Glass has always been a difficult subject for many companies claiming to have professional detailing skills. Most do not understand the very basics when it comes to glass itself as a material. It is much harder than paints, plastics, and metals all together. This is one of the main reasons that it will spot so easily without any protection on it. Water spots can be defined in 3 categories, light, medium, severe. The first 2 categories can usually be dealt with using very little mechanical action (polishing).
Chemical removal of water spots is common for most vehicles and would be done during a prep process prior to paint correction. Whatever is left behind which spot removers do not remove, will be removed by mechanical action or polishing. Crystal clear glass looks great but requires protection as well. The answer is “clear to see”; clean glass is safer and aesthetically more pleasing for those wanting that “perfect detail”. We do also possess the tools and techniques to remove glazing or windshield scratches induced by constant wiper use.