Hi, folks,In preparation for writing the my technical column for the
Chicago Metal Arts Guild newsletter, I’ve been testing fluxes. I
soldered silver to silver with hard solder, using four fluxes: Handi
Flux, Magic Flame, Firescoff and Cupronil. I was so surprised by my
results that I did the test again. Then today, I did it a third time,
using slightly less demanding conditions. Each time, the results were
the same. I got pretty much no firescale using Magic Flame mixed with
alcohol. All the rest left LOTS of firescale, with HandiFlux the
worst and the other two pretty much equal. So, what am I doing wrong?
I applied the fluxes in typical fashion-- dipped the Magic Flame,
brushed on the HandiFlux, sprayed the other two on hot metal (both
sides) until well coated. I flooded the back of a sterling bezel cup
with hard solder, placed it on the fluxed square of sterling and
heated around the edges until the solder flowed. I’m pretty
flabbergasted. I expected Firescoff to do best, then Cupronil, then
the other two. If anyone believes they can suggest a fairer test,
please tell me (though I can’t do anything any more scientific than
solder, pickle and look at the results). --Noel
Hi, folks,In preparation for writing the my technical column for the
well, looking at the results is what counts. go with your results
I am surprised…
I have been using Cupronil now for about 2 years and have had NO
firescale. I do make sure I have a good solid coating before I do my
soldering… I used to use Pripps and then tried the Magic Boric Dip
and with both I always ended up with firescale.
Very interesting Noel. Did you do any testing using gold? And where
did your unmet expectations come from? One other question: What torch
did you use?
Have you tried Boric Acid, powder form, and a 90 + % Alcohol, It’s
worked for me for 38 years.
Stephen Wyrick, CMBJ
Have you tried Boric Acid, powder form, and a 90 + % Alcohol, It's worked for me for 38 years.
Yes, that’s what I used before the Magic Flame, and still use where
I teach. I wish I could have tested more types, and maybe I will
yet, but I’m short of silver to throw in the reclain bucket, and my
article is due!
Very interesting Noel. Did you do any testing using gold? And where did your unmet expectations come from? One other question: What torch did you use?
No, didn’t try gold, as I don’t use much of it and could not afford
to waste it in any case… My expectations came from what people say
here, about how great Cupronil is, etc, and also the lovely even coat
I get = applying flux on hot metal with a spray. I thought that had
to mean no fire scale! And, I use a Meco Midget with propane and oxy.
I feel compelled to add-- on most days, my work is not plagued by
firescale. But then, I mostly use hard solder only to solder the
joints in bezels. I did not do a test with medium solder, as I wanted
the harshest “reasonable” conditions. So the results I got do not
mean these other fluxes don’t work in ordinary fabrication work. Once
my article has appeared in the CMAG newsletter, I’ll post it for
y’all to read if you want. Noel
I am not surprised by your results. I think that the difference
between the expectations and the results shows how marketing, habits,
and tradition can affect our thinking.
The fluxes that I would suggest that you add to your test, that I
used to use and recommend (before I switched to Argentium Silver)
are, for firescale prevention and fluxing while soldering traditional
sterling silver: commercially made Prip’s Flux (I used to buy the
commercially made version made by Griffith, who were bought by
Grobet. This flux is now available from Grobet suppliers); Battern’s;
My-T-Flux (Rio Grande’s liquid flux—very similar to Battern’s, but
I like it better); and home-made Prip’s Flux.
Here is how I used to apply these fluxes when I worked with
traditional sterling: Clean the metal with scotchbrite. Brush a bit
of flux on. Heat. When the flux turns white, start alternately
spraying the silver with the flux, and heating—when done
correctly, the metal gets coated white without discoloring. The torch
keeps the metal at a temperature such that the flux turns to white
powder immediately upon contact with the hot metal.
