What causes copper coins to become black and Porous

Discussion in 'Coin Chat' started by AirborneReams, Apr 18, 2021.

  1. AirborneReams

    AirborneReams Well-Known Member

    Hey all,

    move had a few of these guys now and they look to be well taken care of and better grade. Never understood how they could get like this because they’re not dug. We’re they just kept in a certain environment where moisture was present? I’ll add some examples.

    best regards,

    AB57E0C2-59B8-456E-AD6B-4838CEBE4159.jpeg 757EFB89-5559-4F48-B0BF-C9F339B8E54E.jpeg F22A12E7-BE4E-4143-822F-47BF9ADBF005.jpeg 85417422-DCBB-4779-9A21-BA0202299A99.jpeg
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  3. SensibleSal66

    SensibleSal66 Casual Collector / error expert "in Training "

    Heck ! If you don't want , I'll gladly take .
    Seriously talking . Usually copper turns black because it forms copper sulfide. This is produced when hydrogen sulfide (bad egg gas) or a solution of it comes into contact with the copper, especially if it is moist.
  4. potty dollar 1878

    potty dollar 1878 Well-Known Member

    I'll give you a cent for it:):).
    AirborneReams and SensibleSal66 like this.
  5. SensibleSal66

    SensibleSal66 Casual Collector / error expert "in Training "

  6. AirborneReams

    AirborneReams Well-Known Member

    Thank you sir! I’ve had a few and always pondered the reason why they can get like that in better grades. Now I’m smarter thanks to you :happy:
  7. AirborneReams

    AirborneReams Well-Known Member

    That sounds like a deal to me! :woot:
    potty dollar 1878 likes this.
  8. SensibleSal66

    SensibleSal66 Casual Collector / error expert "in Training "

  9. eddiespin

    eddiespin Fast Eddie

    They're well-kept. It's just end-stage toning.
  10. johnmilton

    johnmilton Well-Known Member

    That 1826 cent may have been dug and conserved. Remember that where you see porosity is a place where metal has been lost.

    Copper toning can turn black as well as several shades of brown. It all depends upon the atmosphere where the coin has been stored.

    To me brown is the best. Given proper storage, away from moisture and up and down changes in temperature, the coin will hold up quite nicely. Copper coins that have had their protective patina stripped are potential trouble, sometimes big trouble. The "virgin" metal can react in many ways, and a lot of those ways are not good.

    Copper experts are good at retoning such coins and in that way preserving them, but that's beyond my expertise.

    This 1806, Small 6 Stems, half cent has been re-colored. This piece has a long history. It dates from the 1880s when it was the discovery piece for this very scarce die variety. It was viewed as the finest known for the variety for many years. Sometime, probably in the 1970s, an idiot stripped it. It has been re-colored, but a fair amount of the value was lost. I sold this piece about 20 years ago.

    1806 C-2 Half Cent All.jpg
  11. AirborneReams

    AirborneReams Well-Known Member

    Holy smokes she’s a beauty! It’s always cool when you get your hands on a piece like this. That’s all good info thank you friend, I also had no idea coins could be “revived”.
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  12. GDJMSP

    GDJMSP Numismatist Moderator

    What causes copper coins to become black and Porous

    Well you can give the scientific explanation, which has already been done. Or you can answer the question quite simply, with one word in fact - corrosion.

    Of course then somebody is gonna ask - well then, what causes corrosion ? And there's a simple 1 word answer to that too - air. That's all it takes, just plain old ordinary air.
    Last edited: Apr 21, 2021
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  13. JimsOkay

    JimsOkay New Member

    Good post!
    AirborneReams likes this.
  14. JimsOkay

    JimsOkay New Member

    Even corroded it is evenly corroded and for some reason I like that! HA!

    Maybe I should start another thread or do some searching, but I'm curious about how one can stop/halt cooper corrosion?
    AirborneReams likes this.
  15. Collecting Nut

    Collecting Nut Borderline Hoarder

    Those are all very nice, definitely keepers but if you don’t want them....

    Basically copper mixed with the air and the environment will turn coins a dark color like this, especially copper.
    AirborneReams likes this.
  16. AirborneReams

    AirborneReams Well-Known Member

    Nice and simple just how I like it!
  17. AirborneReams

    AirborneReams Well-Known Member

    I made another post about this coin in the for sale forums, don’t want to say more then that as I have upset a few people doing so.

    the air makes sense and maybe if the coin wasn’t in a proper protective area during its time?
  18. Paul Chouan

    Paul Chouan Supporter! Supporter

    I used to own some copper ancients that turned black, perhaps centuries ago, and I got rid of them all - I couldn't stand peering at them under strong lights to make out what was on them. If I were to start buying ancients again, I would probably go exclusively for light-to-bright green patinas, or "circulation cameos" with dark fields and light devices. Earthen (orange or yellow) patinas are attractive too, but notoriously easy to fake.
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