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Tricks on dealing with fire-scale

Okay, Okay… I know we have all had fire-scale problems in the past
but I seem to be running into them more lately because I have been
using multiple layers of very heavy gauge metal for some new pieces I
have been working on. Usually if I get a little fire-scale I use
bobbing compound to get rid of it and this has worked well for small
amounts. However, I am running into much larger amounts in these new
pieces and it is taking forever to remove it with bobbing compound.
In addition, the bobbing compound is removing the chasing that I put
onto the pieces. I have searched high and low for a good
anti-firescale solution and I keep finding articles that mention
Prips flux. I pulled the recipe and tried making some but I don’t
think it has turned out right. I desolved the boric acid, borax, and
tri-sodium phosphate in boiling water. It looked good until the next
day when I went to use it the solution had crystallized. Has anyone
had experience making and using this solution? Does it really work?
Any tips or tricks on dealing with fire-scale would be much

Thank you,


I raise silver and my favorite method for dealing with firescale is
to use liquid blue gas flux. I just paint it onto all surfaces and
let it burn off while I anneal. Rio also sells something called
Cuprinol that works very well. This you spray onto your piece before
soldering and annealing.

Ventura, CA


You didn’t mention if your are using any fire scale flux on your
projects. From you post I assume you are not using an anti fire
scale flux. If you are you would not be getting fire scale on your
smaller project. If you use the the same size torch tip on heavier
projects you will have to heat the metal longer. The amount of fire
scale that forms on sterling will depend on how long you heat the
metal. The longer heating period the heavier fire scale.

If you are using an anti fire scale flux and are still getting fire
scale you may be heating the metal for too long a period of time
which will cause the flux to break down. The anti fire scale flux
will work for a period of time than it will start to break down and
fire scale will start to form. The longer you heat sterling with out
the protection of an anti fire scale flux the heavier the fire scale
will be.

Prips flux will not work better than any of the commercial products.

Use a commercial anti fire scale flux,a bigger torch tip and heat
for a shorter period of time. To prevent heating too long you may
have to solder in steps. Be sure to coat all the metal, front and
back, with the anti fire scale flux.

I do manufacture Cupronil. This post is not intended to be an
advertisement for any commercial flux. What ever you do use some anti
fire scale protection. With proper fluxing and heating we should be
able to eliminate that $#%^@#)_*&%@!^& cursed fire scale.

Lee Epperson

Re Firestain.

Jeanne Werge-Hartley’s excellent reference “Enamelling on Precious
Metals” provides a recipe for “FM Solution”, a similar solution, in
my understanding, to that of Prips flux.

I trust that I am not infringing her copyright and would recommend
any enamelling “orchidist” who does’nt already possess the volume to
sprint off to your nearest good bookstore and seize a copy.

The FM solution has worked for me exactly as specified in her
reference, most particularly in its ability to “rinse clean” in water
leaving no borax glass residues and completely eliminating any
appearance of firescale on sterling pieces with cross sections up to
5mm thick and 270mm wide. These have usually been fired at the 830-
850 celcius range.

Her book states " It is essential to be accurate in measuring these
ingredients", an instruction I followed to the letter.

FM Solution.

Boric acid 53.2g
Sodium acid phosphate 35.0g
Sodium hydroxide 3.4g
Borax (powder) 35.0g
Distilled water 0.75 ltr
Teepol - 14.2 ml (teepol is an English liquid dishwashing detergent,
I substituted with an equivalent new Zealand product without any
apparent problem)

" Mix all the chemicals together with the teepol and distilled water
in a litre container and shake gently until dissolved. The distilled
water can be added lukewarm to assist the mix".

“The metal must not be highly polished; the surface should be
slightly matted with fine garriflex or fine emery paper. Paint or
spray the surface with the solution and allow to dry for maximum
effect. The solution should always be clean so, to ensure this, it is
best to work with small amounts and replace it frequently”.

While my use of it has been primarily aimed at preventing firestain
during the kiln firing of the enamels I have found it to be equally
effective in firestain prevention during torch soldering operations.

In my experience it does function as a flux and will encourage solder
flow, sometimes into unwanted locations, to prevent this I simply
wait until its dry and circumscribe the solder area/seam with a soft
lead pencil to inhibit.

I had wanted to order this and try it but had to go with only
essentials this time.

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Silver & Cameo Heritage Jewelry

It really works, the problem that most people have is that they are
not using the right chemicals. Also the formula is in Opie’s book and
is not called Prips.

The right chemicals are.

