While float glass becomes tempered safety glass (ESG) in the transformation process, the ceramic colors also form a permanent bond with the base glass. For years of best readability without change in color, infinitely UV-resistant. Also, in demanding environmental conditions. When walls or the building long since appear dirty and worn out.
In contrast to the concrete wall in the background of the image, with our glass a little vinegar is enough to release the limescale. And then wipe off once with common cleaners: Looks like it did on the first day.