A variety of glass cups were investigated after treatment in a machine dishwasher. Three types of surface damage were found. The first consists of clouding on the inner and outer surfaces, appearing after around 1000 washing cycles. It can be related to the long range granular structure of glass, which is believed to be formed by thermal density fluctuation. During washing, both water & detergents act as weak etchants, first eroding the smooth glass skin, then revealing the granular structure. As soon as the linkages between the granules are entirely broken by the etching, holes manifest themselves at these sites. When the size of the hole reaches the half of the light wavelength, light scattering occurs and the glass appears cloudy. The second type is sheet clouding on the outer surface appearing after 100 wash cycles & the third is a golden film on the inner surface. probably formed by complex formation between the glass surface and the organic compounds in the drinks. All of the damage studied here is irreversible.
