Just as it is possible to buff out small scratches in your car's paint, you can do the same with small scratches on a windshield. Doing this improves visibility while saving you the cost of completely replacing the windshield. It only takes about an hour to go through the glass polishing process.
Clean the windshield thoroughly with a glass cleaner. It's important to get the windshield as clean as possible because surface dirt gets caught under the polishing disc and causes more scratches.
Tape off the area that is going to be repaired from the inside of the windshield. Use two lines of tape, one on either side of the scratch, to act as guides once you begin polishing. Leave enough space between the tape for your polishing disc to fit between.
Soak the felt end of the polishing disc in warm water. Do this for about a minute so it will slide over the glass smoothly.
Mix the polishing compound. Follow the directions carefully and mix the compound until it is smooth.
Apply warm water over the scratch. This will further ensure that the polish goes on smoothly.
Tape off any non-glass surfaces. If the scratch is close to the paint you will want to protect it with masking tape.
Apply the polishing compound. Using the tape as your guide, fill in the area with the polishing compound in a smooth, even coat.
Polish the scratch. Attach the polishing disc to your drill and move the drill along the taped-off area in an even back and forth motion. Use a drill speed of 400 to 600 RPMs.
Wipe off any excess polishing compound with a wet sponge, then clean the area with a glass cleaner.
This process works for shallow scratches in the glass, or scratches that do not catch your fingernail when you run your finger across them. This process might reduce the appearance of deep scratches, but will not get rid of them completely.