Window graphic removal is much different than removing graphics from other substrates. With most substrates, you can use a lot of heat and pull as hard as you want without breaking anything.
Glass can withstand temperatures upwards of 2000°C when heated evenly. But if you heat just one area of a pane of glass, as little as a 150°C, the glass is likely to shatter.
The usual heat sources, found in most sign shops, are heat guns and torches that have an average upper heat range of 1000°C to 2000°C. In less than three seconds, the glass could be breaking.
Another common reason for glass to break is the incorrect use of force. If you are removing a large graphic from a long span of glass, pulling as hard as you can in the middle can bend the glass beyond its flexible boundaries.
Vinyl sticking to glass has a much higher bond than on other substrates. Therefore, it is always easier to remove it in small pieces. I use a liner cutting tool to score the vinyl without cutting the glass. Try to score with straight lines. Evenly cut sections remove much more consistently than odd-shaped pieces.
By scoring the graphic several times, you can pull the vinyl off the window as hard as you’d like, without the risk of breaking the glass.
If there’s a little adhesive residue left over, clean the window with a mild solvent like IPA.
Using little or no heat and the sectional removal technique, window graphics can be removed quickly, but most importantly – safely.