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Author	Replies: 7 / Views: 1,634
KurtS Pillar of the Community United States 5318 Posts	Posted 09/09/2008 11:24 pm Sometimes I run across a coin on eBay that is just so bad that I cannot help but laugh. This one looks like it was stored in a bucket of seawater, then cleaned up with "Brasso" and maybe returned to the bucket. If you browse the seller's other coins, they seem to have corrosion resembling salt-water exposure--and harsh cleaning. Perhaps his boat sunk with his coins on board? I don't even think BadThad's VERDI-GONE™ could help here. Edited by KurtS 09/10/2008 01:34 am Report this Post to the Staff

Peter THOMAS Pillar of the Community Australia 2830 Posts	Posted 09/10/2008 06:18 am G'day, on the bright side: if you look at the striations on the field, you will see clusters of striations: parallel within each cluster, but each cluster's orientation differs from the others. I think this is a good example of "even cleaning". A few green spots assist in highlighting how shiny the rest of the coin is: like the "beauty spots" favoured by some ladies in former times. Obviously it's a "rare coin" (how many people on your last bus ride had one of these in their pocket ?); AND ... it's "good for its age". Peter in Oz Report this Post to the Staff
KurtS Pillar of the Community United States 5318 Posts	Posted 09/10/2008 12:47 pm Peter, right--I guess one should appreciate the care put into making that one so colorful! Edited by KurtS 09/10/2008 2:40 pm Report this Post to the Staff
malissadawn Pillar of the Community Canada 1931 Posts	Posted 09/10/2008 12:49 pm can I ask a question that's probably been asked a lot on the forum? ok 3 questions. 1) What do you have to do to not get that green stuff on coins? 2) Is it true that it can spread to other coins? If it has green should it just be tossed? thanks Malissa Report this Post to the Staff
DL20K Pillar of the Community Poland 3201 Posts	Posted 09/10/2008 1:11 pm 3) Can it be stopped without chemical interference? Report this Post to the Staff
KurtS Pillar of the Community United States 5318 Posts	Posted 09/10/2008 1:30 pm I don't have many coins with "verdigris", but I think storing your coins away from moisture is good prevention. All my joking above underlined my suspicion this coin was subjected to seawater or something similarly corrosive. The color looks like tarnished brass hardware on my boat. I've heard people say the "green stuff" can spread to other coins, but it's more likely the coins were in a bad environment and they simply corroded together. I keep my coins in airtight boxes with silica gel to reduce moisture buildup. Edited by KurtS 09/10/2008 2:43 pm Report this Post to the Staff
Peter THOMAS Pillar of the Community Australia 2830 Posts	Posted 09/10/2008 2:34 pm G'day, "What do you have to do to not get that green stuff on coins?" there are several threads about verdigris in CCF. One quite recent. A couple of forum members are chemists or metallurgists, and can debate the issues scientifically. The green is sometimes called "coin cancer". I believe bronze coins are more resistant to it than pure copper. I have seen it, but not often, on CuNi coins. If you keep your coins way from moisture, damp, & humidity, then I'd expect that you've won the battle before it has begun. I live in the tropics, and we get 66 inches of rain over a few months each year - called the "wet season". During that time, humidity gets over 90% every day. I have a lot of bronze coins that are stored in a dry place, but I take no other measures, and they are fine. Apparently, prolonged contact with some materials can also bring it on. Nowadays, most storage for coins is described as "PVC-free", but a few decades ago, a lot of flips, 2x2, and albums were PVC. Apparently, that goes bad after a while: haven't seen it myself. "Is it true that it can spread to other coins?" "If it has green should it just be tossed?" that's a common belief among collectors. I always isolate my green coins. I have a stack of them on the window sill in my kitchen. I keep them, in order to do experiments: you know, to see if this solvent or that can get rid of it. I regard green coins as pretty much worthless. "Can it be stopped without chemical interference?" I don't know. But I chose my kitchen windowsill as my quarantine because it is away from the rest of my coins; AND because it is well ventilated, and gets a lot of sunlight. I'm really not sure if that can arrest the process. Don't forget, the green stuff is not just gunk on the surface: it is the product of corrosion, like rust on iron or steel. I have seen old bronze coins with deeply pitted surfaces. I have been told that that's what verdigris leaves behind when it is removed. Peter Report this Post to the Staff
KurtS Pillar of the Community United States 5318 Posts	Posted 09/10/2008 3:02 pm Quote: Don't forget, the green stuff is not just gunk on the surface: it is the product of corrosion, like rust on iron or steel. I have seen old bronze coins with deeply pitted surfaces. I have been told that that's what verdigris leaves behind when it is removed. There has to be a loss to the original surface. Whenever a metal corrodes, it combines with other atoms to form a larger molecule. The visible result is a raised lump on a metal surface. Remove the lump and you'll remove some of the original metal, leaving behind a recessed area. There is really no other alternative--someone correct me otherwise. In regards to copper and bronze, I've seen different types of corrosion. Normal bronze patina is pretty harmless and does not lead to the pitting you describe. But I've seen other types of copper/bronze corrosion which are catastrophic, causing deep pits in coins. I can only guess the metal originally had impurities that reacted over time, or a corrosive was introduced that lead to a chain of unfortunate events--corrosion that produces byproducts which corrode the coin further. I'm sure this has been covered before, or perhaps a chemist like BadThad can describe this process correctly. Report this Post to the Staff
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