Another Dreaded Verdigris Question

Use the forum search to find threads, both active and archived, containing the word "verdigris" - you'll find lots of helpful tips.

First thing to do is separate out the "greenies" - don't let them touch uncontaminated coins. This stuff's also known as "bronze disease" and "green death" because it's contagious, jumping from coin to coin when stored together in a jar. If you've got them in an album or 2x2's, that should be sufficient.

For coins that are already damaged, personally, a nice long soak in olive oil (say a week or so), then brush and pick away the green stuff. Repeat as necessary. For people with less patience, and who don't mind their copper coins turning a curious shade of orange, concentrated ammonia can work wonders. Lye (concentrated caustic soda, or sodium hydroxide, solution) is also known to be a cleaning agent of last resort.