Kids, how would you like to turn your nice shiny copper-colored pennies into green ones? All you need is a saucer, a paper towel, vinegar, and 3-5 pennies.

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

Fold the paper towel in half and then in half again to make a square. Put in on the saucer. Pour over enough vinegar to wet the towel, then place the pennies on top of the wet towel. Wait for 24 hours and.....what happens? The tops of the pennies should turn green. Why? Vinegar is a dilute solution of the chemical called acetic acid. The acetate part of this acid combines with the copper of the pennies to form the green coating, which is copper acetate.  

--------------

Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
March 1992