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why is it bad to clean coins?

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New Member
United States
2 Posts
 Posted 12/10/2007  01:01 am Show Profile Bookmark this topic Add Rekced to your friends list Get a Link to this Message

I'm just wondering. I'm so new to collecting I have never even purchased an old coin yet.

Why do people always leave them dirty and corroded.. Aren't there solvents that clean them w/o harming the metals in any way? I had some silver dollars when I was a child and my parents cleaned them for me.

I'm just curious..

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 Posted 12/10/2007  01:32 am  Show Profile Bookmark this reply Add ElleKitty to your friends list Get a Link to this Reply
There are solvents and chemicals that can clean away the 'dirt and grime' from the surface of old coins. However, coins develop over time what is called a patina. This is simply the interaction of the surface of the coin with the air around it. The patina protects the rest of the coin from environmental changes, or damages. To remove this patina exposes the coin, and often changes the luster and tone of a coin.

Unless the grime really is grime, like a layer of dirt; or if it is corrosion that will eat away at the metal of the coin (such as the green on copper coins) it is simply best to just leave a coin alone.

Cleaning always leaves telltale signs such as streaks, spots, scratches, or an odd colour. About the only sort of cleaning I will do is a gentle bath with pure acetone. It takes off lots of inorganic grime such as PVC or sticky tape. :)

I'm sure someone else will come along with a more complete answer. We've got some experts on the subject.
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 Posted 12/10/2007  02:03 am  Show Profile Bookmark this reply Add thingee to your friends list Get a Link to this Reply
Cleaning a coin will significantly lower the value of the coin in most cases. Most coin collectors will not buy a coin that's been cleaned. Also there are 'cleaned' coins that are acceptable when properly done- but it's not called cleaning- I can't think of the word at this moment.
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 Posted 12/10/2007  02:05 am  Show Profile Bookmark this reply Add ElleKitty to your friends list Get a Link to this Reply
Conserved?
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 Posted 12/10/2007  02:05 am  Show Profile Bookmark this reply Add gxseries to your friends list Get a Link to this Reply
Why do you think that we don't clean ourselves up with rough sandpaper or shower in hydrochloric acid? Remmeber coins are awfully small compare to our body size and they do not have the ability to self regenerate once their "skins" get reacted to the atmosphere.
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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 Posted 12/10/2007  03:48 am  Show Profile Bookmark this reply Add thingee to your friends list Get a Link to this Reply
The olive oil, distilled water, acetone and like methods. I won't use dipping either because that term can also be confusing.
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 Posted 12/10/2007  1:01 pm  Show Profile Bookmark this reply Add KurtS to your friends list Get a Link to this Reply
quote:
Why do people always leave them dirty and corroded


Dirty or not, It's also the original minted surface of the coin, which carries those subtleties left by the die. Remove patina, and you remove some of that original surface metal. A cleaned/abraded coin might look shiny on a superficial level, but it can actually lose a lot of original detail.
Edited by KurtS
12/10/2007 1:21 pm
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 Posted 12/10/2007  7:17 pm  Show Profile Bookmark this reply Add longnine009 to your friends list Get a Link to this Reply
When coins are struck the planchet moving over the die, etches microscopic lines in the dies. The lines are transferred to the coin as "flow lines" and are what gives a coin luster. When coins are dipped in a chemical such as a weak acid to remove toning or tarnish or corrosion or whatever you wish to call it, the acid attacks those lines. The claim is usually that one or two dips won't really effect the flow lines that much. But no one really knows how many times the coin has been dipped before. It could have been a number of times because once the original toning is striped away the metal is re-activated and the coin will probably tone/tarnish even faster then it did the first time and probably in a very splotchy uneven manner as well, which will only make someone else want to dip it again. Sooner or later the flow lines will be blunted enough to impair the luster. When that happens, it's over--R.I.P

This is the whole irony of dipping. It's done to expose a coin's luster again and make them pretty and eventually it is what will destroy the luster--Forever.

When it comes to cleaning coins, there is almost no problem that can be solved without creating a new problem. Even removing dirt will leave the area where the dirt was with a brighter color than surrounding area.

