Chemicals and Compositional Abrasive Materials for Coated Glass

Low E Glass is usually coated with extremely thin layers of different metallic compounds.   These can be only 40 angstroms deep.  Which is very thin.  Any damage whether mechanical or chemical can be permanent!  In other words once a coated surface has been damaged there is very little chance of bringing it back to like new condition.

Very powerful acids and alkalies should never be used on coated glass.  Even certain organic solvents can be dangerous.  However solvents are usually the safer chemical.  Razor blades and crude abrasives should never be used.  So when coated glass is covered with very thick hard water deposits it could be easily beyond repair.  Very heavy mineral deposits usually require at least a two step process for restoration.  The first step involves grinding.  The second involves polishing.  Glass is easy to grind.  Since it is so thick.  A quarter of an inch thick.  But coatings are measured in billionths of an inch!  Although it is quite possible to develop various polishing techniques that use nano-particle slurrys.  There are also plastic particles of different micron sizes.  These have different hardness and shapes.  So they can be blunt or "sharp".  Whether or not these so called compositional abrasives are capable of doing harm to a coated surface depends on testing.  You would actually have to buy a sample of the coated glass in question and try to damage it.  The same with any "compo-blade" whether that be plastic or carbon based.  And on that note I will leave off.  Because as some of you know one of the hardest materials in the world is based on pure carbon, that being diamond.  Also pencils use graphite which is very soft two dimensional carbon.  Further carbon black particles used in squeegee rubber is even softer.  So we can see from this that carbon based compounds can be extremely hard or very soft depending on how the carbon atoms are arranged.  Alternative particles and or alternative razor blades can be very interesting ideas.

If you have any questions about this post simply send me an email.  henrygroverjr@gmail.com

To receive these posts in your inbox just type your address in the box at the top right, "Follow by Email".

Stop Scratching Coated Windows Now !!!

Here is some interesting and VERY important information.  I have just started to write a three part series of articles on Glass Coatings for the American Window Cleaner as a member of the IWCA Glass Committee.  They are being published under the running theme "From the Lab to the Field".  The very first thing that should be addressed by you the window cleaner regarding low e glass coatings is that they can very easily be missed.  Most times you just don't know they are there!  Especially when the windows are covered with either dirt or mineral deposits.  So the very first step should be to clear a test spot and determine whether or not the surface is glass or metal.  Is there a low e coating or not.  Then if there is you should not use anything at all that could scratch.  That can be most any type of abrasive.  Because abrasives that would otherwise not scratch glass surfaces at all could easily scratch a glass coating.  There are so many different coatings out there that they are becoming very difficult to identify.  The AWC articles will address this issue.  Razor blades should never be used on glass coatings.  It is a rather sad revelation also that many window cleaners end up revealing damage to coatings that was done by previous window cleaners.  This also can cost you either a lawsuit or simply a great deal of aggravation.  For this reason it is important to do your best in educating any potential or existing customers.  This is another reason why I am writing these articles/posts.  So you can take this information directly to your customers on your phone or tablet and show it to them.

There are time bombs right now all over the world just begging to be discovered by unaware window cleaners in the form of hidden low e coatings.  Take a real close look at this picture! 

Can you see the black haze on the pyrolytic reflective low e coating?  It shows quite plainly the damage that was done likely by hydrofluoric acid.  There are times when this type of glass coating can be damaged but not show.  Then when HF or a mild abrasive is used a second time to remove stains that have formed again the reflective coating is quickly stripped off. So you wouldn't have a clue before any "visible" damage was done.  This is why it is critically important to first determine if the window has a low e coating and then have it in a legal waiver/disclosure. 

Here  is another very interesting problem that could result in a very expensive lawsuit.  You might use a rather crude abrasive hard water stain remover compound on a reflective hardcoat that did what you thought was a great job.  No scratches could be seen.  All the stains were removed.  If used on plain glass it would not cause any damage.  But glass coatings are another animal altogether.  Once you are done and get paid two years go by.  The hard water spots reform.  Especially because you might have decided not to seal.  It becomes necessary to remove the stains again.  The decision maker however decides to save money and have a quick acid wash done.  The demonstration shows no damage to the glass.  Just a bright clean window at one fifth the cost.  So it is done.  Still looks great from the outside.  Even on a bright sunny day.  BUT.  When the windows are viewed from the inside looking out there are zillions of scratches all over every window!  Now after two years later you get a call.  After all.  It appears that you left the scratches.  And you did.  You didn't use the acid which magnified those scratches fifty times over making them highly visible from the inside looking out.  No you didn't do that.  But try to explain all of this to someone that has no clue what actually happened.  It won't be any easier in court.  Further at best, even if you could explain it, you would likely end up sharing the financial responsibility with the other window cleaner that acid washed the building.

Also to receive these free posts from this blog as they are written directly to your inbox just type your address in the box at the top right of this page, "Follow by Email".

Written by Henry Grover Jr.
henrygroverjr@gmail.com