Question

Why would you specify a photocatalytic coating on your new building's glazing?

Answer

You would specify a photocatalytic coating in order to help keep the glazing clean. The first self-cleaning glass was based on a thin-film titanium dioxide coating. The glass cleans itself in two stages. The "photocatalytic stage" of the process breaks down the organic dirt on the glass using ultraviolet light (reflected from the glass) even on overcast days, and makes the glass hydrophilic (normally glass is hydrophobic). During the following "hydrophilic stage," rain washes away the dirt, leaving almost no streaks, because hydrophilic glass spreads the water evenly over its surface.