Kitchen Science: Penny Cleaning

Related Factoid: As of late, Koko has been interested on the images on coins. So, I started some research. Did you know that the back of the U.S. penny with the Lincoln Memorial has a tiny Lincoln sitting in the middle?

On to the penny cleaning! First, we used old toothbrushes to scrub the coins with a little of Dr. Bronner, (any soap would work) rinsed them in the bathroom sink, and then proceeded to make a white vinegar and salt solution (stir salt until completely dissolved). We dumped the pennies first.

I left one untouched to act as the control. We then soaked the rest of the coins and demonstrated that this shining phenomenon only worked with the pennies because only the pennies have copper.

For a scientific explanation of this experiment, read here!

Disclaimer: Adventures in Montessori pointed out that this experiment doesn't work with all pennies. Apparently, the composition of pennies changed several times, but in 1982, it changed drastically from mostly copper to mostly zinc which supposedly doesn't react well to vinegar. So, it your pennies don't shine up, look at the date!