In particular, I am not surprised by the result that Handy Flux was
the worst. When I was an undergraduate, Vickie Sedman, who is now a
prof at Tyler School of Art, was a grad student. She did flux tests,
and told me that Handy Flux creates firescale. I found this
astounding, and doubted it, until I noticed that the firescale
pattern on my silverwork matched the pattern of the application of
the Handy Flux. I have a lot of fun telling this to students—who
generally receive this with similar astonishment and
doubt. Jim Binnion is one of the few people I’ve spoken to about it
who agreed, and already knew it.
While I am on a soap box, I’d like to say this: EVERY flux can be
removed with hot water. Pickle is for removing oxides. It is the hot
water in the pickle that removes the flux. This is why you
occasionally see an etched surface on metal that had thick coatings
of flux in some areas, and none in others—the pickle acts on the
bare surface while the flux covers the other surfaces.
Let us know what happens!
one thing to keep in mind when applying flux is the applicator used:
many use modified acid flux (100 for a couple bucks intended for
plumbing) brushes- modified meaning trimming the bristles to a
reasonable size. The ferrule is aluminum, or at best, brass with
plating of some sort (good sable artists brushes). The metals
affect the flux and reaction when heated…so there are a number of
new very precise plastic break-apart brushes and applicators
available at craft stores, etc. they are one answer to non metallic
ferrules contaminating your applications,also many of the flux
bottles with needle like tips are steel - not-stainless steel which
adds iron into the mix in small amounts- but nionetheless a
contaminanat kids plastic artists brushes can be found without any
metal ferrules- they work however, without the precision of the
break-aparts (some have a wadding tip others a bristle tip and come
in various sizes), a wooden skewer works well too!..rer
a wooden skewer works well too!..rer
I use a wood cuticle pusher from the beauty section of a store as a
flux applicator. One end is pointed (less useful) and the other end
has a diagonal, flat surface with a rounded tip that is perfect for
precision flux application. A baby food jar with a hole (the same
diameter as the wood cuticlestick) in the top of the jar makes a
good container for the flux.
I am not totally surprised by your results. Let me say I would find
it difficult to set up such an experiment in a way as to make sure
each sample is treated in exactly the same fashion, as very minor
variations in conditions can make a big difference in the results. I
have observed in my work that Handy Flux causes severe fire scale
around the perimeter of the flux pool which is in agreement with
your observations. However it is a great soldering flux in that it
really promotes flow of the solder which is what it was designed for.
I am a little baffled about your results with the Cupronil as it
really is only a minor variation on prips flux which I always have
good results with.
Experiment design is a difficult and critical part of setting up
tests like this. With a human in the test it is difficult to have the
kind of repeatability one would want for an accurate comparative
test. I think I would not want to make assumptions about performance
of the various fluxes without doing quite a few tests on each one so
as to average out the variations that are inherent in manual
James Binnion Metal Arts
Experiment design is a difficult and critical part of setting up tests like this. With a human in the test it is difficult to have the kind of repeatability one would want for an accurate comparative test. I think I would not want to make assumptions about performance of the various fluxes without doing quite a few tests on each one so as to average out the variations that are inherent in manual operations.
All quite true, Jim. In my article, I conclude that individual
soldering style probably makes a big difference, and suggest that
people do their own tests of a selection of fluxes, since they are
not ruinous to buy. I am hoping that others will try similar tests
and let me know their results, especially with Magic Flame, since it
worked so well for me.
I am a little baffled about your results with the Cupronil as it really is only a minor variation on prips flux which I always have good results with.
A while ago, I made up a batch of Pripps flux and started to use it,
after having used boric acid in alcohol for several months. I was
using the Pripps as described, ie spraying it onto hot (but not
oxidised) metal. However, I not only got extremely frustrated with
the fact that whatever spray bottle I tried would become blocked,
but also I found that I was getting probably more firestain than I
was prior to using Pripps.
As such I was feeling disappointed with Pripps as a flux, but I
decided to persevere with it and to apply it in a different manner.
