Technique to prevent firescale?

Jewelry Discussion
21 
What is TSP and prips flux? Details for those of us who missed
this thread.

PLEASE learn to use the Orchid archives. I personally have written
the complete description of all this at least a half dozen times on
orchid, some of them quite recently. My fingers are getting cramped
from all tha typing. The orchid archives go back over the complete
history of orchid list postings. What is it, something like 14 years
now? That’s a lot of data. A gold mine of info. Learn to use it. The
search function will find that for you in seconds, without waiting
for a reply to a question to the list.

Having said that, prips is a formula for flux you mix yourself.
Developed by John Prip in the 60s (or earlier, don’t know), and
widely used in schools since. It’s a moderately good soldering flux
(adequate, not great, but it works OK), but it’s prime use is to
prevent fire scale and it’s evil cousin, fire stain on sterling
silver. Fire scale is the black oxide that forms with unprotected
heating, but which pickles off quickly, leaving a white matte
surface. Fire stain is the discoloring penetrating copper oxide you
find about the time you’re rouge polishing the silver. Looks like
faint cream colored cloudy areas on the silver. Prips flux, properly
used, prevents the formation of both during annealing and soldering
of the silver.

TSP is trisodium phosphate. Commonly used as a cleaning agent. In
prips flux, it serves as a surfactant/wetting agent allowing the flux
to “wet” the metal as it melts, rather than balling up and pulling
away. Used to be widely sold for washing walls prior to painting, but
supplanted by non-phosphate cleaners due to water pollution concerns.
These are often confusingly labeled to look similar, so read product
labels carefully. The real stuff can still be bought, but not quite
so commonly. Cascade automatic dish washing powdered detergent (the
green box) is mostly TSP, and can be substituted, giving a mix called
Frips flux (after Fred Fenster, who came up with the substition when
TSP became harder to find.

The other two componants of Prips are Borax and Boric acid. the
latter is used at a ration of 3 parts, to 2 parts each of the other
two. Mix with water. Spray on preheated metal to form a thin white
crusty coating prior to full heating.

For the full instructions, as I said, read the archives.

Peter

22 
Is the TSP you refer to trisodium phosphate?

yes.

How long can you keep a batch of this?

pretty much forever. if it looses water to evaporation, you add more
water, so it’s fully dissolved. The jug of the stuff I’m currently
using was mixed about five years ago. Still works fine. It doesn’t
degrade.

Are there any special conditions needed to store this?

Not really. I use an old plastic bottle that once contained shampoo
for some, and an old plastic gallon size milk jug for the rest of the
batch… If it holds a water based solution properly, and can be
closed tight, you’re fine. You do want to make sure it’s safe as with
any other chemical that, for example, children or pets shouldn’t be
drinking. Less dangerous than some of the cleaning and detergent
products you probably have around the house, but as I said, you don’t
want to drink it. Not sure what the boric acid or borax would do to
you, but I know what the TSP would do. (think about the stuff they
make you drink to clean yourself out for a colonoscopy…)

Peter

23

How about comparing Cupronil to Pripps Flux? Which one works better?

Thanks in advance!
Vivian

24 
Is the TSP you refer to trisodium phosphate? How long can you keep
a batch of this? Are there any special conditions needed to store
this?

Yes, the TSP is trisodium phosphate. I have read somewhere that
monosodium phosphate of bisodium phosphate can also be used but that
trisodium phosphate is more commonly used. I’ve not yet received the
TSP I ordered so I’m not sure how long it lasts or what conditions
are needed. I’m sure Peter Rowe could answer your questions as he’s
a very keen user of Prips.

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

25

Dear Gerald,

Here is the recipe:

RECIPE FROM THE COMPLETE METALSMITH

2 fluid oz borax
2 fluid oz tri-sodium phosphate (TSP)
3 fluid oz boric acid.

Boil the above ingredients in 1 quart water. Longer boiling makes it
better. The stuff is used by putting it in a spray bottle. Heat the
work but not enough to cause discoloration. Spray the flux on the
part and it will dry. Do this a few times till an unbroken coat
forms.

Apparently it is THE best flux for preventing firestain. There are
products such as Firescoff but they cost quite a lot for a little
spray bottle so it’s much cheaper to buy the chemicals and make your
own Prips flux. The chemicals will last for a good while and are
readily available - at least they are in the UK.

