My Silver Enthusiast Newsletter #3 is now available!
http://www.ganoksin.com/gnkurl/1x1
Jeff Herman
Hello herman,
Tarnish, in regards to silver, is a thin layer of corrosion that forms from a chemical reaction on the surface of an object.
Is tarnish a corrosion?
I don’t like to start a war about the use of an expression. The
meaning of corrosion is described as a destructive process. Patina
can be wipped of leaving a nice shinning surface. Corroted surfaces
do not look shiny when removed since they’re attacked chemical
process.
Your work looks outstanding Herman, don’t get me wrong here! The
expression “corrosion” appeals strange to me in combination with a
natural patinating process. Many people already believe that silver
oxidizes which is a complete wrong expression.
It whould be nice to hear the opinion of others.
Have fun and enjoy.
Pedro
That’s great Jeffrey. Love the logo!
Mark
Hello Pedro,
Tarnish isn’t as benign as it may appear. You may be speaking of new
pieces. I have been restoring, conserving, and preserving silver for
27 years. I can tell you that upon removing tarnish from a great many
pieces, I have found profound etching that can be easily seen with
the naked eye. Even contemporary pieces may have etching but can only
be seen under magnification. When I get a chance, the next piece I
remove tarnish from and etching is exhibited, I will photograph that
piece for all to see.
Best regards,
Jeff Herman
Hello Jeffrey,
now that is very awkward indead! Yes, that whould be very nice if you
could come up with some examples to see. The part which I don’t
understand is, what is the etching element in that case? I c
Whether you call it “corrosion” is presumably a matter of how it is
removed- if the chemical reaction is reversed, and the original
metal is left behind, then it isn’t corrosion. But if cleaning it up
involves removing metal within the offending compound (eg.
oxidising and pickling sterling silver to strip off the copper) then
it is corrosion.
Jamie Hall -
Contemporary and Medieval Metalworker
http://primitive.ganoksin.com
I agree with Jeff. From what I’ve seen when removing tarnish from
silver, using the aluminium foil, some sort of sodium carbonate and
hot water method, the surface of the silver is no longer smooth and
shiny, but matt, and therefore somewhat pitted. This then needs to
be polished again - also a destructive process - to get it back to
the intended lustre. People seem to think that the silver simply
returns from silver sulphide to silver, but it seems to me that the
sulphur must actually get right into the surface, such that when it’s
chemically removed by hydrogen to form hydrogen sulphide gas, the
surface of the silver is left pitted. Definitely corrosion to my
eyes.
Helen
UK
Pedro: To me a Patina is something desired that adds to the
appearance of an item. Granted this is in the eye of the person
looking. Tarnish or Oxidation or what ever you wish to call it. is
detrimental to the underlying material. You will see some "Corrosion
that will eat away at a surface leaving pitting or outright holes in
the finish. This is destructive and only detracts from the beauty of
the item.
Patina can be from a color finish or it, as in this case, refer to
the fine wear marks that show age and give old silver its’ character.
This you do not want to remove. This is after all not a new piece.
If you think of silver as a lady you know that what is appropriate
for a teenager is not an appropriate for a woman of 60.
Hello John,
I have very little understanding about chemics and to me precious
metals are what they are because… they don’t corrode (and other
fact’s). By fact, I know that silver does not oxidize under normal
conditions except by ozon So, that is of the shelf talking about the
oxidation of silver. I do know that silver will be attacked by
tablesalt but only when alloyed with copper. Don’t ask me how it
works nor the process of the chemical reaction.
Due to all of this, my believing was that silvercorrosion was another
wrongly translation of the word oxidation. The process oxidation go’s
hand in hand with oxygen clearifying the process.
I do know that silver will be covered with a patina when exposed to
a sulfuric environment. To me, it appeared like a “coloration” of the
metal which is far away from corroding.
In other words, you can remove a patina leaving a blanc metal behind
without a destructive surface. Chemistry was never my best part ( it
was my worst!) in school and never wil.easy to learn.
This will be a challenge to explain people if they ask me about it.
Need to have this cleared out for myself in order to give people the
correct An old time habbit which I still honnor in my
older day’s. The class is never ending even if you don’t go to
school.
If you think of silver as a lady you know that what is appropriate for a teenager is not an appropriate for a woman of 60.
Very well explained John! I’ll keep that one as an example -)
Have fun and enjoy.
Pedro
Pedro,
If the metal combines with another element like in the case of
tarnish where silver and sulfur combine to form silver sulfide then
it is corrosion. Or if metal ions are stripped from the surface by a
chemical or electrochemical reaction it is corrosion. If it is a
chemical patina it is corrosion.
Jim
James Binnion
James Binnion Metal Arts
I do know that silver will be covered with a patina when exposed to a sulfuric environment. To me, it appeared like a "coloration" of the metal which is far away from corroding. In other words, you can remove a patina leaving a blanc metal behind without a destructive surface. Chemistry was never my best part ( it was my worst!) in school and never wil.easy to learn.
Pedro, the chemistry here is quite simple. One atom of sulfur
combines with two atoms of silver to form silver sulfide, which is
the black tarnish. If you remove the tarnish by polishing, you also
remove the silver which went into it. If you use an electrochemical
method, like the classic aluminum foil and soda, the sulfur is
removed and combines with the aluminum, leaving the original silver.
