Verdigris: It's alive! And it is eating my coin.

I found an nearly uncirculated 1827 8 maravidi coin in dirt removed from a 17th century church cellar here in Segovia but it had some small green blotches of verdigris on it. The coin was toned brown having passed nearly two centuries in the dirt but not in weather or water. Had it been in normal ground unprotected by a two story stone building its condition would have been a mess.

This coin would be worth $100 had it been in safe surroundings after its loss. Now it's a curiosity worth about $20?

My dealer friend Juan Francisco had a neat trick: He scrubbed the green growth off the copper coin with a small hand brush with pure silver bristles. Presto - a coin with some hard-to-see brown spots. Now six months later - its back! The green has returned. I am told this cancer of the copper is incurable. Your experiences? I can't find the source for the silver wire brush.

To read the earlier article, see:
NOTES FROM E-SYLUM READERS: AUGUST 23, 2015 : Query: Valuing Colonial Coins With Environmental Damage (www.coinbooks.org/esylum_v18n34a11.html)