is it true that if we use Soap bar to clean the surface of a disc the chemicals from it can eat away the plastic surface of the disc even after washing, even if it's a pressed silver bottomed disc like audio music cds you buy in retail shop? thanks a lots!
It depends on the disc and on the chemicals in the soap bar. It is not likely that soap meant for human skin will affect polycarbonate plastic, and that is the material on the bottom of a CD-R and on both the top and bottom of a DVD. The top of a CD-R is a series of layers: 1) silk-screened ink/lacquer; 2) UV-cured lacquer; 3) photo-sensitive dye; 4) silver alloy. These layers are the weakest part of the CD-R. The chemicals in soaps are often water softeners and fats meant to break ion bonds holding dirt onto the skin. There are often skin emolients and mild abrasives to scrape dead skin cells from new skin. None of these is good for a lacquer surface, particularly the abrasives. (Imaging washing windows with bar soap.) Washing off the soap material from the surface of a disc will probably not leave any detrimental chemicals on the disc, but rough scrubbing or rubbing may cause some damage. The polycarbonate class for optical discs is the same as that for eye glass lenses. The least expensive solution for keeping discs clean is the solution you might use for cleaning eye glasses. Take particular care of the upper surface of the CD-R because its bonded layers are a weak point.
