What's So Bad About A Cleaned Coin?

I take all the coins I plan on putting in an Album and dip it in battery acid. Then srub it with baking soda and tap water to neutralize the acid. Then to protect the surface, I apply some Turkle Wax polish. This makes my entire collection shine, shinek, shine.
In reality it's simply a problem with the amount of cleaning. Some barely clean coins, some get carried away with harsh cleaning. Some use almost anything on Earth to clean coins. So many spit on them and then rub away.
Regardless of how much cleaning, just remember that cleaning in most intances removes the outer layer of material. This makes coins slowly less and less until the entire coin is cleaned away.

"Dirt", "grime", "goo", "ectoplasm" or any other foreign material adhered to the surface of a coin, such as old stickytape residue, paint, varnish or glue, can be removed from a coin, and nobody has a problem with that. This is "acceptable" cleaning, since it does not chemically alter the surface of the coin. "Unacceptable" cleaning removes tarnish, toning and oxidation - basically three names for the same thing. Removing this is considered bad because to remove it, you need to apply aggressive chemicals that actually dissolve away part of the metal.

There are three reasons why removing the oxidation layer is considered bad.

1. It is irreversible. Once you clean a coin, if you change your mind and decide it looked better beforehand, too bad - it cannot be "dis-cleaned" again. Sure, you can re-tone it, but all this does is create a new oxidation layer on the surface - it does not put the old one back. It's gone forever. The reason why uncleaned coins are worth more is because so many coins back in the old days have indeed been cleaned, both by their non-collecting owners and by actual coin collectors. Never-before-cleaned coins are therefore in the minority, and therefore rare and valuable.

2. The damage it causes is cumulative. Professionally dipping a coin in silver dip just once does very little damage; you'd need an electron microscope to tell the difference. But dipping the same coin ten times, or doing a botched job, does damage noticeable to the eye.

3. Removing the oxidation layer exposes raw metal to the atmosphere and can even chemically "activate" it, causing the coin to re-tone faster. So the coin, once cleaned, will need to be cleaned again very soon afterwards if the owner insists on it "looking shiny". And again, and again. As noted above, repeated cleaning causes cumulative damage.


There are several widely recognized and accepted exceptions to the "Don't clean coins" rule. We tend not to mention them to new collectors, because they generally don't apply to them and we don't want to give out mixed or ambiguous messages. But the exceptions are:

1. Ancient coins, shipwreck coins or other coins that have been dug up out of the ground. These need cleaning, sometimes rather fierce cleaning, to remove the encrusted dirt, coral and other things stuck to them over the years. An ancient bronze coin, after being buried for 2000 years, is usually well on its way to being turned back into the copper ore from whence it came; they come out of the ground looking like little green rocks and need careful, patient and expert cleaning to make them look anything like coins again.

2. Coins that have active corrosion on them. This typically only applies to base-metal coins. Bronze disease, zinc rot and aluminium cancer can all "spread" in a pseudo-biological fashion if the coin is left untreated. In this case, a "cleaned-looking" coin is better than no coin at all, which is what you'll get if you don't remove the corrosion. The same logic applies to any chemically damaged coin, even if the damage is not "contagious", such as coins scorched in a fire or covered in verdigris: a cleaned coin is better than a damaged coin.

3. Coins stored in hazardous plastic. Plasticizer-laced PVC found in cheap 1960s and 1970s coin albums is the main culprit, though if it's pumped full of enough plasticizer pretty much any form of plastic can be made hazardous to coins. The plasticizers release acid as they degrade, and the acid eats into a coin in such an album, forming a sticky green "goo" which etches into the coin surface. Not only is it ugly to look at and unpleasant to touch, but the goo can continue to cause damage while it remains in contact with the coin. The goo can be removed by acetone but the damage has already been done.

4. War medals. Nobody can stop old soldiers from polishing up their medals to make them look nice, no nobody really tries to stop them. While it isn't necessary to keep them polished, you'll find that, as far as market value is concerned, being "cleaned", even harshly and repeatedly cleaned, does not affect their value to the same extent that you'll find with coins.

The main problem is that cleaning usually hurts the resale value. I buy cleaned and damaged coins as rarities, for bullion, or for pocket pieces. I'm finicky about buying coins that will eventually be resold.

I own a hole that that I paid negative 50 dollars for. I know this with reasonable certainty because the dealer from whom I bought the coin in which the hole can be found was selling two identical coins: one with the hole for $25, and the other without the hole for $75. Being budget-conscious and just wanting an example of the type, I bought the holed one. I have regretted doing so ever since, because I have often seen it in the album and wanted to upgrade it, but I've never seen a local dealer offer another one. The hole is probably worth a higher negative number today, because to buy the undamaged coin would probably cost $200-$300 now. My holed coin is still only worth $25.

I thought the oven cleaner would hurt the coins. But with that can of coins I had an ugly paper weight. Oven cleaner dont sound good for coins, but it did an almost perfect job. That key shield nickle looked like new, and it looked like it just came out of a coin roll. No scratches etc. I just washed the cleaned off and dried with a soft cloth. silver and copper also.

I did this as last resort only and it worked and I had nothing before I did it

Yes, all good points of view - but I am a little concerned about just_carl .

IMHO cleaning, conserving, preserving, bathing, spit and shining, is in the eye of the behold. While I prefer coins that are not cleaned, I have seen TPG cleaned coins that I would not kick out of my collection. A CCFer who is excellent at cherry picking those is johnny54321. Johnny Countdown recently snagged a SLQ that was amazing and did not look cleaned. I have seen other examples of his cherry picking and am green with envy.

Bottom line, if you it, like buy it. If don't, don't. That way if someone says something negative about your coin it is no skin off your back.

I've heard claims that all old silver coins that are not darkly toned or tarnished must have been cleaned at some time. That point of view has some merit since silver is prone to tarnishing and most old coin collections were not stored in inert atmosphere conditions. Therefore, it's possible that many of the bright, lustrous silver coins currently residing in problem-free TPG holders were in fact cleaned at some time. However, if the cleaning cannot be detected by careful inspection by experienced collectors, I'm comfortable accepting such coins as original and would value them accordingly.

You assemble a collection from the coins that are available. If you limited your choices to coins that could be somehow guaranteed to never have been cleaned you probably wouldn't have much of a collection.

I have several cleaned coins and some of them look hideous. I try to stay away from them when I can.