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Removing firestain


#1

I have heard it’s possible to remove firestain without sanding. I’ve
got a piece that has very delicate imprints on it and only at the
last stage of polished the cursed firestain appeared in a tiny
corner of it, is there any way I can fix it? Incidentally I’ve had no
success keeping firestain away with Firescoff, what do other people
think of that product?

Anna M Williams
www.annamwilliamsjewellery.com


#2

Anna, is this a white metal? ;Sometimes what you can do is get a
thicker mix of boric acid and denatured alcohol and heat of the piece
somewhat…not to red just hot. let it cool and then pickle in strong
pickling solution…See if that helps.

Russ
www.thejewelrycadinstitute.com


#3
I have heard it's possible to remove firestain without sanding.
I've got a piece that has very delicate imprints on it and only at
the last stage of polished the cursed firestain appeared in a tiny
corner of it, is there any way I can fix it? 

Technically you can remove it without sanding by using an acid
bright dip etch, but what that does is remove all the surface of the
metal not just the firestain. It is not a good way to go it requires
very strong acid solutions and careful chemistry control to get a
bright etch rather than a matte surface not to mention all the silver
lost to the process. Your best bet is to plate the piece with silver
to hide the problem, and next time use prip’s flux or Cupronil or
Rio’s StopOx II as a fire coat, any of which will give as good a fire
stain resistance as is possible to get.

James Binnion
James Binnion Metal Arts


#4
Incidentally I've had no success keeping firestain away with
Firescoff, what do other people think of that product? 

I ordered Firescoff when it first came out. The first day I got it,
I used it in accordance with the instructions, and got very good
results. The second time I went to use it, the Firescoff had
crystallized in the bottle. I had to stop and heat the bottle for it
to spray effectively. I wasted a lot of Firescoff getting it to flow.
And this problem has kept up. I no longer use it as it is too time
consuming to get it to work right. And it is far too expensive
to use with all that waste involved…Teddy


#5

Ann,

Some enamellists use Scalex, which is a firestain remover for copper.
Perhaps it also works on silver, I do not know. I heard good things
about it. You paint it on and after heating it basically falls off.
You can buy it a bit everywhere - Thompson enamel etc, it isn’t
expensive.


#6
I have heard it's possible to remove firestain without sanding.
I've got a piece that has very delicate imprints on it and only at
the last stage of polished the cursed firestain appeared in a tiny
corner of it, is there any way I can fix it? Incidentally I've had
no success keeping firestain away with Firescoff, what do other
people think of that product? 

Firestain as you know, penetrates the metal surface so some means of
removing that whole surface layer is the only way to remove it. When
it shows up at the final stage of polishing, what you’re seeing in
that corner is not the firestain, but where you’ve cut through the
firestain to clean silver underneath the firestain layer. If you can
polish the piece without cutting that deeply into the surface, even
though the surface if a fire stain color, it’s uniform, so you don’t
notice it.

One potential solution, rather than trying to remove the firestain
is instead to give the piece a uniform fire stain finish. This was a
traditional solution by the famous silversmithing firm of Georg
Jenson, for example. Take the piece to a state of final rouge polish,
but pay no attention to fire stain. Now get it VERY clean, and with a
soft gentle flame, anneal it and pickle it without any firecoat
protection. Now, very gently repolish off the pickled white finish,
but don’t cut so deeply into the surface that you penetrate the fire
stain. Because you previously removed all scratches and surface
defects, it now needs barely any polishing beyond what’s needed to
restore the rouge shine, so it’s possible to not cut through the
firestain layer to the clean silver underneath. That will look fine.
Note that this surface will take a patina slightly differently from
clean silver. And if you remove excess oxidation/patina with
buffing, you still have to be gentle not to go through the firestain
layer.

