Green Corrosion on old Lincoln Cents

Discussion in 'US Coins Forum' started by houston_ray, Jan 2, 2005.

  1. houston_ray

    houston_ray Member

    I have an old Lincoln cent collection. Many have been stored away for 25 or 30 years in an old Whitman album, the kind that has two clear plastic slides that go over and behind the coin, and the coin is inserted between them in a cardboard-like hole.

    Several of the coins have isolated spots of green corrosion on them. Often they are very tiny spots, and some have an almost hairlike look to them when under a 10X loop. A few spots are larger and are plain to the eye. Even in the "worst" case, the area affected is a small fraction of the surface area of the coin.

    Will this green gunk grow, even if the coins are now removed from the old album and put into a new Littleton album? Can I clean the coin with something that will arrest it? I know that you're never supposed to clean a coin. I just don't want this stuff to grow all over the coin. At the same time, if it's taken 30 years to get these little spots, then maybe I'll be long dead before it's a worry anyway. :)
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  3. cdb1950

    cdb1950 Senior Member

    Sounds like something in the environment is causing these to corrode. Could be the plastic used to store them, or something else. You might want to re-holder them. If they have been stored as long as you say, there is a pretty good chance they were put in soft plastic coin holders that were popular at that time, but contained polyvinylchloride (PVC), a material that exudes corrosive gases over time as it deteriorates. This will settle on the coin surface and start to eat away the metal over time. This green gunk will continue to grow.

    Cleaning is a real bug-a-boo. If the plastic is the culprit, then the coins are already coated with the corrosive plastic and that will need to be 'washed' off. Use acetone to do that, a good solvent, but has little effect on the metal of the coin. It most likely won't remove the green gunk, but it will remove the bad coating so corrosion will stop.

    Removing the green gunk on copper coins is really tough to do without altering the toning/luster/appearance of the coin. I wouldn't do that unless it significantly detracts from the look of the coin. Most dips and cleaners will also remove any natural toning, which is bad, so you have to decide if the coin would look better with artificial toning or the green gunk.

    Check some of the other threads regarding cleaning coins. Lots of good advice, do's and don't's.
  4. GDJMSP

    GDJMSP Numismatist Moderator

    Howdy houston_ray - Welcome to the Forum !!

    The green stuff on your coins is known as verdigris - it is corrosion and it will continue and it does harm your coins. It literally eats away into the surface of the coin.

    What you do about it depends on how important the coins are to you. There are comercial cleaners that will remove most of the corrosion but at the same time they damage the coin too, in particular copper. The cleaners are acidic and while removing the corrosion they also remove small amounts of metal from the surface of the coin.

    So you have a decision to make. If the importance of the coins is sentimental more than value - then you have nothing to lose for you will prevent further damage. But at this point any monetary value will have been greatly reduced depending on the amount of corrosion damage to each individual coin.

    Wish I had better news for you - sorry to say I don't :(
  5. the_highlander

    the_highlander New Member

    i had a lovley big australian I penny that had a area of green on it, realy spoiled the coin just this little area of green the whole coin overwise very lovley.
  6. houston_ray

    houston_ray Member

    Thanks for the advice on my previous query. Good comments.

    Another guy told me that if I dipped the coins in acetone, it would remove any remaining contaminates from the surface of the coin. Another knowledgable person said to soak the coin in olive oil and carefully scrape it with a green rose thorn. Another online collector said to soak the coin in ammonia to arrest the spread.

    I'm ok with not trying to remove the existing green gunk (since it's minor) but I'd lke to try to arrest or just slow down the spread.

    At the same time, it has taken 25 years for these little spots to show up.....if all they did was double in another 25 years, I might be dead by then anyway....:)
  7. GDJMSP

    GDJMSP Numismatist Moderator

    Acetone will not remove verdigris - it will remove pvc. But based on your description and the fact that you say the coins are in a Whitman album - it's not pvc.

    The olive oil may help loosen the top layer so that you can scrape it off. But it will not stop further corrosion. And placing the coins in ammonia - well they'll turn all sorts of colors for you but the corrosion will still be there.

    I wish I had better advice to give you - but I'm sorry there just isn't any :(
  8. Conder101

    Conder101 Numismatist

    The acetone will not remove the verdigris but it will remove most other contaminates, and will ensure that the coin is dry. Verdigris requires mosture to progress so if the coin is throughly dried by the acetone and then KEPT cool and dry the verdigris should stop spreading.
  9. The_Cave_Troll

    The_Cave_Troll The Coin Troll Moderator

    The answer to stopping the spread is storing the coin in a VERY LOW humidity environment. Moisture is required for oxidation to occur and without it the spots will not grow.

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