Can you clean pennies that way? I recently went to Disney World and on the way stopped for a couple of nights in Gulf Shores at an RV park on the bay. Got to do a little MDing on their beach while there. dug a few coins with some crud on them but as I was turning around, a round object on the surface caught my eye. It's a heavily encrusted coin the same size as a penny but so badly encrusted, it's about three times as thick as a penny. Im using the electrolysis on an lighter encrusted Memorial but I've never used it before. There are bubbles coming from both electrodes. Is that normal? Thanks for the help.