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Discoloration after pickling


#1

Hi,

When soldering my sterling silver on many pieces I have trouble with
discoloration after pickling. I am wondering if I am using too much
flux or not enough. I also am having trouble with having the
sterling keeping its polish or texture. It seems that I can not get
it to the shine that the stores have no matter how many hours I spend
at the wheel. And with my texturing it seems they get scratches and
discoloration very easily.

Thank you.


#2

Alex,

I’m afraid traditional sterling silver (alloyed with copper) has
that ongoing problem with oxidation. No matter what flux you use, and
how careful you are with your soldering, it seems inevitable you will
get at least some fire scale. Often, a lot. Even if you conquer the
fire scale issue, just the oxygen in our environment will tarnish
sterling amazingly fast, making it look dull, even on the shelf in a
case. If customers get to handle the pieces, it’s even worse.

One of the things I’ve done with silverwork I’ve had in galleries
was to fine-silver electro-plate my silver pieces. That way, there is
a non-tarnishing coating which will prevent tarnishing from occuring
while on display, although it is not very durable over time. United
Metals’ S88 sterling alloy is absolutely great at keeping tarnish on
finished pieces at bay, although I’ve still had some fire scale,
fabricating with it. Much less fire scale than with traditional
sterling, however. Argentium sterling is great for no fire scale or
tarnishing, you just need to be careful of it’s brittleness when hot.

I would have to say that traditional copper-alloyed sterling silver
is, well, old-fashioned.

Jay Whaley


#3

Fire scale (sub-surface copper oxides) can easily and economically
be avoided with the proper use of cupronil, prips flux or even with
the new Firescoff if you don’t mind it’s cost.

Tarnish is a separate beast and is not from oxygen reacting with
silver. Significant amounts of silver oxide Ag2O are not produced by
the mere presence of oxygen (to produce Ag2O silver nitrate is
reacted with an alkali hydroxide). Tarnish on the other hand is a
corrosion reaction most often caused by sulfur compounds in the air
from burning fossil fuels but, there are other culprits that can
corrode (tarnish) silver like selenium or chlorine or other
chemicals. Yes a chemist calls this type of reaction oxidation
because it is similar to an oxygen reaction but with tarnish it is
not an oxide that results but a sulfide, selenide or chloride of
silver.

All high silver alloys whether they are copper based sterling or S88
or Argentium or whatever will tarnish, even fine silver tarnishes,
get over it, it is just the nature of the beast. Silver is very
reactive with sulfur and it will eventually tarnish when exposed to
it. If it did not do so you would not be able to patina (deliberately
tarnish) it with liver of sulfur. The only difference between the
various alloys is the rate of tarnish which is extremely dependent on
environmental factors which is why we hear so many different
opinions on tarnish and why lab tests of tarnish resistance are of
limited value. Many of the new alloys do indeed tarnish at a lower
rate in some environments than traditional sterling alloyed with
copper. However, you pay a price for that increased tarnish
resistance in reduced hardness or hot short behavior (brittle at high
heat) or increased cost or reduced recyclability (alloying elements
that oxidize off in melting) or other issues. Argentium and S88 and
the other tarnish resistant sterling alloys all have their place and
there are valid reasons to use them for some tasks but…

I would have to say that traditional copper-alloyed sterling
silver is, well, old-fashioned. 

It may be old fashioned but there is not a single new alloy
formulation available that can match all of its properties, some may
preform better in one or more areas but require a trade off in
others. So folks may want to do some research to see if you are
really better off switching to a new alloy or sticking with the well
tested, tried and true silver-copper sterling alloy.

For a good paper on the tarnish resistant alloying pluses and
minuses read Dr Joseph Strauss’s “Tarnish-Proof Sterling Silver:
Understanding the Limitations” in the proceedings of the 2008 Santa
Fe Symposium available from Rio Grande. Also there have been several
papers from the past couple of years at the Santa Fe Symposium that
explore tarnish resistance of various alloys in lab and some
interesting “real world” environments like the bumper of one authors
pickup truck :slight_smile: Not surprisingly there are some differences in
results. They are interesting reading but the conclusion is under
some circumstances all the alloys tarnish.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#4

James, for what tasks would you use argentium silver? I am about to
restock on metals (after many years out of the business) and was
considering using argentium, as I used to constantly have a
firescale problem-- even using my prestolite.

