsewhere here on Orchid there are apparently paste solders that
do not dry out.
The good news… There is a non-drying formula from Unique
Solutions; a silver (or gold) paste solder formula that does not
dry out!!! Imagine that. This formula stays viable for a very
long, long time. I have had two test samples of paste solder on my
bench for over 4 1/2 years. One is in a small jar (plenty of air in
the void), the other is in a syringe. I do nothing special to keep
them viable, I do not even cover they syringe tip. They have not
dried out, so the product is still able to be used. I do use this
sparingly, about every 6 months, just to test the viability of the
paste solder. STILL WORKS just like the day I put them there. The
"old" products that were manufactured years ago has given lots of
people fits when soldering and has also caused some to not want to
try again! Believe me, paste solder works and works well. There are
lots of applications that just beg to have paste solder applied.
There are several descriptions and on my web site of
"How to use paste solder". It is sort of the walk through you
suggested. Check it out so that you can feel more comfortable
knowing that there is a paste solder that works.
After application to the piece and the first heating of the solder,
there will be a small flare up. This, in our products, is normal.
This does not change the viability of our solder in any way. The
flux is all self contained in the paste and does need to flow in
order to get the process started. If you do, however, heat and
heat and heat, you may burn out some of the flux and may have a
problem, not probable but do not overheat to such an extent that it
does happen. Always work in a well ventilated place at all times
when soldering, no matter what products you are using.
You need to make a conscience decision to solder; if you are
soldering silver, to go in with your torch and get the metal hot.
Do not place your torch flame directly on the solder itself or you
may run into a problem with any kind of solder, be it paste, sheet
or wire. One of the “secrets” of paste solder is never go in and
out checking all the time to see what is going on. The more air
you get into the mix the more problems you may have with any
solder. Go in with determination. I am not suggesting that you
overheat your piece, just be aware of what you are doing and commit
to solder that first time you are heating the metal for that
particular part of the operation and then heat the join. It does
take an exceptional amount of heat to burn out the flux in our
paste. Solder will flow towards the heat, use this to your
advantage. If you have heated the metal sufficiently, the solder
will flow directly into the join as you draw the heat over the seam
When using a powder solder, it is imperative that you use a very
heavy duty paste flux (Handy Flux as an example) to stand up to the
heat of soldering; again, if you back off the flame with the powder
solder, you can stand a chance of the paste flux will burn out
giving you a very crusty problem. With powder solder, stay with
the project and come into the project with the idea of a hot and
fast flame (not hot enough to melt the metal) and get it done in
all one application of the torch. Also, practice make perfect in
any skill. It may be a good idea to see how the non-drying formula
of paste solder works. Take a scrap, prepare a seam and go to it.
This will be more than adequate for you to see the advantages of
using paste solder. The many different melting temperatures
available help the jeweler and metalsmith make many soldering
points on any project.
if the joint is not 100% scrupulously clean, failure. It seems
as if the fluxing action of the pasty part of the paste solder is
relatively weak but I'm only guessing.
Paste solder is more forgiving that other flux used with wire or
sheet (pallions). It has more ingredients in order to make the
paste flow smoothly. It holds up for a longer time than a yellow
liquid flux. One thing is that the area to be soldered must be
free of any pickle, as that will not allow any flux to work if that
element is present. If you have any idea that pickle is in your
seam, clean well with a baking soda soak and rinse with clean water
and try again. Good soldering habits must be maintained no matter
what solder you use. If you have lots of contamination, no matter
what products, solder just will not flow. The hard solder formula
also tends to fill tiny gaps. I do not however call it a "filling"
formula, but it does seem to fill in small pinholes.
if you're using some kind of fire scale protector and it flows
into the paste solder, failure. I know from experience that in
the same situations using solder chips instead of paste the
protectant flow would not be a problem.
I have not had any problems using a “normal” fire scale protector
such as boric acid and denatured alcohol. Works all the time. If
some of the other products have given you problems such as Cupronil
or Stop Ox, then simply discontinue use and go to the boric
I have not tried the other products in recent years, so I cannot
speak to the efficiency of their use with non-drying paste solder.
Put that on my list of things to try.
And last but not least, success seems more likely --though by no
means assured -- if you solder on charcoal instead of firebricks.
I'm guessing that the charcoal is sucking up the oxygen and
therefor decreasing the likelihood of oxides forming at or around
the joint when the metals are up to temperature, thus giving the
paste solder's flux less work to do and thereby increasing the
likelihood of success.
I love charcoal for all applications, but I have had no problems
using the firebrick. It is all how you apply the heat of the torch
flame to your project.
Like you I'd like to know what the real story with paste is
because when it actually works it's pretty hard to beat for
overall convenience and applicability. Unfortunately, for me at
least, those successes seem few and far between. I've tried
searching the web for this kind of info and there seems to be
precious little hands-on "this is what you do and how you do it"
info to be found. I do hope that my explanations will be of help
and that you are encouraged to try an organic binder paste solder.
FWIW I know it's been said here before that paste solders are
more suitable for the kiln and furnace than the torch but I've
read enough here and elsewhere to make me wonder if it's really as
simple as that.
When soldering in a kiln, a specific atmosphere must be maintained;
that is not a good alternative for a bench jeweler. It is not as
simple as sticking it in a kiln to solder.
The paste solder works fine, its just investing a little time in
investigating the proper way to use the paste and doing an
experiment or two to see how you can control it yourself in the
application that you are creating. Happy soldering.
Unique Solutions, Inc. Paste and
Powder Solders for Jewelers and Metalsmiths