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Return of the green monster...


ewomack
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I have two coins infected by what looks like verdigris: A coin of Probus (the green does not appear on the obverse) and a Vienne Denarius (the green appears on both sides). Neither have great value, but the coin on the left was the first ancient I ever purchased. I have no memory of the verdigris appearing on either coin when I bought them. Despite their worth, I'd like to keep them from deteriorating further. So far, I've read that soaking in acetone will neutralize the verdigris, but not remove it. Another source said that olive oil would do the same, but then the coin needs a soak in acetone afterwards. I remember hearing elsewhere about a "magic formula" called something similar to "Verdigris-B-Gone" that would take care of the mess, but it has limited availability.

Has anyone had any success in staving off the "green monster?" And are these coins perhaps beyond help at this point?

GreenMonster.png.cb69f2e6495950d2b942686315d6465a.png

Edited by ewomack
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I rolled the dice when bidding on the coin pictured below 😟. The coin has a lot of green incrustation on the reverse & a trace on the obverse that was advertised as "hard", but was it really hard 🤔? I called the auction house before bidding on the coin & was assured that if I didn't like the coin to simply return it with no questions asked 😊. When the coin arrived I wore-out two toothpicks scarping on the green incrustation & nothing came off from the coin 😄.

2011225566_CNG490Lot339_2460AK.jpg.f4530741d50a31465cc9852c0d9299fd.jpg

Byzantine Empire. Justinian I, AD 527-565 (dated year 31, AD 557/8), Nicomedia Mint, 2nd Officina. AE 40 Nummi: 18.43 gm, 33 mm, 6 h. Sear 201. Ex Peter J. Merani Collection; Ex The Time Machine (Mark E. Reid), December 6, 1998. 

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@ewomack, as others are pointing out, verdigris is not Bronze Disease, and it's not harmful. It's often what makes a coin's patina look green. The difference is that verdigris is hard and doesn't flake or crumble off when you poke at it with a toothpick. Bronze Disease is powdery, and needs to be treated. But you can definitely use Verdi-Care to remove small spots or areas of verdigris if you think they make a coin look unattractive.

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As long as it is not bronze disease, I too really like the green deposits; they make the coin "pop" in a way.  Sometimes it is a bit obtrusive, but I still like 'em:

Constantius I Chlorus as Augustus, in need of a dermatologist: 

222221105_ConstantiusChlorusasAugAug2018(0aa).jpg.e2b5fead202e16120193f6828e7e5d7b.jpg

 

This Faustina II sestertius came with a single green blob on the obverse - not my most attractive greeny.  It was clearly visible in the seller's photos and I figured there was a good chance it was BD.  But after picking at it, I found the green stuff was very solid, so I'm letting it be.  

810713235_FaustinaII-Sest.2babiesonthroneJul2022(0ab).jpg.1d38157649c236e58c37b55bf485d7b8.jpg

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4 hours ago, Etcherdude said:

Beautiful coin @Al Kowsky.

E.dude, thanks for the comment ☺️. The die engraver cut unusually deep giving the coin a high relief rarely seen on one of these big bronze coins, & I find the verdigris attractive too. The relief spots on Justinian's face remind me of the pustules he probably developed after contracting the bubonic plague 😬. How he survived that dreaded disease is nothing short of a miracle...

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Posted (edited)

Once again, thank you everyone for your amazing knowledge and advice. As probably seems obvious, I'm utterly new to the variations of green material on coins. From previous threads elsewhere, I learned (or, more likely, misconstrued) that greenish blobs on coins signal only immanent coin death. The discussions (at least the ones that I read) never went deeper than that.

Please correct any inaccuracies: Upon further investigation and abstraction from the above posts, verdigris is not bronze disease, but patination, which is corrosion, but not an emergency call-the-coin-doctor-immediately type of corrosion. And many people even like it. Malachite was also mentioned, and the material on the coins I posted does greatly resemble pictures I found of malachite (one page even shows how to grow malachite intentionally on copper coins). It appears malachite forms from a reaction of oxygen and chlorine. Best of all, it's not bronze disease.

Distinguishing verdigris and malachite from bronze disease appears to involve the following questions: 1. is the "green" spread out over the coin or only on one or two places? 2. Does the "green" crumble off when touched or scraped? 3. Does the coin have pits or rim nicks? 4. Does the coin have a pH of 0 - 4? An affirmative to any of these questions apparently suggests bronze disease. Early warning signs of bronze disease include green fuzz. Another source said that coins from Britain, Australia, SE China, parts of Europe, or from places with high humidity or high amounts of sulfur or chlorine can produce coins subject to bronze disease.

So, the situation turned out far more complicated than I imagined. Green on coins doesn't necessarily indicate a reason to lose sleep or to start running in circles screaming, but it should get examined closer for any possible signs of bronze disease.

So it appears that the coins I posted are in no danger, at least not at this moment, which is good news. Again, thank you everyone for getting me there.

Here are both sides of the Probus coin. From now on I will accept its appearance, unless it acquires any crumbly green areas.