Apparently (and someone else may care to elaborate), borax can be
bought in the form of roach killer and TSP is also sold as some sort
of household product (can’t remember what for) and any extra
ingredients don’t impede the flux’s functionality.

Helen
UK
http://www.hillsgems.co.uk

26

I searched in the Archive for “Pripps”

Article “Polishing small areas” by Peter Rowe

where he reposted his '95 initial post. Helen’s recipe is correct but
Peter gives more and helpful hints about using Pripps,
like what TSP is acceptable. I will continue to look through the 171
references my search pulled up to see if I canfind any more useful
jeanette

27 
RECIPE FROM THE COMPLETE METALSMITH 

2 fluid oz borax
2 fluid oz tri-sodium phosphate (TSP)
3 fluid oz boric acid.

Fluid ounces for dry powdered ingredients? That seems odd to me. If
it seems odd to you too, try 64 grams of each of the first two, and
96 grams of the boric acid. Also in a quart of water. Tap water is
fine. This makes a pretty saturated solution. You can dilute it a bit
more if you like, but then you just have to spray more on. If, after
dissolving it in boiling water, and on cooling, some crystalizes out
again, just add a bit more water to fully dissolve

Boil the above ingredients in 1 quart water. Longer boiling makes
it better.

Unless you mean by making sure it’s all dissolved, I can’t imagine
why boiling it longer would do anything at all. This isn’t ministrone
soup. The ingredients simply need to dissolve, not cook.

The stuff is used by putting it in a spray bottle.

Yes, but most spray bottles use a tiny hole as a spray orifice,
which quickly clogs as flux dries on it between uses. And many spray
bottles don’t give an especially even spray pattern. More effective
are “venturi” type sprayers. These include external mix air brushes,
or the simple “two tube on a hinge” type mouth blown atomizer
sprayers sold in ceramics supply shops to spray glazes. Some folks
have had good results with the type of sprayer/atomizer used for
asthma inhalers, stored with the nozzle under water when not in use
to prevent clogging.

Heat the work but not enough to cause discoloration. Spray the flux
on the part and it will dry. Do this a few times till an unbroken
coat forms.

It needs to dry on contact, not go on wet and then dry. if it does
that, the coating won’t be uniform in thickness, and will tend not to
fully adhere, with more thickly applied areas tending to pull away
from the thinner areas, leaving some bare patches. If this happens as
you heat the metal, just spray a little more to cover the bald spots.

Apparently it is THE best flux for preventing firestain. There are
products such as Firescoff but they cost quite a lot for a little
spray bottle so it's much cheaper to buy the chemicals and make
your own Prips flux. The chemicals will last for a good while and
are readily available - at least they are in the UK.

In my brief tests with it, I found Firescoff to be perhaps slightly
more effective, in that it seems to resist overheating even better
than prips (already good). So it’s a bit more robust in that sense.
And the included spray bottle avoids needing to find something that
will work. But as Helen points out, the stuff is for wealthy jewelers
only, given it’s rather high price. I liked it, but am not, given
it’s cost, at all tempted to switch from Prips. Especially since I
still have a quart of the prips sitting here, and enough chemical to
make several more gallons…

Apparently (and someone else may care to elaborate), borax can be
bought in the form of roach killer

No. Boric acid is sometimes sold as a roach killer. Borax is sold in
the laundry aisle at the grocers. In the U.S., the brand most
commonly seen is Borateem. I’ve also seen it sold as just plain
generic laundry borax.

and TSP is also sold as some sort of household product (can't
remember what for) and any extra ingredients don't impede the
flux's functionality.

In the U.S., at least, Cascade dishwashing machine powdered
detergent is, I think, mostly TSP. Even if that’s not totally true,
it can be used as a substitute. Some reports say it works even better
than plain TSP. I don’t know, not having tried it yet.

Peter

28 
Yes, the TSP is trisodium phosphate. I have read somewhere that
monosodium phosphate of bisodium phosphate can also be used but
that trisodium phosphate is more commonly used.

You read it in one of my old orchid posts, I think. I’ve mixed Prips
up with all three of them, having once had some of the first two from
a chemical supplier. TSP is the most commonly used mostly because
it’s the cheapest and most commonly available.

I've not yet received the TSP I ordered so I'm not sure how long it
lasts or what conditions are needed.

The last time I mixed a batch of prips (five years ago), the TSP in
question was from a box I’d had sitting in the basement for almost
six years prior. It doesn’t degrade. Might get clumped up a bit if it
gets wet, but that doesn’t change the chemistry of the stuff.

