Bronze Disease?

@Kentucky, when I started reading this thread, and then found and read some older threads about this subject, I started to get a little concerned that a Claudius bronze as I had recently purchased -- but had not yet arrived, so all I had was the seller's photos -- might be afflicted with bronze disease. Here is the coin:

Claudius I AE As, AD 42, Rome Mint. Obv. Bare head left, TI CLAVDIVS CAESAR AVG P M TR P IMP P P / Rev. Libertas standing facing, head right, holding pileus in right hand, left hand extended, LIBERTAS AVGVSTA / S - C. RIC I 113, Sear RCV I 1860, BMCRE 202. 31.62 mm., 11.18 g.



From the photos, there seemed to be areas on both the obverse (around Claudius's ear and the back of his neck, and in the right field) and the reverse (around Libertas's lower legs and in the lower part of the right field) with raised and/or grainy green deposits that might fit the descriptions I've read of bronze disease, and looked different to me from the normal green patina on a bronze coin. Of course, I couldn't tell just from the photos whether those deposits were soft and powdery or flaky. And I have very little experience with bronze Roman coins from this time-period in the first place. So I emailed the seller (a reputable seller whose name would be familiar to many of you), and this was his response:

"Bronze disease is something that is horrible when encountered, but of the 100,000 plus coins I have handled in 25+ years, I have really only seen a handful of coins with real bronze disease. This is largely due to the fact that I don't ever buy a coin that has been tainted, and if one comes in a collection it is immediately isolated and dealt with.

The answer to the Claudius is no, it has hard green verdigris. Bronze disease is actually an active chloride that is eating away the metal and is always found in a pit on the coin...because it ate the metal away. If left untreated, it will actually destroy the entire coin.

A good friend, who is also a chemist, taught me how to neutralize it, but even then, any coin I cure goes into isolation in a dated envelope in a wooden box on the shelf in my closet for 5 years...if it is truly cured, I will now by then. The 20 or so coins I have done this to have all been cured 100%."

This response did reassure me, and when the coin arrived, what the seller said proved to be accurate: everything I was concerned about is hard; there's nothing powdery or flaky, and nothing came off when I gently prodded the surface. And you can't see any of the grainy areas without magnification anyway. So, as long as everyone's correct that verdigris in and of itself isn't dangerous if it's solid and not powdery, this is a happy ending, I think,

 

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I think I may have been confused with some of my coins showing the exact same thing. Two of them do have BD though which I am currently treating, luckily they arent valuable coins. I'll try to do a before and after once its done.

 

I just bought some uncleaned ancients I am cleaning and a couple of them have a beautiful green coloration that has stood up to soaking and brushing. I tend to call this a patina. Happy your coins are OK.

 

Here's an AE 80 drachms that is currently in ICU for bronze disease mitigation.

This coin had a good, even red and green patina when I bought it last year. I sent it to NGC for slabbing. A few days ago I was going through the ancients box, and found that bronze disease has spread like wildfire over both side of this coin. Apparently the humidity of Florida, couple with encasing in plastic was enough to trigger the corrosion process.

Lesson - be very careful submitting bronze coins for slabbing, especially types such as Cleopatra VII bronzes, which seem to have a tendency to susceptibility for bronze disease.

The coin is currently in a bath of distilled water and cleaning soap. However, the bronze disease is so pervasive that I doubt this coin can be salvaged, even in this drier climate of California. Bummer.