Verdigris on Widow’s Mite? Help please

[FormerTeller]

I picked up some Widow’s Mites from the FUN show last month from I believe a reputable dealer in ancient coins. Gave one to my cousin in St. Petersburg, then headed back home to Indiana. Today he texted me the following picture.

If you zoom in, you can see what looks like green verdigris on the coin. Quite sure it wasn’t there 3 weeks ago. My question is what caused it?

I gave it to him in a plastic flip, which I know isn’t ideal for long term storage, but that shouldn’t react with the coin this quickly, should it? Does it have anything to do with being in proximity to the ocean - salt in the air? When I bought the coins they were stored in a sealed plastic bag.

He originally questioned whether the coin was authentic - understandable for a coin this old. Now he’s wondering if the corrosion indicates that the coin is modern. I don’t think so, but am open to outside opinions. Thoughts?

Lastly, what is the best way to conserve the coin? Obviously he would prefer to have a verdigris/corrosion free coin. Best way to “clean” the crud off it?

I’d be appreciative of any comments!

 

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[Mackaydon]

What does the other side look like?
Don.....

 

[huntsman53]

More than likely, someone handled the coin with their' fingers. Body oils along with any contaminants that their' fingers may have come in contact with, can and will cause the verdigris due to the chemical reaction of the contaminants on the metal of the coin. Another possibility, is a reaction of the coin's metal with the mylar in the flip. Acetone will arrest the verdigris but the verdigris will likely have to be removed with a hydrogen peroxide bath and toothpicking. Once done, bathe it one more time to ensure the verdigris has been arrested, rinse with distilled water, pat dry with a soft cloth/towel and then place it in a 2x2 not a mylar flip.

 

[FormerTeller]

Don, I’ve asked him to text me a pic of the reverse, will post it once I get it.

Huntsman, it’s probably a combination of both handling and Mylar. I’ll pass along your instructions.

Many thanks! [emoji120]

 

[ILikeMoney]

Would that be considered “cleaning” the coin?

 

[smokeythecat]

Yes, it probably would then be considered "cleaned".

 

[FormerTeller]

View attachment 1677635

Here’s the other side. I use that term clean in quotes because I wanted to conserve the coin, yet I knew it would be considered “cleaned” in a numismatic sense. My goal was to give him a nice looking coin with historical/biblical significance. He could care less about its numismatic value, and I feel certain will never try to sell the coin. I felt bad about giving him the contaminated coin and the flip, and wanted to make things right.

I’ll admit it still boggles my mind that verdigris could set in that quickly. I keep many coins on flips, many handled similarly, yet never saw that reaction even after years of being in flips. I can only assume it’s got to do with the alloy used back then, and again wonder if salt air has anything to do with the speed of the reaction.

 

[Plumbata]

Hmm, development that quickly is likely due to chloride contamination, which infects bronzes with "Bronze Disease", a nasty affliction common with ancients that will progressively destroy a coin without treatment. It is usually "powdery" in my experience. Cleaning like Huntsman suggested is the way to go, with picking-out the "diseased" portions or pits being very important and soaking in several changes of distilled water for days at a time to try to dissolve and remove remaining traces.

As with 99% of ancients generally and almost every identifiable ancient bronze coin in existence the coin was already "cleaned", so cleaning some more to arrest the decay isn't a bad thing. Ancient coins are a different animal than "modern" coins and proper cleaning is almost always a value-boosting process.