The name self-cleaning can be as always misleading and therefore irrespective of how you treat the glass it will still actually require cleaning and maintenance.
So, what is self-cleaning glass, and what types of self-cleaning glass are there?
Well I would divide this area into two categories, two distinctively different approaches to the same proble
1) Glass coated or applied with hydrophilic layer that uses photo catalytic decomposition
2) Glass coated or applied with a hydrophobic protective coating.
Glass being a very porous and microscopically uneven surface full of valleys and peak is a magnet to dirt, contamination, bacteria and various other deposits. This, over time, deteriorates the surface, brilliance and clarity of the glass. This is why you will find glasses, in particular those that have been exposed to the elements for a long time, which cannot be cleaned, no matter what cleaning material is used. This happens because the dirt, grime and contamination are so deep and so rooted into the surface of the glass that it cannot be removed.
Here are the main differences with their respective positives and negatives. Let’s start with the two major differences; hydrophilic and hydrophobic.
Hydrophilic (Hydro = water + philic = to attract or like) simply means that the glass attracts water and make it spread out like a thin film on the surface. Hydrophobic (Hydro = water + phobic = to repel or dislike) which means the glass will repel water and any water that comes in contact with the glass will attempt to have as little contact as possible with the glass and will create spherical droplets on the surface.
If we begin with the first type, the hydrophilic; this is glass that is based on having a film of titanium dioxide coating. The glass works in two stages. The "photo catalytic" stage (simply meaning the accelerated process of using the ultraviolet light to break down the organic dirt on the glass) and hydrophilic sheathing stage, During the following "hydrophilic" stage rain washes away the dirt, leaving almost no streaks, because hydrophilic glass spreads the water evenly over its surface.
Pluses of the hydrophilic type: Under the right conditions, meaning frequent sun and rain, or if hosed down regularly will reduce the cleaning cycle required of glass. The coating is stable and has a long life span.
Minuses of the hydrophilic type: Titanium dioxide–based glass cannot decompose inorganic dirt, thick non-transparent deposits, such as paint or silicone, water stop fingerprints, or dust produced during construction. This glass also negatively reacts with silicone and will require specialist glazing.
If the glass gets damaged it will require replacement of the glass as no onsite application is possible.
The second type of self-cleaning glass is glass applied with a hydrophobic coating also known as having the “lotus effect” which refers to the very high water repellence exhibited by the leaves of the lotus flower.
This type of self-clean coating works in fact like a shield. Dirt particles are picked up by water droplets due to a complex micro- and nanoscopic architecture of the surface which enables minimization of adhesion. This form of glass works in a similar way to "Teflon" on a frying pan. It produces a non-stick surface and water will run off of this surface quickly and not streak. The coating or applications of this type are silica based and create a nano scale film that covers the microscopic valleys and peaks on the surface of glass. This type of self-clean coating prevents the contamination, dirt and grime from clinging onto the glass or fixing to the surface.
Pluses of the hydrophobic type of self-clean glass: Works on organic and inorganic dirt alike. These type of coatings are scratch resistant and will reduces the need for use of chemicals in any cleaning required as dirt will easily wash off. Protects the glass from graffiti and paint. This type of coating can be replied on site if required. The hydrophobic coatings be placed on BOTH sides of the glass if required
Minuses of the hydrophobic type of self-clean glass: Products will vary from manufacturer to manufacturer and require professional application. Factory applied coatings, depending on the exact product, have a life span of 3 to 10 years in external conditions.
Cost wise, the hydrophobic coatings and applications are usually about half the cost of the hydrophilic type glasses.
Until the day we hear of a new breed of self-cleaning glass that requires zero maintenance these are the options on the market.
In conclusion we can safely confirm that to date there still is no ideal self-cleaning glass or a glass that requires zero cleaning but there certainly are some great advantages to the use of these two types of glass products.