As an avid coin collector and numismatist, I‘m often asked about the best ways to clean old pennies. It‘s a tricky topic – while everyone loves the look of bright, shiny copper, cleaning collectible coins can actually do major harm to their value and appearance. In this in-depth guide, I‘ll share my expertise on when and how to safely clean pennies while preserving their integrity and numismatic worth.
A Brief History of the Penny
To understand the challenges of cleaning pennies, it helps to know a bit about their history and how their composition has changed over time. Here‘s a quick timeline:
- 1793-1837: Pure copper large cents
- 1856-1864: 88% copper, 12% nickel small cents
- 1864-1962: 95% copper, 5% zinc and tin
- 1962-1982: 95% copper, 5% zinc
- 1982-present: 97.5% zinc core, 2.5% copper plating
As you can see, the U.S. penny was made of pure copper for its first few decades before switching to various bronze alloys to reduce minting costs. In the last 40 years, pennies have only contained a small amount of copper in their plating over a mostly zinc core. These differences in metal content can affect how pennies age and how they respond to cleaning.
The Science Behind Penny Tarnish
Pennies can become darkened and corroded due to exposure to various environmental factors, including:
- Oxygen and moisture in the air causing copper oxide to form
- Oils and salts from skin contact
- Chemicals like sulfur dioxide which can turn copper surfaces black
- Acidic substances which accelerate the oxidation process
A penny‘s surface is like a living record of its history and surroundings. Older pennies often develop a natural toning or tarnish over many decades, ranging in color from reddish to brown to black. Numismatists actually value this patina as a sign of originality. Improperly cleaned ancient coins are often considered damaged or altered in the collecting world.
The Dangers of Overcleaning Coins
While shiny pennies may look attractive to the eye, most coin experts advise against cleaning collectible specimens if you want to maintain their value. Here‘s why:
- Cleaning a coin improperly can cause permanent damage like scratching, pitting, or discoloration
- Removing the original patina makes a coin look unnatural and reduces its desirability
- Abrasive cleaning wears down a coin‘s surfaces, negatively impacting its condition and grade
- Coins that have been noticeably cleaned are often regarded as less valuable
If you have a valuable penny or one that you plan to sell in the future, think twice before putting it through any cleaning regimen. Unlike some antiques, original surfaces and aged patina are actually highly prized by coin collectors. Shiny does not always equal better in numismatics!
Proper Penny Handling and Storage
The best way to avoid having to clean your pennies is to handle and store them properly to prevent damage and contamination. Follow these tips:
- Always hold coins by the edges, not the faces, to avoid transferring skin oils
- Wear soft cotton gloves when handling high-value coins
- Use inert plastic flips or holders to store pennies, not envelopes or bags
- Keep coins in a cool, dry location away from sunlight and harsh chemicals
- Consider using silica gel packets in coin storage containers to absorb excess moisture
- Separate pennies by composition (all copper, copper/nickel, copper/zinc, zinc) as different metals can cause corrosion when stored in contact
If you follow these guidelines, your pennies are much more likely to stay problem-free and maintain stable surfaces. Prevention is the best method for keeping coins clean and safe!
When Cleaning Coins is Appropriate
Now that I‘ve spelled out the risks, there are some situations where carefully cleaning a penny can be harmless or even beneficial:
- Removing loose dirt, debris, or sticky residue from a circulated penny
- Enhancing the appearance of a corroded or damaged low-value penny for display
- Restoring a sentimental or heirloom penny that has no numismatic value
- Cleaning a large batch of modern pennies for use in an art or craft project
If you have a common penny (one minted after 1982) or a wheat cent in poor condition, giving it a gentle bath probably won‘t negatively impact its value. In fact, cleaning off built-up grime and revealing details of the coin‘s design can actually make it more attractive and displayable.
However, if you have a key date penny, an uncommonly nice one, or one minted before 1962, I would advise having it evaluated by a numismatic professional before attempting any cleaning yourself. Rare pennies like the 1955 double die obverse or the 1922 no D cent can be worth thousands of dollars in pristine condition. It‘s not worth the risk of damaging these!
