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. 

Why is that a problem?

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

Fabricating debris, if present, becomes a problem when the property owner, clean-up crew or professional window cleaner uses a window cleaning scraper. Though virtually invisible to the naked eye, bits of this abrasive fabricating debris can be trapped by a moving scraper, causing visible scratches to appear.

So if fabricating debris is present on your tempered glass, your cleaners will never be able to use a window cleaning scraper to remove paint, caulk or any other goop from that batch of tempered glass without scratching that can result in expensive claims and customer relations problems. 

Beyond that, your customers need to know whether or not fabricating debris is present on tempered glass, because vigilance will be required of them to somehow assure that scrapers are never used, or that the need to use scrapers never arises - for the life of the window.

How do I know if it's there?
Ironically enough, the window scraper is one of the best tool for this job - but don't count on finding fabricating debris during a challenging construction clean up. That's when it's hardest to detect.

When fabricating debris is present on tempered glass, it can usually be felt, and a distinct gritty sound can be heard when a window cleaning scraper - or the edge of a credit card - is moved very lightly over a clean surface.

So that you have an idea what to listen for, 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.

OK, we don't want fabricating debris on our tempered glass - but what can we do?
We've been urging fabricators to test their own glass for this problem since 2005.

Fabricating debris is a manageable problem. Builders, architects and remodelers are urged to specify that tempered glass surfaces be free of fabricating debris, and to indicate that any tempered glass with fabricating debris will be returned for a full and complete refund.

Try to follow that up by testing your new tempered glass for fabricating debris upon arrival - before it gets scratched, and before you are committed to installation.

You're not asking your suppliers 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.
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