Penny Chemistry

Have you ever seen the Statue of Liberty? It’s a pretty iconic statue in the United States that was given to the country by the people of France in 1885. At over 150 feet tall (or over 300 feet if you count its base), it was quite the gift! But why would France give the US a green statue?

It actually was not green when it was first built, but slowly turned green over time due to exposure to the sea, sun, and weather. The reason? Because the statue is coated in copper! That’s right, the same metal that pennies are made of.

As shown in the video above, today we are going to turn some pennies green, just like the Statue of Liberty! Here’s how it is done:


Materials Required

Non-metallic bowl

Plastic spoon

¼ cup white vinegar

1 teaspoon salt


Paper towels

Pennies (best if they are dirty)

Nuts and/or bolts (optional)

Adult supervision (Adult supervision at all times please) 



  1. First, pour the ¼ cup of white vinegar into your non-metallic bowl. Then add 1 teaspoon of salt to the vinegar and stir with the plastic spoon until the salt is completely dissolved. The mixture becomes clear when the salt is all dissolved.
  2. Take some of your pennies (about half) and carefully place them in the vinegar-salt mixture. Within 30 seconds, you should see the pennies becoming clean in the mixture. Let them sit for a minute or two until they are nice and shiny.
  3. Carefully remove the pennies from the vinegar-salt mixture and place them in some water. This will stop the reaction and gives you some nice and clean pennies!
  4. Optional Step:Take the nuts or bolts and place them in the same vinegar-salt solution you used to clean the pennies. Within a couple of minutes, you should see that they become darker. This is because the copper removed from the pennies sticks to the new metal (usually steel coated in zinc). Remove the nuts/ bolts from the mixture and place them in the water.
  5. Now, we’re going to take the rest of the dirty pennies and place them in the vinegar-salt mixture. Again, you should see them becoming cleaner the longer you leave them.
  6. After a couple of minutes, pull the pennies out of the vinegar-salt mixture, but instead of placing them in the water, place them on the paper towel to dry. Be sure they are not overlapping. Wait several minutes (at least 10 to 15) and you should see the pennies slowly changing color.



Before the experiment the pennies looked so dirty because over time, copper oxide became built up on them. This copper oxide was removed by the vinegar-salt solution and coated the steel nuts or bolts when they were later added.

When the pennies were set out to dry instead of being rinsed in the water, the copper oxides coating the pennies were able to react with oxygen in the air and the chlorine in the salt to form malachite, the bluish-green compound that formed over time. And this is how the Statue of Liberty gets its color, the build-up of malachite over time.