Step 1: Materials
For this simple yet cool project, all you need is a file and some pennies. Any type of penny will do, though shiny ones look nicer, and I found that a fine to medium file works best.
Step 2: Penny Filin'
Begin rubbing one of the penny sides against the file. Either side works. Gradually, the copper will wear off and the silver colored alloy will be revealed. First, the rim will be effected, then the images on the penny will be worn down. It starts to look really cool, but don't do it for too long or else the whole face will be worn to nothing. (Be careful not to file your finger - not fun!)
Step 3: Have Fun!
Try out different ways to file the pennies. There are lots of different things you can do with them. I tried this with other coins, but I guess all their inside metals are the same color as those on the outside. Please comment any suggestions or ideas! Thanks!