I use to take the time to clean them better, electrolyzes, fine wire brush with the dremel tool, then some baking soda............... but since the silver just comes out so beat up I just take a pair of pliers and break off the cookie crust if it has one. Then use a stiff wire brush with the drill, cleans them up very nice but does scare them some. If I get a silver that is has no cookie I just clean with baking soda by rubbing, those are the ones that look almost like they were just dropped..........The gold comes out very nice but once and awhile I will get one that is tarnished or has a little crude on them, those I do electrolyzes for maybe 20 seconds then polish with some Mothers Mag wheel polish. I do enjoy breaking up or cleaning the coins because you just never know what they will turn out to be....