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United States
136 Posts
 Posted 12/10/2007  8:28 pm  Show Profile Bookmark this reply Add dahoov2 to your friends list Get a Link to this Reply
I have been guilty of cleaning; but mostly Lincoln cents and because I can't read the mint marks because it's corroded or dirt or discolored. I wouldn't clean them otherwise and do replace the cents in my books with others that are more legible and "uncleaned" if I come across another. Today I had to clean a "new" penny 1999 even just to read it. But I'll replace when I come across another. There was a point made above about color changing. The color doesn't look right when you clean them. They also seem to discolor faster and more unevenly. It's like any silver item of antique, or furniture. Never clean or strip... it ruins value. I do feel sometimes it may be needed though? Just my opinion as a newbie.
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 Posted 12/10/2007  9:01 pm  Show Profile Check Prethen's eBay Listings Bookmark this reply Add Prethen to your friends list Get a Link to this Reply
There are proper ways to "clean" or conserve a coin. When done right, it removes none of the metal, causes no direct harm to the coin, and removes only the agents that the "cleaner" intends to remove. That said, I wouldn't aim at removing dirt off the coin unless the coin is already corroding. Crusty, original surface coins are almost always better than their ugly, "white" counterparts. If a coin can be guessed as cleaned, it's value is usually significantly decreased, if not decimated.
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 Posted 12/10/2007  9:15 pm  Show Profile Bookmark this reply Add collect4fun to your friends list Get a Link to this Reply
Ever watch the tv show Antiques Roadshow? They will sometimes have a piece of furniture that has been "Fixed", "refinished", or like terms that had it been left in it's original condition would be worth thousands of dollars more. Well, coins are like that also. You want to keep them in their "natural" condition.
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 Posted 12/11/2007  10:30 am  Show Profile Bookmark this reply Add just carl to your friends list Get a Link to this Reply
It also depends on your future plans for coins. If, for instance, you just want a nice, shinny looking coin collection, not worried about future values, clean away. Way, way back when I was a kid it was normal, even necessary to clean all coins. If you showed anyone a coin collection the first thing you would hear is why don't you clean them, they are all dirty. And clean them we did. Used to use things like baking soda/water, gasoline, kerosine, battery acid and anything else that would get that dirt off.
As already noted lots have changed since the good old days. Antique Roadshow usually explains removing a layer of material deminishes the value due to loss of originality. An example is an old car, 57 Chevy, if all hoses on the engine were replaced with wrong color hoses you've lost originality. If radial tires put on, not only lost originality, but now unsafe.
One problem with cleaning coins is if the so called dirt is in reality a substance formed from the coins metal with an outside source, the removal of that substance removes some of the coins material. The darkening of a Copper coin is in reality the normal Oxydation process forming CuO, Copper Oxide. Further exposure to the air with moisture and Carbon Dioxide will form Copper Carbonate, a greenish Patina or layer. Removing this removes some of the Copper and it will start all over again. Continuous removal will slowly show up as massive wear making the coin less desirable to collectors.
just carl
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 Posted 12/11/2007  6:52 pm  Show Profile Bookmark this reply Add longnine009 to your friends list Get a Link to this Reply
I'm not chemist but it seems to me if toned or "tarnished" coins are just left alone the corrosion to the coins metal should arrest once the toning is heavy enough. The whole corrosion process requires oxygen doesn't it?

Too many things in the world are better off just left alone to find their own stability and equilibrium.
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 Posted 12/12/2007  11:21 am  Show Profile Bookmark this reply Add Conder101 to your friends list Get a Link to this Reply
Very briefly it is because while it is POSSIBLE to sometimes clean a coin in such a way as to improve it, it is not easy to determine the best method to use. And it is VERY VERY easy to damage a coin by cleaning it improperly. So the knee jerk reaction is to always tell newbies just not to clean them. Because every coin has to b evaluated on its own merits an you could easily write at least a pamphlet on the advice and methods for cleaning each individual coin because what works on one will not work on another.

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 Posted 12/12/2007  12:47 pm  Show Profile Bookmark this reply Add thq to your friends list Get a Link to this Reply
I find myself buying dog coins more often these days. If I can improve one of them by cleaning it, I will. What's the difference with something that I'm going to stick in my pocket and carry around?

Current case in point. I've given up on finding a presentable Liberty Cap cent. 99% of what's available is corroded, pitted, scratched, cleaned, etc etc. The 1% slabbed or slabbable material is astronomically expensive. So why try? I just picked up a blackened, corroded, pitted but readable 1795 cent on eBay. Fine details at half the price of a G4. Hit it with clorox and ammonia - no big effect - silver polish - nothing - so time to bring out the big guns Comet and a plastic scouring pad. The coin is now attractive (enough) and in my pocket, rubbing up against an 1859 florin and an 1834 shilling.

Would I do this to a nicely patinated 1795 cent? No, that would be stupid. I'd be wrecking the value of a $1500 investment coin. But doing it to an ugly corroded 1795 cent has done nothing to decrease its value. I don't have to worry about keeping it locked up in a safety deposit box, either.
"Two minutes ago I would have sold my chances for a tired dime." Fred Astaire
Edited by thq
12/12/2007 4:00 pm
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 Posted 12/12/2007  2:48 pm  Show Profile Bookmark this reply Add Conder101 to your friends list Get a Link to this Reply
thq, you would be surprised by how nice that black, corroded, 1795 cent would look after a year or two riding around in our pants pocket with your other change eve without any preliminary cleaning. I've carried black corroded 1798 and 1802 cents for a couple years and come out with nice brown fairly smooth coins. They were pretty much junk when I started and fairly attractive collectible coins when I finished.
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