Acetone

Correct, Carl. Most nail polish remover has much MORE than acetone in it!

I had an 1863 Indian cent in my 7070 Type Set album that was COVERED in verdigris. I decided to test the suggested solutions and grabbed my bottle of acetone (NOT nail polish remover. Goof Off! seems fairly pure). The suggestion I read said to try distilled water first, then acetone. I didn't have any distilled water, but I had some bottled water which seemed to be more reasonable than tap water (I'm not sure why that made sense at the time. That might have been the beer talking). I poured a bit into a cup over the coin and left it for about half an hour. I was not surprised that it had no effect, so I pulled it out of the cup and dabbed it off with a lint-free cloth so I could move on to acetone. I was surprised to see patches of green on the cloth, so I dabbed the coin some more. With a VERY gentle rub I was able to remove ALL of the verdigris from the coin. Don't underestimate the ability of a soak in water to solve the problem, but next time I will buy some distilled water (or capture some rain water) to minimize contaminates.

I thought nitrates were mostly due to runoff (via fertilizers) and more likely to be in the local water supply than in the rainwater. Sulfides are indeed a problem in some areas, but I live in the boonies where land based pollution (nitrates) are more of a problem than acid rain pollutants (sulfides).

Regardless, a 30 minute soak in tap water, rain water or bottled water would seem to be better than acetone for a first step. Distilled water would be best if treating lots of coins, but to try it out on one coin to see, any reasonable drinkable water source would be a good test. I would argue that tap water (with flourides) and bottled water (with flavor enhancers) are certainly no better than rain water. I used Deer Park Natural Spring water which claims to be 100% pure spring water, but springs, by definition, have mineral deposits that would likely play a role.

Agreed, distilled water would be best. If I ever need to remove verdigris again, I will buy some distilled water. I was sure it wouldn't do any good and was ready to move on to acetone, so I just used some bottled water I had handy that was at room temperature. I was very pleasantly surprised by how a 30 minute soak in just water with a gentle rub of a lint-free cloth did the trick!

You can just boil water to see the reside. You can also create your own distilled water on the stove if you wish. I was cleaning a lower grade coin that had endured many hardships so I didn't bother distilling the bottled water I used. If I were going to do it again then I would make or buy distilled water.

Depends. If a recent print, Acetone should remove it and no problem. IF, it's been there for a long time may be to late.

If the print has been there for a while and won't come off with acetone (and sometimes acetone can't get recent prints off either) a dip may work on it.

If that fingerprint is more than 4 days old, it's there for good.

"Dipping" a coin describes stripping the surfaces with thiourea, an acid which attacks silver. In numismatics it's best-known under the brand name "E-Zest." The use of that substance counts as one of the harshest of cleaning methods and the easiest way to completely screw up a coin short of a wire brush; although there are very narrow conditions under which this treatment might be recommended, it is not for the faint of heart or anyone but a collector extremely experienced in its' proper application. Fingerprint or not, I would not bring that coin within half a mile of thiourea.