How to Clean Old Coins Without Damaging Them

Most people who attempt to clean coins use harsh methods that permanently damage them. Improper cleaning can drastically reduce a coin's value by:

• Removing its natural patina (the colored layer that develops over time)
• Creating microscopic scratches that are obvious to trained eyes
• Stripping away thin layers of the metal surface
• Accelerating chemical deterioration

But with the right knowledge and gentle approach, cleaning can safely remove dirt without harming your coins.

When to Clean Old Coins (and When Not to)

Before reaching for any cleaning supplies, ask yourself these critical questions:

DON'T Clean If:

• The coin has potential collector value
• You're unsure of the coin's composition or age
• The coin has an attractive or stable patina
• You're dealing with rare or valuable specimens
• The coin is in generally good condition with just light toning

Consider Cleaning If:

• The coin has no significant collector value (common modern coins)
• There's caked-on dirt that obscures details
• The coin shows signs of active deterioration (like "bronze disease")
• You're confident in identifying the metal and appropriate methods
• You're willing to accept the risk of potential value loss

When experts work with old coins from colonial times, they often find them covered in years of dirt. Most coins only need gentle cleaning, but sometimes they have to clean more thoroughly to see important markings. Using the right cleaning method for each coin helps keep both their history and value intact.

Safe Cleaning Methods for Different Coin Types

Let's explore some of the safest methods for cleaning different types of coins:

1. Copper and Bronze Coins

Copper coins develop a natural green or brown patina that often protects the metal beneath. Harsh cleaning can strip this patina and expose the coin to further corrosion.

Safest approach: For light dirt, simply soak the coin in distilled water (never tap water) overnight. Gently pat dry with a soft, lint-free cloth.

For stubborn dirt, some conservators use the olive oil method:

1. Submerge the coin in pure olive oil
2. Let it soak for several days or even weeks
3. The oil gradually loosens dirt without harming the patina
4. Rinse with distilled water and dry carefully

2. Silver Coins

Silver tarnishes naturally over time, forming a dark layer that many collectors find attractive. Removing this tarnish completely often decreases value.

Safest approach: For light cleaning, use warm distilled water with a tiny amount of mild, phosphate-free soap. Rinse thoroughly and pat dry.

For more valuable silver coins, professional numismatists sometimes use special conservation methods that preserve the details while stabilizing the surface.

3. Gold Coins

Gold is relatively stable and doesn't corrode like other metals, making it easier to clean safely.

Safest approach: Soak in warm distilled water with a drop of mild dish soap. If necessary, use a soft-bristled brush (like a clean child's toothbrush) with extremely gentle pressure. Rinse thoroughly and pat dry.

How Ultrasonic Cleaners Transform Coin Restoration

Credits to @SalivateMetal

One tool that professional dealers often use is the ultrasonic cleaner. 

The microscopic bubbles created by ultrasonic vibrations penetrate even the smallest crevices and cracks in the surface of coins, ensuring they're thoroughly cleaned without using harsh chemicals or abrasive materials.

If you're serious about coin collecting, a small jewelry-grade ultrasonic cleaner might be worth considering, but with important caveats:

• Only use it with distilled water and minimal additives
• Never use it on valuable collector coins without expert guidance
• Keep cleaning sessions short (under 5 minutes)
• Always test on common coins first
• Monitor the process closely

Many coin collectors now use ultrasonic cleaners for their more common coins as ultrasonic cleaners can gently remove dirt from all the small details without harsh chemicals or scrubbing. Just remember to use distilled water, keep cleaning sessions short, and check on your coins regularly during the process.

Further reading: How does Ultrasonic Cleaner Work

What You Need to Know Before Attempting Coin Cleaning

The key difference between damaging your coins and successfully cleaning them is knowledge, proper tools, and patience.

For coins with significant potential value, consider these approaches:

• Start with the gentlest methods: Always begin with the least invasive cleaning approach
• Practice on common coins: Test your cleaning techniques on ordinary coins before attempting valuable pieces
• Consider professional conservation: Services like NCS (Numismatic Conservation Services) specialize in preserving valuable coins
• Proper storage: After cleaning, use appropriate holders and control humidity to prevent future deterioration
• Documentation: Take clear photos of your coins before and during the cleaning process

How Proper Coin Cleaning Preserves History and Value

Every old coin tells a story—of the people who used it, the places it traveled, and the history it witnessed. When you hold an old coin, you're touching a piece of the past.

Cleaning coins is about finding the balance between revealing their beauty and preserving their history. With knowledge, patience, and respect for these artifacts, you can make informed decisions about whether and how to clean the coins in your collection.

For high-quality ultrasonic cleaners perfect for cleaning old coins, check out Creworks' ultrasonic cleaners.