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Hard soldering sterling silver


#1

Hello Everyone,

Thank you very much for all your advise re: my soldering question!

I just have one question which might make me a bit clearer on the
subject.

Initially, I was using a 1.5" to 2" inch flame (little torch
propane/oxy) to try to solder 2 small pieces together, with no
success. (5mm by 20mm, and a strip of 2x1mm rect wire on top)

One of the suggestions was that I was not getting my piece hot
enough, and that I needed a bigger flame.) I adjusted my flame to
be 4"-5" inches long (trying to get a bigger, softer flame), and
this seems to be working better…

Also, to use a solderite board, instead of a charcoal block.

Also, to use firecoat in addition to paste flux, which seems to be
helping

So, my question is:

When I was using the smaller flame, my piece would get glowing red,
and the surface would sometimes shimmer like liquid…so, if my
smaller flame was getting the metal hot enough to melt (the
surface, at least), why was it not hot enough to flow the solder
thru the join? The solder did flow, but only around the join, not
thru it (between the 2 pieces)…

I was wondering if it was because the smaller flame put the hot blue
cone nearer to the metal, so that the surface got intensely hot,
but the whole metal mass did not?..I was just trying to think
it thru to understand what was happening…I am trying to
improve my skill at thinking things thru to figure out
situations…it is a constant challenge!

I was also wondering if maybe the firecoat helped to keep oxidation
away from between the 2 pieces…but why did’nt the flux do
that?..(I am still trying to figure out why it appears that there
is flux residue between the 2 pieces…

Just wondering about it all…

Thank you,
Julie


#2

Julie,

It is difficult to answer your questions without having seen your
set up and technique but I will try.

One possible reason the solder did not flow even though the piece
was “hot and shimmering” could be that when using a small flame it
takes longer to heat the metal. This results in the solder itself
becoming oxidized (if not the metal which will also oxidize). Use
the old computer adage ‘garbage in - garbage out’ but in this trade
its, ‘get in - get out’. The longer you have your heat on the
pieces, the more likely you are to get firescale.

Next, there is the possibility that you were heating the locale
around the join but the rest of the larger piece was eating the
heat! You should use as wide a reducing flame as you can and heat
the entire piece before moving the flame tip near the join being
soldered. Always identify the largest piece of those being
soldered…this is the sink. It should be heated first. As it
heats, it will transfer the heat to the smaller piece and the
solder. When the entire set up reaches the proper heat, the solder
will simply transfer and flow through the join. Try to keep the
flame away from the solder! The solder has a higher copper content
than the SS and will oxidize more quickly.

You use two kinds of flux when soldering. The first, which is
applied before setting up the pieces, is a ‘protective’ flux. It
helps preclude firescale by forming a protective glassy layer over
the broader areas to absorb and/or reflect excess oxygen. The
second flux applied directly to the join area is a ‘wetting’ flux.
It ‘wets’ the metal where it is applied, cleans it and facilitates
the flow of the solder. Sounds like you are now getting the
idea…keep trying.

Cheers from Don at The Charles Belle Studio in SOFL where simple
elegance IS fine jewelry! @coralnut2


#3
I was wondering if it was because the smaller flame put the hot
blue cone nearer to the metal, so that the surface got intensely
hot, but the  whole metal mass did not?......

Julie,

I think you hit it right on the head here. The best thing to
remember is you cannot force solder to flow. You need to heat the
metal so it “takes” the solder. Silver makes it a little more
difficult than gold because it is such a good conductor.

Mark


#4

Julie,

In order to solder or fuse Standard Sterling Silver you need to
evenly heat the pieces being joined. This generally requires a larger
brush like flame. Deox and Argentium Sterling require different
procedures.

If you are using a short flame it is possible that you were
concentrating the heat to a small area and in doing so may have been
oxidizing the metal where the pieces meet.

If you are fusing the metals you will want the metal to become
bright and liquid looking but since solder will flow at a
temperature lower that the melting point of the metal you are
soldering, you are allowing the metal to become too hot if it is
looking fluid at the surface.

