I get asked this question once a month at least. Do you think I should clean my coins before I put them in your
coin cases? While we sell many
coin cleaners, in most cases from what I understand from many
coin dealers, the value of a cleaned coin will typically go down, rather than up. This makes a difference if you have a coin worth $1 vs a coin worth $500 or more. So before cleaning a specific coin and placing them in a
coin capsule, I would advise you to talk to your local
coin dealer.
In reality, for kids just getting involved in the hobby itself, they typically have less expensive coins and I think that cleaning the coins allow them to see the actual coin a little clearer and would peak their interest more. Rather than using a chemical
coin cleaner or
coin dip, perhaps try a
coin wash, or a 100% cotton
coin cloth to get started. You might be amazed at how much dirt comes off. We have a wide variety of
coin accessories that might help you through this process.
Again, coin cleaning is a funny thing and a personal thing. I am re-posting a copy of an article posted online by Bob Reis from years ago to give you a more detailed look at cleaning coins (again this is his opinion, not the opinion of myself or SAFE Publications):
COIN CLEANING SECRETS
OF THE ANCIENTS by Bob Reis
I'll start this with a couple
of axioms. The first I heard from another dealer, to the effect that
EVERY ancient coin has been cleaned. The second, self-generated,
is my personal assertion that any dealer who deals in loose coins has cleaned
them on occasion. These statements offered for amusement only, as
many dealers will deny ever doing such a thing.
One should look upon old coins
with suspicion should they completely lack toning. Example: I have
seen a number of bright 18th century Russian coppers. Their owners
swore by them of course, but I could not bring myself closer to their point
of view than "maybe." I have, on the other hand, seen British conders,
USA large cents, etc. with full luster, but they were subdued, not bright.
Bright old copper is improbable, but bright old silver does happen, and
on silver you can do such a good job that you can't tell. The fact
is modern cleaning techniques are very good and you can be fooled.
When discussing this subject two categories of
state are important:
A) the condition of the
surfaces before the cleaning, and
B) the material from which
the item was made.
In this exposition I will not
go deeply into the chemical interactions which take place. I will,
rather, confine myself to practical considerations: what works with what
kind of "dirt," what won't work, what reduces value, what enhances, etc.
A. STATE OF PRESERVATION
A. Circulated
B. Uncirculated
C. Proof
B. MATERIALS
1. Gold
2. Platinum & palladium
3. Silver
4. Copper & bronze
5. Brass (including aluminum-bronze)
6. Iron and ferrous alloys
7. Zinc, tin, lead, aluminum, nickel
A. STATE OF PRESERVATION
The basic principle is that
the better the grade the more likely the possibility that one can perform
an undetectable cleaning job. On some of the late proofs in precious
metal, where all there is is some superficial toning, a "dip" may restore
the thing to blazing original perfection. This will be less possible with regular issue Uncs, and nothing will
restore original luster to a circulated coin. Details will be discussed
below.
B. MATERIALS
1. GOLD
Gold by itself will not tone,
but coins are never pure gold, there is always some alloy, and the alloy
will be subject to chemical attack. Old gold will most likely have
been buried in earth or water, and will be subject to physical encrustation
and abrasion, as well as facing possible attack on the alloying metal. Straight out of the ground these
things will often have a coating of dirt. Base specimens may show
pitting where the alloy has been leached by acid conditions.
On good gold there should be
no pitting. The color might be a bit dark. This will more likely
be due to dirt than oxidation, so a bath in soapy water would not be amiss.
You want to be careful what you use to scrub your gold with though, because
nothing is easier to scratch and abrade than gold. I'd suggest fingers
and perhaps a carefully wielded Q-tip or similar. No pressure should
be applied. The lightest of touches only. But look carefully
at your old gold. Probably someone has already tried to clean it,
and probably you can see where they tried too hard.
Biggest problem with gold is
not dirt, but jewelry mounting. Many old coins were so treated.
Many times the evidence has been skillfully removed. Five out of five 18th
century Russian gold coins recently examined by me showed ambiguous evidence
of having been mounted. The removal of the traces was skillful enough
that the seller was able plausibly to deny that the traces existed.
This kind of tooling is common on old gold and silver, and often is of
high enough caliber that you can't tell with naked eye. 20x magnification
will usually clear up the ambiguity, but not always.
2. PLATINUM & PALLADIUM
Coins made of these metals typically
don't get dirty, are not reactive, are hard, and thus are not usually cleaned.
Nevertheless, one often runs into 19th century Russian platinum coins which
have been treated with abrasive or polished, the desecrations performed
not doubt by idle rich of bygone years with nothing better to do than ruin
coins. As far as the chemistry is concerned, you can dunk these into
most anything: acid, base, organic solvent, etc. and it won't hurt the
coins.
3. SILVER
Now we get to the real business.
