Quick summary
- Cleaning leaves fine scratches and removes a coin’s original surface.
- Grading services identify cleaned coins, and they usually receive a ‘details’ grade rather than a numeric one.
- Natural toning is often valued by collectors and should be left alone.
- For valuable coins with problems, use a professional conservation service.
- Polishes, abrasives, baking soda and vinegar can all cause permanent damage.
Many people’s first instinct with an old, dull coin is to clean it. Unfortunately, cleaning is one of the most common ways that coins lose value.
What cleaning does
- Scratches: even soft cloths and gentle rubbing leave fine “hairline” scratches.
- Removes original surfaces: the luster of a coin comes from how its surface was struck, and cleaning strips it away.
- Creates an unnatural look: experienced collectors can spot cleaned coins quickly.
How graders treat cleaned coins
Professional grading services look for signs of cleaning. Coins that have been cleaned typically receive a “details” grade, noting the problem, instead of a numeric grade. That usually makes them worth noticeably less than similar coins with original surfaces. Our guide to coin grading explains how grades work.
Be careful
Never use metal polish, abrasive cleaners, baking soda, vinegar, toothpaste or jewelry dips on coins. These can cause permanent damage in seconds.
Toning is often a plus
Over time, coins can develop natural color, called toning. Attractive toning, especially on silver coins, is prized by many collectors. Removing it can turn a desirable coin into an ordinary one.
What to do instead
- Leave circulated coins as they are. Wear and some grime are expected.
- Store coins properly to prevent further problems; see our guide to handling and storing coins.
- Ask an expert at a coin club or reputable dealer before doing anything to a coin you think may be valuable.
- Use professional conservation for valuable coins with harmful residue, such as PVC damage. Major grading companies offer conservation services.
The one-sentence rule
If in doubt, don’t clean it. A coin left alone can always be conserved later by a professional; a coin that’s been cleaned can’t be restored.
Collector questions
My coin is dirty. Will it be worth less?
Usually, leaving it alone is the safest choice. Collectors understand that circulated coins show wear and grime, but they avoid coins that have been cleaned.
What is toning?
A natural change in color on a coin’s surface over time. Attractive toning can increase a coin’s appeal and value.
Is conservation the same as cleaning?
No. Professional conservation aims to remove harmful substances, such as PVC residue, while preserving the original surface.
Can ancient coins be cleaned?
Ancient coins dug from the ground are often cleaned by specialists using careful methods. That’s a different field from modern coins, so seek expert advice.
Coin values change with demand, condition and metal prices. This guide is general information, not an appraisal or investment advice.
