Research

When researching I found that some people disagree whether acid damages pennies or cleans them.

For the people who do say that the acid cleans the pennies, this is their hypothesis: pennies are made of zinc with a layer of cooper, over time the copper forms an oxide on its surface, this is what makes the penny seem dull. The lemon juice’s acid dissolves the oxide and makes it seem clean again.

Those who disagree say that over time the acid can damage the penny by slowly eroding it away from the edges, inwards. Some scientists say that applying heat to a penny immersed in vinegar will speed up the eroding process. When researching, I found that some scientists have preformed experiments where along with the penny being eroded, it turned green.