The cleaning of the coin is made by friction of the piece in a cotton flannel with a small amount (a pinch) of calcium carbonate – a neutral product, with a very thin granulation not to scratch the piece (approximately the same granulation as toilet talcum). Calcium carbonate may be used in any metal.
Distilled water is recommended as tap water contains chlorine. The coin is dipped into olive oil which according to Hudgeons, works best for common copper or bronze coins.
Pour your coins into one bowl and fill with cold water until the money is well covered. In the other bowl, pour about 1 teaspoon of baking soda. Dip the toothbrush into the bowl of baking soda and scrub the coins. The baking soda should remove any dirt and grime and won't scratch the metal.
Soap. Cleaning your old coins with gentle dish soap and water can loosen some of that built-up dirt. Fill a small plastic container with warm water, add a few drops of mild soap, immerse the coins, and rub with your fingers or a soft toothbrush to clean.
Never use metal polish or acid dip to clean your coins! Using these chemicals will cause abrasions or chemical reactions with the metal, permanently damaging your coin. This damage can never be fixed or undone. Additionally, these chemicals can be caustic and cause injury or even death.
Most Cleaning is Destructive: It Can Literally Change the Surface of a Coin. Any cleaning that requires rubbing leaves microscopic scratches. They are not apparent to the naked eye, but a collector will see them. A collector will look for them.
Cleaning an old coin would remove the patina or toning that helps make it even more unique and visually appealing. Removing this effect can significantly reduce the value of the item. The other main reason you shouldn't clean old coins is that you can easily damage them.
Don't clean your coins! Not only does this cut their value by as much as half (or possibly even more), but it will be an immediate deal-breaker for many dealers who would've otherwise wanted to buy your coins if only they were left in their original condition.
Make sure your coins have been cleared of all dirt, debris and other objects prior to visiting the kiosk to ensure a successful transaction. Items like food, screws, dirty or sticky coins and other objects will jam the machine.
Add a small amount of water to a tablespoon of baking soda to form a paste. Apply the paste to each coin using an old toothbrush and scrub gently. Rinse the coins to reveal the now-shiny surfaces.
Ultrasonic cleaning has emerged as a highly effective technique for cleaning coins and ancient coins. This method involves the use of high-frequency sound waves to remove dirt, grime, and other contaminants from the surface of coins without damaging them.
Our cola contains phosphoric acid which is why cola is acidic. The acid reacts with the oxide rusty coating that has covered our coins and returns them back to almost as good as new.
Since oil and dirt cannot be removed without cleaning, a small touch can cut a coin's value in half or even more because, again, numismatists would rather have an oxidized but untouched coin than a shiny but damaged one. The bottom line for anyone looking to sell coins from a coin collection: don't clean your coins.
Even though it's counterintuitive, you should never clean a coin, as it can significantly reduce its value. Even coins that have substantial dirt, tarnishing, or toning should be kept in their original condition.
You might be surprised to read that but both Hydrogen Peroxide and different types of mouthwash actually work great and remove stains from old coins. Use a small container or a bowl to fill up with either Hydrogen Peroxide or a mouthwash of your choice, and let the coins sit and soak.
Don't use toothpaste - Toothpaste is extremely abrasive. It can make your coins appear shiny, but cause significant damage to the surface.
Use Hand Sanitizer
This buildup causes the metal to tarnish and can increase the amount of wear and corrosion on the face of the coin. The more the face of the coin is handled, the more subdued the features will become. Hand sanitizer will remove the bulk of those troublesome oils.