Coin Repair - Copper Turning Green

Yes, a forum search on "verdigris" is quite disheartening for someone with a prized coin where the "green death" is slowly taking hold.

First, don't put it back in the holder/album it was in, and don't re-use the holder for anything else you care about - it obviously "didn't work". Of course, the coin may have had some kind of wash or treatment just before you acquired it which has only shown up recently, but ordinarily in this sort of case I'd blame the holder and/or storage conditions.

Is it genuine verdigris, or just "PVC gunk"? It looks like the former to me, but we're desperate to save your coin here. Try rubbing on a little acetone or other "dry" (mostly water-free) chemical solvent. Given the position of the green (on the low points rather than the high points) I wouldn't hold much hope for that angle.

Verdigris is irreversible and effectively destroys collector value and interest in a coin. That doesn't mean nothing can be done, especially if this coin holds meaning and value for you. I once found a few pointers over on the CU forum, posted by guys who dig up a lot of green coppers. There are two treatments which seem to be favourites, but remember, these are "last ditch" methods, only to be used when all else (except concentrated acid) fails.

The first is olive oil. It's a tried and true conservator's method of making old copper and bronze presentable, especially useful for "dug up" coins like late Roman or detector finds. Soak for at least a week, even up to a month. If the green stuff is going to come off, it should do so with minimal effort after that.

A second method is to insert the coin into a raw potato. That's right, a raw potato. Leave it there overnight. Pull it apart next morning and the results are apparently surprising.

Alternating the routines (oil-potato-oil-potato) is also said to work. Lastly, don't use water to wash it afterwards - water is a key catalyst for the appearance and spread of verdigris.

Your coin should only have a thin film of the green if it's only just appeared, so hopefully the damage can be contained. Have a go at these two methods if you like, but mind you I haven't personally tried these. Best to test it out first on a couple of "junk coins" with similar verdigris before you subject your pride and joy to either regime.

Can anyone else give a "yea" or "nay" to either of these methods?

I am not too sure if you should use acetone on copper coins. I had plenty of mixed results on them and they give some awful toning. Depending on the degree of the verdirgis, I would rather use a toothpick and remove as much of the verdirgis possible beforehand, just in case it contains some nasty chemicals in it. You should thne use acetone but be VERY quick with it.

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Originally posted by Sap


...The first is olive oil. It's a tried and true conservator's method of making old copper and bronze presentable, especially useful for "dug up" coins like late Roman or detector finds. Soak for at least a week, even up to a month. If the green stuff is going to come off, it should do so with minimal effort after that.

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Sap, Thanks for your advice. The coin is now soaking in olive oil. I'll take it out in a week and see if I can make it look any better. Then I'll take a photo and post it here. If I'm still not happy with the result, I'll soak it an additional three weeks and try again.

I'll attempt to find another coin and then see what a potatoe will do.

Here it is...After a weeks soak in olive oil and a couple hours of careful picking out dirt with a cotton bud and plastic toothpick.

Looks alot better to me (but of course its not my coin) looks 100 % better after the soaking to me. Thats a neat little trick that I am sure will come in handy for others, thanks for showing us the results

it may work on other coins but you shouldnt use water on a copper coin

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yeah and the better grade of olive oil the better job

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Tastes better too.