Self-cleaning glass. 
The functionality.

Pilkington Activ™ benefits on two counts from the forces of nature in order to achieve its unique cleaning effect. First, the Activ™ glass surface absorbs the ultraviolet sun rays causing a chemical reaction in the compound with oxygen: organic dirt particles are disintegrated and removed. The real cleaning work is then done by the next rainfall. Based on the hydrophilic properties of the Activ™ glass surface, the water forms an evenly spread film instead of forming drops and washes the partially dissolved dirt off.

In contrast to conventional glass, on Pilkington Activ™ surfaces water dries very quickly without leaving drop marks. The result: a clean pane.