Pennies tend to get dirty and oxidized over time, losing their shiny copper color. While there are many penny cleaning methods available, some can potentially damage the coins if not used properly. The key is finding a cleaning solution that will remove tarnish and dirt without being too abrasive on the penny’s surface.
Why Do Pennies Get Dirty?
Pennies are made primarily of copper, with a thin zinc coating. Over time, the zinc coating wears off through normal circulation and handling, exposing the copper underneath. Copper readily reacts with oxygen in the air, causing the formation of copper oxide. This oxide layer appears as a brownish or greenish discoloration on the surface of the coin.
Pennies also accumulate dirt, grease, and grime from normal everyday use. Fingers, purses, pockets, cash registers and coin sorting machines all introduce contaminants that can stick to the metal surface. This buildup dims the bright finish of a new penny.
Problems With Harsh Cleaners
While it’s tempting to use strong chemicals and abrasives to clean dirty pennies, this can permanently damage and reduce the value of rare or collector coins. Harsh cleaners like vinegar, bleach and baking soda can erode the coin surface detail over time with repeated use.
Abrasive materials like steel wool or sandpaper can scratch the penny by removing tiny amounts of metal. This diminishes intricate designs and lettering on the coin surface through progressive loss of detail.
Excessively rubbing or brushing a penny can also lead to wear. Soft mint marks and date digits will gradually fade under too much mechanical cleaning action.
Safe Cleaning Methods
The best penny cleaning solutions are mild oxidizing or reducing agents that chemically convert copper oxide back to metallic copper. This restores the penny’s shine without being too harsh on the underlying metal.
White distilled vinegar is a popular penny cleaner because it is inexpensive and readily available. The acidic acetic acid in vinegar reacts with copper oxide to dissolve it off the surface. The reaction also generates heat, which speeds up the process.
To use vinegar, simply submerge several pennies in a bowl of undiluted vinegar for at least 15 minutes. Agitate the coins occasionally, then rinse and dry them. Avoid prolonged soaking, which can strip away copper from the coin.
Salt and Vinegar
For a more effective treatment, dissolve 1-2 tablespoons of salt in 1 cup of vinegar. The salt acts as a mild abrasive to help loosen stubborn surface oxidation and grime. Let the pennies soak for 30-60 minutes, then rinse and dry.
As a condiment made from tomatoes, vinegar and spices, ketchup contains gentle acids that can dissolve copper oxide off pennies. The thicker consistency also acts to scrub away dirt. Soak several pennies in ketchup for at least 20 minutes before rinsing.
The citric acid in lemon juice works similarly to vinegar at removing copper oxide tarnish. Simply soak pennies in undiluted lemon juice for 30 minutes or more. The fruit acid will react with the copper, wiping away dullness from oxidation.
Baking Soda and Water
Baking soda is a slightly abrasive yet harmless base that reacts with copper oxide to convert it back to copper metal. Mix a paste of three parts baking soda to one part water. Gently rub it onto dirty pennies using a soft cloth or toothbrush. Rinse thoroughly afterwards.
Toothpaste contains mild abrasives like silica to polish away stains on teeth. When rubbed onto pennies, these same abrasives can scrub off tarnish without damaging the coins. Use a small dab of regular (not gel) toothpaste and a soft toothbrush to gently clean pennies.
Tips for Safe Penny Cleaning
When cleaning valuable copper coins, it pays to be cautious to avoid permanent damage. Here are some tips for safe penny cleaning:
- Never use harsh acids, bases, or oxidizers like hydrogen peroxide
- Avoid metal scouring pads, sandpaper, or anything abrasive
- Only clean a few coins at a time to monitor their condition
- Rub gently in straight lines, not circular motions
- Rinse coins thoroughly after soaking or rubbing
- Dry coins well with a soft, lint-free cloth
- Handle coins carefully on the rims to avoid re-fingerprinting
- Store coins in protective sleeves or albums after cleaning
Cleaning Pennies in Bulk
While soaking or gently scrubbing is fine for small numbers of coins, it’s impractical for large batches of pennies. Here are some tumbling methods that can efficiently clean hundreds of pennies at once:
A rock tumbler rotates containers of coins and abrasive media to gradually wear off tarnish and oxidation. Add pennies, a teaspoon of lemon juice and a tablespoon of coarse salt to the tumbler barrel along with water. Tumble for 1-2 days until clean.
Coffee Can Roller
Attach a small electric motor to a sealed coffee can to make a improvised tumbler. Put pennies, salt water and a few marbles or ball bearings inside. Seal the can and let it rotate overnight to clean the coins.
Ultrasonic cleaning uses high frequency sound waves to agitate a soap solution. The vigorous cavitation bubbles dislodge dirt and oxidation. Ultrasonic jewelry cleaners work well for pennies too. Just add coins and an ammonia-based cleaner and run for 5-10 minutes.
Cleaning Pennies Naturally Outside
Some people report good results cleaning large batches of pennies through natural outdoor methods. While slow, these techniques avoid chemicals and scrubbing:
Collect rainwater in buckets or bins and let pennies soak for weeks. Rain is naturally distilled water that can slowly dissolve copper oxide and dirt.
