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Pennies - turning green - how do I treat them?

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Pillar of the Community
Australia
1360 Posts
 Posted 08/01/2006  09:56 am Show Profile Bookmark this topic Add Snooba to your friends list Get a Link to this Message

Hello,

My son has a set of Australian pennies and half-pennies that are turning green, not all-over green, just mottled little patches. I'm not sure, but I think that more of them are green now than there used to be.

How can I go about cleaning them? Is there a treatment for this? I know you have probably discussed this before, and I tried searching for a thread regarding this, but I couldn't find one, sorry!

Thank you.

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Australia
11283 Posts
 Posted 08/01/2006  10:52 am  Show Profile Bookmark this reply Add Sap to your friends list Get a Link to this Reply
There is a general rule, "Don't clean coins". Green stuff appearing on coppers, however, is an exception to thus rule.

First, we should point out that there are three different types of
"greenness" which might be visible on copper coins. "Patina" is what will gradually form on copper, over centuries. Patina is good, but your pennies aren't centuries old yet, so we can dismiss this one.

How are they stored? If you're storing the coins in a plastic album, it may be chemicals from the album itself which are damaging the coins. Believe it or not, some coin albums are actually dangerous to store coins in! If this is the case, the recommended treatment is a rinse with acetone or some such similar solvent.

FInally, there's the "green death" of verdigris - every coin collector's nightmare. If you're storing the coins "loose" in a jar or bucket, this is the likely culprit. I've got a thread going (well, OK, it's more like a blog-thing) on my trials and tribulations with getting rid of the "green death" from a badly affected copper token. Here it is. I haven't had much luck with it so far, so for now, "do as I say, not as I do" may be good advice!

As to your sneaking supicion that the green gunk is contagious, you're quite correct - it can slowly spread across the coin's surface, and it can jump from coin to coin if they're stored together in a jar or container.

Your best bet for now is separating out all the ones showing even a trace of Green. For common-date, "typical" condition Aussie pennies where the green is winning the war, your best bet may well be to get rid of them; or use them to "experiment" with like I'm doing, so if you notice a more valuable specimen with the affliction, you can treat it.
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
Pillar of the Community
Australia
1360 Posts
 Posted 08/01/2006  11:00 am  Show Profile Bookmark this reply Add Snooba to your friends list Get a Link to this Reply
Thank you Sap,

They are all stored together in a tin, so I will separate them straight away. They are not particularly valuable or rare at all, so I shall give it a shot at treating them, it's not like I have a lot to lose!
Pillar of the Community
Australia
1360 Posts
 Posted 08/01/2006  11:20 am  Show Profile Bookmark this reply Add Snooba to your friends list Get a Link to this Reply
Sap,

I just looked at your thread, and WOW is your token bad! Thank heavens the pennies are not that bad yet. I'm tempted to try your bi-carb/citric acid remedy, but I'm a bit worried about the pink.

Have you conducted any more experiments? Any completely successful?
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Australia
11283 Posts
 Posted 08/02/2006  03:49 am  Show Profile Bookmark this reply Add Sap to your friends list Get a Link to this Reply
I have indeed had more success with today's experiments - ammonia seems to do the trick. If you've got a few "greenies", grab yourself some ammonia and try some experimenting of your own (in a well-ventilated area!).

Note: always give copper and bronze coins a thorough wash and dry after any kind of treatment, otherwise you can get a serious delayed reaction from damp spots or residual chemical, and the coin could end up looking much worse than when you started. I've been rinsing with either tap or deionised water, followed up with acetone to dry it.
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
Pillar of the Community
Australia
1360 Posts
 Posted 08/02/2006  11:59 pm  Show Profile Bookmark this reply Add Snooba to your friends list Get a Link to this Reply
Hello Sap,

I have got some ammonia and I will start my experiments today!

I will report back on how successful your method has been as soon as I have some results. Thanks.
Valued Member
Australia
172 Posts
 Posted 08/03/2006  10:45 am  Show Profile Check Eric's eBay Listings Bookmark this reply Add Eric to your friends list Get a Link to this Reply
Hi snooba,
Yes, I agree with Sap. Cleaning verdigris from your copper is a must if you want to preserve the coin. Have you tried submersing the coin in olive oil over night, and the next day, wash it and the verdigris should come off, although "craters" will be left behind, for which there is very little one can do. If you try this, do tell me how it went. Good luck :)
Eric
PCGS-graded Australian coins: http://www.drakesterling.com
Pillar of the Community
Australia
1360 Posts
 Posted 08/04/2006  01:55 am  Show Profile Bookmark this reply Add Snooba to your friends list Get a Link to this Reply
Hello Eric,

I tried the olive oil method, but found that there was still so much verdigris on the coins that I was forced to try something more drastic. I really recommend looking at Sap's token/medal link to see how the ammonia worked. I used the ammonia method and was very successful.
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Australia
11283 Posts
 Posted 08/04/2006  04:32 am  Show Profile Bookmark this reply Add Sap to your friends list Get a Link to this Reply
Olive oil is still the first preference for verdigris treatment - a mildly affected coin should show some results. "Overnight" may be a bit optimistic for an effect to become apparent, though - up to a week seems to be the recommended time.

Olive oil is preferred because it shouldn't alter the colour of the coin - the oxide layer is kept intact. Other treatments with stronger chemical agents (like ammonia) should only be used as a last resort, and should not be used at all on rare or historically significant items. For instance, I wouldn't try ammonia on any of my ancients; the effects on the patina are just too unpredictable.
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
Pillar of the Community
Australia
1360 Posts
 Posted 08/04/2006  04:41 am  Show Profile Bookmark this reply Add Snooba to your friends list Get a Link to this Reply
I defer to Sap as the expert!

As I only used it on the worst, cheapest, and most affected of my pennies, I really had nothing to lose, no matter what happened to them. Besides, I must say, it was kind of fun. There's nothing quite like playing at 'mad scientist' for a kid at heart.
Edited by Snooba
08/04/2006 04:46 am
Pillar of the Community
Australia
2248 Posts
 Posted 08/14/2006  01:03 am  Show Profile Bookmark this reply Add gxseries to your friends list Get a Link to this Reply
Using ammonia is a terrible mistake and that I can vouch it. If you have the time, you SHOULD use olive oil and leave it for MONTHS

I had several coins that are not too cheap, and this was the only way to deal with it. And as to get rid of the oily residue, the best is to dip it in acetone when you are done.
My partial coin collection http://www.omnicoin.com/collection/gxseries

My numismatics articles and collection: http://www.gxseries.com/numis/numis_index.htm Regularly updated at least once a month.
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