I now also have oxy-propane and look forward to a hotter flame for
some applications. I thought part of the problem was the prestolite
was not hot enough-- and therefore I ended up training the flame on
the piece way too long. I used to quench my pieces in pickle and dip
it briefly in a jar of water-- so now I’m thinking some of my joint
problems (and subsequent overheating) were due to pickle pollution. ?

Can one mix argentium and tradtional sterling without problems?
(Don’t know why one would do this-- perhaps if one ran out of
materials).

Cheers-- Carol


#5

Jim,

I defer to your most highly educated expertise. My experience is far
less with chemistry and scientific research than it is with common
experience in the workshop and classroom. I do not dispute your
expertise, as it is obviously based on much study and research. Thank
you for clarifying the actual processes of fire scale and tarnish,
and how they differ.

It is through the highly scientific you bring to the
Orchid forum that all of us, including us “Old Dogs”, can learn new
tricks. We all try to pass along we have learned,
practiced, and taught others, but all of us, including myself, can
benefit from better, more scientifically based

Thank you, Jim, for your considerable knowledge and your willingness
to share it so openly! I hope to meet you in person some day.

Jay Whaley


#6

Wow thank you for the responses.

I talked with a local jeweler and she recommended dipping the piece
in a alcohol and borate solution first then burn off the alcohol.
Flux and then solder. Would this help? Does anyone have pictures to
show the difference between fire scale and oxidation?


#7

If you get a laser you can discard your pickle pot. Silver is
extremely easy to fabricate with a laser.

Ron Carter


#8
James, for what tasks would you use argentium silver? I am about
to restock on metals (after many years out of the business) and was
considering using argentium, as I used to constantly have a
firescale problem-- even using my prestolite. 

I am not the best person to ask about where I would use Argentium as
my limited experience with it has not convinced me that I need to
use it anywhere. My work involves using sterling in mokume laminates
and for my process I need something that has more hot strength than
argentium exhibits. Philip Baldwin is offering copper Argentium
mokume laminates now and he likes it for that purpose but I don’t do
much in the way of copper sterling laminates now days. My friend
Cindy Eid is very fond of it and if she is monitoring the list now
can provide her views of why she has switched to using it. I think it
is all she uses now. I have worked out processes that for the most
part eliminate fire scale and Argentiums main benefit in my mind is
it’s fire scale free properties.

Your prestolite torch is not the source of your fire scale problems.
No torch will keep you from having fire scale but too much oxygen in
the flame will make it worse. To prevent fire scale you need to
completely coat the work with a suitable flux like prips or my
favorite Rio’s Stop Ox II. To do this you gently heat the work and
spray it with the flux till you have a even complete coat of flux.
then yo apply a very small amount of a soldering flux to just the
joint area. Then heat and solder as normal.

I now also have oxy-propane and look forward to a hotter flame for
some applications. I thought part of the problem was the
prestolite was not hot enough-- and therefore I ended up training
the flame on the piece way too long. 

The problem here is not that your torch is too cool but rather not
enough heat output. There is a very common misconception that you
need a hotter torch to do larger work. What you need is a larger
flame from a larger tip. There is not a lot of large jewelry scale
work that can not be done with a #6 prestolite tip or a large propane
/ compressed air torch The torch flame from a prestolite is almost
four times as hot as most silver solder melting temps and adding
oxygen only boosts that to just under five times as hot. The place
you need the oxy fuel torches is when you need a tiny flame and need
to heat small work fast or for melting to cast.

I used to quench my pieces in pickle and dip it briefly in a jar of
water-- so now I'm thinking some of my joint problems (and
subsequent overheating) were due to pickle pollution. ? 

Maybe but more likely just not enough heat

Can one mix argentium and tradtional sterling without problems?
(Don't know why one would do this-- perhaps if one ran out of
materials). 

