This 35 minute video displays the difference between hard water spots, tin etch haze and glass corrosion.  Discussed is the use of chemicals like hydrofluoric and phosphoric acid for the removal of hard water spots and the problems associated with acid use.  The video addresses some of the misconceptions about tin etch haze and offers suggestions of how to avoid this issue while removing hard water spots.  It also includes a slide show which contains close-up images of hard water spots, tin etch haze and glass corrosion on various glass samples.