But by far the easiest way to deal with firestain is simply not to
get it in the first place. Prips flux is cheap to make, and works
well. So does cupronil, or stop-ox. All are far cheaper than
firescoff. I’ve had decent luck with firescoff the couple times I
tried it, but I don’t happen to have an excess of first born children
with which to pay for the stuff. Way to costly, and doesn’t do
appreciably more than the already fine results I get with Prips.
Check the Orchid archives for more info on Prips. It’s been written
up by me, and others, many many times over the last fifteen years.
(Has it been that long? Sheesh. Maybe it was only 14…)

Cheers
Peter Rowe


#7
Incidentally I've had no success keeping firestain away with
Firescoff, what do other people think of that product? 

If you look in the archives, you should find a longer post I wrote a
while back-- I did a side-by-side test of several fluxes, including
Firescoff. To my surprise, for me, in my test, it didn’t do all that
well. Magic Flame works best for me. But I love the super-fine mist
the Firescoff bottle sprays, and use one now for Cupronil. And for My
T Flux. I like to have a bunch of fluxes. As I’ve said before, if the
soldering goddess doesn’t like one, on a particular day, maybe she’ll
like another, or a combination.

Noel


#8
Some enamellists use Scalex, which is a firestain remover for
copper. Perhaps it also works on silver, I do not know. I heard
good things about it. You paint it on and after heating it
basically falls off. You can buy it a bit everywhere - Thompson
enamel etc, it isn't expensive.

Scalex is not a fire stain remover or a fire stain preventer. It
does act to reduce the amount of oxides that form on copper where it
is painted, and this oxidation is sometimes called fire scale hence
the name Scalex.

James Binnion
James Binnion Metal Arts


#9

Hi Anna, what about reheating the piece (gentile)… and than
pickle it… so that you’ll get/keep a fine layer of fine silver on
the surface. and than tumble… in the Lortone for instance…
preferable no polishing unless nessesary: gentily with suede and a
little polish (red or alike) for high gloss finish… etc…

good luck,
Stephen


#10

It’s been written up by me, and others, many many times over the last
fifteen years. (Has it been that long? Sheesh. Maybe it was only
14…)

Ouch—have I also been there that long? It’s simply that the Fridays
approach faster and faster…

Hans


#11
Scalex is not a fire stain remover or a fire stain preventer. It
does act to reduce the amount of oxides that form on copper where
it is painted, and this oxidation is sometimes called fire scale
hence the name Scalex. 

I’ll add to Jim’s post the comment that in following this thread, it
seems there may be some confusion with some posters as to exactly
what “fire stain” refers to. In working with sterling silver, there
are two basic types of heat induced oxide problems.

The first and most obvious, is the black surface oxide you get when
heating unprotected silver. This is what dissolves in pickle, leaving
a white fine silver surface. This type of oxide is called “fire
scale.” You also get fire scale on many other jewelry alloys,
including gold alloys. It’s characterized by being a surface oxide
layer.

The second type of oxide problem is much more specific to sterling
silver made with copper as the alloy. When hot, silver is relatively
permiable to oxygen, which can penetrate a bit into the surface of
the still solid silver. When it does this, it is able to reach atoms
of copper contained in the silver, and it will oxidize them. The
copper oxide formed this way is the red oxide (one oxygen atom per
copper atom), rather than the black oxide formed in fire scale (two
oxygen atoms per copper atom). And the result is fire stain, a
slightly reddish or pinkish creamy hazy color to the silver.
Different enough so that when you polish through it to clean silver,
the difference is obvious, but not so different from clean silver
that it’s instantly obvious without that visible contrast.

The overall result of all this is that heating oxidizes the surface
copper to black, at the same time pulling just a little of the
subsurface copper (via diffusion) to the surface and oxidizing it
too, to black fire scale. Under this surface, which after pickling is
a thin layer of fine silver, begins the layer of fire stain going to
a depth proportional to how hot and how long the silver was heated.
Under that, is the clean sterling silver unaffected by all this.

Cleaning off fire SCALE is easy. Pickle does it. Cleaning fire
STAIN, though, is more difficult, since things like acids cannot
reach into the silver to remove oxides contained within the surface.
So you have to remove the affected surface layer of fire stained
silver.

