Another thread on 'eraser cleaning' made me think of this: When is cleaning good? To be fair, for most of us on CT, the answer is NEVER!!! But . . . most would agree shipwreck salvages cleaned of barnacles to uncover the coins is generally accepted. Most of the comments on CT are consensus: "don't clean!", then under what other circumstances would you agree a coin should be cleaned (anything other than rinsing with distilled water?) I'll bet this could reval some funny stories (e.g. "one time my dog ate, then pooped my coin . . .") Happy collecting!
Simply put, never if you don't need to. If it's covered in mold or mud or the like, then you can use distilled water or acetone but nothing beyond that should ever be done.
When is cleaning good? When it removes something that could damage the coin. (acetone dip for a coin that's been in a PVC holder) When contaminants prevent identification of the coin. (your "barnacles") Anybody else?
When done in an old, frequently discredited, and harmful way and then posted on CT to troll the assembled masses. :too-funny:
If you do not know how, and why, you are cleaning a coin the answer is never. If you know what you are doing, and why a coin needs cleaned, then its fine. Problem is 99% of collectors don't know how and why, and 100% of new ones do not know. THerefor, we tell all new collectors to NEVER clean a coin.
Cleaning coins is generally seen as taboo but there are exceptions. Metal detector coins and coins found in the ocean will often need some kind of cleaning done. Some coins are just simply dirty. I remember about ten years ago I had an Australian penny from the 1940s that looked ok enough but I decided to hook it up to an electrolysis set. The results were amazing, the coin came out looking much better and revealed toning and mint lustre that had probably been covered for decades. That is not to say that electrolysis is perfect by any means, you have to be very careful as it can eat away at the metal of coins when the current and solution used is too strong.
The only time cleaning is acceptable is when it's not cleaning, but conservation. Most people aren't qualified to do conservation because they don't know the methods or have the resources to do so properly. Therefore, NEVER clean a coin, and if it is valuable have some qualified person/entity (like NCS, just as an example) evaluate and do it for you. Don't rely on museum or other historical presevation qualified personnel to conserve it, because the standards for doing so for a museum and what is acceptable for post-conservation grading is vastly different.
When the coin is so gunked up that you don't know what it is. Even then it's gonna be for pure curiosity, not likely that coin will be worth anything.
And on a side note, that I'm sure some of the posters here will be upset I'm saying this: And the other reason to clean a coin is to be able to get it out of your system. If you want to experiment with a totally worthless coin or two (a few) just to see what happens when you clean a coin in a certain way, that actually would be ok. But do get it out of your system quickly and do make double sure none of the coins you use will be collectible in any way, shape, or form, because you will ruin them. Once you see that that true and you have lost whatever value they could have had uncleaned, then you will be saying "Never Clean Your Coins" to others. It is really not the person 'experimenting' with a coin or two to see the result that bothers me. Let them do that, and return the coin to circulation, or simply keep it as another thing gone bad, but when people come on to forums where a lot of people who may have valuable coins in their possession come to find out what to do with it, then people who post here have the responsibility not to let those people think that cleaning a coin to be shinier or easier to read is the thing to do before they go to a dealer to find out its value or sell it. It is too late when they get there and are told that they should not have cleaned the coin. Sometimes people assume that the posters here have the knowledge to pass on, whether that is true or not. So keep saying to not clean coins. And yes, I cleaned 4 coins, but I waited 5+ years into my current collecting timeframe to do so, and I waited until I could determine for sure that the coins I had (all silver dimes) had absolutely NO numismatic value above the silver melt. I then used a bunch of stuff that is regularly spouted as being good for cleaning coins easily on them, and I can tell you it did ruin the coins. They are now in my silver melt pile, and will (hopefully, with the rise of Silver prices) when I sell them, they will be melted for their metal content, never to grace anyone else's presence as a piece of money. And I did not touch my numismatically valued coins. I have gotten that out of my system. The only thing I want to try sometime is acetone. '
