self cleaning glass, anyone?

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Kenny G
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Joined: Mon Oct 15, 2007 11:03 am

self cleaning glass, anyone?

#1 Post by Kenny G »

Hi there. Can someone tell me if there is really such a thing as self-cleaning glass? It seems too fantastic. Does this mean once installed, I need not worry about cleaning anymore the glass as it will always look spic and span? What if the installation is in the tropics and the pollution factor is high, and the rain is contaminated? Will all glass be cleaned equally well if some are exposed fully while others are half-exposed (to rain and sunlight because of the roof eaves)? I don't want to get my hopes up only to be told that there are "many hidden factors" for it to be self-cleaning. Please, someone enlighten me as I would have to import these expensive glass but do not want to be saddled with lemons. Thanks

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self-cleaning glass

#2 Post by Oberon »

Window glass described as “self-cleaning” has a special photo-catalytic coating - titanium dioxide - applied to the surface. The titanium dioxide coating makes the glass surface hydrophilic which means that water will sheet and flow off the glass.

As a comparison, most after-market coatings (such as Rain-X) are hydrophobic which results in the coated glass surface repelling water causing it to bead up on the surface. A hydrophobic coating will leave dirt and mineral deposits (spots) behind when the water evaporates whereas a hydrophilic coating results in a surface layer of glass that is “slippery” to water which then sheets off carrying the dirt along with it.

In addition to being hydrophilic, the titanium dioxide coating chemically reacts with the ultraviolet rays in sunlight to oxidize organic material on the glass. This process, called photo-catalysis, breaks down dirt and other organic materials and prevents them from sticking to the glass. It works on organics, but the coating does not break down inorganics.

Some of the folks that produce glass with the titanium dioxide coating like to say that their glass is self-cleaning (Pilkington, PPG), whereas some manufacturers (such as Cardinal, Guardian) avoid the term “self-cleaning in favor of “easy cleaning” which is probably a bit more understandable.

While the difference between “self-cleaning” and “easy-cleaning” might be considered to be trivial, there is some concern in the window industry that eventually glass with the titanium dioxide coated glass will need to be cleaned – even if it is simply a matter of spraying the windows with a garden hose – which will lead to grumbling from consumers about being mislead by the “self-clean” description. .

Still, this is a very nice add-on product and it does work as advertised as long as people realize that “self-cleaning” requires sunlight and an occasional wash-down with water – be it rain or a garden hose – to remove whatever debris might be on the glass surface.

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#3 Post by Randy »

Recently I sold some windows to a customer, with Cardinal's Neat glass, and they are upset that the windows are not "cleaning themselves".

The issue in this case is the proximity of the windows to a swimming pool. Apparently the chlorine from the pool is etching or somehow damaging the exterior surface of the glass.

We are going to have to get Cardinal involved on this one.

Oberon, do you have any wisdom to offer on this?

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Joined: Thu Oct 07, 2004 10:25 am
Location: East of the Mississippi


#4 Post by Oberon »

Hi Randy,

I hate to use the word interesting in this context, because I can certainly understand the customer's complaint, and from their perspective and yours, this is not an "interesting" problem. But from a purely analytical perspective this really is a unique situation and I tend to deal with lots of those.

I don't know that I have ever heard of anyone who offers titanium dioxide coatings testing to that particular scenario - but in hindsight if no one did, maybe it should have occured to someone to do so. However, people who do such things try to consider every possible angle and invariably there are a couple that pop-up that no one has ever considered.

I would love to know what Cardinal's response is to this one.

Sorry I couldn't offer more...

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