By the way, on a related topic, this whole mechanism is why the
traditional preparation of silver sheet metal for reticulation
works. On heating, any unoxidized copper becomes a bit mobil via
diffusion. Some of it will travel towards the surface, where it
becomes oxidized. That traps it, preventing diffusion back into the
metal, so the oxidiztion mechanism means it’s a one way trip for
copper to the surface. Deep enough into the surface, the fire stain
version of the copper is not sufficiently mobil to move much, only
that quite close to the surface does so. But you pickle, and heat
again, and eventually all the copper that was close enough to the
surface to make it there and be oxidized black, has done so. And
because the usual gentle scratch brushing or burnishing after
pickling only compresses and strengthens the fine silver layer rather
than removing any of it, the repeated heatings end up making that
fine silver layer thicker and thicker, until it’s reached a point
where additional heating no longer gives you any black oxide on the
surface. That then is the surface you can reticulate. It consists of
that thickened fine silver layer, then the subsurface (and by now,
thicker too) layer of fire stain, and then clean silver. Overall,
the surface has a higher melting point than the core of clean silver,
thus you can get the inner silver to melt and flow, while that skin
on the surface holds intact, giving you reticulation patterns. Fun
how many of these bits of metalurgy are interrelated between pain in
the backside aspects, and useful ones.

cheers
Peter Rowe


#12

I use a ceramic coat called, “firescoff”. It is a firescale
preventer. I am able to solder very heavy silver without any
firescale now. I highly reccomend it!


#13
I did a side-by-side test of several fluxes, including Firescoff.
To my surprise, for me, in my test, it didn't do all that well. 

I don’t know. I just soldered silver that is 4mm deep using
firescoff, and it worked graet!


#14
I use a ceramic coat called, "firescoff". It is a firescale
preventer. I am able to solder very heavy silver without any
firescale now. I highly reccomend it! 

firescoff does indeed work pretty well, IF you use a heavy enough
coating. Like many fluxes or protectants, if you don’t spray it on
thick enough, or if the metal isn’t clean so the coating doesn’t stay
in place properly, then it doesn’t work. The main problem with
firescoff that I’ve found, is simply that I don’t have enough first
born children or right arms to pay for the stuff. Just way too
unreasonably costly, considering how quickly you can go through it.

And I’ve not had problems with fire stain or fire scale on silver
since 1972, when as a Sophomore taking Fred Fensters beginning metals
class at the University of Wisconsin, he claimed that while some
other school programs said they had problems with fire stain, at U.W,
they did not. And he proceeded to show us how to make and use Prips
Flux. Over the years, I’ve tried any number of other methods, out of
curiosity. Many work. But none that I’ve found both work well, and
cost as little as Prips, which you mix up yourself.

Though these days, I do mostly gold and platinum work, when I need
to make something in silver, the old bottle of Prips (which has been
refilled many times with a new batch) comes out, as does the old
mouth atomizer. No, not the same one from '72. They last a long time,
but do get yucky after a decade or so… And for about three bucks, I
guess I can afford to buy a new one now and then. As with the flux
itself, I’ve tried various other methods of applying it, but still
end up back with the mouth atomizer sprayers Fred taught us to use.
Still the simplest, most reliable solution.

And over the time Orchid has been in existence, every so often
people new to the group come in and announce they have trouble with
fire stain. This, despite the fact that Prips flux has been taught in
many schools over the years, and is in most of the better books on
jewelry making. But because you mix it yourself and suppliers don’t
get wealthy from it, it’s not prominently featured in the Rio
catalog, so many people somehow don’t discover this or similar
methods.

So several times over the last decade and a half, I and others have
fully written up the recipe, and means of use of this simple and
effective solution to fire stain. And Hanuman makes all of this
available through the Archives.

So why, I wonder, do people still often not know how to deal with
fire stain. I’ve come to the conclusion that this is an artifact of
the Internet age. It’s easier to quickly google a thing, and if the
answer isn’t found in seconds (though in this case, even Google will
find those archive articles if pointed at the actual name of the
stuff), then people go and just ask the group instead of actually
taking the few seconds it takes to search the archives.

