Those new to coin collecting may have a predisposed idea that the best coins are shiny coins, and while that can be true in some cases, it’s not always. This idea tends to lead to the cleaning of coins, which can reduce their appearance and, ultimately, their value.
Ask any seasoned coin collector how to clean your coins, and their immediate response may be, “Don’t!” But that doesn’t mean it isn’t possible. There are “safe” ways to clean coins when you absolutely must, but even those do not guarantee to make your coin “better.” It is almost always a bad thing to clean coins. The advice to leave your coins alone rather than cleaning them first appeared in the 1962 edition of Seaby’s Standard Catalogue.
Coin Cleaning Methods
When discussing cleaning coins, there are several terms used that refer to the various methods of cleaning coins, such as “whizzing,” “dipping,” polishing,” and “thumbing.” Each of these terms refers to a different practice used in coin cleaning.
MCM does not condone any of these methods, nor do we recommend trying any of them. We are identifying these methods to help you spot them while buying coins.
Thumbing is a form of coin altering where a small amount of body oil is applied to the surface, which dulls the luster in an area where there are marks. Body grease eventually turns a brownish tint and attracts other pollutants. This contamination can make the coin start to tone an off-golden color. Thumbing also occurs naturally when a person mishandles a coin. If a person does not handle their coins with gloves or other safe methods and instead uses their bare hands to pinch the obverse and reverse with their thumb and pointer finger, “thumbing” can occur.
While dipping CAN be done at home, this method carries risks and is best left to professionals. Dipping is a common practice where a toned or tarnished coin is dipped into a mildly acidic solution that removes the tarnish and restores a bright appearance on the surface of the coin. When done expertly, the coin is rinsed to remove acid altogether. After a coin has been dipped, it should be nearly impossible to tell that it was. It is, however, possible to over-dip a coin. Over-dipping a coin will leave the surface acid-etched and dull in appearance. There is no way to reverse the process of an over dipped coin.
Polishing is a coin cleaning technique that is done by hand. Typically, a person puts some silver polish on a soft cloth, folds the fabric in half, and then places the coin in between. They will then rub the coin in the cloth using their thumb and index finger to clean both sides at once. When polishing is finished, the coin will be wiped on a clean part of the cloth to remove the polish.
Whizzing is a technique in which the surface metal is moved mechanically to create the illusion of luster. Whizzing can be done expertly. The most common method involves using a high-speed drill, like a dentist’s drill, with an attachment on the top similar to a fine-haired brush. This tool is used to enhance the surface and smooth away scratches, marks, and hairlines. In some cases, heat may be added to the process to melt the coin’s defects, but these treated coins can have an unnatural appearance.
Cleaned vs. Uncleaned Appearance
Telling the difference between a cleaned and uncleaned coin can be nearly impossible just by the photo of a coin. However, when seen in-person, there can be some giveaways to determine if a coin has been cleaned. When under light, a coin should have a cartwheel-like shine that moves as you turn the coin. This cartwheel effect is caused when the metal is squeezed as the coin is struck, resulting in a delicate appearance that is instantly degraded or destroyed by most of the aforementioned cleaning methods.
Some other tell-tale signs that a coin has been cleaned is too much unnatural shine, too many dull or shiny spots, the rims do not appear as “clean” as the rest of the coin, or the coin appears clean except around the devices, where a person may have had trouble cleaning.
NGC Details Grading
The Numismatic Guaranty Corporation (NGC) accounts for cleaned coins with their NGC Details grading. NGC’s Details designation applies to coins with any number of surface flaws that make the coin not eligible for a numeric grade but eligible for NGC’s Details grading. Coins that fall in this category may be characterized by Environmental Effects, Altered Color, Mechanical Damage, and Cleaning factors. NGC will designate coins that have been cleaned in an unskilled and improper manner and generally indicate the cleaning method on the certification label alongside the Details Grade. Designations like Polished, Spot Removals, Whizzed, and even the generic term Improperly Cleaned can be applied to coins the grading company determines have not been expertly cleaned, yet another reason to leave the cleaning to the professionals.