How to Clean Pennies
Today, not much is available to buy with a penny; so many people tend to toss them into a jar, saving them until they are worth dollars. Or worse, they pile up in your cup holder and start getting sticky. However, if you want to Coin Stack a Penny Bridge or Play Penny Ante, it may be nice to have clean, shiny pennies at your disposal. Note: For pennies minted after 1982, refer to method 5. For pennies of any possible value, do not clean them!
1. **Put enough ketchup in the cup to cover up the coin or coins.** For the record, with this method, you may be able to smell the ketchup on the penny when you are finished. Tabasco, on the other hand, may leave an orange tint. However, they will be clean!
2. **Put the coin in and wait three minutes.** If you have a toothbrush handy (preferably your roommate's), after the three minutes are up, scrub the penny, working into the little ridges.
3. **Wash the coin off in hot water.** And if you used your roommate's toothbrush, wash that off, too!
If the pennies are clean, but not shiny, mix a paste of baking soda and water and rub into the pennies. Wash it off and, tada!
4. **Put 1 tsp (5 g) of salt into 1/4 c (2 oz) of vinegar.** For many pennies, one tablespoon (15 g) of salt in 1/2 cup (4 oz) of vinegar will get the job done. Stir the mixture to dissolve the salt.

If you don't have vinegar, use lemon or even orange juice. Copper oxide (the gunk on your pennies) dissolves in weak acid, and that's just what all three of these liquids are.

You can also use lemon juice instead of vinegar.
5. **Place your pennies in the vinegar or the lemon juice.** Make sure they are  directly on top of each other.
6. **Leave the pennies for around five minutes in the glass of vinegar or lemon juice.** If they're extra dirty or if you're cleaning a lot simultaneously, give them a few more minutes for good measure.
For those especially nasty pennies, scrub them with a scrubber or toothbrush after they've been resting in the solution for a bit.
7. **Take the pennies out, and wash them off.** Let them dry for around five minutes so they will no longer be wet. They will now sparkle.
If you don't wash them off, a blue-green sheen will develop on your pennies. That's what happens when the copper, oxygen, and chlorine (from the salt) combine (called malachite).
8. **Get a can or bottle of Coca Cola.** It doesn't have to be Coke per se; a generic brand will work, too.
9. **Set the pennies in a dish so they are not sitting on top of each other.** The acid in the Coca-Cola needs to work into each penny directly.
10. **Put just enough Coca-Cola in the dish to cover the pennies.** More is not necessary, so grab a straw for the rest!
11. **Let sit for about 4-5 hours.** For best results, flip over halfway through the process. While this method works well, the downside is that it takes much, much longer than the others.
12. **Take the pennies out and wash them off with warm or hot water.** 
13. **Obtain some Bar Keeper's Friend.** This cleaning solution works on all copper quickly, like pennies and copper bottom cookware. If you don't have this brand, another metal cleaner (like Brasso) should work as well.
14. **Wet the coins and put on some Bar Keeper's Friend.** The oxalic acid takes away the gunk. Let it sit for a few minutes.
15. **Rub lightly and rinse off.** Your pennies should now be so shiny you could signal planes, call Batman, or invoke temporary blindness. Doesn't get much easier than that!
16. **Grab a dirty penny and an eraser.** While this method should work on any penny, it's safe on the more recent ones, while the previous methods are not. The acidity of methods 1-4 will turn your zinc pennies black.
After 1982, copper became too expensive to justify using on a coin just not worth anything. Therefore, zinc (a much cheaper metal) started being used.
17. **Rub the penny with the eraser as if you were trying to erase a mark on paper.** If you are handy (or if you have a thousand pennies to clean), you could attach a pencil (with an eraser) to a drill and have it do the work for you. There is also, incredibly, such a thing as electric erasers. Who knew?!
18. **Flip the penny and repeat above steps as needed.** This will take about 10 seconds per penny. The only downside to this is at the end, your hand may be tired, and you will be out a pencil or two! Other than that, it is a quick and easy path to shiny riches.
{"url": "https://www.wikihow.com/Clean-Pennies", "language": "en"}