Fine scratches and scuffs left by wipers, sand, or keys do more than spoil the look of a car or its mirrors: they can also impair visibility. Replacing a windshield at a garage is expensive, but you may be able to solve the problem yourself. Shallow damage can be removed with ordinary polishing compounds and a basic set of tools. One thing you must never use, however, is sandpaper.
Assess the Depth and Prepare the Surface
Before starting, perform a simple fingernail test. Run your nail across the scratch at a right angle. If it catches easily in the groove, polishing may soften the edges but will not remove the defect completely. Deep damage like this requires photopolymer filling. If your nail glides smoothly over the mark, you can proceed:
- Wash the surface: Clean the glass thoroughly with car shampoo or window cleaner to remove all dust and fine grains of sand.
- Degrease the area: Wipe around the scratch with isopropyl alcohol or degreaser, then dry it.
- Protect nearby surfaces: Mask the area around the damage with painter's tape to keep polishing compound off bodywork and plastic trim.
How to Polish a Windshield
Apply a polishing compound and work on the damaged area. For very fine marks, use plain white toothpaste with no abrasive granules mixed with a pinch of baking soda. For faster, professional-grade results, use a cerium oxide compound, a specialist glass-polishing powder sold by automotive retailers.
Use a thick microfiber cloth or a soft felt pad. Apply a small dab of compound directly to the scratch, then polish the glass in circular motions with moderate pressure for 3–5 minutes.
Keep the work area damp with water from a spray bottle. This prevents the compound from drying and protects the glass from dangerous overheating. Move the cloth smoothly across the entire scratched area and do not linger in one spot, or you may create a lens-like optical distortion.
Watch the video guide to see how to remove a scratch from a windshield:
How to Polish a Car Mirror
Use the same method on a mirror, but apply less pressure. Put a small amount of compound on a felt pad and work slowly over the damaged area.
Take particular care around the mirror's edges. Do not allow large amounts of water to get behind the glass, as moisture can damage the reflective coating. After polishing, remove any residue with clean microfiber and inspect the surface from several angles. If the scratch remains, repeat the process.
How to Avoid Damaging the Windshield
Follow these simple precautions closely to avoid ruining the windshield while you work:
- Control the heat: Check the glass temperature regularly with your hand. If the surface overheats, internal stress can cause it to crack.
- Avoid coarse abrasives: Never use sandpaper, powdered dish cleaner, or coarse GOI polishing paste, as they can leave a cloudy, frosted patch.
- Do not press too hard: Avoid excessive pressure on a drill or polishing machine, or you risk distorting the surface of the glass.
What Not to Use on a Windshield
Never use sandpaper on standard automotive glass. It can create scores of new scratches and alter the geometry of the surface.
Toothpaste, baking soda, and powdered cleaning products are also poor choices for polishing glass. These compounds are not designed for professional scratch removal and can produce unpredictable results. Do not force the polishing pad against the glass. Pressure is no substitute for the correct abrasive and only increases the risk of overheating.
When Windshield Polishing Will Not Help
If your fingernail drops noticeably into the scratch, the damage is too deep for ordinary DIY polishing. Do not try to level the area through aggressive abrasion. A deep scratch in the driver's field of view can produce glare and distortion. In this situation, the safer option is to consult a specialist and assess whether professional repair or glass replacement is needed.
The rule is simple: a fine surface scratch can be polished out gradually, but there is no safe shortcut for removing a deep groove without risking changes to the glass.
