Fix Hairline Cracks in Car Windows

Like windshields, car windows are highly susceptible to nicks, scratches, and hairline cracks. It can be tedious to repair a car window yourself, but not impossible. Read on to learn the do-it-yourself method on how to fix hairline cracks in car windows.


  1. Inspect all windows on your car including the back window and windshield. There may be additional cracks that require your attention.
  2. Purchase a specific type of windshield repair kit called a bridge kit. Bridge kits have suction cups at each end of the bridge that latch onto the window and are the best option for hairline cracks on vertical car windows. These kits are available at various auto supply, hardware, or retail stores.
  3. Clean the crack and its surrounding area so that it is free of dirt, loose glass, and other debris. A metal probe works best for the cleaning process.
  4. Use the metal probe to create bull's-eye cracks at each end of the hairline crack. Gently tap the metal probe so that the inner plastic layer of the glass is not damaged. This prevents further widening or spreading of the crack.
  5. Load the specified amount of resin into the injector as instructed on the bridge-kit packaging.
  6. Position the bridge apparatus so the injector is directly above the crack. Secure the suction cups in place. Add resin into the crack using the injector or use the pressure and vacuum controls of the injector to suck air out of the crack while forcing the resin in. When the crack has been filled with resin, remove the bridge from the window.
  7. Allow the resin to completely harden and dry. Windshield repair kit resin does not air-dry; it requires UV light from the sun or an artificial UV lamp to adequately dry.
  8. Apply a generous amount of resurfacing resin directly to the repaired hairline window crack. Use a cellophane patch, and cover the area that you just applied resurfacing resin to. Expose to direct sunlight or UV lamp, and allow the area to dry. After it is dry, remove the cellophane patch and gently scrape off the excess resurfacing resin with a razor blade to make it level with the surrounding glass to complete the car window hairline crack repair.
  9. Clean the window with glass cleaner.


  • Do the hairline crack repair as soon as you see it. The sooner you repair it, the better the results of the repair will be.
  • Even though the repair kit is meant for windshields, it will work just as well on car windows as the glass is the same.
  • Do the repair on a sunny day if you plan to do it outside. This allows the resin to dry faster and better.


  • If the crack on your window is longer than 3 inches (7.6 cm) then a windshield repair kit will likely not work for you. In this case, it is best to contact a professional.
  • Professional resin injection methods usually provide better results than a do-it-yourself kit.

Things You'll Need

  • Bridge windshield repair kit
  • Cellophane patch (if not included with repair kit)
  • UV lamp (optional)
  • Razor blade
  • Glass cleaner

Related Articles

Sources and Citations