Due to its mild abrasiveness, it removes stuck-on particles and will polish most hard substances, including coins. You can clean most coins using baking soda and water alone; however, you should note that cleaning old coins may decrease their value.
If you want to go ahead and clean corrosion off of your old coins, baking soda likely is the safest route to follow. Wet the affected coin with clean tap or distilled water, roll in baking soda, then gently scrub with a soft toothbrush.
With a little time, minimal effort and some basic household supplies, such as vinegar and baking soda, you can bring out the shine in even the dingiest of tarnished pennies. Cleaning coins with baking soda and white vinegar is effective and easy to do.
In a plastic container or bowl, mix 1/2 - 1 cup of warm water and a teaspoon of liquid dish soap. Hold the coin between your thumb and index finger and rub it as you hold in under running water for about 10 seconds.
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.
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.
Coins that are obviously dirty can be run under water (with a very mild detergent) and left to air dry. A short soak in olive oil may remove unwanted gunge. For cleaning corroded coins the damage is already done, they will forever show pitting into the coin surface. This is as far as anyone should go with cleaning.
Coke and off-brand colas will quickly remove the tarnish. Just don't drink the coke afterward. Coke contains phosphoric acid that cleans the oxides. Try a variety of citrus juices to see which works best or simply let your pennies soak in lemon juice.
1. The most important thing NOT to do is clean your coins. Cleaning rare numismatic coins will significantly reduce their value – plain and simple. Although you don't lose much by cleaning a coin which derives value only from its silver content, it's not worth the risk.
The combination of vinegar (a weak solution of acetic acid), and table salt (sodium chloride) helps to dissolve the copper oxide, and also forms the blue copper(II) ion, which is soluble in water. The penny becomes shiny again!
Generally, it is better to leave your antique metal currency alone than it is to try and erase all the grime and grit off of those coins. Cleaning or polishing rare coins devalues them. So, if you're planning on selling them, get an appraisal before attempting to clean your coins.
When copper oxidizes, it turns a blue-green color, forming a compound called malachite. In Bowl 2, the vinegar and salt create a chemical reaction. This reaction dissolves the copper oxide (the dirty looking spots) and some of the copper on the outside of the penny.
Don't use toothpaste - Toothpaste is extremely abrasive. It can make your coins appear shiny, but cause significant damage to the surface.
Vinegar and lemon juice both work really well for cleaning pennies. But, ketchup was the clear winners for our pennies, with soy sauce next, maybe with a little more time they would have gotten a little bit cleaner. This is a fun experiment to try with younger kids!
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.
However coins will often have on them built up dirt and grease. This may get into the nooks and crannies of the coin. To remove this type of build up you can use a weak detergent solution with a soft cloth (Clux Wipe or similar will do the trick) to take this material off.
Hard Plastic Holders are preferable for more valuable coins. They are self sealing, and not known to contain any materials that harm coins and offer good protection against scratches, touching and handling, air and chemicals, and other physical damage.
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.
If the coin has a flat luster but yet is dated it has probably been dipped, most coins will have a frosty, smooth or glossy lustre if they are untouched and you can easily see the difference. Wizzed or tooled coins can be detected by small abrasive marks on the surface of the coins, often the finish will be mirrored.