We have been talking about fabrication debris for a long time. Personally I believe in fabrication debris. I absolutely do not believe that it can fuse to tempered surfaces however. something else is going on here. During the short time that I was with the IWCA Glass Committee I learned that. But whatever IS going on is definitely NOT a simple matter. Paul West called it a “perfect storm”. And all you have to do is look at the animal as Richard Feynman said we need to do when trying to understand physics. So lets do that friends. Right now!
If you take a penny and lightly drag it across a clean plate of glass you will be able to tell if it is smooth, rough, loaded with “defects”, or not a single one. What IS so fascinating is the fact that in general bad surfaces are not all the same. Some are very very smooth with defects. Such defects seem like particles that can be very small even microscopic, whereas others can be very large. You can tell this by how they feel and sound. You can almost tell how many there are per square foot. If they are very very small there are millions of them. If they are rather large then there are usually only hundreds. And again the glass in general can be very smooth (accept for the defects), or it can be rather rough. The roughness can vary too. It can be very rough or only slightly. It can also be rough only in certain areas but spread out over the entire surface.
The other day I ran into an interesting situation. Two plates of tempered glass. Both on the same door. The upper plate was exceptionally smooth but had hundreds of defects. They sounded loud and could easily be broken off causing scratches. Or so it appeared because there were scratches on that plate. Which did NOT mean that those scratches were created with a razor blade. I have come across situations like this before and could not scratch with a razor. Moved in the opposite direction so I could tell. What was interesting about this door however was that the other lower plate was indeed rough. But no apparent defects, and no scratches. So we can see from all of this that defective surfaces are very different. Rough surfaces can be scratched or not depending on what is doing the scratching also. In other words it is possible to scratch more easily with a broken piece of glass than it is with a piece of metal. Such as a penny, copper pipe, car keys, or such. Even a rock most times does not scratch as easily as a piece of broken glass. Of course cut diamond, silicon carbide, or another very hard material (harder than glass) scratches very easily. Especially on rough glass.
So there are many things to consider here. To break it down to one simple statement however I will just say this. If the glass is either rough, defective, or defective and rough, we must use extreme caution when performing non-routine window cleaning. And that demands a waiver. Or just walk away!
Henry