I poured the Pripps from the spray bottle into an ordinary container.
What I now do is to heat the metal gently and quickly dip it into
the flux. I then continue to heat it to dry the layer of flux it’s
picked up. Nine times out of ten, the dipping is insufficient to
provide a complete covering and so I use a bristle paint brush to
fill in any gaps.
Initially, when trying the dip and brush technique, I was still
getting firestain and noticed that when the metal was heated,
sometimes the flux layer was bubbling in places, and when the
bubbles burst, the metal was exposed and therefore I was still
getting that leopard skin patchy appearance of the firestain.
So now I spend as long as it takes to get a perfect coating of flux
prior to soldering, with no bubbles, both front, back, inside and
outside of all parts of the piece to be soldered. Starting with the
underneath surfaces, it then gets turned over for the upper surfaces
to be fluxed. Using Pripps and applying it by this method, I am now
getting absolutely no firestain whatsoever. In my case (as has been
said many times before, we all work differently and get different
results), I don’t think the sprayed layer of flux was thick enough
to form an effective barrier and so I much prefer applying it with a
brush and building it up in layers until it’s thick enough to form a
good fire coat. I also find it to be a very good soldering flux too.
A while ago, I made up a batch of Pripps flux and started to use it, after having used boric acid in alcohol for several months. I was using the Pripps as described, ie spraying it onto hot (but not oxidised) metal. However, I not only got extremely frustrated with the fact that whatever spray bottle I tried would become blocked, but also I found that I was getting probably more firestain than I was prior to using Pripps.
I’m a fan of a slurry of denatured alcohol/boric acid instead of
Pripps because I end up with a more even application of boric acid
after the burnoff of the denatured alcohol. I’m interested if anyone
has tried making Pripps (Borax, boric acid, TSP) with denatured
alcohol instead of water? Is it more/less effective? Safe?
I'm interested if anyone has tried making Pripps (Borax, boric acid, TSP) with denatured alcohol instead of water? Is it more/less effective?
I did experiment with doing the boric acid/alcohol thing first
before the Prips as I wasn’t happy about heating the metal (prior to
applying the Prips) without some protection. However, the solder
would not flow whatsoever. I doubt that was anything to do with the
alcohol, which was burned off, but more to do with the fact that I
interfered with the ratio of boric acid. Prips is made up with a
specific ratio and when I applied extra boric acid at the start, I
think it rendered the Prips useless.
I'm a fan of a slurry of denatured alcohol/boric acid instead of Pripps because I end up with a more even application of boric acid after the burnoff of the denatured alcohol. I'm interested if anyone has tried making Pripps (Borax, boric acid, TSP) with denatured alcohol instead of water? Is it more/less effective? Safe?
Borax is not soluble in denatured alcohol so it will not work,
James Binnion Metal Arts
Ive been using a mixture of alcohol, boric, and some luxiflux about
1/4 to the volume of denatured alchohol the luxi is great stuff but
i think its too concentrated as is i hardly ever have a problem with
fire scale my recipe works really well on white gold and all the
stuff i do. I think most problems people have is they dont really
understand thier torch and dont have a feel for the flame and how
the heat eddies and flows and fills up the space around it.
Most people dont see the torch as a diverse instument of beauty. The
torch works with the forces of nature around it and in it. it
depends on physics like a carbureator on an antique engine it will
work beautifully if you have the compromise worked out and pay
attention to what is goingon around the torch not just what you
think you are trying to accomplish with the THING !
Your torch depends on your skill with the solder pick the two things
work together and all of what i am saying will be ignored by those
who are not willing to have the aha… moment.