It seems unlikely that every atom of silver will return to the place
it came from, so I would expect changes in the surface eventually.
Al Balmer
Pine City, NY
the chemistry here is quite simple. One atom of sulfur combines with two atoms of silver to form silver sulfide, which is the black tarnish.
The chemistry of the process is not simple at all, and understanding
of this process contains clues to preventing tarnish. I was staying
away from this topic, but it is time to jump in.
The falsity is that sulphur can directly react with silver. No it
cannot. Sulphur has to be in form of H2S, or hydrogen sulfide. But
even this form cannot react with silver. What requires is presence of
moisture ( H2O ). In the presence of moisture H2S degrades to HS-
(negative ion), which directly react with silver forming Ag2S.
Another important point is that presence of Cl (chlorine) makes
reaction more aggressive.
To make things even more interesting, Ag2s has 3 crystal forms. The
form that is found as silver tarnish called acanthite and
crystallizes in monoclinic form. The other two are varieties of
argentite, both are cubic with one having body centered structure (
atom of sulphur in the center of the cube ), and another is face
centered ( atom of sulphur in the center of each cube face ). A
metallurgist should see parallel with forms of austenite. For some
reason, argentite was never found to be a part of silver tarnish. One
theory is that argentite, like austenite, can exist only at elevated
temperatures, which is not the case with silverware stored at room
temperature.
To prevent silver from tarnishing is to control moisture. If
cleaning is required, do not use tap water because of chlorine and
always dry items completely. Storing silver with moisture absorbing
packets will keep it shining for years. Remember, no moisture, no
reaction. That brings another interesting question. Are there
gemstones which can keep silver from tarnishing ? Tiger’s Eye is such
a gemstone. Also some Turquoises.
Tiger’s Eye forms when some of crocidolite is replaced by silica. The
same silica replacement happens with Turquoises ( not all, but some.
I have a write-up on my website ) Silica is what is inside the
moisture absorbing packages, so mechanism is the very much the same.
This also has been known for centuries. Traditionally turquoise was
always mounted in silver, and so was Tiger’s Eye. And now we know
that it wasn’t just the fashion statement.
Leonid Surpin
Hello all,
Thank you Jeffrey, James, Al and all the others one which I can’t
recall by name for the clarification of the corrosion process in
simple words. Leonid, thank you aswell (without sarcasm!) for
telling me in a very complicated way how the reaction takes place. It
will take some time before I figure this all out but I will. Being
hardheaded is sometimes a good thing to be…and sometimes not.
Before I get deeper in this material, I need to do some castings ie
applying what I always write…having fun and enjoying.
Pedro
Any sulfur-containing compound with the sulfur in a reduced
oxidation state (e.g., hydrogen sulfide, sulfur, carbonyl sulfide)
will cause silver to tarnish.
Moisture does indeed play a role. The higher the relative humidity,
the faster silver tarnishes (if sulfur-containing compounds are
present). However, even if there is no moisture in the air but it is
contaminated with hydrogen sulfide, the silver will still tarnish
because there is a direct reaction (water not involved) between the
silver and the hydrogen sulfide. So it is not good enough to remove
all the moisture because the silver will still tarnish if there is
hydrogen sulfide present (or other tarnishing gases).
Jeff Herman
If you think of silver as a lady you know that what is appropriate
for a teenager is not an appropriate for a woman of 60. LOVE this
analogy! Thanks for verbalizing what we all feel but may have
trouble expressing.
Blessings,
Sam Kaffine
The chemistry of the process is not simple at all, and understanding of this process contains clues to preventing tarnish. I was staying away from this topic, but it is time to jump in.
You can make anything complicated, but the essence is what I said.
We are discussing the consequences of removing tarnish. Preventing it
is another subject.
Al Balmer
Pine City, NY
It is true that oxygen does not seem to react with silver whereas
sulfur does. However confusing it might seem, it is also the case
that when sulfur reacts with silver that the reaction is technically
understood to be an oxidation of silver by sulfur? A substance is
said to be oxidized or reduced depending upon whether the substance
gains or loses electrons in the reaction. I am relatively certain
that this is correct. Does this fact clarify the matters under
discussion? Right, I don’t think so either. I suppose It is possible
that, for practical purposes,one could receive too much
This understanding of what oxidation is has no practical impact on
the position that it is sulfur rather than oxygen which tarnishes
silver.
I couldn’t resist the opportunity to muddy the water a bit.
Chemistry is fun.
Gerald Vaughan
I have a pyritized ammonite pendant wire wrapped in sterling. The
pyrite has completely tarnished the silver, and I’m wondering how to
polish it out and not harm the fossil. I guess I’ll go with a soft
polishing pad at first, and if that doesn’t do the job, I’ll be back
asking for advice!
Take care, make lots of sales, and enjoy!
Vicki K, SoCal
Thank you, Leonid, for your interesting and educational comments on
silver tarnish. Now I understand well enough to explain it to my
customers. I appreciate you taking the time to elucidate us.
Blessings,
Sam Kaffine