Window Washing Questions | Why should I be concerned about using a razor blade on my windows?

Most windows in the last twenty years are tempered glass and treated with a coating to block UV rays from the sun.  As a result the glass is easily scratched when using a razor blade. If you have to use a razor blade to take off construction material there are a few rules you need to know. First the razor blade must be new and fresh out of the package. Razor blades exposed to the air tend to rust after time. This will cause scratches. A razor blade should only be used for one window. The edge becomes dull with each use. Nicks in the blades will cause scratches on the window. It is cheaper to use a lot of razor blades than to replace a lot of your windows. A good solution is try a chemical cleaner like goof off. As long as the surface of the window is free of dirt and grit the cleaner should take off what ever is left.