I'm sure Peter Rowe could answer your questions as he's a very keen
user of Prips.

Mostly just have strong memories of the way Fred Fenster taught the
use of prips in his classes at the university of Wisconsin, where I
first learned it. I’ve used it since. It’s a bit funny that I seem to
find myself a strong proponant of the stuff these days, since my own
work now is actually mostly in gold and platinum and the like, and
often using a laser welder which doesn’t need flux or fire scale
protection, and I personally only occasionally need to bring out the
prips flux any more. But when I see questions asking how to solve a
problem I had thought most, or at least many people knew how to
prevent 30 years ago, I kind of feel compelled to jump in…

Peter

29

There is a lot of witchcraft out there even in some "Scientific "
circles. Prips is a pretty clean mixture not as much of throw a bit
of everything in as some of these things are.

The recipe for FM that Bea reffences (or another one for FM) is also
in “Enameling on precious metal” by Jeanne Werge-Hartley. Sodium
acid phosphate is considered a toxic pesticide (ant and roach killer
and more) and it was included in several household cleaners at one
time…still?

The FM concoction includes more “stuff” than Pripps and I don’t
think it is a saturated solution.

I can’t justify all the components or the quantities or even how
well it works- it is a real “concoction” Firescoff seems to be just
collodial alumina. This is used for Ceramic shell molds for higher
melting temperature metals. Collodial silica is the normal base for
ceramic shell up to stainless steel temperatures.

jesse

30

I haven’t been following this thread very faithfully but my way of
dealing with heat scale is to work in thick enough metal to be able
to remove it when it happens, as it will always happen. Another
suggestion is to use Argentium which doesn’t heat scale. I have also
had to use low temp solders like Stay Brite when putting a bezel on a
polished surface to avoid the problem altogether.

More ideas,
Sam Patania, Tucson
www.Bahti.com, www.silverhuntress.com

31 
It's a bit funny that I seem to find myself a strong proponant of
the stuff these days, since my own work now is actually mostly in
gold and platinum and the like, and often using a laser welder
which doesn't need flux or fire scale protection, and I personally
only occasionally need to bring out the prips flux any more.

You are the Prips guru Peter, just as James Binnion is the Mokume
Gane guru and Wayne Emery and others are lapidary gurus. :wink: There
are many such gurus on Orchid that we learners look up to - just
don’t fall off your pedestals please!

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

32

Hi Peter,

I quoted the recipe from The Complete Metalsmith because it was the
first succinct recipe that made itself readily available when I
quickly Googled it to answer someone’s query. I was obviously aware
that you had given the recipe many, many times on Ganoksin but
didn’t have the time to route through your many posts on the subject
unfortunately.

Unless you mean by making sure it's all dissolved, I can't imagine
why boiling it longer would do anything at all. This isn't
ministrone soup. The ingredients simply need to dissolve, not cook.

The part about boiling it was still included in the quote I lifted -
which I assumed was taken from The Complete Metalsmith - I don’t
have the book myself, I was quoting someone else who did so I’m not
sure whether that’s Tim McCreight’s advice or the person who quoted
his recipe.

Heat the work but not enough to cause discoloration. Spray the
flux on the part and it will dry. Do this a few times till an
unbroken coat forms.

Again, this was still from the other person’s advice.

No. Boric acid is sometimes sold as a roach killer. Borax is sold
in the laundry aisle at the grocers.

I meant to say Boric acid and don’t know why I said borax - sorry.

TSP is also sold as some sort of household product (can't remember
what for)

I’ve since discovered that it’s used to clean painted surfaces such
as walls, prior to painting.

I think, all things being considered, I should have waited and let
you explain all this Peter! You are clearly a very experienced user
of Prips and I’ve only just had my TSP delivered this morning so
still haven’t tried it. I do get carried away sometimes and should
arm myself with the facts more thoroughly before posting.

Thanks as always for your good advice.

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com

33 
In Sarah Macrae's book "Designing and Making Jewellery", on page
25, she describes a product called FM Solution. This is a firescale
prohibitor.

That recipe ( or another one for FM) is in “Enameling on precious
metal” by Jeanne Werge-Hartley. Sodium acid phosphate is considered
a toxic pesticide (ant and roach killer and more) and it was
included in several household cleaners at one time…still? TSP would
be a suitable substitute.

The FM concoction includes more “stuff” than Prips and I don’t think
it is a saturated solution.

