SPECIFIER REVIEW
Self-cleaning glass – how it works

Self-cleaning glass – how it works

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by Effi Wolff – Managing Director – Balcony Systems

Some might argue the concept of glass that cleans itself is too good to be true. While not 100% true, technological advances have made this close to a reality and an affordable, maintenance-reducing addition to the home.

Introduced to the market relatively recently, self-cleaning glass coating uses nanotechnology to create a microscopic coating that makes a smooth surface which repels water, dirt and grime to help keep it looking clean for longer.

For glass balconies exposed to the elements, particularly in coastal or city environments, a self-cleaning glass coating option greatly reduces the amount of cleaning needed to keep the glass clear and retain the views.

So how does it work? There are two basic types: glass coated with a ‘hydrophilic’ layer that uses photocatalytic decomposition and glass coated with a ‘hydrophobic’ coating – also known as the ‘lotus effect’.

Hydrophilic simply means that the glass will attract the water and cause it to spread out in a thin film. Hydrophobic means the glass will repel water and any water molecules coming into contact with the glass will have minimum contact as spherical droplets on the surface.

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Hydrophilic coating

The first type of self-cleaning glass is coated with a film of titanium dioxide. This glass works in two stages. In the ‘photocatalytic’ process, the coating reacts with ultraviolet light to break down the organic dirt on the glass and reduce the adherence of inorganic dirt. This makes the glass ‘hydrophilic’, causing it to attract water and distribute it across the surface in a thin film.

During this second stage, rainwater washes away the dirt, leaving almost no streaks, as the hydrophilic effect spreads the water evenly over the surface of the glass. The resulting advantages are that under the right conditions of frequent sun and rain, or if hosed down regularly, less cleaning is required. This coating is stable with a long lifespan.

The downsides are that titanium dioxide-coated glass cannot decompose inorganic dirt, thick non-transparent deposits, such as paint or silicone, greasy fingerprints or dust produced during construction. This glass also reacts negatively with silicone and will require specialist glazing. If damaged, full replacement of the glass is needed as on-site application of the coating is not possible.

Hydrophobic coating

The second type of self-cleaning glass uses a hydrophobic coating – also known as having the ‘lotus effect’, which refers to the very high water repellency exhibited by the leaves of the lotus flower.

Dirt particles can be picked up by water droplets due to a complex micro and nanoscopic architecture of the surface, which minimises adhesion. This glass works in a similar way to Teflon on a frying pan. Its non-stick surface causes water to run off quickly without leaving streaks.

To the naked eye, glass has a smooth and even surface. However, a microscopic examination would reveal numerous peaks and troughs capable of holding dirt and grime deposits. When applied to glass, the silica-based hydrophobic coating covers the surface with a nanoscale film to create a perfectly smooth finish which largely prevents dirt sticking to it.

The advantages of hydrophobic coatings are that they work on both organic and inorganic dirt. They are scratch-resistant and reduce the need for cleaning chemicals as any muck will easily wash off. Protecting the glass from graffiti and paint, the coating can be reapplied on site if required.

On the downside, this application, depending on the particular product, has a lifespan of five to 10 years in external conditions. Hydrophobic coatings and applications are generally about half the cost of hydrophilic types.

As a leading manufacturer and supplier of glass balustrading, Juliette balconies and curved sliding patio doors, Balcony Systems developed its own patented self-clean glass coating as a lower-maintenance option across its entire product range. This innovative coating can be applied on all colours of glass, providing an affordable, readily available and convenient extra benefit for architects, specifiers and designers to offer their clients.

While there is no self-cleaning glass on the market that requires zero cleaning, these two types of coated glass products will certainly reduce the cleaning effort – leaving more time to enjoy views from glass balconies.

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For further information please call 01342 410411 or visit http://www.balconette.co.uk

Balcony Systems Solutions Ltd, Unit 6 Systems House, Eastbourne Road, Blindley Heath, Lingfield, Surrey, RH7 6JP

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