What environmental issues causes this color.

Discussion in 'Coin Chat' started by Peter Economakis, Oct 20, 2020.

  1. Peter Economakis

    Peter Economakis Well-Known Member

    I see quite few copper pennys with this red color.
    Could it be a long time storage issue in a moist or wet area? It does take away the eye appeal but what about value? Can the value drop dramaticly? Capture.PNG
     
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  3. Randy Abercrombie

    Randy Abercrombie Supporter! Supporter

    I do not know if this is a true story. I read it somewhere and it made perfect sense to me. I have seen many early Lincoln's with a very red hue to them. I read that in the days before mass advertising, the traveling circus would send a runner ahead of the circus to disperse red painted cents into the local economy. If you went to the local merchant and received a red cent in your change, then you knew the circus was about to come to town...... Anyway, I cannot reference the story but it made sense to me.
     
  4. SensibleSal66

    SensibleSal66 Well-Known Member

  5. Peter Economakis

    Peter Economakis Well-Known Member

    Randy, is sure does look like paint. The paint on the high spots of the coins are worn which would add evidence to this story.
    I'm sure many have seen some with signs of cleaning to were they couldn't reach the lettering without further damage??
     
  6. medoraman

    medoraman Supporter! Supporter

    Actually, looks a lot like an ancient. Sure it wasn't a MD find?

    Copper is fairly reactive to soil, so if not buried in a pot it will tend to slowly leech ions away from the surface, leaving a look like this sometimes.
     
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  7. Peter Economakis

    Peter Economakis Well-Known Member

    Another 1914D penny with some red on the surface>
    Huh this is weird! Capture.PNG
     
  8. dltsrq

    dltsrq Grumpy Old Man

    Natural oxidation of copper (patina).
     
    Last edited: Oct 20, 2020
  9. SensibleSal66

    SensibleSal66 Well-Known Member

  10. Peter Economakis

    Peter Economakis Well-Known Member

    Other than eye appeal, would this patina really lower the value?
     
  11. John Burgess

    John Burgess Well-Known Member

    the natural oxides for copper.
    Copper(I) oxide -red (4 Cu + O2 → 2 Cu2O)
    Copper(II) oxide - black (2 Cu + O2 → 2 CuO) (heating copper with oxygen to 300-800 Celsius.
    CuO Cupric Oxide - green/blue...... (CuCO3.Cu(OH)2) or (2CuCO3.Cu(OH)2)

    there's others of course, that's the main 3 that are the least complicated and replicate even on accident or naturally, this is how ceramics were colored in the glaze in the old days by using various copper oxide powders in the ceramic mix to color it.

    So, it could be hypothesized that a red oxidized "patina" was due to oxidization without the presence of sulfur but in a wet environment that is acidic, and likely also chlorinated to some extent, not simply freshwater with a neutral pH. a "pond penny" or "fountain coin" most likely.

    A black oxidized "patina" cent would be hypothesized to have been exposed to high temps above 300 Celsius but below melting with a respectable introduction of oxygen (air). a household wood fire, fireplace or wood stove burns at about 600 Celsius, wood is combustible at 300 degrees Celsius, as an aside. normally boiling water, 100 degrees Celsius just to give an idea of where conditions have to fall as far as temperature and then oxygen.

    Green oxidized cent would be hypothesized to be exposure to sulfur and oxygen and water. Even atmospheric sulfur from cars and factories, pretty much why the statue of liberty is the color it is.

    Coppers red oxide is the likely culprit here, and in my opinion, coins that look like this spent time in a chlorinated fountain under the right conditions with chlorine as the likely oxidizer.

    I am also certain someone that knows a heck of a lot more about science, elements and minerals, and formulas than I do, may declare shenanigans on this post and what I've written, I am not 100% clear that I understand it all.
     
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