Metals can't scratch glass. Cat claws have even less chance. "Q. Do metal scrapers or razor blades scratch glass. A. No. Metal scrapers and razor blades alone

Metals can't scratch glass. Cat claws have even less chance. "Q. Do metal scrapers or razor blades scratch glass. A. No. Metal scrapers and razor blades alone will not scratch glass. However, abrasive materials, such as sand or fabricating debris from the tempering process, trapped by a metal scraper or razor blade, can scratch glass."