Self Cleaning Glass
As a Window Cleaner I have constantly come across people talking about how self cleaning
glass must be threatening my business. But I have to say that it has had no noticable effect upon
my particular business.
So what is this mysterious self cleaning glass?
It is glass that has had a coating applied to it's external surface, either when it was produced in
the factory, or later "in situ".
There appear to be 4 main types of coatings :-
- (1) Photocatalytic.
- This is a coating that reacts with the ultra-violet
part of sunlight and it breaks down the organic dirt that attaches itself to the glass. This
coating needs to be applied with further coatings to enable the broken down dirt to be removed
from the surface of the glass. It is dependant on the action of wind and rain to remove the
- (2) Hydrophilic.
- This coating stops water from forming droplets and increasing
it's ability to "sheet" down the window, hopefully bringing with it the dirt.
As a Window Cleaner that uses water fed poles to clean windows, I have to say we love
windows that have had this coating applied, because it certainly speeds up our rinsing of the
- (3) Hydrophobic.
- This coating makes the glass "water hating" which increases
the waters tendancy to form droplets. The idea is that the water droplets run down the windows
taking the dirt with them.Problems come when applied to glass on Conservatory roofs or
skylights etc. as there is not a steep angle and the droplets only run down the glass
- (4) Super Hydrophobic.
- This coating is an extreme form of the previous Hydrophobic
coating and makes the glass so "water hating" that the water forms circular droplets that run
down the glass quickly.
Over the last few years, when I have talked with customers that have bought this self
cleaning glass, I have found a disappointment with the performance of the coatings. There is no
doubt that they work, but what I have found is that the glass is always cleaning but never
This is because the dirt falls on the windows at different times and so whilst some is
cleaned off the rest is still in the process of being cleaned off.
It is also dependant on the action of wind and rain to help remove the broken down
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