Make sure you have a good firescale coating and flux the items to be
soldered together. Use a flame size that will allow you to heat the
metal evenly.

Good Luck
Greg DeMark
Longmont, Colorado
email: greg@demarkjewelry.com
Website: www.demarkjewelry.com
Custom Jewelry - Handmade Jewelry - Antique Jewelry


#5
    One of the suggestions was that I was not getting my piece hot
enough, and  that I needed a bigger flame.)  I adjusted my flame
to be 4"-5" inches long  (trying to get a bigger, softer flame),
and this seems to be working  better.... When I was using the
smaller flame, my piece would get glowing red, and the  surface
would sometimes shimmer like liquid.......so, if my smaller flame
was  getting the metal hot enough to melt (the surface, at least),
why was it not hot  enough to flow the solder thru the join?  The
solder did flow, but only  around the join, not thru it (between
the 2 pieces)..... 

Your solder should flow just after the silver reaches a dull red.
Glowing red that produces a shimmering look is too hot. You’ve
actually “depletion gilded” the piece so that there is now a thin
layer of fine silver (no longer sterling) at the surface, and that
changes things (like soldering temperature). It also explains why
you’re getting better results with the softer flame.

Are you bringing all of both pieces up to soldering temperature at
the same time? With skill and experience, you can "spot solder"
somewhat with sterling, but you really need to concentrate on
bringing the entire mass of both pieces up to temp simultaneously.
Make sure you dim the lights so you can see the silver reach the
dull red it needs to be. With too much lighting, it may look the
right color, but it is probably too hot.

    I was wondering if it was because the smaller flame put the
hot blue cone nearer to the metal, so that the surface got
intensely hot, but the  whole metal mass did not?... 

Not to put too fine a point on it, but you are the one who puts the
flame nearer the metal, not the smaller flame, itself. Adjust your
oxy/fuel ratio for as large a flame as you need without a hissing
sound. This is known as a reducing (low oxygen) flame. Some call it
a large, brushy (or bushy) flame. Sometimes with large pieces of
silver, this isn’t hot enough, and you’ll have to pour on the oxygen
a bit more. Experiment with moving the flame closer to and further
from the metal, as some parts of the flame are hotter than others
(another element of torch control). Flame size matters less than
torch control, but you do need a flame large enough to bring the
entire piece up to temperature. Torch control is a technique that is
extremely difficult to describe. It can be demonstrated, but is best
learned through personal experimentation, and different techniques
are required for different soldering operations.

Also, a flame that is too hot, or applied for too long will burn off
the flux and render it useless. Once you’ve gotten the solder to
flow, longer exposure to the flame will raise the flow temperature
characteristics of the solder, and it will not flow until the
melting point of the silver. Get in, and get out quickly with your
flame. Use a solder pick (I use titanium) to spread the solder
across the join once it has flowed. You can’t always rely on the
solder to go exactly where you want it. If the solder doesn’t flow
shortly after the pieces reach a dull red color, chances are you’ll
have to start over: Pickle, clean, mate the join flush, firecoat,
flux, place solder, heat.

    I was also wondering if maybe the firecoat helped to keep 
oxidation away from between the 2 pieces.......but why did'nt the
flux do that?.....(I am still trying to figure out why it appears
that there is flux  residue between the 2 pieces... 

The firecoat does help keep oxidation from the two pieces, as well
as cleaning them off. Also, the firecoat actually is a type of flux.
I don’t remember if you mentioned in your original post that you
used your own self-made flux, but that could be why it didn’t
protect from oxidation. My favorite commercial flux is Prip’s, which
you may want to try. Battern’s is also very good, and there are
others. If there is flux residue actually between the two pieces,
you haven’t filed/sanded enough to mate them properly. While solder
actually can fill SMALL gaps (it really can, despite what you’ve
read) it’s not easy to do, and weakens the piece. Pay close
attention to the fit of the join you’re trying to make.