Yes but it is less than an optimum solution, more findings and mill
products are being made in Argentium now so there is less need to do
so.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#9
Thank you, Jim, for your considerable knowledge and your
willingness to share it so openly! I hope to meet you in person
some day. 

The truly great thing about Orchid is that so many people like
yourself bring their significant experience and insight to share
with the others here. I am always learning form those who bring their
questions and insights to this group.

If you are ever up here in the Northwest corner of the country stop
by to say hello please, and if I get to San Diego area I will attempt
to do the same.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#10
I talked with a local jeweler and she recommended dipping the
piece in a alcohol and borate solution first then burn off the
alcohol. Flux and then solder. Would this help? Does anyone have
pictures to show the difference between fire scale and oxidation? 

That’s the standard commercial jewelers solution to preventing
oxidation and fire scale on GOLD, as well as preventing heat damage
to diamonds. However, simple boric acid is not effective at
preventing fire stain on sterling silver. It may reduce the obvious
black oxide called fire scale, but fire stain is different, and
somewhat more important to prevent. it’s the faint cloudy/milky/rosy
toned shadow you find showing up in your highly polished silver when
you go from tripoli to rouge. The clean silver looks darker, clearer,
more highly reflecting, and the fire stained areas are a bit lightler
and cloudy looking areas. It’s a subtle difference, not obvious
unless both colors show, but typically, when you fabricate something
and get fire stain, your polishing and buffing will be just uneven
enough so it cuts through the fire stain in some areas, and not in
others, leaving an unattractive blotchiness to the surface. Gold, it
should be noted, does not do this. The oxides formed on gold alloys
when you solder it are confined to the surface, so when you pickle
the metal, you’ve removed the oxides and only need to refinish the
metal you see. The problem is that with silver, oxygen penetrates
INTO the surface, oxidizing the copper in the sterling to a certain
depth within the metal, so your silver, instead of being a mix of
silver and copper metal, is a mix of silver and reddish copper
oxides. They’re dilute enough in the silver so the reddish color may
not be all that obvious, but the damage to the finish remains a
problem.

As I and others have posted many times throughout the history of
Orchid, fire stain and fire scale are only a problem with sterling
silver if you don’t bother to prevent it. The solution has been
around and taught in many art schools, published in a number of
books, and otherwise not hidden, since the 60s, or earlier, when John
Prip first devised his flux recipe.

In short, prips flux, used correctly, solves the problem. it IS a
seperate step, and takes a little more time, but what the heck. Do
you expect your jewelery to make itself? it’s just another part of
the process, and once you get used to using it, it’s second nature
and works like a charm. Prips flux is easy to mix up and use, though
if used in too small a soldering area, the overspray can make a
little bit of a mess, but this too is easily solved. It’s cheap to
buy the chemicals, cheaper at least than commercial products, and for
a few dollars in chemicals, you can mix gallons of the stuff, enough
for years of working.

The recipe is simple. 3 parts boric acid, 2 parts each borax and
Sodium phosphate. The latter can be monosodium phosphate, disodium
phosphate, or trisodium phosphate, the last of which is the most
commonly used, since it’s usually the cheapest and easiest to find.
Normally, about 96 grams boric acid and 64 grams each of the other
two will form an almost saturated solution in a quart of water. You
can mix it more dilute if you wish (schools often do, to avoid
wasting flux with students who tend to not know when to stop
applying it) All three chemicals can be simple technical/industrial
grade, and tap water is fine. For borax, you can use some laundry
products, like Borateem, which is mostly borax (the littlle blue
crystals are whiteners, which have no effect on the flux.) Boric acid
can be purchased sometimes as a cockroach powder in hardware stores,
or through chemical supply houses. Trisodium phosphate, also known as
TSP, is widely known as a fairly strong alkaline cleaning agent,
used for things like cleaning walls prior to painting. It’s become
harder to find over the last decade, because, like all phosphate
detergent products, it presents some water pollution issues (It’s a
fertilizer, promoting algae and other water plant growth) So you may
not be able to find it in the paint section of your hardware store.
Some stores carry it still, perthaps on a bottom shelf not so
visible. Be careful if buying it like this that you actually have
TSP, since there are a wide number of products confusingly labeled
TSP, or similar, which actually have different chemicals in them, so
read the label. it should be a white granular dry powder, and the box
needs to say Trisodium Phosphate as the ingredient, not just “TSP”.
If you can’t find it in a hardware store, it’s easily sourced through
any chemical supply house.

