This update contains several clarifications, including the statement that "The incidence of fabricating debris is greatly minimized when temperers adhere to all recommended maintenance procedures for washers, rollers and other tempering equipment."

Print copies and show it to builders. Help them realize why they should insist on quality tempered glass - that can be scraped - and why they need to sign your waiver.

Builders are encouraged to manage fabricating debris as a manufacturing defect on some of the tempered glass they are getting, and address this issue with their suppliers. We've been urging fabricators to test their own glass for this problem since 2005.
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Dan Fields, a highly regarded expert on the subject, presented a seminar called "Fabricating Debris Awareness"  February 2007 at the IWCA Convention.
This seminar was recorded by IWCA - but no longer sold

The day after a tour of the local Arch Aluminum & Glass tempering facility - during their 2005 convention in Orlando - the IWCA recorded a very interesting discussion about how hard these fabricators worked to produce better quality tempered glass for their customers.
During this discussion, these fabricators agreed that an ideal way to check for fabricating debris was to use a razor during regular QC checks on glass exiting tempering ovens.
Window cleaners were bussed to the Arch plant one day before the IWCA seminar. The editor of Glass Magazine - Nancy M. Davis - wrote an account of the discussion at the IWCA/Arch tour for the April 2005 issue. In that article, Max Perilstein, the Vice President of marketing for Arch, and leader of GANA’s Building Envelope Contractors division said, “We believe we're doing things the right way.” He advised window cleaners to “Investigate local glass fabricators. Ask if they’re doing the things we’re doing here.” That article was removed from the Glass Magazine website after only a few days.

This seminar was recorded by IWCA - but no longer sold

They also offer laboratory analysis as a free service to their clients, to properly identify "glass surface conditions or markings".

At one point, this article says, "Most often the conditions that appear on glass surfaces during the heat treating process are related to foreign materials that have been mechanically impinged into the glass or that has damage the glass as it passes over the rollers. "

An illustrated article from the 2001 International Glass Review entitled,
The dynamics of ceramic rollers
Operating and maintenance practices to produce quality tempered glass; By Renald D Bartoe, is no longer available online from International Glass Review - but back issues can be ordered.

This article also discusses issues related to tempered glass quality from the perspective of the roller manufacturer, and  advocates good housekeeping and good fabricating practices. At one point, this article says, "Glass dust and debris deposited on the furnace rollers can be picked up by the glass." There are several color photos. 
International Glass Review is a tri-annual review of glass production and manufacturing, published by Contract Communications Limited a subsidiary of Euromoney Institutional Investor PLC, in London, England

It does not, however, address the variable presence of fabricating debris. On most tempered glass, one side is fine, and the other side may or may not have fabricating debris. There is no explanation for why that occurs, or what is being done about it.

The truth is that proper maintenance in the tempering plant yields a better tempered glass surface - but this GANA bulletin doesn't mention that.

There is also the suggestion that ASTM standards allow the presence of fabricating debris, which suggests that builders have no choice but to accept tempered glass. However, the ASTM C 1036 standard contains disclaimers which seem to contradict that - and clearly, the ASTM standard does not actually state that detectable fabricating debris is acceptable.

The conclusion suggests that "millions upon millions of square feet of glass have been installed with trouble free performance", the inference being that this is because this glass has been cleaned and maintained by professional window cleaners who didn't use scrapers.

A window cleaner's view would probably be that most of those "millions upon millions of square feet of glass" have in fact felt a scraper - with no ill effect, because there was no fabricating debris problem. Scraper use among window cleaners is widespread - nearly universal. Window cleaning scrapers are offered by every major squeegee manufacturer, and sold by every major window cleaning supply house.

Listen to MP3 file      
Listen to .WAV file (much larger file - slightly better quality) 

A microphone was attached to a scraper..... the scraper was placed on a piece of tempered glass, pushed a short way, then lifted and placed on a nearby piece of tempered glass which was loaded with fabricating debris and pushed again - lightly, so as not to scratch the glass. 

The smooth surface that you hear first would have been the top side when that particular piece of glass was tempered, and the rough surface you hear next was the bottom - the side that was touching rollers when that particular piece of glass passed through the tempering oven.

The tinkling sound you hear is little glass fines and other fabricating debris. This is the "tinkle test"....   If you've never heard this before, you'll be impressed - or maybe you'll think we faked it.  

Caution -  Fabricating debris is variable, and this is a more extreme example. It won't always sound this bad, and you cannot count on feeling or hearing this surface defect while you are working - particularly on a messy construction site.  It is also important to realize that hearing this sound does not prove the glass will be scratched. (Some fabricating debris won't budge.)