Here is a collection of answers to the question of cleaning coins.


ANCIENTS

From: HVUR50A@prodigy.com (Hugh Kramer)
It sounds like the coins you have are so corroded that only a chemical 
cleaning will have any effect. Most methods strip off the patina as well 
as the corrosion so your main problem will be replacing the patina once 
the coin has been stripped down. Most any kind of acid will strip the 
coin. You can (with great care) use naval jelly, lye, sodium 
metabisulfate (Sparex #2) to strip the coin down. Be forwarned though. 
Quite often you will lose any detail as well as the corrosion. This is 
especially true of the type of uncleaned coins you get in those offers 
since the easily cleaned ones have generally been picked out.

The problem of repatinating the cleaned coins can be addressed by getting 
a book on metal sculpturing and reading about the methods found there.




ZINC
How can I clean/preserve zinc coins?


From: rasmith@crl.com (Richard A. Smith)

I have experimented with alcohol-soluble lacquer on zinc coins to prevent 
or retard corrosion.  I am still not convinced that it does any damage to 
the surface, even "uncirculated" pieces.  It seems to prevent corrosion 
if none has started, but once the lesion is in place, I doubt that 
lacquer helps.  I have also tried glass-fiber brush to remove corrosion, 
but that really falls in the realm of harsh cleaning and I don't 
recommend it; better leave the white spot, rinse with isopropyl and 
lacquer--and hope.  Some of the zinc coins have significant value, maybe 
the purists would say, as they do for rare silver and copper coins, leave 
these alone.  On these, I agree.  I will be interested in other reponses.


From: gordon8816@aol.com (Gordon8816)

As an avid collector of WW2 coins, I can tell you for a fact that zinc is
the most volatile metal for a coin to be made of. It corrodes at the drop
of a hat, and once it starts, you can kiss it good bye.

I always wondered how a grading service would handle a MS zinc coin. Even
in unc they have striations all through the planchet and tend to look like
crud. If a zinc coin is acquired in unc condition, (very few and far
between I might add!) it is best to immediately place it in a
non-corrosive holder and watch it closely for a month or so for signs of
spit spots. If none occur, you got it made, go ahead and lock it away or
whatever you plan to do with it.

Gordon


From: ken@kaiwan009.kaiwan.com (Ken Leonard)

You can try blue ribbon or a light oil to enhance the appearance of these 
coins and remove some surface dirt.

-Ken



COPPER
How can I clean/preserve copper coins?



My question concerns the cleaning of coins, especially pennies.  
I'm not looking to restore coins, but just clean some especially
"cruddy" and corroded coins.  Is this possible without damaging
the coins.  If so how?  Is this recommended?




From: lockem@clipper.robadome.com (Mike Locke)


"Cruddy" and "corroded" are very different situations with
different problems and solutions.


First off, 99.9% of the time, if you disturb the patena of a copper
alloy coin, it will permanently take on a "cleaned" appearance and
be significantly devalued.  Cleaning is generally only done to remove
dirt, and then only with caution and when the dirt is a problem.


A corroded coin has metal damage, verses a "cruddy" coin which merely
has crud adhering to it's surfaces.  Most of the time, it is best to
leave corroded coins alone: if the corrosion is minor it's best to leave
the majority of the coin and its patena intact, if the corrosion is major
cleaning isn't going to help


If a coin has a lot of dirt on it, try the following:
	Acetone is a volatile, toxic solvent available at most
	hardware stores that will strip paint, varnish, tape
	'stickum', grease, and similar contaminants without
	affecting a coin's patena.  Soak the coin in acetone
	(avoid the fumes, avoid touching the acetone) then pat
	dry.  Medium and lower grade coins can tolerate mild
	rubbing to facilitate cleaning.  *NEVER* rub a proof!


	Soap and water is a more chemically active cleaner that can
	remove or loosen dirt.  Many soaps will react with bright
	copper/brass/bronze, leaving a blue irridescent patena.  It
	doesn't seem to have much affect on brown coins, or silver coins.
	Use similarly to acetone.  Rinse the coin very thoroughly
	with distilled water after applying the soap.


	Isopropyl alcohol (sp) is a solvent, much less active than
	acetone, but much less toxic also.  It will remove some types
	of grease and other muck without affecting a coin's patena.
	Use similarly to acetone.


Some bronze coins in medium and lower grades will tolerate brushing
with a soft brass or camel hair brush to remove dirt.  Not recommended
on high value coins! (ie, don't try this if you can't afford to ruin
the coin)  Using soap and water as a  lubricant lessens the scratching 
and produces a nicer looking result.


As always, practice on some worthless coins (pocket change) first is 
recommended.




From: DDEZ53F@prodigy.com (Frank Leone)


This is a very sticky subject - no pun intended.


There are all sorts of ways to clean coins. It is always best, in my 
opinion, to do some cleaning to remove agents that may harm a coin in the 
future. These agents come from "plasticized" coin flips, saliva, air. 


There are a few products on the market which aid in cleaning and 
preserving coins. These are to be used conservatively and only as 
instructed. Corrosion on coins is usually best left alone. There is 
nothing to cure this and once it is removed you would see unsightly pits 
on the coin. Never use anything abrasive - this would only leave 
hairlines ruining much of a coins numismatic value.


If you must clean- practice on a few worthless coins and perfect your 
methods. One slipup can ruin a coin forever. When in doubt - don't.



SILVER
How can I clean/preserve silver coins?



First - I am not a collector, so not familar with treatment of coins. I have 
several old German silver pieces which are black by now. I understand, I 
cannot clean them with silver polish. Is there a "safe" cleaning solution 
which would not devalue the coins?




From: nick@potomac.com (Nick Maas)


The best and most sober advice is to never clean a coin.  An old coin is 
supposed to look old, what might look unattractive to one at first could in 
fact be very collectible or important in and of itself.  The color or toning 
on a coin's surface - the patina -- is an important item to many collectors 
and does affect value.  If its been cleaned away, so has the coins value, both 
in terms of salability and more importantly, desireability.


Your coins may not be silver, or they may be composed of a silver and other 
metal alloy that naturally turns this color over time.  If this is so, 
cleaning them could totaly ruin the aesthetic value of the coins.  It would be 
like scraping the paint off of a Cezanne to keep it looking good.


Since you are located in VA, please stop by my store, show us the coins, and 
ask us about them.  They probably should not be cleaned, but a dealer 
(including any other reputable dealer) can give you more info by taking a look 
at them.