Glass is too hard for razor scrapers to scratch.
Sadly, that wasn’t the point I was going for, quite the opposite, in fact!
A razor blade’s edge is typically of similar hardness, so scratching glass while scraping is definitely a possibility! (Usually, the pressure being applied is too low to scratch)
glass is almost always scratched by moving Rock or a piece of Grit caught under the Magnetic Scraper.
this is definitely a good way to scratch glass, too!
— outside of grit related damage, the scratches I’ve made while scraping glass have typically been due to using a worn/damaged razor or scraper blade… if the blade has a bent corner, or a folded over blade edge, it can create a pressure point (or a “dam” to contain grit), and the distinct “nails on a chalkboard” screech as it scratches!
I didn’t have much free time today, but I did rush through a quick demo earlier… ~12mm annealed float glass scraps; standard vs. low iron:
Low-iron on bottom:
After a quick rinse and wipe to clean off glass grinding dust:
Standard float glass scratches from razor blade (including a tiny chip the blade broke free):
Scratches on low iron float glass from razor blade:
All this to say that glass isn’t indestructible, it’s just a lot harder to scratch than plastic! (I had the very corner of the blade perpendicular to the glass and was carving at it to get that level of scratching, hence the damaged blade corner)
