Dramatic effect of acetone on roman coin

[Jay C]

I usually rinse coins in acetone that have been stored in a PVC flip, or even a flip that I suspect is PVC

I have never seen such a dramatic effect from doing so. The coin was in the acetone for a minute or two. Yes it was 100% acetone not nail polish remover.

Before, the coin was a very dark 'patina', I thought unusually glossy. Afterwards, it is green and crusty.

I believe that the acetone has removed a layer of oil or something that was on the coin. Note, this came from one of the best known global auction houses. It wasn't labelled with anything that suggested a fake patina, but it was described as "Dark brown patina, roughness, smoothing. Good Fine."

Do others agree that the acetone has removed a layer of something deliberately placed there to make the coin look better? Should the auction house have noticed this/disclosed it?

I probably wouldn't have bought the coin had I realised, although it wasn't expensive. It's still a large (34mm) interesting Roman coin.

Just thought it would be useful to get others' perspective

[Jay C]

Should I mention this to the auction house I bought it from?

I realise cleaning is “at your own risk” but clearly the acetone has removed something very easily that was not a natural appearance. I’ve never known acetone to do anything like this

[Jay GT4]

I wouldn't have suspected anything looking at the original picture.

[Kevin D]

If you have dipped a number of ancient bronzes in acetone, I am pleasantly surprised you haven't seen other coins show dramatic changes. Bronzes are not my main collecting interest, but I do like them and I have ended up with many in my collection. I have bronzes that I feel look too good for something 2,000 years old, to have not had something done to them. From reading online blogs, I know people like to 'treat' their ancient bronzes in a number of ways that they feel helps with protecting and preservation. Oils and waxes are sometimes mentioned in these blogs.

You could mention your experience with this coin to the seller. I don't fault the seller for possibly missing a coating on your coin. These commercial sellers have less time to study each coin they sell, than do the collectors who buy the coins. As a buyer and collector, I realize there are going to be instances when I see something on a given piece, that the seller missed, simply because of the amount of time I can spend looking.

[Jay C]

I wouldn't have suspected anything looking at the original picture.

It was more when I had it in hand that I was suspicious, it looked unnaturally glossy

[Jay C]

If you have dipped a number of ancient bronzes in acetone, I am pleasantly surprised you haven't seen other coins show dramatic changes. Bronzes are not my main collecting interest, but I do like them and I have ended up with many in my collection. I have bronzes that I feel look too good for something 2,000 years old, to have not had something done to them. From reading online blogs, I know people like to 'treat' their ancient bronzes in a number of ways that they feel helps with protecting and preservation. Oils and waxes are sometimes mentioned in these blogs.

You could mention your experience with this coin to the seller. I don't fault the seller for possibly missing a coating on your coin. These commercial sellers have less time to study each coin they sell, than do the collectors who buy the coins. As a buyer and collector, I realize there are going to be instances when I see something on a given piece, that the seller missed, simply because of the amount of time I can spend looking.

Honestly it is quite a worn coin and the coating didn’t change that, it just made it a bit more attractive. I will think twice about rinsing in acetone although I have seen what pvc does to a coin and that is what I am trying to avoid. But I think it’s a $60 coin now rather than the $90 I paid for it. In hindsight I would take my chances with the pvc.

[Ken W2]

It appears to me the coin had only been waxed and the acetone just removed the wax.  Note how the waxed version presents more detail. Did the acetone take on a tint of any color?
I don’t have any experience with pvc residue on bronzes, but have used acetone many times to remove it from silvers always to a good result. Imho if you suspect pvc residue you should remove it with acetone, otherwise there is the possibility of continued/future damage. 
Fwiw, I don’t think being waxed or removing the wax changed the value of the coin. Sure, wax changes the presentation some and folks do it for a few different reasons, but the underlying coin is what it is, assuming of course the wax or other treatment can be removed without harm.
Imho “treating” and waxing sometimes detracts from the presentation. Take for example this MAL IMP.VES and I recently acquired.  In retrospect I believe as received (top photo) it had been treated with something that made it darken (perhaps a long soak in sodium thiosulfate or dip in liver of sulfur) and then waxed.  I did not like the dark somewhat glossy appearance. I soaked in acetone and lemon juice but with little effect on the darkening. I then made a small test rub on the edge with diluted prelim on a water soaked cotton Qtip which easily removed the darkening.  So I gently cleaned the entire coin in that manner and then removed any prelim residue under warm running water with a soft brush. I think now the coin makes a better and more genuine presentation. 

[Jay C]

Thanks Ken. I didn't notice any tint in the acetone, which come to think is odd.

I am paranoid about PVC because my childhood coin collection (which I didn't touch for 20 years) was covered in green slime after being carried around from place to place (including the tropics). Ironically in a "coin" album that I won in a competition (great prize). Acetone did the trick, coin by coin.

I agree that your natural appearance Mark Antony coin looks better... not sure mine does. At least the green doesn't appear to be bronze disease (it is stable).

[Joe Sermarini]

A lot of bronze coins have enhanced patinas. When I say a lot, I don't mean it is a high percentage of them, but still... This includes some very very expensive coins, some very beautiful sestertii. Some were enhanced decades ago. My advice, don't dip your coins in acetone if you like the coin the way it is. If I see a coin that I am confident has been enhanced, I will say so in my descriptions, but I expect I miss more than I catch.

[Jay C]

Thanks Joe, great advice. With hindsight, I thought this coin was unnaturally shiny when I had it in hand. My preference would be to not purchase a coin that I felt had been "enhanced" like this, but if I had bought it in an auction and had my time over, I would not have done anything with it.