Pumice Stone:
It is also used as an abrasive, especially in polishes, pencil erasers, cosmetic exfoliants, and the production of stone-washed jeans. "Pumice stones" are often used in beauty salons during the pedicure process to remove dry and excess skin from the bottom of the foot as well as calluses.[/b][/color][/i]

So basically, it takes your skin off and the ink comes off with it ...