Letter 11111 Penny cleaning    Hi, I am doing a project for a seventh grade science fair, and I would like to know what liquid cleans pennies best. Also, I was wondering how I should do my experiment and what liquids I should use. Thank you! Olivia M. - Arlington, VA, U.S.A.   Hi, Olivia. This question has been asked and answered here many times before. So please start with our FAQ on Cleaning Pennies. Good luck! Ted Mooney, P.E.  finishing.com Brick, New Jersey     My First Grader is doing a science fair project on cleaning pennies and we have our cleaning products but what we cannot seem to find out is how does the penny seem to get so dirty? Is it because of the copper and people holding it and touching it? Compared to all the other coins it seems the penny gets dirty faster than the rest. If you could help I would appreciate any info you could give. Margaret S [name deleted for privacy] - Moreno Valley, CA

Hi, Margaret. All metals except gold (and a few rarer precious metals) tarnish. But copper, which pennies are coated with, tarnishes a bit easier than the nickel that the other coins are made of. Also, the copper tarnish is a fairly dark and distinguishable brown color whereas the slightly yellowish tarnish on the nickel-based coins is not as obvious. So, pennies don't get dirtier, the oxidation products are darker. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

 

Ed. note: For every metal finisher in the world there are a thousand students with this question, and we are drowning under variations on the question although we've already answered it hundreds of times already. Please read our F.A.Q. on the subject. If that doesn't fully answer your question, please search the site. Thanks!