Firescoff seems to be just colloidal alumina. This is used for
Ceramic shell molds for higher melting temperature metals. Colloidal
silica is the normal base for ceramic shell up to stainless steel
temperatures.

34 
Make a mix of boric acid and borax (50/50) and add alcohol. Add
extra Alcohol so the whole mixture can be shaken to mix. Then the
item is dipped in the mixed up solution, taken out and the alcohol
if burned to "stick" the boric acid and borax onto the piece.
Solder away with no fire scale....

Ah, if only this really worked!

Noel

35

This is a firescale preventative solution recipe found in “Enameling
on Precious Metals” by Jeanne Werge Hartley. (the book is excellent)

boric acid 53.2 gm, borax 35.0 gm, sodium hydroxide 3.4 gm, sodium
acid phosphate 35.0 gm, distilled water…75 liter, Teepol 14.2 ml
Teepol is a generic brand name for a UK family of detergents –
which one? I would suspect it would be a non foaming liquid automatic
dishwasher detergent.

It is not a saturated solution and would not build up a protective
layer as easily as Prips.

I can’t rationalize the quantities or the use of the significant
numbers.

it is a concoction.

Jesse
posted on orchid and the enameling forum

36

Boric Acid, powder form, and Alcohol, the higher the proof, the
better it workers as far as how clean you want your inhibitor to be.
Rubbing alcohol has to much impurities in it and will give you a
yellow or orange flame. Speaking of flame, - if you light or ignite
pure or high percentage alcohol, you may not see the flame under your
lights and your lamps may explode or you may reach across it and burn
the “H” eck out of your hand or arm.

It is the greatest but please be very careful and "know your stuff
about chemicals and hazards. Also, depending on the amount of heat
you need to do the job, this solution may serve as a flux and if not
just put a toothpick drop in the slice or joint and brush flame it
until it is dry and then put the blue to it. Moving to close to the
boric and alcohol to fast will cause it to roll back to a cooler
spot before you melt the powder or liquid

The Stephan

37 
You are the Prips guru Peter, just as James Binnion is the Mokume
Gane guru and Wayne Emery and others are lapidary gurus. ;-) There
are many such gurus on Orchid that we learners look up to - just
don't fall off your pedestals please!

No, not the guru. I’m a parrot regarding this subject. I didn’t
develop it, didn’t improve it, and am hardly the only one who knows
about it. I just seem to be the most prolific typist repeating it
when people have asked. Mostly, I’d chalk that up to amazement at how
often people haven’t happened to run across this already.
It’s always seemed to me that so many college art programs have
taught the use of the stuff for so many years that the info should be
relatively common knowledge. But of course, that set of people
doesn’t include the commercial jewelers who didn’t happen to learn
the craft at an art school, nor does it include all those who are
teaching themselves, since most of the books about jewelry making,
seem (oddly) to give the whole subject of fire scale and fire stain
kind of passing notice, often just in an appendix. This, lacking a
teacher to mention it and make sure students understand that this is
a pretty basic technique not to be ignored, means the self study
learners miss it, and instead, often find themselves trying to solve
the problem by reading product listings in tool catalogs, where of
course they don’t find this at all…

But thanks for the thought. Still, please try to avoid putting any
of us on tall pedestiles. It’s hard to balance on those things. We’re
all just fellow craftspeople. Some of us have been doing it longer,
and have refined our skills a bit. That makes us useful to those who
need advice and guidance, but this is just sharing of
Nothing mystical. Unofficial teacher, perhaps if you like. Guru? No,
I don’t think so.

cheers
Peter

38

Rio sells a product called stop Ox II it is also a flux, I dip my
entire piece into it then run a flame over it and it gets a nice
protective coating if you get very hot or are heating for along time
you can dip again during the job. But I have found it works pretty
good. In the old days we just used boric acid and methyl alcohol and
dipped the piece into it then ran the flame over it and the alcohol
would burn off then go ahead with the solder.

Good luck… Frankenstein

39 
Unofficial teacher, perhaps if you like. Guru? No, I don't think
so.

I know what you’re saying and the guru comments were said with an
element of tongue in cheek.

You’re right. The books I used to teach myself didn’t mention
firestain. They just talked about the black firescale that’s removed
with pickle.

I’ll be mixing up my Prips today.

Helen
UK
http://www.hillsgems.co.uk
http://www.helensgems.etsy.com