Safe and Gentle Cleaning Methods for Pennies
If you‘ve determined you have a penny that would benefit from a careful cleaning, here are some conservative and minimally abrasive methods to try, ranked from gentlest to strongest:
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Soak in warm water: Submerge pennies in warm distilled water for 5-10 minutes, then rub gently with fingers or a soft toothbrush. Pat dry with a soft cloth. This is the mildest method and is good for removing light soil.
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Soak in soap and water: Mix a few drops of a mild, non-lotion dish soap into warm distilled water. Soak pennies for 15 minutes, brushing lightly if needed. Rinse well with distilled water and air dry. The soap helps loosen grease and dirt.
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Soak in acetone: Place pennies in a shallow glass dish and pour acetone over them to cover. Let sit for 1-2 minutes, then remove and rinse thoroughly with distilled water before air drying. Acetone dissolves organic residues and helps prevent spotting. Use in a well-ventilated area and wear gloves.
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Soak in vinegar or lemon juice: Submerge pennies in white vinegar or lemon juice for 30 seconds to a few minutes, checking often, then rinse and dry. The acetic acid works quickly to dissolve copper oxide. Don‘t soak too long or the acid may cause pitting.
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Soak in ketchup: Coat pennies in a thin layer of ketchup and let sit for 1-2 minutes before rinsing clean and drying. The acidity of the tomatoes and vinegar helps cut through oxidation and restores shine.
Here‘s a summary table showing the effectiveness of each method on different cleaning needs:
| Method | Light soil | Heavy tarnish | Organic residue |
|---|---|---|---|
| Water | Good | Poor | Poor |
| Soap & Water | Better | Poor | Fair |
| Acetone | Poor | Fair | Excellent |
| Vinegar/Lemon | Poor | Excellent | Fair |
| Ketchup | Fair | Good | Fair |
As you can see, each cleaning technique has its pros and cons. The key is to start with the gentlest method that will get the job done and avoid over-cleaning. Remember, a penny doesn‘t have to be blindingly bright to be clean and attractive. Sometimes just removing the worst of the gunk is sufficient.
Cleaning Large Batches of Pennies
Got a big jar of pennies you want to clean all at once? The good news is that all of the methods outlined above can be scaled up for larger volumes. You‘ll just need a sufficiently sized non-reactive container (glass, ceramic or plastic) to soak your pennies in.
Some tips for efficient batch cleaning:
- Sort pennies by degree of dirtiness so you can remove cleaner ones sooner
- Use a large strainer or colander lined with a towel to rinse and dry pennies
- A toothbrush or soft scrub brush can help speed the cleaning process
- Change out soaking solutions as they become heavily soiled
- Lay pennies out on a towel in a single layer to dry; use a fan to speed up drying
- To bring out extra shine, tumble clean pennies in a rotary rock tumbler with ground walnut shell media
Professional Coin Conservation
In some cases, a valuable penny may require professional help to address cleaning needs, especially if it has PVC damage, stubborn encrustations, or delicate toning. Qualified coin conservators use techniques like ultrasonic cleaning, controlled chemical baths, and focused lasers to safely clean coins without altering surfaces.
If you have a coin with numismatic value that you think needs cleaning, it‘s always best to consult an expert first. The American Numismatic Association maintains a list of reputable dealers and conservators who can evaluate your coins and recommend an appropriate treatment.
Conclusion
In summary, cleaning pennies can be a fun and rewarding way to reveal their hidden beauty, but should only be done thoughtfully and carefully to avoid potential damage. Collectible key date and high grade pennies are usually best left original to preserve value. More common pocket change can be gently cleaned for display using dilute acids or soaps and soft tools.
Proper storage and handling is ultimately the best way to keep pennies looking their finest. When in doubt about cleaning a penny, always err on the side of caution and consult a knowledgeable coin expert. With the right techniques and a conservationist approach, you can safely spruce up your pennies and keep them in tip-top shape for years to come!
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