Since Penn State University was hired by the IWCA over nine years ago to help identify the reason why some soda lime window glass scratches so easily and why other glass surfaces are extremely smooth and are quite resistant to scratches;...not much has been happening. At least not to my knowledge. However a fantastic amount of research was performed by Penn State at that time. Which went on for several years before Paul West left the Glass Committee. At the very end of his time there I remember one of the last white papers which listed the results of a spectrographic analysis of what we have been calling fabrication debris for many years. More specifically we have also been calling this feature glass fines. But the truth is that we really haver not known exactly what we are talking about. The idea has been that the particles are either dust/dirt in the air or from the rollers on the float line, or microscopic pieces of glass released at the end of the line when the ribbon is scored and broken into plates. If indeed this is true then the elements, and how much of each, should match that of the glass ribbon. Which should be easy to prove with a simple spectrographic analysis. But there was no perfect match. In fact it actually showed a much greater amount of aluminum than what is typically in glass. So simply put, what's up with that?!
If you go back to the post I wrote in this blog nine years ago you will discover some rather fascinating information. The post is called A Glimpse of the Ghost Particle? As I have written certain authorities have explained that microscopic glass inclusions, which occur just below or above the glass surface, are in fact a very common occurrence. They are NOT called defects by the glass manufacturers. However the properties of the tin bath and atmospheres in the factory are VERY closely monitored and controlled. Testing is a regular part of the manufacturing process. Also there are over 50 different types of inclusions that have been conclusively identified. Almost all of these are not considered a problem or a default by the glass manufacturer.
So you tell me. Are we talking about a ghost here that cannot be seen, and cannot be identified? There are many pictures of this particle zoo. Many tests have been done and much information has been written. We even have books on the subject. What I personally find fascinating at this juncture is that our experience in the field matches perfectly the information we have uncovered here.
The most interesting discovery is the variance. The surface defects can be very small and there are millions of microscopic particles. Or they can be somewhat larger with not so many. Or even larger yet but very few. I have also learned that the very small particles seem to scrach easier than the larger ones. Some of the large particles don't scratch at all!
I advise anyone reading this post to go back to the first one I wrote and study it. I will be researching the references made in that one and will be writing about what I learn there.
I do not believe that we will ever be able to get through the secrecy surrounding this science. The glass industry are not going to completely draw back the curtains on this matter. But I think we have already come a long way. And have enough to use in the field. It will always be a subject for my inspection and consulting work.
Written by Henry Grover Jr.
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