Car Direst recommends cleaning the window to remove any loose dirt and debris. Then, carefully apply a rubbing compound that contains cerium oxide over the scratch, with moderate pressure. Doing this protects the window from further damage and scratches. Then, remove the rubbing compound with a soft cloth, and rinse the window. The window should now be cleaned with a cleaner that is provided in an auto window repair kit.
Before attempting to repair the window, rubbing a fingernail over the scratch is useful in determining if it can be repaired. If the fingernail catches on the scratch, then the window needs to be taken to a glass technician to do a more extensive repair. Also, the cerium oxide in the rubbing compound is an important ingredient since this is what seals bonds the crack in the window and prevents it from deepening any further.
For proper maintenance, the entire process should be repeated once every six months. Continually monitor the crack, to ensure that does not return and cause further damage to the window. All scratches, no matter how big or small, must be addressed immediately in order to restore the structural integrity of the window and prevent more costly damage.