So I’ve been in the window cleaning business for a long time now (only 2 months lol), and sometimes it is very hard to figure out what kind of windows your dealing with. [I]Low-E, Tempered glass, Solarblue, etc etc[/I]. And in a lot of cases it seems like the time you do figure it out, its too late. You scratched the glass.
[U]So to try and prevent that I thought it would be a good idea if we all pitched in all of the tricks of the trade to figure out what type of glass where dealing with, and how to handle that type, the best way possible.[/U]
I’ve seen various ways and learned different techniques such as “if the glass looks grape (purple in color in polarized lenses), you must not scrape” in regards to tempered glass. But I had to really go searching for the answers. So lets try to keep all of the different techniques and all the different types of windows under one thread for the newbies like myself.
Get a heat treated glass scratch waiver signed by your client, stating they will not hold you responsible for scratched heat strengthened or tempered.
The polarized glasses thing is more of a fun fact than critical information.
Polarized glasses - as if you could wear them all the time anyway - might also show a colored haze on low-e coatings on annealed glass that are inside an IG unit. (So the glass might not be tempered, and the coating is probably out of harm’s way.
And the better job they do with tempering, the harder it will be to spot the tempering strain marks - so you’re not always looking for the same thing.
Don’t blade or steel wool any window until you look in one of the corners to figure out what kind of glass it is. There’s always a little print in the corner of every pane to tell you what it is.
You probably meant, look in all 4 corners - but that won’t always tell you “what it is”.
There’s actually a lot to think about if you’re looking for tempered glass because you want to clean it differently (because you didn’t have your client sign a heat treated glass scratch waiver).
The reason you’re worried about tempered glass in the first place, is because the side that touches rollers in a horizontal tempering furnace MIGHT have defects on the surface that will scratch when you scrape. (If the temperer keeps a clean furnace, it won’t.)
So you need to know which is the roller side - because the other side won’t have this problem.
And if the glass was tempered in either a vertical or gas hearth tempering furnace, neither side touches furnace rollers, so neither side will have the defects that cause scratches.
So - if you know it’s tempered, and you really want to know what it is, you need to figure out if there’s a roller side or not.
You can often tell the difference, but it’s really hard to explain.
And to make things worse - you won’t always find a logo.
You can order glass tempered without logos - and heat strengthened glass is not required to have a logo.
So looking for logos is kind of a crap shoot - pun intended.
It really depends on residential or commercial. Here 90% of resi you have annealed glass on all windows except sliding doors which are tempered.
While commercial its quite opposite most glass at ground level or high rise will be generally tempered while internal office glass and stuff is generally not.
It never really bothers me since I don’t scrape widows unless its already arranged, I have a disclosure on my quotes that price does not include removal of construction debris or removal of stains ( for that price. can be done for additional price).
I see so many videos of a window cleaner scraping every inch of glass just as part of their general service, what a waste of time and a cause of many scratches, Clean the window first then remove the debris not with huge strokes up the glass just small movements over the debris.
So if it’s already arranged (for additional price), you’ll scrape.
By “It never really bothers me”, do you mean you don’t worry what kind of glass it is unless you have to scrape?
If it is already arranged I will remove the construction debris, a blade is the very last resort on tempered glass then it is only used carefully not in full arm length strokes. I have scratched quite a bit of glass in my early years and learned what not to do, just cause it will scratch doesn’t mean it has to. I believe window cleaners need to adapt to what surface we are presented with and clean it accordingly without damage under any circumstances not using a blade on glass you KNOW will scratch if you do it with a blade because its fast and efficient then stand behind a waiver. It might mean instead the glass takes longer and you need 3-5 different spray bottles with various chemicals in them.
And the it never really bothers me should be it rarely bothers me, I can 99% of the time know what type of glass I am cleaning due to its size/location and of course the polarized prescription sunnies I wear when I leave the house.
So during construction cleaning, if you encounter construction debris, you remove it - because you’re getting paid extra.
And during maintenance cleaning, if you encounter construction debris, you just leave it there - because you’re not getting paid extra.
(We have that in common.)
It’s not clear what you do differently when you believe glass is tempered - whether you scrape less, or not at all.
Maybe you believe all tempered glass is soft or somehow more likely to scratch simply because it was tempered - but that’s simply not true.
I learned to use a scraper on tempered glass when I worked for 3 years at a glass tempering factory - using a company issued scraper for removing stickers and such.
The problem you are trying to “adapt to” is due to a surface defect only on one side of some horizontally tempered glass - on the side that lays on furnace rollers - IF the fabricator has allowed rollers to be contaminated with glass fines from pre-processing.
If the rollers were dirty, there may be defects on the roller side that break off and cause scratches during cleaning with a scraper.
There’s still no problem on the other side.
If the glass was tempered horizontally, on properly maintained clean rollers, there’s no glass fines/scratch problem on either side.
If the glass was tempered vertically, there were no rollers involved, and no glass fines/scratch problem on either side.
If the glass was tempered in a gas hearth furnace (travelling on one edge through the furnace, held upright by blowing air), there were no rollers involved, and no glass fines/scratch problem on either side.
You’re free to assume all tempered glass will scratch when you scrape, but you can’t teach that it will, because that’s simply not true.
I realize that I am adapting to the defects in the glass rather than to solve the problem at its source. As far as I see it, whether or not glass manufacturers change their methods it still leaves several billion panes of glass out there that have a chance at least of having the FD on a side.
As for what I believe about tempered glass, there is no belief structure I do not think the glass is soft I am fully aware of what you speak of and have been since I originally found your document around 2000-2001 on the causes of scratches and fabrication debris. The company I was working for at the time was getting ever more concerned with how many guys were scratching glass I took it upon myself to research it where I found your publication and tried to inform my co-workers.
What I can say is if people scrape the way you see in most videos on the wrong side of the wrong glass they have just scratched it. From what I have experienced in the past 18 years 80% of tempered glass that I have cleaned at the CCU level has had FD.
