PPG says.....
According to the U.S. company, PPG Industries* that offers the product:
"PPG defines self-cleaning glass as a product that has three distinct characteristics. First, the glass has a durable, long-lasting coating that has been fused into the glass at high temperatures during the glass manufacturing process. Second, the coating exhibits photocatalytic properties, i.e., it will slowly decompose organic material. Third, the same coating also exhibits hydrophilic properties, i.e., it will cause water to sheet over the coated surface and dry with minimal spotting and streaking. Other companies offering 'self-cleaning' glass products should be evaluated as to whether their products provide these three distinct characteristics.
"The self-cleaning property of ...[this PPG] glass is made possible by a durable, transparent coating of titanium dioxide (TiO2) applied during the manufacturing process. The application process...makes the coating an integral part of the outer glass surface, providing...a durable, long-lasting product.
"In a photocatalytic process, ultraviolet (UV) light from the sun energizes the...self-cleaning glass to help slowly break down and loosen organic dirt. Since UV light is abundant even on cloudy days or in shaded areas, this process works nonstop throughout the day.
"The coating also has a hydrophilic property that makes water droplets spread out, or sheet, across the surface of the glass. When rain or a light spray of water hits the window, the water carries away the loosened dirt. This sheeting action also helps the window dry quickly with minimal spotting or streaking.
"Will windows that have this glass ever have to be washed again?
"Yes, but not in the same way you are accustomed to washing...windows...[The] windows will be easier to clean. Either let mother nature do it for you or occasionally wash your windows with a light spray of water. Of course, the interior surface will need to be cleaned like any other window glass."
