Self-cleaning glass is an ordinary float glass with a special photocatalytic coating. It is made by chemically bonding and integrating a microscopically-thin surface layer to the exterior surface of clear glass. The integrated coating reacts to the sun's ultraviolet rays to gradually and continuously break down organic dirt through what is called a photocatalytic effect.
In other words photocatalytic means that the active integrated coating on the outside of the glass absorbs the sun's ultraviolet rays. This causes a reaction on the surface which breaks down dirt and loosens it from the glass. This type of glass also has hydrophilic properties, meaning that rain flows down the pane as a sheet, washing away the dirt instead of, as with normal glasses, leaving the dirt behind. As a result of these two effects, the special self-cleaning coating keeps the glass cleaner for a longer period than with normal glass in applications where it is exposed to the rain.
In a nut shell, when organic matter builds up on the glass, the UV-rays act to catalyse some reaction that breaks down the organic matter. When rain or water is sprayed onto the glass surface, the organic matter washes right off the glass’s surface, which has been treated to be hydroPHILIC instead of hydroPHOBIC (hence no beading).
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