The salt and minerals in seawater can work to break down oxidation and grime on pennies over time. Seaside dwellers can try soaking pennies in ocean water.
Placing pennies in porous potato sack bags and burying them in soil introduces mild earth acids from groundwater than can clean coins over months.
Waste vegetables, manure, leaves and grass in compost piles produce useful organic acids as they decay. Burying pennies in an active compost bin can slowly clean off tarnish over time.
Cleaning Pennies with Electrolysis
Electrolysis uses an electric current to trigger a chemical reaction that removes copper oxide from pennies. This leaves brilliant shiny copper with minimal abrasion to the surface. Here’s how to clean pennies through electrolysis:
- Battery or DC power supply
- Alligator clips (2x)
- Copper wire
- Non-metal bowl
- Tap water
- Salt or baking soda
- Sacrificial steel object (nail)
- Fill bowl with water and dissolve some salt or baking soda in it.
- Attach an alligator clip to each end of the copper wire.
- Attach one clip to the nail, and dangle it in the water.
- Attach the other clip to the rim of the bowl.
- Add pennies to the bowl, ensuring they touch the nail.
- Connect nail and bowl to the battery terminals to complete the circuit.
- Let run for at least 30 minutes, checking on pennies periodically.
- The nail will corrode, driving the electrochemical reaction.
- Once the pennies are clean, rinse and dry them well.
Storing Cleaned Pennies
After going through the effort of cleaning pennies, it’s important to store them properly to prevent quick re-tarnishing. Here are some good options:
- Coin folders or albums made of inert plastics
- Capsules designed for coins that seal out air
- Paper envelopes – absorb oils and limit air exposure
- Freezer bags with the air squeezed out
Avoid storage in materials that can damage coins like PVC, vinyl and paper with sulfur content. If housed improperly, cleaned pennies may start to oxidize and spot again within weeks.
Cleaning Pennies for Crafts
Cleaning pennies can be a fun arts and crafts project, especially for kids. Parents can teach children about coin care while making decorative objects. Here are some crafts that involve cleaned pennies:
Coat a floor or tabletop with adhesive and overlap rows of cleaned pennies in a mosaic pattern. Seal with polyurethane for a durable engraved metal look.
Penny Picture Frame
Solder or glue cleaned pennies together to create your own custom picture frame. Enclose a meaningful photo behind the shiny copper border.
Lucky Penny Jewelry
Make rings, necklaces and bracelets featuring a cleaned “lucky penny” soldered to a setting or wrapped in wire loops.
Adhere cleaned pennies around the outside of terra cotta pots and planters. Let greenery sprout up through copper-coated pots indoors or outdoors.
Penny Wind Chimes
Construct wind chimes from cleaned pennies and copper wire. Space pennies apart on the wire to create pleasant ringing tones as the chimes sway.
Cleaning Collectible Pennies
While common modern pennies only have melt value, older rare pennies can be quite valuable to collectors. Special care should be taken when cleaning vintage coins.
Key Date Pennies
Key date pennies like the 1909-S VDB, 1914-D, 1955 Doubled Die Obverse and others are best left untouched. Any cleaning or damage will hurt value.
Naturally toned vintage pennies can display attractive rainbow hues. Cleaning removes these delicate tones, decreasing desirability.
Under a loupe, cleaned coins will show tiny hairline scratches even with gentle cleaning. This is unavoidable but lowers grade and prices.
Harsh acids can microscopically etch the fields and design elements of coins. These changes are invisible to the eye but still considered damage.
Proof coins with mirror fields and frosted devices require intricate manufacturing. Any cleaning can impair the special proof finish.
In most cases, professionally certified collectible coins are worth more if left untouched rather than cleaned. Attempting to clean valuable coins usually ends up reducing their market value and appeal to knowledgeable numismatists.
Selling Cleaned Pennies for Scrap
While cleaning improves the appearance of pennies, it doesn’t increase their base melt value. Here are some points to consider when selling cleaned pennies for scrap:
- Circulated pennies are only worth about $0.02 each for the copper content.
- Accumulating significant copper value requires large volumes, often tons.
- Scrap dealers assay metal purity and weight, not appearance.
- Cleaning pennies takes time without improving scrap payment.
- Bulk unsorted pennies actually sell for below face value per pound.
While metal prices rise and fall, pennies are rarely worth melting down on a small scale. The time spent cleaning them usually outweighs any potential profits from scrap metal recycling.
Pennies tend to oxidize and get dirty over the years. While there are many coin cleaning methods, safe options like vinegar, lemon juice and baking soda effectively remove tarnish and grime without damaging the coins. For large batches, tumbling or electrolysis works well. Proper storage and gentleness prevents re-tarnishing. Rare collectible pennies are best left uncleaned. Cleaning pennies can be satisfying, but provides little increase to scrap metal value. With some simple household products and care, you can safely clean pennies to restore their lost shine.