Here it is, on that other forum weirdo from wissconsin I stated that “we” collectively as professionals should be able to not damage glass while cleaning it.
That being said there is a very different feel when scraping between the two. It is our fault. Maybe not the first time but the second for certain.
How do you clean “bad” glass without damaging it?
Is “feel” the way you determine glass is bad?
If glass doesn’t “feel” different at one location of the pane, does that mean it’s “good” glass?
In my waiver I make clear that I don’t claim to know if or when FD is present on the glass. We run into glass w/ all kinds of debris on it. How are we supposed to tell the difference consistently? We can’t. You could be scraping a piece of glass that has FD and never feel or hear anything. The next one will feel different because of the concentrations of FD on the surface being cleaned. You simply can’t tell for certain.
As always Excellent post Tony 
bad glass has a roll to it rather than a glide when scraped. test a lower corner scrape once to remove debris then scrape the clean part a second time. you will feel the difference. In my experience bad glass is bad all the way across the pane.
five years ago I bought a family new windows because it was my fault, I scratched them. And I haven’t scratched a window since.
I know of panes where half of it was covered in FD and the other was fine.
If you haven’t had an issue lately then that’s great.
However the vast majority of FD is undetectable and the only way to know if it was there is if the lighting is just right and you look thru the glass at the right angle and see the telltale scratches. Of course it’s too late then but that’s why we need the waiver signed.
When you state “debris,” are you referring to construction debris or fabricating debris?
In my experience, scraping a surface with fabricating debris does not remove all fabricating debris – scraping a second time still yields the same sound (sandpaper-ish) and feel.
How do you clean “bad” glass without damaging it?
I can relate to the original poster. There is a sound and feel that I’m very aware of. I have scratched glass before but never glass that didn’t have these traits. I have never encountered any that only had half. Years ago I was on a job and ran across this. I thought it was the razor. We changed the razor and it still did the same thing. We got up on the glass and scraped the identical pane next to it = No noise, no feel. Went back to the flawed glass and it made the sound. I programmed that sound/feel in my head and pretty good at recognizing this kind of glass today.
I am no expert and no very little about Fabricating debris (which is dumb having this forum and all the knowledge about it), I do know the sound and feel though.
I don’t know how close I am but my explanation to customers is this. When the glass was manufactured there are two sides, a rough side and a smooth side. The rough side is supposed to be inbetween, however sometimes it’s put together backwords and the rough side ends up on the outside. This cannot be scraped with a razor or it will leave scratches.
Can one of you experts tell me if this is even close or did I just dream it up?
Justin, there is no rough or smooth side. You have a roller side which is as the name implies is the side that faces the rollers in the tempering furnace. Sometimes glass will shatter in the furnace covering the rollers w/ glass fines. These (if not cleaned off) will deposit fines on that side of the glass which becomes fused to the surface and causes the feel and sound you are experiencing. On some glass though the roller side is not the problem. Some tempering facilities don’t keep their glass washers maintained. Since glass can’t be cut or sized after it’s tempered those procedures are done first. Then the glass is supposed to be washed. If it isn’t or if the washer isn’t cleaned out regularly then glass fines remain on the surface that faces away from the rollers and can have the same sound and feel because FD is present on it. The reason we are dealing w/ this problem is that if they turn either of these defective surfaces in they run the risk of a reaction between low-e coatings and FD. I’ve attached some pics of what this looks like.
One point that needs to be made here is that it doesn’t matter if you can feel or hear a bad surface. By the time you feel or hear it there are scratches on the surface! Get the waiver signed and never tell someone you can identify “bad” glass or you are accepting liability for any scratches.
Very good explanation Tony, thanks!!
When you have time, i’m interested in the “get the waiver signed”. When you have time I’d like to know your exact approach.
I address the issue when scheduling the job giving them a basic explanation of the problem. Basically that since it’s a microscopic debris we are dealing w/ I have no way of identifying if or on which tempered panes it might be present. Then I try to get their e-mail and I send them info from Dan Fields site and the waiver. I require the a signed copy of the waiver before we begin work.
Well your first scrape will get off all the construction debris and your second will tell you what your dealing with
Hey in my minds eye I see that crap being there forever. So now I know its there, I never scratched glass with the wool, earned me one big ass bicept though.
dude it looks like those panels are effected on the inside which has nothing to do with me.
Check a out of the way corner! problem solved.
Those were examples of why we have to deal w/ this garbage and not directed to you but for the education of anyone interested.
If you are content w/ the way you do things that’s fine. My intent is to help others see the potential downside and liability of claiming to be able to identify bad glass.
Your corner method solves nothing as FD is rarely, if ever, evenly distributed on the glass.
Huh?
well i personally have done 200+ ccus since I scratched the sh__ out of somebodies glass. I bought that glass and then Surprise no more scratches.
What is your experience with fd only on part of the pane?
good glass or bad
I’ve run across panels that had a gritty sound on the top half and not on the bottom. By the standard you set that would mean FD on top and not on the bottom. Of course I never say I can tell if FD is present because my eyes aren’t microscopes.
Again I’d say just because you haven’t seen scratches doesn’t mean you haven’t had any.
You’re not making sense.
I’m confused – you seem to state that a first pass with a scraper only removes the construction debris, and that a second pass with a scraper will determine whether fabricating debris is present. I find that illogical.
Right I see what your saying. You are saying that the fab debris would be removed by the first pass, and then one would have no way of telling if it was there on the second pass. But I believe that the bad glass that will carry that same sound no matter how many passes you throw at it.
