Blue powdery color on denarius

Discussion in 'Ancient Coins' started by Basileus Antialcidas, May 5, 2020.

  1. Basileus Antialcidas

    Basileus Antialcidas Active Member

    Hello to everyone! I just received this Alexander Severus denarius and I realized that there is a blue poudery matte color on it around the figure of Zeus in the reverse, which I easily removed with a cotton swab . I haven't seen any silver coin with something like this, what could it be. I am really sure if anyone asks that it is silver and also it seems quite pure. Any ideas?
     

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    Last edited: May 5, 2020
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  3. Orielensis

    Orielensis Well-Known Member

    Welcome to CoinTalk!

    The cleaning experts might chime in eventually and tell you more, but if I were you, I wouldn't panic. I doesn't look as though this nice denarius were affected by any active corrosion.

    I'd suspect that what you see likely are either the remains of the coin having been improperly stored in a plastic flip for a long time, or that the seller has applied some powdery substance to the surface of the coin to enhance its eye appeal. The latter is cringed upon and more common with bronze coins – search for "maybelline" in this forum and you'll find some discussions.

    In any case, a short bath in acetone will likely help and most probably not hurt the coin.

    (Edit: Or it is a fourrée and the patina of the bronze core is seeping through the silver coating – but to me it doesn't look like that in your pictures.)
     
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  4. Basileus Antialcidas

    Basileus Antialcidas Active Member

    Thank you for your answer. I don't believe that acetone will be needed, it is very easy to remove it just by using a cotton tip.
     
  5. Andres2

    Andres2 Well-Known Member

    Looks like copper showing through in the bleu circles = fourree

    these denarii struck under Severus Alexander cointained only 40% silver the rest is made out of copper.
    The green stuff is copper oxide.

    alexander severus denarius.jpg

    I have beautifull denarii of Sev.Alex and terrible ones.
    The Roman mints used a technique to force the silver up to the surface,sometimes that didn't work out.

    P1170943 (2).JPG P1170943Providentia ric 174 (4).jpg
     
  6. robinjojo

    robinjojo Well-Known Member

    I don't see any indications of a copper core, such as places where silver plating has fallen off. I would tend to agree that debased silver, with it high copper content, is likely the source of the blue powder, which is copper oxidation and not PVC damage.

    PVC damage tends to be dark green and kind of gooey, although it can harden over time. A bath in pure acetone will remove it, but depending on the degree of deposit the process might take some time and more than on bath.

    Be careful using acetone: it is very flammable and it should only be used in a well ventilated area. Avoid breathing in the fumes. Allow the coin to dry and stabilize for several days before putting it in a PVC-free flip or paper envelope.
     
  7. Basileus Antialcidas

    Basileus Antialcidas Active Member

    Thank you for your answer. The blue circles you have put on the photo are just the lighting making it look like if it is golden in colour in the photo. In hand is completely silver with no indication of coper showing off and also the edges seem typical to a normal denarius and not a fouree.
     
  8. Basileus Antialcidas

    Basileus Antialcidas Active Member

    I tend to believe it is some kind of oxidation too. Should I worry about it (like if it was bronze disease) or it is something different, stable that will not affect other coins if it comes in contact with them? Also I believe that bronze disease tend to look way more poudery and green. This is very blue.
     
  9. robinjojo

    robinjojo Well-Known Member

    I'm sure the coin does not have bronze disease.

    It's a nice coin. I would keep an eye on it. The less that is done to it the better.

    One more possibility is that the blue deposits are just remnants of the original surface of the coin, when it was found. Ancient coins usually are quite encrusted with dirt, clay, oxidized minerals (such as copper), horn silver and other materials that are the result of centuries of deposition. Most coins, especially silver coins are cleaned, as is the case with your coin. So, it is possible that the blue deposits are areas that retain some of the original surface.

    As I suggested, leave the coin as-is and check it over from time to time to see if there are any changes. With time (several years) the coin will tone to a nice color, as the air reacts with the silver.
     
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  10. Basileus Antialcidas

    Basileus Antialcidas Active Member

    I agree. I just used a cotton tip and it came of very easily. I will keep an eye to see what will happen. As you said it might be some kind of remaining encrustations, maybe some kind of flaky blue oxidation like the one that you find in some coin s that some people say that were found in near graves.
     
  11. octavius

    octavius Well-Known Member

    This does not look like bronze disease. I agree that it is probably some copper oxide due to the high amount of copper in denarii of this period. Your coin looks very nice and I wouldn't worry.
     
  12. robinjojo

    robinjojo Well-Known Member

    Yes, some coins recovered from burial sites have a really nice, blue patina.

    Dem Bones!

    Fats Waller-

     
  13. Marsyas Mike

    Marsyas Mike Well-Known Member

    Welcome to Coin Talk, BA. That's a nice Severus Alexander you have there.

    I offer no advice as to the blue spots, but at the risk of sounding ridiculous, I did buy an Antoninus Pius sestertius on eBay that had been painted blue.

    Why? Who knows? At first I thought it was some weird and wonderful patina, but I noticed it grew sticky as it warmed up in my hand. A little hand sanitizer revealed the truth:

    Antoninus Pius - Sest. Quadriga cleaned and blue.jpg
     
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  14. PeteB

    PeteB Well-Known Member

    It is possibly reflected lighting coming from the bottom of the coin.
     
  15. Basileus Antialcidas

    Basileus Antialcidas Active Member

    It is actually. I mentioned it in a previous reply. It is completely silver in hand.
     
  16. dougsmit

    dougsmit Member

    What I see here is a common photo problem resulting from taking a photo with daylight balance lights but somewhere in the room there was a table lamp with a 2800K bulb placing a yellow glare on the reflective surfaces on the inclined surfaces pointed at that lamp. Note how each of the yellow spots is on a place inclined the same way as to reflect glare from that lamp to the camera.
     
  17. Basileus Antialcidas

    Basileus Antialcidas Active Member

    The famous painted coin. I have seen your post a while ago about this coinon before I became a member on this forum, when I was searching for blue patinas on copper coins. Very interesting story. It actually reminds me of a recent discovery of mine. I bought a cleaned without any patina Maxentius, which if I remember correctly felt a little sticky in hand and even if it was bronze in colour it seamed kinda brown. I took some distilled water and a cotton tip and discovered that it was covered in a strange brown color. It didn't give any appeal to the coin just made it look a bit darker and more matte. It looks much better now.
     
    Last edited: May 5, 2020
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  18. Basileus Antialcidas

    Basileus Antialcidas Active Member

    You are right. This is the photo of the dealer. I am 23 years old professional photographer and I started lately to experiment with my coins. I am not sure, but I believe I have seen an article/post of yours on coin photography and learned a lot. Here is one I made lately. The idea of the reflection I took it from a website with very beautiful coins called colloseo collection, I hope the person that has it will not mind...
     

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  19. Marsyas Mike

    Marsyas Mike Well-Known Member

    I actually have one copper (bronze?) coin with (partial) blue patina that I think is not painted on - this is a Byzantine follis of the emperor Phocas.

    My photos are pretty poor, but this shows the colors fairly accurately.

    Byzantine - Phocas - Follis Con Feb 14.jpg
     
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  20. Basileus Antialcidas

    Basileus Antialcidas Active Member

    The graveyard patina as some people call it. I am not really sure though if it is 100% true that indeed has a connection with dead bodies producing enough of any kind of chemical in the soil as to affect the coins.
     
  21. Marsyas Mike

    Marsyas Mike Well-Known Member

    Ooo. I've never heard of a graveyard patina. :dead:

    I hope it's not cursed!
     
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