Posted 11/07/2008 1:42 pm
If you are just swishing them back and forth through water to dissolve off dirt or possibly an organic solvent such as acetone, xylol(xylene), isopropenol(rubbing alcohol), or methylethylketone (to dissolve oily dirt) and no rubbing is done on the surfaces then I don't see any problem. The problem comes when you rub the surfaces which can cause scratching of the surfaces, or the use of chemicals that attack the metal itself or any coating such as oxides, sulfides etc that have resulted in coloration of the surfaces. These chemicals with result in unnatural appearnces to the coin or even etching of the surfaces.
