Why the best way to preserve a coin's value is to leave it dirty
In short: For decades, collectors used everything from pencil erasers to potassium cyanide to make coins shine. But this pursuit of brilliance often backfired, destroying the very patina that makes a rare coin valuable. Today, the most prestigious experts agree: the most beautiful coins are often the ones left untouched.
The history of coin cleaning is a tale of shifting philosophies. In the mid-19th century, as copper costs rose and large cents were discontinued, collectors sought to restore a 'mint red' appearance to older coins. By the 1930s, the community embraced the motto 'brilliant is best,' leading to widespread use of abrasives and even vinegar with pencil erasers to brighten surfaces. This trend peaked in the 1960s with advertisements for 'lotions and potions' designed to enhance luster.
The impact was profound; in 1960, expert Q. David Bowers estimated that 90% to 95% of Lincoln cents from the 1910–1920s era had been chemically 'dipped'. Nevertheless, the emergence of encapsulated holders and external grading services during the mid-1980s transformed the industry. Under microscopic inspection, the damage from historical cleaning methods—such as 'whizzing' Indian Head cents with rotary wire brushes—became undeniable.
Modern numismatists now largely view cleaning as detrimental. Experts like Kenneth Bressett and A. Kosoff note that once a coin is stripped of its original luster, it can never truly be restored to an 'Uncirculated' state. Consequently, coins showing signs of damage are often labeled 'Improperly Cleaned,' a designation that can significantly depress market value. There are exceptions for specialized conservation, such as shipwreck finds. Recovering coins from sites like the Sveti Pavao shipwreck requires delicate desalination using tap and distilled water to remove corrosive salts. While gold coins survive underwater more easily than silver or copper, the goal remains preservation rather than aesthetic enhancement. In these cases, grading services like the Numismatic Guaranty Company may use the label 'shipwreck effect' to honor coins recovered through archaeologically sound methods [S1:CO:p10].
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- Summary by Intellect · source: Coin cleaning
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