For years, window cleaners have been blamed for scratching glass, when in fact, fabricating debris on tempered, or heat-treated, glass is at fault.

Fabricating debris is only a problem with tempered glass. After a piece of glass is created, it’s tempered by reheating it and then rapidly cooling it. However, before it goes back to be reheated, small glass particles or dust can settle on the surface while its being stored. When the glass is heated again, those particles get fused onto the glass.

Then, when window cleaners are hired to clean glass during post-construction cleanup with razor blades — the industry standard for equipment for decades — the blade is scraped along the glass and it dislodges the fabricated debris, scratching the window.

Replacing these windows are costing building owners and window cleaners millions of dollars each year. But when cleaners can prove that the glass was defective, they often win if taken to court. Ask the glass fabricator if they are doing their own scrape tests to check for fabricating debris. If they don’t, chances are the glass is to blame, not the cleaner. Also, it’s a good idea to require the building owner to sign a damage liability waiver that indicates window cleaners are not held responsible for damage to tempered glass with fabricating debris.