Cleaning Coins
"Never clean your coins." – is one piece of advice offered by well-meaning coin collectors. This is frequently offered both on-line and off-line.
Still, many coins, both modern and ancient are improved and cleaned. It pays to know exactly how to clean a coin perfectly. Some methods include soaking in soap and water, using acetone, and dipping in E-Z-Est Coin Cleaner. Ancient coins can be cleaned by, soaking in olive oil, lemon juice or vinegar, rubbing with a toothbrush or copper brush, and scraping with dental tools. Before cleaning you need to know what are considered satisfactory surfaces for any given coin, the techniques of cleaning that are suitable for any given coin variety, and then how to best use them.
Practically all antique coins have been cleaned, since virtually all of them have come into collectors' hands from having been concealed in the earth for 2,000 years, and are tremendously covered with dirt, raw matter, horn silver corrosion, bronze disease.
Countless coins in the past and present have been spoilt by callous scrubbing, primarily by being rubbed with a fabric and coarse cleaning substance or scrubbed with steel wool, causing their market value to be greatly reduced.
You have extra leeway with very old coins when it comes to cleaning than you do with present coins. Collectors don't typically assess an antique coin's value, and judge its market value, by penetrating its surfaces under magnification, though looking at a very old coin through a magnifier or a microscope can help decide its authenticity. In its place, collectors look at very old coins in hand with the bare eye, first and foremost. Its held and felt, just as coins were meant to be held, felt, and looked at.
There are collectors who concentrate in cleaning ancient coins, and there are numerous online discussion groups that deal exclusively with this.