What is self-cleaning glass and where is it best used?

Self-cleaning glass has a durable hard-coat layer (typically titanium dioxide) on the outermost surface that keeps the glass cleaner for longer through a two-stage process. First, a photocatalytic reaction: the coating reacts with UV in daylight to break down organic dirt on the surface. Second, a hydrophilic effect: instead of beading into droplets, rainwater spreads across the glass as a thin sheet, washing the loosened dirt away and drying quickly without leaving streaks or spots.

It’s at its best where glass is awkward or expensive to clean by hand and is exposed to daylight and rain — conservatory and lantern roofs, skylights, hard-to-reach windows and large glazed areas. A couple of practical points: it relies on natural daylight and rainfall, so in very sheltered spots an occasional hose-down helps; and silicone-based sealants must be avoided against the coating, as silicone can mask the self-cleaning action. It reduces cleaning frequency rather than eliminating it entirely.