STEAM Fun: How To Clean a Penny

Simple science fun that kids love!

By Kara Murphy, Macaroni KID August 19, 2023

Did you know you can make your dirty and dingy pennies bright and shiny with just a little chemistry?

Kids love this STEAM activity because they get to experiment, and you'll love it because it'll cost you ... hardly a penny!

First, let's talk about how to clean a penny: The easiest and most common method is combining vinegar and salt. You'll find when you take your penny out of a vinegar and salt bath, it is much shinier and cleaner than before!

Here's how to clean pennies with a vinegar and salt solution:


  • 1/4 c vinegar in a non-metal bowl
  • 1 tsp salt
  • Old, dirty pennies
  • Bowl of water
  • Paper towels for drying


  1. Mix the salt into the vinegar. 
  2. Add your dirty pennies. 
  3. Let them sit for about 20-30 seconds (longer if your pennies are super dirty).
  4. Remove them from the vinegar and rinse in your water bowl. 
  5. Remove them from the water and dry them with a paper towel.

Your pennies should be clean and shiny! 

Experiment with other products

Vinegar and salt aren't the only common household products that will work.

You can also try ketchup!

Ketchup contains vinegar and tomato acid, which can dissolve copper oxide. Simply apply a small amount of ketchup to the penny and rub it with a cloth or toothbrush for a few minutes. Rinse the penny with water and dry it off with a towel.

@macaronikidnational Did you know you can use KETCHUP to brighten up your dirty pennies? #steamfun #steamactivity #kidsfun #activityforkids #steam #learnthroughplay #cleantok #fyp #foryoupage #cleaninghacks ♬ Joyful - ProSounds

Why are ketchup and vinegar so effective at cleaning pennies?

Pennies are made of copper, a metal that easily reacts with oxygen and other substances in the air, causing it to oxidize and turn dull and brownish over time. Vinegar contains acetic acid, which can dissolve the copper oxide on the penny's surface, while the salt helps to speed up the process by providing a conducive environment that allows the ions in the vinegar to react with the copper. This reaction creates a thin layer of copper ions that dissolve in the solution — revealing the shiny, clean surface of the penny underneath.

Regular ketchup contains enough vinegar and tomato acid to dissolve the copper oxide that has formed on the penny's surface. 

But which works better? This is where the science experiment comes in! Experiment with different products and techniques to find the best way to clean pennies! Try not only your vinegar and salt mixture and ketchup, but also other products: Does water or soda clean the pennies? What about juice? 

Fill several cups with just enough experimental liquid to cover several pennies, then drop them in and see what happens!