The solder pick is the most under rated tool at your disposal. I
think most of you people are having so many problems with fire scale
because you dont understand what you are trying to accomplish and
you over heat your metal and you dont use the right solder ! "Y’all
go an git enny ole sawder that sume boddy sales en jist spect it
tuhwerk ! "
Most people have disregarded the use of the solder pick as a tool
but instead consider it a liability because thier solder falls off
or sticks to it they allow thier lack of skills to formulate opinions
and then proceed with those assumptions that a solder pick should
only be made from titanium, and solder should never stick to the
Have you thought about trying different materials to use a a pick???
and adjusting the flame ??? reading or watching the flux as it
performs its function ??? from the sound of this thread most people
think flux is some sort of hooddoo vodoo magic stuff you put on a
project and your problems are solved and then you collect the money
and you get glory in a magazine !!
best regards - goo
However, the solder would not flow whatsoever. I doubt that was anything to do with the alcohol, which was burned off, but more to do with the fact that I interfered with the ratio of boric acid
Think of boric acid and borax as an alloy, though they are not
really. Boric acid has the high melting point, borax is considerably
lower. I’m not going to look up the numbers, though I’m sure they’re
out there somewhere. The difference is at least a couple of hundred
degrees. When you mix the two, you can get a flux that hits a
certain temperature, and the reason we use the boric acid dip is
because it is a coating of the highest temperature. I don’t use
boric acid on silver because II’ve found it’s too hot - it actually
insulates the surface because the solder melts before the coating
does. That doesn’t mean you can’t make it work, and I’m sure some
do. I just found it got in the way more than it helped. Thank god
The difference is at least a couple of hundred degrees. When you mix the two, you can get a flux that hits a certain temperature, and the reason we use the boric acid dip is because it is a coating of the highest temperature. I don't use boric acid on silver because II've found it's too hot - it actually insulates the surface because the solder melts before the coating does.
A little backwards John,
Borax MP 741C / 1365F
Boric Acid begins to disassociate (looses its chemical water) at
170C/ 338F and turns into metaboric acid which melts at 236C /456F
James Binnion Metal Arts
The discussion about testing several anti fire scale fluxed has led
me to make several comments.
First I must admit that I manufacture Cupronil. Because of that I
normally do not comment about Cupronil as I do not feel the orchid
section for comments from members is a place to advertise.
a little history: Early on in the development of Cupronil I learned
that comparing the anti fire scale capabilities of fluxes is very
My partner, a chemist who worked in a crime lab, and I were given
the formula for Cupronil by a noted Hopi Silversmith Laurence Saufki.
He gave me a sample of his flux with the comment it prevented fire
scale when soldering. Being cursed with fire scale when soldering I
said RIGHT!!!. But it did exactly what he said it would. It
prevented fire scale.
My partner felt he could improve on the formula so he would concoct
several batches and give them to me in bottles marked A, B, C etc.
It was my job to test each batch and decide which worked best. That’s
when I learned that it is difficult in comparing the fluxes.
In the early days Cupronil was applied to hot silver with a soft
brush. That in it self took a lot of patience. Too cold and the flux
would puddle. To hot and the brush would stick to the silver.
After MANY trial I was presented with the final three bottles of my
partners concoctions. The one I selected was the exact formula
Laurence gave us.
I learned several things while testing my partners concoctions. If
the coating is too heavy the affect can sometimes be less affective.
I learned that some sheet silver came with a coating of fire scale.
You can imagine how I felt when I tested anti fire scale flux on this
silver. All of a sudden nothing worked.
I learned that Cupronil is not as good of a flux as Handy Flux at
the solder joint. I use just a dab of Handy Flux at the solder joint.
To much Handy Flux will flow from the joint and wash away the anti
fire scale coating producing a terrible ring of fire scale around the
I learned through testing that the various anti fire scale fluxes on
the market all work to varying degrees. I may be prejudice but I feel
Cupronil is still the best anti fire scale flux on the market.
However I think that what ever anti fire scale flux works best for
you is the best anti fire scale flux for you.
There is absolutely no reason for anyone soldering sterling silver
to get fire scale.
Lastly I will say I am very proud of our product as it has prevent
fire scale for many silversmith for at least 34 years.