Silver surfaces are chemically responsive, and can develop salt and oxide
layers of various colors, depths, and degrees of adherence. All of
these can be removed. Some are more difficult than others, and with
some you'll wish you hadn't. But by and large, most silver coins
will clean nicely, and often the appearance of a coin can be improved considerably
without leaving any definite evidence that something has been done.
I've cleaned a lot of silver
coins. The vast majority had favorable results. I've done this
for so long that I've developed a general routine I follow for silver.
Here's a list of my personal dos and don'ts:
1. For dirt and minor
toning (brown is oxide, gray and black is sulfide) I carefully place the
coins in a jar of straight household ammonia and leave them there for 15
minutes to 3 days or so. The dirt and most of the toning come off.
The solution always takes on a blue color after a while, sooner with base
coins, later with purer alloys. The blue is copper in solution, but
I have never, over 20 years of doing this, created pitting, not even under
20x magnification.
What you get at the end of this
treatment is a dirt free coin, lighter in color than it used to be.
If there were any deep tone spots they will still be present. Silver
coins will pick up black marks from contact with steel staples, such as
are used to close 2x2 cardboard/mylar sandwich-type holders. Ammonia
won't touch them. Green crust on old coins will eventually come off,
you just need to be patient. However, under the green you will often
find a red copper oxide adhesion, which is difficult. Best
result on red crust comes from alternate immersions in ammonia and vinegar
or lemon juice (works just as well as hydrochloric or sulfuric
acids). Patience is required, and occasionally one might consider
a little physical help with a sharp tool, if one trusts one's hand.
One can eventually get it all off with no marks.
One occasionally finds coins
from Central Asia and other places with what I call "purple yuck," and
more refined people call "horn silver." The coins have patches of
dark encrustation that obscure the designs. Yuck is a sulfur salt
of some kind, but it is acidic, and under the crust the coin's surface
has been lost to corrosion. Ammonia won't touch yuck. Neither
will vinegar or lemon juice. A long soak in battery acid will take
it off, but then you'll have a pitted area. Whatever you do, your
coin will be worth less than when you started.
2. After the ammonia bath comes
the vinegar or lemon juice bath. (Wash coins in soapy water between
baths.) Why acid? The deeper sulfate layers will respond to
acid where they won't to ammonia, I suppose because they're denser?
At any rate it's true. Some people don't do the ammonia, start right
with the acid. The problem I see with acid is that its action is
a little more vigorous, and if your spots or toning are too deep you will
start to visibly erode the surface. Large areas of deep toning will
strip to an off-color matte gray, spots will turn into pits. You
need to know when to stop. That takes experience, which comes from
ruining coins. So get some cheap coins to practice on. This
kind of problem hardly ever arises with ammonia.
3. Both ammonia and weak acid
will leave a circulated coin with a nice, mildly tony, completely natural
looking "old silver" appearance. High grade coins will have their
luster. Some deeper toning will remain in the recesses, and the overall
result will usually be salubrious. One can go further and strip the surface completely. This is done by things
like Jeweluster, Tarnex, etc., all of which are basically the same thing:
versions of thiosulfate and various secret ingredients. These will
take away all of the toning and leave a bright coin. The thiosulfate
compounds give excellent results with high grade coins, but deeply toned coins are subject to the
overkill mentioned above, and these chemicals will ruin your coin in minutes
versus hours for weak acid. Still, I use Tarnex frequently to brighten
up tired proofs. Thiosulfates have limits too. They often won't work
on staple marks, or the heat sealing defects on some Franklin Mint proofs
of the 70s and 80s. They have no effect on crusts of any kind.
To repeat my progression: ammonia,
vinegar, Tarnex. When all done wash in soap and water. Handle
by edges, carefully dry, place in inert package. I think that's enough
for silver.
4. COPPER & BRONZE
Might as well include bullion
too, any silver under about .350 fine. Copper divides into two categories:
been buried or hasn't been. Unburied pieces will either have original
red surfaces or will be toned various degrees of brown, but will have no
encrustation or patina. I generally don't mess with these other than to clean them if they're dirty.
That I do with soapy water or organic solvent. I don't use ammonia
or vinegar on these. The result will be a mottled surface.
Won't look good. In fact, I think there's very little to be gained
from working on coppers of the 18th century onward. You can always tell when one's been messed with.
I think it's useless to try to restore mint appearance to toned copper.
Just stick it in an inert capsule and leave it as is.
On older coins I follow a different
policy. A bunch of late Romans, or Indian dumps, or medieval European
billons will most likely end up in the ammonia bath, some pieces staying
in for weeks. The solution becomes very blue. Many of these
coins are very dark or encrusted to the point that they have no value as is, and must be improved if anything
is to be done. Ammonia works on copper as on silver, except that
pitting will happen to some small percentage of the coins. "Silver
wash" on late Roman coins is not disturbed by ammonia. Usually you
will have a cleaner coin with a normal looking surface. Coins with
green patina will lose the entire patina, and are likely to be pitted underneath.
