I recently found a small reprint from a series of articles by Clyde D. Mervis, from the old magazine Numismatic Scrapbook published by Hewitt Numismatic Printers in the 1960s, titled “Cleaning Coins.” 

Cleaning remains a taboo topic, and one of the first things that collectors learn as they enter our hobby is that one should never clean coins. As collectors progress on their journey, they learn that there are some cleaning methods that can be used with caution and by experimenting on low-value coins, but that, generally, cleaning is something that should be left to professionals. 

Mervis starts by addressing the seemingly off-limits nature of the topic, writing that collectors can generally be placed in two groups: “One group will emphatically state ‘Why I never clean my coins!’ ‘I understand that you’re not supposed to do it,’ while the other group goes along quietly cleaning their coins, but as though they were doing something forbidden, they simply never admit it. Why?”

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For all levels of collectors, the term used by third-party grading services — Improper Cleaning — raises the question, what is a proper cleaning, and at what level does a coin become improperly cleaned? 

In fact, some dealers make a living working at this intersection, making coins look more appealing to grading services, with the hopes of getting them into nonproblem holders. 

Mervis writes, “all my cleaning episodes haven’t been disastrous, nor have they all been successful. All coins cannot be cleaned successfully, and the experienced collector knows that.” Take corroded coins, where Mervis notes, “Cut away the rotten parts of the apple and get down to the solid core and you no longer have an apple. So it is with the coin.” 

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Metal reacts with nature and its environment. The results can be spectacular — such as a rainbow toned Morgan silver dollar — or disastrous, as seen on many corroded bronze ancient coins.

Mervis even anticipates the issues that would follow decades later as rare and valuable gold and silver coins would emerge from shipwrecks. That the market accepts gold coins from the SS Central America shipwreck and other sunken treasures attests to the advanced technology used in restoring these coins and the market’s acceptance of conserved coins.

Of course, the book’s closing words should ring true to coin collectors and investors today: “It is often thought and expressed that the chemist is a modern magician and miracle worker, but his puny efforts sink to insignificance when pitted against Nature and Time, while the chemist’s sole aim is to reclaim all objects.”