Puzzling. But I suppose, so long as people eventually find a
solution they’re happy with, that’s what matters. In this case,
Firescoff IS a product that can solve the problem for people. And I
did find it convenient and effective. Though not dramatically better
than Prips. So if people like it, fine, Problem solved, and retailers
are happy. But if anyone out there using firescoff gets tired of
paying something like 25 dollars for a half cup of the stuff (which
makes it dramatically more costly than any other flux I’ve ever
used) that is barely enough to get through more than two or three
projects, well…

check the archives, folks. Email me if you have further questions
after reading those articles.

Just one note about the stuff I’ve written that’s in the Archives. In
a couple of the first such articles, I misspelled Jack Prips name.
Put two "p"s at the end for some reason. That error seems to have
replicated itself a few times with other people’s writings. Spell it
right. Prip’s. And check for the variant Fred Fenster came up with,
which substitutes Cascade dish washing powder for the TSP, which in
some parts of the country, can be harder to find. That variant is
called “Frips”.

Peter Rowe


#15
Scalex is not a fire stain remover or a fire stain preventer. It
does act to reduce the amount of oxides that form on copper where
it is painted, and this oxidation is sometimes called fire scale
hence the name Scalex. 

Yes, that is true, sorry. And Mr. Rowe is right too: the first thing
to do is to prevent fire stain and there are good ways of
accomplishing that. I never used Scalex, I just use a picke.


#16

To remove fire stain, I was told you need to heat the metal many
times- not to the point of annealing. Pickle in between each heating
to pull the fine silver to the surface. This is one trick to "cover"
the stain.

Plating is a common solution in mass production. Finish the piece
completely stain and all, then plate. I always disliked getting
plated jewelry for repair, so I do not like this solution.

After reading James Binnion’s first post, I am wondering, if ferric
acid would remove because it will etch copper, but not silver. Maybe
someday I will have to test.

I use a combo of boric acid and denatured alcohol as well as battens
flux on the seam as a preventative. Rarely encounter fire scale in my
career before switching to argentium for most of my stock silver
materials.

Peter in the different processes you describe, I have always heard
fire stain referred to as firescale. Thanks for clarifying. Also, if
I remember correct, the pink copper film that pickles of was called
"copper flashing".

This might be informative, too:

Melissa Stenstrom


#17

here is an article at the Ganoksin Project which touches on ways of
removing firestain

best
charles


#18
To remove fire stain, I was told you need to heat the metal many
times- not to the point of annealing. Pickle in between each
heating to pull the fine silver to the surface. This is one trick
to "cover" the stain. 

This will not remove firestain it will however cover it. You are not
pulling the fine silver to the surface, you are dissolving out the
copper from the surface leaving a super thin layer of pure silver
that if gently handled will cover the firestain. but you cannot
polish this surface as polishing will cut right through to the
firestained surface below.

Plating is a common solution in mass production. Finish the piece
completely stain and all, then plate. I always disliked getting
plated jewelry for repair, so I do not like this solution. 

Yes, I am not a fan of plating either but you can get a high
polished finish with a plated surface unlike the above method.

After reading James Binnion's first post, I am wondering, if
ferric acid would remove because it will etch copper, but not
silver. Maybe someday I will have to test. 

If you mean ferric chloride it leaves a pretty ugly surface behind
on the sterling.

James Binnion
James Binnion Metal Arts


#19
To remove fire stain, I was told you need to heat the metal many
times- not to the point of annealing. Pickle in between each
heating to pull the fine silver to the surface. This is one trick
to "cover" the stain. 

The above process is indeed one solution to fire stain problems. But
do note that it does not actually remove fire stain. If anything, it
can make the fire stain layer within the metal thicker. But as you
note, it also makes the fine silver layer at the surface thicker, so
if this is then preserved in finishing, the result is the desired
uniform surface. Also note that the phrase “pull the fire silver to
the surface” is incorrect. What happens isn’t moving or pulling
silver anywhere. Rather, it is removing the copper from the surface.
The copper atoms do actually move around via diffusion during this
process. But the silver doesn’t need to. It’s already there.