Thanks for letting us know how you’re coming along. I, for one, like
to know if my suggestions have helped anyone. Keep it coming.

James in SoFl


#6

Thanks to all the tipsters on this subject, especially James in
SOFL. I have tried Batterns, but because of the surface tension it
just lays there and is very difficult to spread effectively. Maybe
I’m doing something wrong. I’m inspired to try Prips, but wonder if
it has the same problem.

Allan Mason
www.silvermason.com


#7

Allen

Remember, Batterns is a wetting/cleaning flux. It is not meant to
cover the entire piece in a protective manner. The flux James is
talking about, boric acid in alcohol or Prip’s are intended as
protective fluxes and are meant to spread over broad areas to protect
against fire scale.

If you look in the Orchid Archives, you will find some indepth
discussions about the properties of each. James Binion has done a
lot of research on the heat properties of borax vs boric acid and
shared that with our forum. >From what he has provided and from my
own research, each medium provides specific protection in different
heat ranges. That is why I teach my students to use Prip’s flux and
why I myself changed quite some time ago from boric acid to Prip’s.
But its up to each individual to use what gives them the best
result.

Batterns or pure borax fluxes are intended, as I mentioned in a post
a day or two ago, are used to specifically wet/clean only the area
of the join. Thus, it is supposed to just lay there and not spread.
First you use Prip’s (or boric acid if you wish) on the whole piece
to protect it, then you apply Batterns or borax just to the join to
clean and wet it so the solder will flow and fill.

Hope that clarifies. Cheers from Don at The Charles Belle studio in
SOFL where simple elegance IS fine jewelry! @coralnut2


#8
     I have tried Batterns, but because of the surface tension it
just lays there and is very difficult to spread effectively.
MaybeI'm doing something wrong.  I'm inspired to try Prips, but
wonder if it has the same problem.

Keep in mind that the primary role of Prips flux is to protect the
metal from fire stain and fire scale. It works as a soldering flux
as well, (better, on silver, than batterns sometimes, since by
better preventing fire scale, it removes one possible impediment to
solder flow). but it is not as active a flux as the fluxes
specifically sold as silver soldering fluxes. This is part of why
it’s effective at protecting the metal. It does not burn off
quickly. I often find, with difficult solder seams, that the
addition, after the prips has been applied, of a SMALL amount of one
or another of the white paste fluxes sold for silver
brazing/soldering can increase the apparent ease with which the
solder then flows. Use too much, and it then spreads out, and you
end up with fire scale near and around the joint, often where it’s
hardest to clean up. But a small amount, right at the joint, can
help.

But as I think others have pointed out, the most important factors
in good silver soldering (or with other metals as well), are the
proper fitting of the joint, and proper heat control. Without those,
no flux or solder choice will give you a good joint. Both sides of
the joint, must be at the proper temp for solder flow. If either
side is too cool, or too hot, the solder flows just to the heat and
away from the cool side. Often, the hardest part about a soldering
operation is figuring out how to control the torch so that a larger
heavier piece of metal, which often is also the harder one to reach
with the torch, can be heated sufficiently without overheating a
smaller piece of metal sitting on top. Supporting the work up on
pins, cotter pins, nails, a screen, or by slotting the surface of a
soldering block to allow a flame directed at the sides of the piece,
to travel underneath the work, coupled with moving the flame rapidly
over the work, around the sides (and therefor underneath), and back
over the top, is often the required technique. Just pointing the
flame at the joint and waiting for something to happen is a good way
to watch the smaller piece of metal on top melt to a blob while the
larger sheet to which you were trying to solder it, just sits there.
It’s a bit of a dance. Watch the fluidity and clarity of the flux to
help judge the temps (prips helps with this, since it totally covers
the whole piece when used correctly)

Peter


#9

Try Easiflo flux that the plumbers use and which is recommended for
all silvers and golds by Johnson Matthey.

I use the powder form and add it with the (heated) soldering pick.
Very effective. It has to be if plumbers can hard solder copper in
crazy situations.