276_to_282_Probus_01.png.b134ed99dbb285ddcf9b9ffabad05052.png

276_to_282_Probus_02.png.4f15a91d85a3f8e79272f8f07b64b7a1.png

Probus AE Antoninianus. Siscia, 281 AD. IMP C M AVR PROBVS AVG, radiate draped bust right / CLEMENTIA TEMP, Probus standing right, holding sceptre, receiving Victory from Jupiter standing left, holding sceptre. Officina letter in lower centre. Mintmark XXI. Cohen 87, Ric 644.


Edit: and here are both sides of the Anonymous Vienne dernier

1000_to_1100_Vienne_Denier_01_01.png.2b7d0a1f574d65ee18ea753c7b164328.png
1000_to_1100_Vienne_Denier_01_02.png.7c2af5a60511b86381b097f9c163f8f2.png
France ARCHBISHOPRIC OF VIENNE - ANONYMOUS AR Denier, 11th - 12th Centuries; Obv: .+. S. M. VIENNA. (Saint Maurice of Vienne), profile of Saint Maurice, facing left; Rev: MAXIMA. GALL (Grand Gaul)

Edited by ewomack
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Posted (edited)
23 hours ago, ewomack said:

I have two coins infected by what looks like verdigris: A coin of Probus (the green does not appear on the obverse) and a Vienne Denarius (the green appears on both sides). Neither have great value, but the coin on the left was the first ancient I ever purchased. I have no memory of the verdigris appearing on either coin when I bought them. Despite their worth, I'd like to keep them from deteriorating further. So far, I've read that soaking in acetone will neutralize the verdigris, but not remove it. Another source said that olive oil would do the same, but then the coin needs a soak in acetone afterwards. I remember hearing elsewhere about a "magic formula" called something similar to "Verdigris-B-Gone" that would take care of the mess, but it has limited availability.

Has anyone had any success in staving off the "green monster?" And are these coins perhaps beyond help at this point?

GreenMonster.png.cb69f2e6495950d2b942686315d6465a.png

You could try soaking the coins in 100% acetone to see if the green stuff is PVC based.  Make sure the acetone is pure and the diluted perfume scented type.  The acetone will not affect the metal.  The green deposits seem thick in places, so leave the coin in the bath for 30 minutes or so.  If the green deposits shrink that means the acetone is working.  When you're done with the acetone rinse the coin with distilled water. If the green deposits show no signs of dissolving, then you have two ancient coins with the very common rock-hard green oxidation deposits.  These deposits, as noted, are very hard to remove, often requiring the use of a hand tool such as a dental pick.  Using such a tool is a tricky proposition and dangerous for the coin.  You could try a long term soaking in distilled water to see if the deposits soften to the point when they can be reduced using wooden toothpicks.  You may not be able to completely remove them, but at least they will be less intrusive when viewing the coins.

Were these coins stored in soft plastic flips?  These old style flips have PVC and over time green gunk can build up.  Acetone should remove these deposits, but if they have been building up over many years, there might be some damage under them.  Still I would try the acetone, but it's your call, of course.

Edited by robinjojo
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A very informative discussion.  Here's another one of mine I've been working on - a Julia Maesa sestertius with a nice hard green patina, and, unfortunately, lots of spots of bronze disease.  Green on green!  I didn't do anything with it for a couple of years, but I figured I'd better give it a try.  All I did was put it in for long soaks in distilled water and lots of sessions with the steel dermatology pick (I don't have a dental pick).  

The top photo is the coin untreated.  The bottom one shows it after the soaks and picking - the over all color dulled some, but it seems the light green BD is pretty much gone.  You can see areas of brown/bronze core where the BD came off - no beauty, but perhaps it won't get any worse...

1214775132_JuliaMaesa-SestertiusFelicitasJan2020(0COMPARE).jpg.683105970da22c1d46d9d58b03430e99.jpg

 

 

 

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I understand feeling nervous about green spots and green monsters... Here's one with a LOT of different greens on it (but a beloved favorite Alexandrian). To be honest, I was a bit nervous for a moment. Luckily, there are multiple photographs of this coin going back almost 40 years, though the earliest ones are black and white, the first from Malter XXVIII in 1984, a copy of which was happily included with the coin, both ex-collection of "the other A.K." 🙂 .

As far as I can tell, it hasn't changed. This is one I've left inside its NGC case partly for that reason. I couldn't live with myself if I opened it and then the coin caught B.D.! (The middle photo is NGC but not their website photos, which are apparently strictly copyrighted, but the one used for Heritage's auction. Very accurate to how it looks today, more so that CNG's, on the right, which also seems to show some marks from the holder itself.)

image.jpeg.b222f3996c6e80e8f214604f93c47d6c.jpeg

Edited by Curtis JJ
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Posted · Supporter

I just discovered a coin I have with bronze disease - a LRB that came in a lot. It was a powdery light green deposit that left dust on my finger when I rubbed it. I went to work with a toothpick and it's currently sitting in some distilled water, so we'll see how it turns out. At least it's not a valuable coin!

Regarding the OP and others, all I can say is if that blotchy verdigris appeals to you, more power to you! Personally, I find it hideously ugly. 😝 😉

 

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