Notes on the Cleaning, Appearance, and Handling of Coins
The varied fields of collectibles are rife with story and legend. In numismatics, one of the most common stories involves an individual that devalues or nearly ruins a coin by cleaning it. Almost every collector or dealer has a first or second hand account of this story. Sadly, this tale still repeats itself as individuals without knowledge of what makes a coin desirable to collectors literally rub the appeal from their coin.
As a coin ages, its surface reacts to the environment. Oxygen and chemicals act on the metal and produce oxidation. Under the right conditions a light patina forms. The extent of patina depends not only on the environment but also the properties of the metal being affected. Silver, copper, nickel, and gold all react differently to a particular set of conditions. The result of oxidation is referred to as toning and can increase the value of a coin. Although it is technically a discoloration and a deviation from the condition of the coin in its original state, it can be very striking visually and is sought out by collectors. Toning creates a quality that is unique to an individual coin. Take the 1935 Mercury Dime shown here. Certainly, there are many dimes of the same date and mint. But only one exists with this particular pattern and tone.
To the untrained eye, toning might make the coin appear dirty and result in an impulse to clean the coin. Do not do this. Not only could you remove toning and thus value, but abrasive cleaners can cause pitting and scratching. This degrades the coin even more. It may appear clean and shiny to a non-collector but will be seen as damaged or even ruined to an expert. The best option is to do nothing to the coin and seek the advice of a trustworthy collector or dealer. There are rare cases where a coin may be cleaned but that decision should only be made after consulting an expert. If you are unable to show the coin to an expert in person, good sources of information are PCGS (Professional Coin Grading service) and NGC (Numismatic Guaranty Association). Both organizations contain divisions that specialize in coin restoration and conservation. Both groups will professionally clean coins that meet a list of criteria. Links to both of these groups and others that can help with restoration are listed at the end of this article.
Now that cleaning and how it affects the appearance of coins has been discussed, it is appropriate to mention a few other habits and tips that can help you preserve your coins. It is important to handle your coins gently. If you remove a coin from its holder, it is a good idea to have some sort of soft cloth on the surface you are using to examine the coin. Everybody accidently drops things and you’ll be happier if your coin lands in a soft spot when it happens. Coins should only be held on their edges between the thumb and forefinger. This ensures the coin’s surfaces remain free of fingerprints and corrosive oils from your skin. Avoid touching the obverse or reverse surfaces. It is a good idea to use soft cotton gloves when handling proof or uncirculated coins or at least make sure your hands are clean before doing so. It is good coin etiquette to not talk directly over coins. Saliva can fall onto the coin and spotting can result. Like fingerprints, those marks are very difficult to remove.