Use with good ventilation taking the fumes away from your face.

Brian
B r i a n A d a m
e y e g l a s s e s j e w e l l e r y
Auckland NEW ZEALAND
www.adam.co.nz


#10
    Thanks to all the tipsters on this subject, especially James
in SOFL.  I have tried Batterns, but because of the surface tension
it just lays there and is very difficult to spread effectively. 
Maybe I'm doing something wrong.  I'm inspired to try Prips, but
wonder if it has the same problem. 

You’re welcome, Allan. I suggest you do try Prip’s. I also suggest
you try every commercial brand you can get your hands on. I
recommend you try paste flux, as well. Try paste solders with
built-in flux. Powder your solder with a file and use every flux you
have on hand. Experiment, and see what works best for your
applications. Sure, it costs a bit, but I’m not saying you should
drop a wad of cash immediately. Just have fun.

James in SoFl


#11

Allan,

Try white paste flux from welding supply, I have used this for my
gold and silver soldering for about 30 years…because it works. I
usually don’t even wash metal to clean it, cause I am lazy. I just
rub the flux over the surface with my finger if it won’t coat evenly.
Occasionally I have to pickle and reflux and reheat to get the solder
to flow somewhere it would not.

You need to thin it down a bit because it is too thick the way it
comes.

Richard Hart


#12
... I also suggest you try every commercial brand you can get your
hands on. ... Experiment, and see what works best for your
applications. 

I enthusiastically second James’ advice. I’d suggest you might want
to try mixing your own fluxes and firescale protectants too. That’s
what I did a few years ago and was pleasantly surprised to find that
one of my home-mixed brews served me better than anything I’d bought
off the shelf.

Erhard Brepohl’s book “The Theory and Practice of Goldsmithing” is a
great book and it has got a few sections on the basic chemistry and
recipes of fluxes. It’s all described in layman’s terms too so you
don’t need a Chemistry degree to understand what he’s talking about
and why it all works the way it does. The home-mix recipe I mentioned
above is one of his (page 300).

If you do decide to try a bunch of commercial mixes it can be
worthwhile to look offshore to see what other companies offer. Things
seem to be done a little differently in each country and sometimes
that can make a pleasant difference in your bench work. For instance
I’ve recently started using a pre-mixed “just add water” flux from
Thessco in the UK and found it to be the best I’ve seen so far for my
work in Argentium. Don’t know why but it works great for me.

It’s easy to forget that as metalworkers we are also amateur
alchemists too, whether we like it or not. I say embrace that and run
some tests. The results can be well worth the time spent.

Cheers,
Trevor F.
in The City of Light


#13

Lots of great flux advice! Thanks! I will try Prips. I normally
use a paste flux because I do a lot of heavy sweat soldering, mostly
on bracelets. I “paint” it on the components before assembly and
soldering. This process requires lots of heat and I’m not always
successful. Probably just shoddy technique. I recently got some Magic
Flame paste flux, thinned it with water as instructed, but the result
was the same as with the Batterns- it just beads up and doesn’t
spread. I haven’t tried mixing it with denatured alcohol, though.
Always looking for something easier/better!

Allan Mason
www.silvermason.com


#14

Re: surface tension with flux.

I think you’ll find that using the boric acid/denatured alcohol
firecoat/flux solution deposits a bit of the borax onto the metal
after you burn it dry (you’ll see a bit of a powdery layer on the
surface). That coating virtually eliminates the surface tension you
described and will allow any other liquid flux you use to spread over
the entire piece. Again, keep the firecoat separate from your
soldering area, dip into the firecoat, replace the lid tightly before
burning, place solder, flux, have fun!

James in SoFl


#15

I have found if I am brazing the paste works well on silver. You
might try the green flux for the silver bracelet.

Andy " The Tool Guy" Kroungold
Tool Sales / Technical
Stuller Inc
Phone 800-877-7777 ext. 94194
Fax 337-262-7791