Old Coins Cleaning - main rules
Beginners in coin collecting, as well as people who find (or inherit) a stash of old coins, frequently ask how they can clean their coins. The simple answer to this question is "don't do it!". If you clean your coins improperly you will significantly reduce their monetary value.
Below are several rules concerning coins cleaning.
1. As a general rule, it is not advised to clean old coins and other collectible coins especially when you do not know their numismatic value. Coin experts and buyers would usually prefer coins to be in their original state and condition.
2. The second rule of cleaning coins is take your coins to a professional do the cleaning. Professional dealers often offer a coin cleaning service using a method called "dripping" that should not be attempted by an amateur.
3. The third rule is, if you absolutely, positively must clean your discovered coins, you should clean them with the least harmful method that will give the desired results. Do not be tempted to use harsh chemicals, vinegar, sulfuric acid, abrasive pastes, polishing cloths, metal brushes, rock tumblers, rotating tools, or impact devices which can result in smooth, shiny, metal slugs. You can a lot of information in Internet concerning types of cleaning.
4. After selecting the method you will use, you should experiment on low-value coins before cleaning high-value coins.
5. Handle the coin properly – you may not use bare hands; only hold the coin by the edge and not on the surface.
6. Clean coins one by one – unpleasant chemical reactions among metals may occur.
7. And the last rule is, if you know a coin you are selling has been cleaned, you must inform buyer about it.
CLEANING DIFFERENT TYPES OF COINS
Uncirculated Coins Cleaning
Never clean a Proof or Uncirculated coin as doing so will invariably introduce minute hairline scratches and ruin any mint luster. If there is dust on the surface, use a photographic squeeze-bulb air blower to remove it.
Gold Coins Cleaning
Gold coins, when first struck, are a bright yellow-orange color. Over a long period of time, copper and other trace elements alloyed with gold cause it to tone to a deep orange color, possibly with light brown or orange-brown streaks. Light toning does not affect the value of a gold coin.
Being of a "noble metal" that doesn't itself react chemically with its environment, gold coins are not likely to discolor during cleaning although a centuries-old tone could be removed. Wash carefully in clean, warm, soapy, distilled water with a fluffy cotton washcloth or very soft toothbrush. Because gold is softer than silver, be careful even when using a soft toothbrush for cleaning, as any grit present it will make minute scratches on the surface.
Silver Coins Cleaning
Silver coins, when newly minted, have a bright silvery-white surface. A chemically active metal, silver tends to tone deep brown to black. Circulated silver coins will often have a dull gray appearance, sometimes with a deep gray or black area. Silver coins acquire a blue, green, or violet oil-like tone through tarnishing that can enhance the appearance and desirability of an old silver coin and should not be cleaned.
Many collectors will not buy silver coins that look as if they have been cleaned. When tarnish becomes dark brown or black, and a coin's design is hard to see, there may be some desirability to cleaning it using non-harsh methods, but never with an abrasive paste or cloth.
Copper Coins Cleaning
Copper is among the most chemically active of all coinage metals. When a copper coin is first struck it has a brilliant pale orange surface and turns brown when circulated.
Copper coins tend to look worse after being cleaned and are more easily ruined than gold or silver coins. When absolutely necessary, clean dirty, green crusted, badly corroded copper coins without scrubbing them. Try soaking them in grape oil (or olive oil if grape oil is not available).
Some results can be obtained in one to four days, but don't be afraid to wait several weeks, months, or even a year for desired results. Remember, some of the green patina may be desirable in a copper coin.
Another way to clean copper coins, use a product called MS70, it is available from any good coin supplier.
Nickel Coins Cleaning
Nickel coins, when first minted, are dull silver in appearance, not as bright as silver. Circulated nickel coins have a gray appearance. Nickel coins are best cleaned with clean, warm, soapy, distilled water and a soft toothbrush. For stubbornly stained nickel coins, ammonia, diluted 3 to 1 with distilled water, has been used successfully.
Steel Coins Cleaning
Steel cents actually rust in the presence of humidity. Although difficult to store properly, "steelies" were made in such large quantities that they are never likely to become rare.