However you get the chemicals, dissolve them in hot water, and allow
it to cool. If needed, add more water to keep it all in solution.

To use it, spray it on preheated metal so that it freezes/dries on
contact to a white slightly crusty film which is thick enough to hide
the metallic reflective surface of your silver. It should not go on
wet, or it will not form a stable clear coating. If, upon heating,
some of it balls up or draws back from areas leaving them
unprotected, spray a bit more on till it stays there. That can happen
if you put too much on, put it on wet with the metal too cool, or if
the metal isn’t clean.

Ordinary trigger bottle sprayers tend to quickly clog up. You can
use an external mix air brush, such as this one from harbor freight

http://tinyurl.com/5ybdf7

Notice that with this, as with other cheap airbrushes, the
paint/liquid mix feed tube comes up and ends IN FRONT of the air
nozzle, not inside of it. That’s what keeps it from clogging. The
liquid never goes through any sort of small orifice to clog.

Eveh simpler, avoiding plastic air tubes on air brushes while you’re
also using a torch, or air cans or compressors, etc, are mouth
atomizer sprayers. They are the type I prefer. They last almost
forever, are too simple for words, and work well. Sold in ceramics
supply houses for application of glazes. here is a link to one source
(though they may have an annoying minimum order). halfway down the
page, you see numbers 126-86 and 126-87

http://tinyurl.com/5xhyp4

note that they’re shown folded down for storage. In use, the two
tubes are positioned at right angles to each other (and L shape)

A few other notes to be aware of. When TSP started to become hard to
pick up in hardware stores, Fred Fenster, the amazing silver and
pewter smith who taught at the University of Wisconsin for many
years, and who first introduced me to Prips flux in my first
sophomore metals class some 35 years ago, started experimenting. The
same sort of inspired “kitchen chemistry” that had John Prip coming
up with the original formula, had Fred coming up with an altered
version, which he calls “Frips” flux. In short, he figured that since
Cascade dishwashing powdered detergent (that green box) is primarily
composed of TSP as the main cleaning agent, it might work just as
well as pure TSP. Or so goes the story from some other former
students of Freds who first posted that info here on Orchid a number
of years ago. Personally, I’ve not tried this mix, since I’ve
already got enough TSP to last me a long time. But those
aformentioned posts suggest that Fred, at least, felt this mix was
actually an improvement on the original. I’d guess that the Cascade
formula includes other surfactants, things to promote clean rinsing,
lowering surface tension of the surface, etc. etc. And since that
function is the main action of the TSP in the flux (allowing the
melting boric acid and borax to wet the silver and coat it instead of
pulling away), it sounds reasonable to me that the Cascade version
might be better. But I don’t know, since as I said, I’ve not tried
it, and won’t need to till I’ve run out of the gallon or so of prips
flux I already have sitting here. Search through past archive
postings on orchid for mention of Frips flux, and you should get the
needed details on it’s use.

Now, if this whole posting is too long, and you’re scared of taking
the time to source the materials and mix your own in order to save
money, you CAN buy the mix from suppliers, though if bought as a
liquid, most suppliers seem to sell it pretty dilute, which is
annoying to me. Or use Cupronil, which I never liked as well, but it
does sort of work, or the new Firescoff product. It DOES work very
well. Maybe even a little better than Prips, in terms of not burning
off if you overheat the metal, or in terms of being also a decent
soldering flux (Prips is too, but not an especially active flux). The
main trouble with Firescoff is, of course, the cost. Might as well
sell your first born kids for that that stuff costs. Even if it works
very well, (and it’s used the same way as prips flux, sprayed on
preheated metal), I’ll bet that once you mix up some prips, and
compare performance and costs of the two, you’ll agree with me that
prips or frips is just fine…

