All builders should know the difference between high and low quality tempered glass so they can make an educated decision about what is used in the windows installed on their projects. It is frequently encountered in the field, and has been repeatedly confirmed by experts, that some tempered glass will scratch during normal construction window cleaning. This scratching is a direct result of fabricating debris which was not properly removed from the glass surface prior to the tempering process. As a result, these particles are detached during normal construction window cleaning and cause major scratching, usually over the entire glass surface. During the past several years, defective tempered glass has been the leading cause in most cases of excessively scratched glass. The general contractor has a responsibility to select quality window manufacturers that will stand behind their products, if and when scratched glass problems arise.