I just finished my second window sign, and this one required removal of the old vinyl graphic. It had been on the window for many years and I was having a heck of a time trying to remove it with a "little chiseler" and some solvent. I heated it with a heat gun and that helped quite a bit, but then a guy came along and told me I was doing it wrong. He pulled out a metal knife blade (linoleum knife) and began scraping away. It came off easily using the metal blade and the solvent, but I'm reluctant to use that method because I've read a lot of articles that say a metal blade can damage the window. Does anyone here use metal blades on glass?