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I think know cleaning coins is a no-no.
but then i read about " improperly cleaned " coins.
is there a certain way to clean a coin acceptably ?

Dosen't NGC offer a coin restoration service.....then they slab the coin as a normal (non-tampered with)?

Come on MH you have gotta know something about this.

Yes, NGC does have a branch called NCS (National Conservation Service). They have undisclosed techniques of cleaning coins properly. They do a fairly good job of removing foreign substances and verdigris, but they can't do everything. Thick, heavy verdigris and some foreign substances will result in pitting if removed.

If you're trying to get rid of tarnish you can "dip" the coin using some chemical that I can't remember off the top of my head. If you're trying to get rid of a fingerprint dip the coin in PURE acetone. Also dip the coin in acetone after you use the chemical to remove the tarnish or it will develop spotting and possibly worse things.

Rodebaugh wrote:...Come on MH you have gotta know something about this.

rakattack answered most of the questions. For silver and gold coins, there is a solution called EZest Coin Cleaner which contains sulfuric acid and thiourea. It is typically only used by professionals to remove non attractive toning on MS coins. Unscrupulous people or inexperienced collectors will sometimes use this to dress up their coins. Many people want bright and shiny SAE's, so there are many dipped SAE's out there.

A properly dipped MS coin is OK according to grading companies.

Pure acetone (not nail polish remover) is used on some deposits as a nondestructive means to ameliorate coins. There is a product out there for copper coins call Verdigone, I think. I'm not sure of its use, but it is primarily copper coins if I have my facts straight.

It is important to know about these products, their proper uses and applications, and how misuse affects coins and what look for. I have done my own personal tests in an attempt to see if I could determine "properly" cleaned and "improperly" cleaned coins. After several years, I'm still learning something new every once in a while. But for the most part, you should be able to get some test coins and try it out... Or just buy slabbed and forget about the rest.

Market you are right, it's called Verdigone and it removes light to moderate corrosion (verdigris) or the green stuff that grows on copper. Heavy verdigris will be STOPPED by Verdigone but won't be removed.

By the way, don't dip coins too long or the original luster will be removed and the coin will look darn ugly

I wash just thinking about a light washing to clean the surface dirt off of a couple.
somewhere in here i read a person just soaks them in warm water then wipes them clean with a soft cloth.
another post mentioned baking soda in the water.
coincidently, last night i left a 1038s quarter i had just bought in my pants pocket,
it was in one of those clear plastic 2x2 jackets, when my wife washed them.
it came out much cleaner than when i bought it.
now it doesn't match all the other quarters in the album.

I always use acetone and a cotton swab to remove gunk and that thin build up that occurs after 75 years. I dab verdigone on the green spots and it does work some, but like said earlier, its not a miracle cleaner its a preservative.

chemical dips = properly cleaned if done right
mechanical cleaning, i.e. rubbing, scrubbing, polishing = improperly cleaned

If you have a coin that is ugly due to patina (whether silver or copper) then you should only use weak chemicals that do not affect the coins surface. Anytime that you actually affect the surface of the coin, you are damaging it. This goes for polishing cloths, Q-tips, pin points, toothpicks, putty, and other "mechanical" cleaners. If you use baking soda and rubs the coin with your fingers, then you are basically using an abrasive on the surface

Only buy coins that you are happy with when you see them the first time. A damaged coin is typically worth far less than its original counterpart. Only test cleaning solutions on coins worth just their bullion content.