I been digging alot of blackened clad lately and have been struggling to get them clean. i built a tumbler out of an old canon printer, tried many different mixtures of items and chemicals to clean them. i bought household cleaners copper cleaners ketchup vinegar salt etc etc. still came out blackened. Then tonighti rigged up the phone charger salt water thing. Boy Howdy ! the first quarter i did came out perfect like i just got it in change from mcdonalds. A half doller i had that was black came out a little copper colored but otherwise perfect. i definitely recommened everyone tries this. takes about 5 minutes and it is clean and shiny.