60 grams borax.
90 grams boric acid.
60 grams TSP (regent).

If you only buy TSP at the local paint store it is not regent and
will not work.

Also you will only have to heat the chemicals in one quart of water
until dissolved.


We have switched over to Rio’s Stop-Ox it works as good or possibly
even better than Prip’s but stays in solution. We use it just like
Prip’s heat the metal, spray on to develop a coating over the entire
piece. Works like a charm.


James Binnion
James Binnion Metal Arts


I always use Stop-Ox (from Rio Grande). Almost never have firescale.

J. S. Ellington

60 grams borax.
90 grams boric acid.
60 grams TSP (regent).

I have never made any Prip’s because I don’t like water-based
fluxes-- they either have to be sprayed on a hot piece, or they boil
and move the solder chips around. I have long used just borax or
boric acid and alcohol, and more recently, “Magic Flame”, which you
can mix with either water or alcohol.

Has anyone ever tried making Prip’s using alcohol instead of water?
I suppose it would not dissolve-- but neither does the stuff I’m
using now!


Has anyone ever tried making Prip's using alcohol instead of water?

I use a combination of two… First I coat with boric acid/alcohol
mixture and heat then I spray on cupronil. I do a lot of overlay so to
prevent the pieces from ‘jumping’, I heat the cupronil until it is
clear and then apply my elements and solder I never see firescale!


Marilyn O’Hara Studios

The best way to use Opie’s formula that I have found is, heat your
silver to straw color and dip it into the mixture, the reason is that
any oils from handling will be burnt off, I happen to use blue flux
and make all of my solder wire into 1/4 to 1/2 to 1/3 circles, this
way they do not move as much and will stay in place when heated.

Have a nice day.


I have never made any Prip's because I don't like water-based
fluxes-- they either have to be sprayed on a hot piece, or they
boil and move the solder chips around. 

Noel, why not place your chips or, better yet, balled up solder on
the predryed flux? With no water left to boil out, the solder stays
where it is put.


Firescoff[T] is a revolutionary heat activated ceramic spray

This stuff looks very intriguing, but I hate the idea of a spray-
too much waste and mess from the overspray. Has anyone had luck with
another method of application such as brushing or dipping ? Thanks!

Allan Mason


I mix boric acid and borax with denatured alcohol and it mixes. So
why wouldn’t adding the TSP work? Does anybody out there know the
answer? It would certainly make an nice difference with the Pripps.


I plan on trying dipping myself don’t want to spray and waste it
either at $10 a bottle lol

Silver & Cameo Heritage Jewelry


I use a combination of two... First I coat with boric acid/alcohol
mixture and heat then I spray on cupronil. I do a lot of overlay so
to prevent the pieces from 'jumping', I heat the cupronil until it

The pieces in the collection I am working on also have a lot of
overlay. Sure does take a lot of heat to heat up a layer of 16 gauge
and 18 gauge to solder together. My pieces are about 2 inches long
and 1 inch wide. I looked at your pieces and they are beautiful. Do
you use the cupronil as a flux with the boric acid/alcohol. I am
going to sound a little dumb for a second but I thought the boric
acid/alcohol was the flux. I don’t know anyone who works in silver
who uses boric acid/alcohol. I think I like your solution and will
give it a try. My supply store told me that the boric acid/alcohol
does not mix well and has to be stirred before every use. Is this
correct? Currently I have only been using dandex and wishful
thinking ; )


I don’t know anyone who works in silver who uses boric acid/alcohol.

This is what I have used for years. After all the posts here, I began
to think I was missing out on something, and have tried some other
fluxes. A lot of people use borax and alcohol as a “fire coat” on
the whole piece, then add another flux to the joint. I do this
myself with gold-- sort of a “belt and suspenders” approach.

Yes, you have to stir the b/a mix every time. I just stick the piece
I’m fluxing down in the container and stir with it-- voila! I bought
some “Magic Flame” flux that you can mix with either water or
alcohol, and did the latter. Guess what? Gotta stir it every time. I
can’t really say it works any better than the plain b/a.

I have Cupronil, Handi Flux and Batterns on my bench as well. I use
the paste flux when I use powdered solder (stick the tip my
soldering pick in flux, then in the jar of powder, to pick up just
the right amount of solder. I like this better than paste solder,
which makes smoke when you heat it), Batterns in a bottle with a
steel needle when I need to add a tiny drop in one spot, especially
on hot metal, and the Cupronil spray when things aren’t going well
and I’m worried about firescale.

These things don’t cost much, so I say buy 'em and try 'em!