Verdigris Copper Cancer and Coins

September 12, 2010

An unsorted accumulation of old 1c and 2c

We get a lot of questions from newbie collectors and non-collectors about coins or accumulations of coins they've either found or inherited. Maybe you've given the shed a clean-up and have a jar of old 1c and 2c or you've been given a bag of old pennies or halfpennies that Grandpa has had hiding in the garage for 40 years. What do you do and where do you start? We've written a more detailed article before about where to go from here, this article is more about identifying verdigris on copper and what verdigris is.

Verdigris is a corrosive copper cancer and once it has formed on copper coins it's impossible to remove. It eats into the coin surface and will grow and spread assisted by a damp environment....even onto other coins nearby. So the first most important step when deciding what to do with those coins you've found is go through them and remove the one's that have green on them, the more severe is shown below.

2c Affected by Verdigris

What I suggest to people is to remove these green affected coins and place them into a "quarantine" bag or area for the time being until you can go through them and see if any are worthy of attempted salvage. For common date coins the most practical solution now is to send them for recycling. For potentially more valuable coins such as the 1925 penny in the group I'd suggest talking to your dealer or getting advice from numismatic experts as cleaning these coins or attempting to clean them will almost always do more harm than good. Attempted conservation should only be sought on rarer errors or key date coins. For more general coins in your collection which don't have significant value that you have interest in keeping there's only one method that I'd try on verdigris on copper. That is a good soak in olive oil. This will soften any debris on the coin surface so the damage won't worsen but for a severe verdigris which has eaten into the coin surface there isn't really any solution.

The answer to this is to store the coins properly from the start and remove those affected by verdigris so it cannot spread onto other coins.

Posted by harrisk at September 12, 2010 2:42 PM
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