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 Replies: 10 / Views: 1,456 |
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Pillar of the Community
United States
581 Posts |
I have a few coins with a type of green scum on them. A good percentage of it comes of with a simple tissue. I know "cleaning" is generally frowned upon. I think regular soap and water might just take this stuff off. Any other thoughts or warnings.  |
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Moderator
 United States
16677 Posts |
Looks to be heavy PVC residue. Try an acetone soak. What are the other coins?
swcoin.ecrater.com
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Pillar of the Community
 United States
581 Posts |
Here are the rest  |
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Moderator
Australia
16807 Posts |
Not all "green scum" on coins is the same. The Queen Victoria coin looks like PVC damage; this sticky residue forms on coins that have been sitting in cheap plastic coin albums for too long. Acetone or a similar solvent should take the green goo off without too much effort, or further damage to the coin. Acetone is considered "good cleaning" because it doesn't react with either metal or metal oxides; it only removes organics. The 2½ centavos in the OP looks worse; looking at the rim, there actually appears to be chunks of metal missing, especially below the "C" of "centavos"; I've never seen PVC do that to a coin; I suspect this is actual corrosion we're seeing here. You can try acetone on it (acetone will almost never hurt a coin), but from what I can see I wouldn't hope out much hope of seeing an improvement. The usual caveats when recommending acetone: it's highly flammable, use only in well ventilated areas away from ignition sources, no smoking. It's also very good at depolymerizing plastic, so only use glass containers. If it's corroded, you're free to do whatever you wish to a corroded coin, since it's too far gone to be made to "look like new again"; it'll always look like a cleaned corroded coin. I've used lab-grade ammonia to clean stubborn green crust off old copper coins. It turned them orange, but at least they're not green anymore.  Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Pillar of the Community
United States
581 Posts |
thanks, I will have to go out and by some acetone.
I think the worst of it is PVC theough.
If I use the back of my fingernail, I can get the heavier gunk off
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Pillar of the Community
Australia
1040 Posts |
Make sure you get 100% pure acetone, not nail polish remover. Nail polish remover has additives that may damage your coins.
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New Member
United States
46 Posts |
What a coincidence. I had registered today to seek the help of this community on just such an issue, but I'll post my problem in here so to avoid mucking up the forum with two near-identical threads. I purchased an 1832 Half Cent in XF/AU at a flea market yesterday, having examined the coin (apparently not good enough) to ensure that it made a sufficient grade before purchasing it. I was really happy with my purchase until I made it back home and took the coin out to look at it again, when I discovered to my disappointment that it had the dreaded light green coating on the back. Turns out, the flea market stall I was in was too dark to see the green...somehow I was able to see the details just fine, but the dark green was close enough to the dark patina of the copper that they blended together in low light. Anyway, here are pictures: Obverse:  Just fine :D Reverse:  NNNOOOOOOOOOOOOO!! So basically, before I decide what to do, I'm wondering whether this is verdigris or PVC damage. It looks to be very light and there's no pitting or serious corrosion underneath, so I'm hoping I can find a substance to get some of this stuff off. Anyone recommend that Verdi-Gone stuff? I saw the thread on it here and if the pictures of results are anything to go by it looks like it can restore old copper without harming the patina. Any other useful substances? I've heard all the household remedies like leaving it in olive oil for a year and whatnot, but I suppose I'm looking for something slightly faster. Thanks for any help. |
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Moderator
Australia
16807 Posts |
PVC deposits from an album are usually found on the high points, like on the Queen Victoria coin in top left of mrwisker's composite pic. Green down below in the field and in the cracks and crevices of the devices is usually verdigris. So I don't think acetone will help you much, but you're welcome to try it as a first option before hitting it with anything nastier.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Bedrock of the Community
United States
20753 Posts |
To be on the safe side always start such cleaning with distilled water. It's cheaper, safer and may well do just as good a job as other, more expensive and dangerous substances. If the coin(s) have a large amount of that green stuff, try heating the distilled water but use a Pyrex type container. If no Pyrex available, try any glass type cooking utensil that can stand the heat. Do not boil, just gradually heat the water. The warm water has a greater absorbsion ability and may well dissolve that contamination. If this fails, then attempt the Acetone dipping. Note too that Acetone will not effect the coins so the amount of time a coin is left in Acetone makes little difference. Again, use glass for the Acetone. Regareless of what you attempt for cleaning, remember that any metal or plastic type of container may only add to the problem. Remember that most contaminations on coins is a combination of the coins metals and other substances. Removing such contaminations occationally leaves pot holes, scratches, etc. that makes the coin even look worse. That Centavo's coloration really kind of looks like an artist rendition and may well be worth keeping as is. That much green almost looks good.  |
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Bedrock of the Community
United States
20753 Posts |
Once more thing I alway recommend is if you must attempt to clean any coin, do it experimentally. By this I mean do it gradually using safe, cheap substances that are easily available. Many people have tried Lighter fluids, Lemon Juice, Lime Juice, Tamato Juice, Vinager, Molases, Olive Oils and on and on and on. As a rule they are safe and usually already around the house. Just be carefull using the Vinegar. The coins may smell like a salad and you may well be tempting to eat them.  |
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New Member
United States
46 Posts |
Ah, it makes sense that PVC residue would appear on the high points of a coin, considering that those are the points that make the heaviest contact with whatever is containing the coin. I'll experiment with some of the provided remedies on cheap green wheaties that I have laying around, but I'd also like to know if there is anything that is absolutely proven to be somewhat effective at removing a green oxidization film on copper while preserving at least some of the patina. I'm your stereotypical broke (well, not totally if I can still buy coins) college student and can't afford to botch a cleaning on a hundred-dollar coin  |
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Replies: 10 / Views: 1,456 |
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Posted 07/19/2009 7:55 pm
