Ok... So Tell Me... Why Shouldn't Coins Be Cleaned?

Lot of questions to unpack but I'll do my best.

The number one rule to stand by is that altering a coins surfaces is a no-no. That being said there are methods to "clean" a coin without altering the surfaces.




Even then no. You can use acetone or xylene to conserve the coin, but don't clean it.




Any form of cleaning damages the surfaces and removes the originality of the coin.




Corrosion isn't okay, that's why we have methods to remove some types of corrosion. But I'll ask this, if we assume the corrosion has eaten into the surfaces, and it can be removed, would you rather have a coin with a light layer of corrosion or one that looks like the surface of the moon?




Well yeah, anything uncirculated is gonna be worth more than something that was circulated.




Of course it would have been handled, the difference is whether it caused wear on the surfaces or altered them. I have no problem picking up a raw uncirculated bust dollar, it's a matter of how you handle it that matters. I've handled 7 figure raw coins before it doesn't cause wear (but is cool).




Yes they do tarnish, but some tarnish can add value, colorful attractive tarnish is referred to as toning and usually adds value. Black dark toning usually detracts from value, but there are exceptions where it adds value, it's best to assess on a case by case basis.




Any form of cleaning effects the metal unless you use a method that doesn't. Long story short. If you have to touch the metal with something to clean it, it's bad. If it's an acid, it's bad. Some bases are bad too.




Again, case by case basis, and there are very specific things you do in this case. I've known high six figure coins ruined by cleanings.




You can treat any metal as long as you do it correctly

Coins recovered from ground burial (by detectorists or archaeologists) need to be cleaned, just to be able to identify them.
Sometimes, scrubbing in the field with a soft copper wire metal brush is necessary to remove hard encrustations that have fused with the coin.
Museums use a variety of methods to clean and preserve ancient coins. There are always risks involved.

I am not an archaeologist, a museum curator, or a metal detectorist, so I never clean coins,
except perhaps, circulated gold coins in soapy water, rubbing with clean fingers that have been softened in the water.

Impossible to remove fingerprints from coins, if they have been there for more an an hour or two. Immediate acetone bath after exposure is necessary.

Some coins need to be cleaned but I think the advice to never a clean a coin is more to stop people who don't know what they are doing from irreparably damaging a coin.
I would always try and remove corrosion or anything that will make a coin worse over time.

I'll second that.




This is not "technically" an accurate statement. Corrosion, tarnish and toning are all the same chemical reaction. There is just a value judgement embedded in each word (corrosion = bad; toning = good), and "corrosion" usually refers to a greater extent than tarnish or toning (which pertain to a surface layer).

well stated.

@ Nells250:
As an aside to this thread: colored canuba wax on the leather steering wheel cover should work fine! (I have three old classic cars).

Incidentally, museums sometimes use Renwax on ancient bronze coins, to help preserve them.

@morgannerd, I've handled raw coins worth well over six figures before. Just don't be stupid about it and there's no risk. Gloves also have chemicals in them that can be harmful to coins.

On the other hand, at the rare book library that I frequently consult, the practice was to use gloves but they then discontinued it. They currently consider the actual feel of the page against the bare skin is safer than through gloves. They do require well-washed hands. For example, I've handled Isaac Newton's Principia Mathematica, as well as other rare books, with my bare hands. Thus I understand the TPGs handling of rare coins with their bare hands.