Green Substance On Silver Coin ? - Coin Community Forum

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Author	Replies: 14 / Views: 23,267
RealPeso Valued Member United States 426 Posts	Posted 10/07/2011 9:35 pm Hello everyone! I have a silver 8 Reales with some green stuff on the reverse. The obverse has some too but not as much. It almost looks and feels like a wax coating of some kind and it will come off if I scratch the edge with my fingernail but I don't want to attempt any real cleaning yet. I am familiar with verdigris but this green substance does not have the same "crustiness" or feel as dry and encrusted as verdigris. I have no experience with PVC damage so maybe this is it? It doesn't really smell like old plastic or have an odor as I have read. I also remember reading something about how in the past, collectors would coat their coins with something to protect them but I don't remember where I read that or if that type of coating could turn green with time. What do you guys think? Your comments are appreciated before I break out my arsenal of acetone, lemon juice, dips and what not. Edited by RealPeso 10/07/2011 9:38 pm Report this Post to the Staff

CaptainFwiffo Pillar of the Community United States 4132 Posts	Posted 10/07/2011 10:11 pm Could be PVC, but acetone is the cure for almost any kind of goo, so that might work even if it's something else. Report this Post to the Staff
jfransch Pillar of the Community United States 1801 Posts	Posted 10/08/2011 02:52 am You can give the coin an acetone soak but beware the coin may be discolored under that green. If it is PVC contamination, the slime will come off with acetone. If it is verdigris or some other chemical reaction going on, it may or may not come off and will leave a damaged surface because it has reacted with the silver. Either way, if the coin is a common date, you can always clean it, sell it and buy yourself an undamaged one. Report this Post to the Staff
sel_69l Bedrock of the Community Australia 21788 Posts	Posted 10/08/2011 05:32 am The coin seems to have the presence of a copper compound of some type in the surface. If my nemory serves me correctly, these coins were .903 fine, so I assume the other parts per thousand are copper metal. If that metal corrodes to verdigris, (copper hydroxy carbonate) it would show up as green. A couple of types of chemistry would need to happen. The copper would have to find some way to surface enrichment, and conditions to arise where hydroxyl and carbonate anions can form or are present. Carbon dioxide and alkaline conditions would help promote this storage environment. The other thing that bothers me is that the vast majority of Spanish milled silver never attains this type of green cast, and this tempts me into thinking that the coin may be a copper rich forgery. In this case, a condition of self enrichment of the copper in the surface would be unnecessary. Verdicare or similar may be of great help. Removal to a dry storage storage environment that also excludes the presence or the formation of carbon dioxide certainly would. Despite of all of the above, the very first thing I would do is wash the coin in acetone. I do not know nearly enough about these coins to judge this one as a forgery or not. I am only making speculative comments on the chemistry. Report this Post to the Staff
just carl Bedrock of the Community United States 20753 Posts	Posted 10/08/2011 7:40 pm I actually think that the coin looks sort of nice as is. Has that old, tarnished statue look you see on the Antique Road Show on Bronze. If both sides looked like that, I would put that one in something to stop any further reactions and leave it as is. Of course I don't know the date so unless it is a rare or valuable coin, you may have a nice discussion piece. Report this Post to the Staff
RealPeso Valued Member United States 426 Posts	Posted 10/08/2011 7:44 pm Well I have the coin soaking in acetone at the moment, at first the green stuff broke up a bit and a good amount came off making me think that it was just a coating of some sort but now whats left doesent want to come off and it looks like verdigris which might be a indication that this coin could have more copper content than it is supposed to. Once I finish the acetone soaking I'm going to take new pics and post it on the world coin section to see what the experts say. Report this Post to the Staff
BadThad Bedrock of the Community United States 19949 Posts	Posted 10/09/2011 12:05 am Definately a verdigris layer on the surface....no question whatsoever. It could be cupric chloride from exposure to PVC (probably not, no PVC traces I can see) or generalized verdigris. I have no clue on the value of this coin, but you have a few choices when this happens to any coin: 1) Dehydrate the verdigris with acetone and immediately put it into a holder (airtite recommended) and protect it well from any air exposure. 2) Address the verdigris using conservation. However, in this case, I believe you'll find the surface under the layer unattractive. The verdigris is moderate to heavy. 3) Pay NCS to conserve the coin (somewhat expensive). 4) Buy a problem-free replacement. Lincoln Cent Lover! VERDI-CARE™ INVENTOR https://verdi.care/ Edited by BadThad 10/09/2011 12:07 am Report this Post to the Staff
RealPeso Valued Member United States 426 Posts	Posted 10/10/2011 12:18 am Hiya BadThad! I think you'll be pleasantly surprised with the results considering I put your product to some use. I wasn't able to get all of it off but I think I did pretty well. First I soaked in acetone for 24 hours, rinsed then I did light rubs with acetone and then gave it several light rubs with some Verdi Care. It's a shame I wasn't able to get it all off, there is still some left when you look at it real close and there is some build up in hard to reach places but I didn't want to take it too far with the rubbing. Thanks for all of your comments guys! Edited by RealPeso 10/10/2011 8:21 pm Report this Post to the Staff
jbuck Moderator United States 188481 Posts	Posted 10/11/2011 3:18 pm Looks much better! Coin Collector Since 1978 Avatar Old Avatar 7070 Eisenhower Australia Canada World CCF Members on eBay CCF eBay Search Engine Report this Post to the Staff
BadThad Bedrock of the Community United States 19949 Posts	Posted 10/12/2011 12:09 pm WOW! Huge improvement....great job at the conservation. That's as good as it's going to get! Lincoln Cent Lover! VERDI-CARE™ INVENTOR https://verdi.care/ Report this Post to the Staff
BadThad Bedrock of the Community United States 19949 Posts	Posted 10/12/2011 3:56 pm RealPeso - Please send me a PM, your PM's are off in your profile. Thanks Lincoln Cent Lover! VERDI-CARE™ INVENTOR https://verdi.care/ Report this Post to the Staff
googoo Valued Member United States 466 Posts	Posted 10/12/2011 11:06 pm wow very nice job on cleaning that coin not bad looking at all anymore I would be very pleased with that if I were you Report this Post to the Staff
BadThad Bedrock of the Community United States 19949 Posts	Posted 10/13/2011 10:02 am Not cleaned.....CONSERVED. Lincoln Cent Lover! VERDI-CARE™ INVENTOR https://verdi.care/ Report this Post to the Staff
RealPeso Valued Member United States 426 Posts	Posted 10/13/2011 10:06 pm BadThad PM sent. Quote: Not cleaned.....CONSERVED. Exactly! I was actually surprised with the outcome because I didn't think I was going to be able to remove so much but it worked out great. Report this Post to the Staff
BadThad Bedrock of the Community United States 19949 Posts	Posted 10/13/2011 11:58 pm Thanks! I made a side-by-side image using your pictures. Lincoln Cent Lover! VERDI-CARE™ INVENTOR https://verdi.care/ Edited by BadThad 10/14/2011 12:04 am Report this Post to the Staff
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