I just wanted to see if anyone has really compared options. I
guess I amcheap and wondering why not to use borax if it is cheap
and plentiful?
I wrote an article for our local guild on this subject-- here it is:
Gem of an Idea: Fluxes
By Noel Yovovich
We all use fluxes. And we all have at least occasional difficulty
with soldering, and sometimes we have trouble with firescale.
Myself, I keep about half-a-dozen different fluxes on my bench, and
if things are not going well, I’ll try a different one, or use more
than one. My thought process is something like "The soldering
goddess doesn’t like this one today, maybe she’ll be happier with
another one."A while ago, after reading glowing testimonials, I sent
for a free sample of Firescoff, a “revolutionary” new type of flux,
or so they say. The sample was so tiny that I couldn’t finish a
piece of jewelry with it, but it was intriguing because when I
washed the piece after soldering, it was still bright and shiny.
That got my attention!
So when I decided that I would do some actual testing of fluxes,
both for this column and for my own benefit, I ordered a bottle of
Firescoff. It is quite expensive, compared to other fluxes-- $25 for
a 4.25oz bottle. And because you spray it, a lot of that is going to
be wasted. But if it truly lived up to its hype, well, maybe it
would be worth it. My standard flux for several years was borax and
alcohol. I like alcohol flux because the alcohol evaporates or burns
off quickly, so there’s no boiling and bouncing that moves the
solder snippets out of position as so often happens with paste
fluxes. A few months ago, I came across Magic Flame flux, which
comes in a jar as a thick paste and can be mixed with either water
or alcohol.
I now keep a jar of this, with alcohol, as my usual flux, but
recently I have been more and more enamored of the fluxes that are
sprayed on hot metal. If the spray is really very fine, you can get
a very even coating with no gaps by spraying while heating, bringing
the temperature back up between sprays so that the flux dries on
contact. An even coating should mean no firescale, right? There are
many more flux es than I tested, so your favorite may not have been
included. I was reluctant to commit more silver than I already used,
since all of it will just goin the “refine” bucket.
So I apologize that these tests were not more comprehensive, but I
hope they are of some use.I tested:c Magic Flame ™, made of boric
acid, borax, and sodium fluoborate, $12 for 8oz at Rio Firescoff
™, which the company’s web site says “combines a scale preventer,
a high performance non-fluorinated flux [and] a revolutionary heat
activated ceramic spray coating”, $25 for a 4.25oz bottle from
Nventac Cupronil {tm), containing borax, boric acid and disodium
phosphate, $13 for 16oz from Rioand, to round things out,
Handy Flux ™, “contains fluorides, potassium and hydroxide”,
$10.75 for a pound.The first test I tried consisted of soldering a
piece of square wire to a strip of 20g silver that I divided into 4
sections. I applied flux to each section by the preferred method,
covering the other sections when I sprayed. I used hard solder in
all tests, and used a Meco Midget propane/oxygen torch. I was so
surprised by the results that I repeated the same test. The results
were the same. Just to be sure, I did one more, in which I cut four
separate squares of 24g sterling, 3/4" x 1".
My thinking was that this gauge sheet would require less heat and
would be a slightly less demanding test, even with hard solder. I
applied one flux to each, then flooded the backs of four
machine-made bezel cups with hard solder, placed a bezel cup on
each, and heated around the edges of each sheet until the solder
flowed. After pickling for an extended time, I lightly sanded all
the pieces and examined them. The results matched the other two
tests.The worst-performing flux was Handy Flux, which showed
firescale over about a third to half of the surface. Cupronil and
Firescoff did about equally, with firescale on about a quarter of the
surface area. With Magic Flame, there was no firescale at all.
After talking to some other metalsmiths about these results, I did
just the bezel cup test on two more fluxes: purchased Prips (boric
acid, borax and trisodium phosphate, $5.88 for 8oz at Contenti), and
Rio Grande’s My-T-Flux (boric acid and ammonium chloride; $8.50 for
16oz.) The My-T-Flux did pretty well, with firescale on about 10% of
the surface; Prips did badly, with maybe 80%.The proponents of each
of these products have said that with their preferred flux, they get
no firescale, so it seems likely that personal soldering style makes
a difference in the results. If that is true, then my tests may not
apply to you. This kind of test is very easy to try with whatever
flux(es) you have on hand.
Even if you have just one, you can try what I did and look at the
results. Firescale is most visible on a sanded (rather than
polished) surface, especially if it is held vertically, perpendicular
to a piece of white paper. Also, this is a pretty harsh
test"personally, I do not typically do this kind of task with hard
solder. I use hard for soldering bezel seams and not too much else.
So bear that in mind when evaluating these results. If you do any
tests, please let me know how they come out! My conclusions after
this experiment:
The spray bottle used for sprayed fluxes makes a big difference.
Firescoff’s bottle sprays so fine that the spray dries instantly
without getting thick. Cupronil’s sprayer tends to wet the surface
because the droplets are large, and wetting causes beading up and
pulling away from areas.
The flux that is best for hard solder may not be best for other
solders.
Personal style may be a factor in what flux will be the best choice,
so buy a few fluxes and try them. Consider doing a test like mine,
rather than rely on “anecdotal” evidence by just working with the
different fluxes.
Consider switching to Argentium{tm) sterling so the whole question
of firescale becomes irrelevant. Why don’t I? I own pounds of
sterling stock of all sizes and shapes, plus I’m reluctant to learn
new habits, I guess. By the way, I have not put Firescoff to the
test in terms of not needing to be pickled. The claim is that you
can just soak pieces in hot water, and eliminate the use of pickle
solution altogether. This could be very useful in some situations,
especially if heated parts don’t need re-polishing when soldered
with Firescoff. But this test was all about firescale. I will say
that it seemed as though the solder flowed better with Firescoff,
but that is not a scientific result. “Your mileage may vary!”
Joy