Expert: PAPAJACK - 12/6/2006

Question

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The text above is a follow-up to ...

-----Question-----I understand that I don't want to clean away the patina that has developed over the years.  But what about actually dirt and grime and grease that makes the features of the coin, such as the date and mint mark, difficult to see?  Is there a recommended method of removing this dirt and grime and grease?

Hello,

I've decided to start a collection of pennies that have been in circulation.  I'm wondering if there's anything I should do to clean the older pennies, and if there are methods of cleaning that are inappropriate.

Thanks.
-----Answer-----
Hello Michael,  

Great question. And yes there are methods absolutely inappropriate, like a rubber eraser or acid polishing mediums etc.  

Let me first state as a Coin Collector that coins are worth much less to coin collectors after having been cleaned. There is usually no reason to clean a coin. Unless the substance is destroying the coin (like acid, PVC damage etc.). Any coin that has ever been cleaned will sell for much less.
True coin collectors don't recommend cleaning coins at all.
When a coin is cleaned the original surface is removed thus removing the luster that the purest collectors want to see.
The cleaned surface allows other contaminates to attack the surface. Also the cleaning may deposit other particles on the surface.

Also note that coins that are naturally toned (specially silver coins) bring higher prices than cleaned coins. Usually double the amount. Also if the coins have an unusual blue, olive, or rainbow colored toning they sometimes can be sold for many times their usual price.

Cleaning of Bronze, Copper, Silver or any coin can render it virtually valueless! Collectors would rather have a dark deep chocolate brown specimen or spotty brown than a cleaned coin. Even rubbing a coin with a very soft cloth can leave minute scratches on the surface that will adversely affect collector value.

To improve a coin's appearance it sometimes in the past was acceptable--on a very limited basis to gently swish it in a diluted solution of pure soap, rinse with distilled water and allow to air dry.  (or pat dry lightly with a very soft cloth) Never use any type of commercial jewelry  polish on coins. These compounds contain abrasive grit that will mar their surface, and if used often will eventually wear away the metal. The same advice goes for "home remedies" such as vinegar, lemon juice, tomato juice, etc. All will do more harm than good.

Feel free to ask any question on U.S. Coins.

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Below is an excerpt from a professional society (authorized by the US Congress) in reference to cleaning coins.:

"Rule number one of coin collecting is "DON'T CLEAN YOUR COINS." Improper cleaning will reduce the collector value of your coins by 50 percent or more, so don't clean your coins.

If you do not care about the value you should experiment on some non-collectable coins first, see how they look after about a year after cleaning before you do the every cent in your collection.
Some have used gun oil and cotton swabs to remove debris and I don’t think pure acetone would hurt the coin if you need to get something sticky off.

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Good Luck

PapaJack

Answer
Hello Again Michael,  

As I said gently wash it in a diluted solution of pure soap like a dishwashing liquid, rinse with distilled water and allow to air dry.  (or pat dry lightly with a very soft cloth).  
You can try other PH natural inert solvents at your own risk like lacquer thinner, acetone etc.. Some people have said letting it soak in non corrosive oil (olive oil, gun oil etc.) wiping and washing or even chipping away  at crusty dirt with a tooth pick or orange stick.
Solutions that are too acid or basic will change the surface of the coin since copper is very reactive.
I notice on some older large cent copper coins that there is a shellac or lacquer coating on them. Possibly to preserve the finish but more likely to hide defects. I have never tried to remove it.

Whatever method you may use try it on pre 1982 us cents that you are not collecting to see how it will work for you.

Sorry I cannot be more help.  
Please remember to rate this answer at the bottom of this page. And check the nomination box on the rating page below any comments you may have.

Thank You and Good Luck

PapaJack