How to repair knife scratches on windshields

Method 1: If the scratch is light enough, it can be sanded down, and then polished out. But if you try this process on a bigger scratch, the amount of sanding and polishing you’ll have to do will create a dip in the glass causing optical distortions. In situations where the scratch is too deep, you will have to replace the glass completely. To avoid these scratches, use a clean, stainless blade, and use a Glass Aid or similar product to protect the glass. You can also opt to avoid using blades altogether and just use a plotter, especially on new models. Vintage vehicles are easier to sand and polish out glass scratches because of the different composition of their glass.