Red oxide is not touched.
On copper I often end up scraping it. Sometimes this works, but sometimes
there's nothing underneath the red patch. A couple of times I've
actually used a ball peen hammer to percuss patches off large Ptolemaic
bronzes with good result. A heavy duty ultrasonic cleaner might occasionally
give similar results.
By and large I've found ammonia
worth applying, as it has turned many pieces of worthless junk into saleable
pieces of junk. Use a utensil to get the coins out of the blue solution.
It'll stain your fingers.
Acid is not nice to copper.
Pitting almost always occurs. I recommend not to use.
Tarnex on copper will give bad
results to all except proofs and BUs. It will not yield desirable
results with fingerprints, nor will it restore lost lustre.
I think artificial toners are
stupid. You can always tell. Wipe the thing with an oily rag
and put it in sunlight for a year or so.
How to stabilize bronze disease
(green powder). This is a carbonate caused by acid conditions.
The easiest way to deal with it is to soak the coin in ammonia until all
I mean all the green is gone, neutralize it in soapy water, dry carefully,
and tuck it in an inert holder. If it comes back that means you didn't
bathe it long enough. Do it again.
5. BRASS (including aluminum-bronze)
The brasses do not clean well.
None of the things described above work. Ammonia will mess up modern
brass and aluminum bronze. It will leave spots and create a "wrong"
color. Ancient orichalcum will respond more poorly to ammonia than
copper or bronze. Acid is murder on brass, and tarnex is only useful
to freshen BUs and proofs. I admit it, brass has stumped me for 3
decades.
6. IRON and ferrous alloys
Start with ammonia for the dirt.
For rust you'll need an extended pickling in acid. If the rust is
too bad you'll have pits. Rust is a fact of life. Tarnex is
useless.
7. ZINC, TIN, LEAD, ALUMINUM, NICKEL
When you get an Unc piece of
zinc or tin you need to put it in an inert holder immediately if not yesterday.
It's probably too late already. These things suck up oxygen and grow
spots in the dark. You can then clean the spots off with acid, but
they ALWAYS leave pits. You can always tell when zinc has been cleaned. Other than soapy water for
dirt and organic solvent for pvc scuzz (you're probably too late) I wouldn't
bother trying to clean zinc or tin. As for lead, I wouldn't do anything,
no matter what shape it was in, how deep the patina, how ugly it looks.
Old lead coins will be covered in tannish patina. Strip that and
it looks disgusting. I don't mess with lead.
Aluminum reacts badly with ammonia,
and there's nothing else that works either. This is not a problem
though. Aluminum doesn't do much other than get dirty and corrode.
Corrosion in the numismatic context usually comes from contact with acid
paper envelopes, and is a whitish powder. This can be removed with
acid and stabilized, but you'll be left with a pit. Either way your
coin is ruined. With aluminum at this point prevention is really
your only option.
Pure nickel will clean in ammonia
or vinegar, and responds to tarnex like it should. Copper-nickel,
on the other hand, will quickly develop pitted surfaces in all three solutions.
I still dunk copper-nickel coins when I have to because of unsightly spots,
etc., but I get them in and out fast: not more than a few minutes for ammonia
and vinegar and not more than a couple of seconds for thiosulfates.
ORGANICS
Organics come in two varieties:
lacquer and scuzz. Both have to be stripped before any chemical cleaning
can be done.
1. LACQUER
Lacquer happens. It can
save a coin when the alloy is reactive. Lodz Ghetto 10 pfennig coins
are examples of coins which should be lacquered, anything made of magnesium.
But most lacquer jobs are terrible and you have to strip it.
All lacquer will come off with
acetone. Use a sealed jar, provide good ventilation, and work patiently
with soft rag and Q-tip. It'll come off. On some coins, zinc
for instance, lacquer may actually be a good idea. In fact, why shouldn't
we consider restoring precious metal coins to circulation with thick coats
of lacquer to preserve intrinsic value?
2. SCUZZ
The term is usually applied
to green, adherent, acidic, sticky stuff that gets on coins that have been
kept in PVC, a substance that is still in use for coin storage. PVC
scuzz can be removed with most organic solvents. Acetone usually works
fine. The scuzz occasionally ruins proof surfaces, and base metals
in any condition can be spoiled, in which case nothing can be done.
Another kind of scuzz is simple grease
or wax. Use any organic solvent.
SUMMATION
I clean silver coins often, and "dip" them frequently.
I clean copper coins only when their salability in their uncleaned state
is severely restrained, which is to say when I have nothing to lose.
Many times I get an improved coin which does not look cleaned, but a decent
percentage end up worse than before. I usually take the rust off
iron. I don't mess with brass, zinc, tin, aluminum.
Know the Value of Gold
