Coin conservation

[Paint Your Wagon]

You can call it what you want
Preservation; restauration or cleaning
Just look at the color of the gold ; it went from orange to yellow because the copper
content was harshly attacked

http://www.ncscoin.com/gallery/conserved/index.asp

[Goose]

In my observation, the 'after' pics look lousy! And many snows ago when I first started collecting copper cents, I thought a pencil eraser was the neatest way to 'conserve' the coins. Oh, how times have changed.