Oh, absolutely-putty scrapers can damage glass if you're not careful! I learned this the hard way when I scraped old putty off my kitchen window and left a huge scratch-still bugs me every time I look at it. But don't worry, there's a way to use a scraper on glass without ruining it-you just gotta know the tricks.
First, the blade type is everything. Never use a stiff metal blade on glass! That's a one-way ticket to scratches. Instead, use a plastic putty scraper or a metal scraper with a super flexible blade (the kind that bends almost all the way). Plastic is softer than glass, so it won't scratch-think of it like usin' a rubber spatula on a non-stick pan. I switched to a plastic scraper after my kitchen window mistake, and I haven't had a scratch since.
Then, prep the glass! If you're scrapin' old putty or paint off glass, warm it up first with a hair dryer (low heat, keep it moving). Softening the gunk means you don't have to push hard with the scraper-pushing hard is what causes scratches. I once tried to scrape dried paint off a mirror without warming it, and I pressed so hard the plastic scraper almost bent in half-luckily, no scratch, but it was a close call.
Also, angle the scraper flat-around 15 to 20 degrees. If you hold it too steep, the edge of the scraper will dig into the glass. Keep it low, and use light, slow strokes. And never scrape back-and-forth-go in one direction only. Back-and-forth motion rubs any dirt or tiny particles into the glass, which acts like sandpaper and causes scratches.
Another tip: clean the glass first! Wipe it with a glass cleaner and a rag to get rid of dust or dirt. Even a tiny piece of sand can scratch the glass when you scrape. And after you're done, wipe the glass again with cleaner to make sure you got all the gunk off.
So yeah, putty scrapers can damage glass-but only if you use the wrong blade or push too hard. Use plastic or flexible metal, warm the gunk, keep the angle flat, and you'll be fine. No more staring at ugly scratches on your windows!
