Some tempered glass surfaces have what are known as fabricating debris defects on the surface, including microscopic glass particles, which become fused to glass as it rolls through some tempering ovens. 

This presents a problem when you or your window cleaner try to use a window cleaning scraper. Though virtually invisible to the naked eye, bits of abrasive fabricating debris can be trapped by a moving scraper, causing visible scratches to appear.

When there is too much fabricating debris, your tempered glass will be harder to clean and maintain - and it will be more susceptible to damage.

When fabricating debris is present on tempered glass, it can sometimes be felt, and a distinct gritty sound can be heard when a window cleaning scraper is moved very lightly over a clean surface. So that you will have an idea how rough some tempered glass surfaces can be, we attached a microphone to a scraper, and produced a 6 second audio clip showing the remarkable difference between smooth and rough tempered glass surfaces.

As explained in the IWCA's tempered glass quality Talking Points,  testing "may confirm the presence of fabricating debris, but can not confirm the absence of fabricating debris on a jobsite. Thorough testing might involve actually trying to cause fabricating debris scratches on each tempered window with a scraper, using bright lights to locate scratches, and then using magnifiers to confirm that they were fabricating debris scratches. This can take hours, and obviously cannot be done if the objective is to avoid scratching the glass.

Fabricating debris is preventable.
Talk to your building or remodeling contractor beforehand about getting tempered glass that can be scraped without suffering the effects of fabricating debris. 

You're not asking them to provide a perfect product - absolute perfection is probably not possible. What you are looking for is suppliers who take pride in a quality product - who will work with you when there is enough fabricating debris to cause problems.
And by the way, when they are building IG (insulated double glass) units with uncoated tempered glass, they can probably meet your cleaning specs simply by taking care to assemble your windows with the higher maintenance roller side INSIDE the unit, out of harm's way.

Please visit the International Window Cleaning association (IWCA) website for more information.

You may also wish to print this page, along with other resources linked to by our Scratched Glass Documents & Links Page - including the International Window Cleaning Association's IWCA Tempered Glass Informational Bulletin 2004 - Scrapers & Fabricating Debris

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