I have several ancient coins that are green in color from what I assume is normal copper oxidation (like on the Statue of Liberty).What is the difference between this and verdi gris? I'm just wondering if I need to do something to make sure these coins last another 2000 or so years...wire brush,Brasso??
Verdigris is just copper oxide, so it's the same. Defination of verdigris: http://en.wikipedia.org/wiki/Verdigris
Thanks gx, OK,so that leads to my next question. It's obvious that the verdigris has done little or no harm to the first coin and in fact,seems to have protected it somehow.The details are almost as struck,so when is verdigris harmful? Is it when silver coins that have some copper content are exposed to it or what? I know when it is cleaned off of some coins,there is pitting damage from the reaction.What gives?
I would say Acetone but don't know if that will work on Verdigris...I think GDJMSP knows a "cleaner" that takes care of it... Speedy
Acetone will do zero effect on verdigris. Acetone only works to dissolve organic material and verdigris unfortunately isn't organic. In fact, dipping copper coins into acetone is not recommanded as it might give some awful toning effect. Appearently, the only way to kill verdigris is to dissolve it in a solution of WEAK acid, such as vingear, or in fact brasso. But wait, don't do this, I remember GDJMSP had a solution that is supposed to remove verdigris effectly, although I haven't tried it out yet.
I was just kidding about the cleaning.These coins have probably been this color for many centuries and I doubt they're in jeopardy.In fact,I LOVE the green color. I was just wondering why verdigris is sometimes deadly to coins and sometimes protects them from further corrosion?
Verdigris is like a two-edge sword if you wouldn't like to believe me. It is a corroded piece of metal and if you were to clean it, most likely you would see pitted holes as the verdigris is happily eating away the copper. However on the other hand, reaction will only occur on surface area and hence, whatever that has reacted on the surface area will most likely not be able to pentrate the layer of verdigris, hence protecting some areas. The trick I guess when cleaning such coins is to find out what areas would show up horrible pitting and to take special note of and to preserve it next. I'm sure Mike (mmarotta) will be able to tell very speificially on such cleaning / preservation process. edit: sorry, I wasn't paying attention to my grammer (lol)
