As documented in the IWCA Tempered Glass Informational Bulletin 2004 - Scrapers & Fabricating Debris © 2004 International Window Cleaning Association.
Fabrication debris on tempered glass is a problem that all building owners should be familiar with.
"Fabricating debris" refers to abrasive microscopic particles, including glass fines, which may become fused to glass as it contacts the rollers in some tempering ovens. Glass scrapers, which won’t scratch uncoated glass when properly used, have long been the industry standard and most practical method for removal of debris such as paint, adhesives, or stickers from uncoated glass, not only during construction cleaning, but throughout the useful life of the window. However, if fabricating debris is present, it can be dislodged and trapped by a scraper during window cleaning. The result will be scratches caused by the dislodged fabricating debris. Another type of heat treated glass known as "heat strengthened" may also be affected.
No current ASTM standard addresses this issue. Fabricating debris is a known quality control issue that can be minimized when temperers follow all recommended maintenance procedures for washers, rollers and other tempering equipment.
Fabricating debris is permanent, and these issues may persist even if windows are protected during construction. Scratched tempered glass is often associated with fabricating debris. Scratches due to fabricating debris are normally lighter than scratches due to common abrasives like sandpaper. With the aid of a magnifying device, some of these scratches will look like comets. When a "comet scratch" can be located, the cause is obvious. The comet’s "head" is fabricating debris, broken and trapped by a scraper, creating a "tail". Fabricating debris itself is usually invisible to the naked eye, but when it is present on tempered glass, it can often be felt, and a distinct gritty sound heard when a scraper is moved very lightly (so as not to cause damage) over a clean surface.
For additional information on scratched glass visit https://www.scratched-glass.net (This website is not endorsed by or affiliated with IWCA.)