Nuff rambling. Email me or post on the list if you need more info on
this. But the bottom line is that there’s no reasonable reason you
should be having trouble with fire scale or fire stain on sterling
silver when you fabricate it. It’s completely avoidable, without
needing fancy alloys, fancy acid dips or other removal methods, or
much of anything else other than proper use of this sort of
preventative. This is one situation where ignorance is very much not
blissful. Learn to avoid fire scale and fire stain, and the small
amount of extra time this step takes will be saved back several times
over in not having to polish or abrade it off later.

cheers

Peter Rowe
Seattle


#11
The problem here is not that your torch is too cool but rather not
enough heat output. There is a very common misconception that you
need a hotter torch to do larger work. 

I’ll pin down Jim’s statement even more exactly. This comes up ALL
the time, and it’s here now on a “sweat soldering” thread. It’s all
about BTU’s, which is the amount of heat needed to raise the
temperature of water a certain amount. I could look it up, but
neither I nor you need to know the actual definitions, just the
concept. Note it doesn’t say the the temperature, but the amount of
heat.

So - you burn acetyline in air. That’s what a Prestolite does, but
it could be any gas(es) or any torch, it’s still the same. If you
have a 1/4"/6mm gas line, the flame will burn at 4500F (whatever it
really is - it’s just a number here). I’m not going to go track down
the BTU rating of that - let’s just say it’s 1000 BTUs.

So, you want to upgrade, so you change over to a 1/2"/12mm gas pipe.
Low and behold, the temperature of the flame is still 4500F. That’s
the temperature (made-up, here) of acetyline burning in air.
However, since you have 4 times the gas volume (plumbing/piping
isn’t doubled, it’s squared - the area of a circle is piRsquared),
you are getting 4000 BTUs out of it. The temperature is the same,
but you’re getting four times the heat…That’s what BTUs
mean…I’m sure someone could give a more erudite lesson on
thermodynamics, but that’s at least the essential concept…

http://www.donivanandmaggiora.com


#12
So, you want to upgrade, so you change over to a 1/2"/12mm gas
pipe. Low and behold, the temperature of the flame is still 4500F. 

Turns out, with oxygen it’s 6000F. I tend to think of it in terms of
energy. If we have a block of steel that’s a 1/4" cube, and a block
of steel that’s a 6" cube. A given amount of energy is needed to
raise the temperature of the small block one degree, will have a much
smaller effect on the larger block. I can take a little blazer butane
torch and get the little block red hot. It won’t hardly touch the
large block.

Paul Anderson


#13

Hi,

For what tasks would you use argentium silver? I am about to
restock on metals (after many years out of the business) and was
considering using argentium, as I used to constantly have a
firescale problem-- even using my prestolite. Jim Binnion said: My
friend Cindy Eid is very fond of it and if she is monitoring the
list now can provide her views of why she has switched to using it.
I think it is all she uses now. Can one mix argentium and
tradtional sterling without problems? (Don't know why one would do
this-- perhaps if one ran out of materials).

Sorry about the delay in response----it is difficult to keep up with
Orchid, sometimes.

Jim is correct. I only use Argentium Sterling Silver. It is all that
I have used for at least 5 years, now. The only thing that I still
use traditional sterling for is hot-twisting (a blacksmithing
technique that I learned from Munya Upin, who learned it from Brent
Kington). It IS, however, possible to work AS hot—both Phil Baldwin
and Ian Ferguson forge mokume billets at annealing temperature—if
you are careful to keep the AS at black heat, rather than red hot.

I started using AS because of the lack of firescale, but I have
found that it has other properties that I also like, including:

-greater ductility and malleability
-hardenable in an oven
-tarnish resistance
-fuses and welds well
-the poor heat conductivity means that you can do complex
constructions without worrying so much about the prior seams
re-flowing.

Yes, you can mix AS with SS, but I don’t see the point, really. I
sold all my SS to a friend for a price that was good for both of
us—more than scrap silver price, but less than current retail.

I hope this helps!
Cynthia Eid
http://www.cynthiaeid.com