Plating is a common solution in mass production. Finish the piece
completely stain and all, then plate. I always disliked getting
plated jewelry for repair, so I do not like this solution. 

Well, yes and no. It’s got extra costs involved. But silver plating
over a fire stained piece is simply doing via plating, the exact same
thing your first process of repeated heating is doing, which is to
build up a surface layer depleted in copper. Silver plating puts down
a fine silver surface, so the result is the same (and can be thicker,
if you wish). It does have to be a thick enough plated layer to be
able to hold up to some wear and tear, but the same holds true of the
depletion gilded surface.

After reading James Binnion's first post, I am wondering, if
ferric acid would remove because it will etch copper, but not
silver. Maybe someday I will have to test. 

Ferric Chloride, not ferric acid. (no such thing as ferric acid).
And no, that won’t affect fire stain because acid etching of any sort
only acts upon the surface. Fire stain penetrates. Acid bright dip
treatments for fire stain are etching off the entire surface layer
till they are below the fire stain. You need an acid that will also
remove the silver within which the copper oxides are suspended.
Usually, bright dip formulas are based on nitric acid or nitric acid
salts, not hydrochloric acid or it’s salts (like ferric chloride).
Cyanides are sometimes also used for this.

I use a combo of boric acid and denatured alcohol as well as
battens flux on the seam as a preventative. Rarely encounter fire
scale in my career before switching to argentium for most of my
stock silver materials. 

Now that’s got to be a mistake. Argentium was specifically designed
so that it does not form fire stain. Fire scale, to a degree, but not
fire stain. Since the alloy is less prone to oxidation, I can’t see
why your normal protections wouldn’t work as well with argentium
against fire scale.

However, I should also note that in general, boric acid by itself is
not known to be a good fire scale or fire stain preventative with
silver. The reason is that upon heating, the surface tensions of the
silver and boric acid tend to keep the boric acid from remaining as a
good surface coating. It balls up, leaving most of the surface
unprotected. In Prips flux, the two protective elements are borax and
boric acid, long time traditional means of protecting precious
metals from oxidation. But the TSP is there as a surfactant, a
wetting agent. it’s what allows the boric acid and borax to
sucessfully cover the metal surface while heating, to provide
protection. Borax or boric acid do offer some protection, but it’s
far from perfect. The classic way silver was protected was called
"burning in", which amounted to multiple coats of borax, lightly
heated and recoated until it formed a decent surface, before
prolonged heating to useful temps was done. See the description in
Seitz and Fiengolds “Silversmithing”. But in short, I’m surprised not
only that you’ve had more trouble with argentium, since it’s purpose
is to limit oxidation problems, but as well, that you had few
problems using just boric acid and alcohol. That’s traditional with
goldsmiths for use with gold, where it IS effective. But on silver?
Most people find that it’s marginal at best.

Peter in the different processes you describe, I have always heard
fire stain referred to as firescale. Thanks for clarifying. Also,
if I remember correct, the pink copper film that pickles of was
called "copper flashing". 

As good a term as any. I don’t know that it has a formally correct
name. I’ve heard “flashing”, plating, coating, or just a strung of
unprintable words… I assume you’re talking about copper that plates
out on the silver when iron or another reactive metal is accidentally
in contact with the silver when put into the pickle…

This might be informative, too:
http://www.ganoksin.com/borisat/nenam/firescal.htm 

As always, our good friend Charle’s writings are always erudite and
informative. I do note that he, too, seems to be using the terms
fire scale and fire stain slightly interchangeably in this particular
20 year old article. Do remember too, that usage of particular names
is not always universal to everyone or every metals traditions.
Obviously, names differ in different languages. But they can find
different usages even among various english speakers. The main point
is that in general, they’re talking about the same two distinct
types of copper oxide that forms on sterling silver (and as Charles
points out, a few other alloys as well. But the gold alloys where a
true fire stain appears, rather than surface only oxide films, are
unusual, not the norm at all.)

Peter