Long Crack Repair Tips

windshield crack
Single Line Crack

Long crack repair is often seen as something to avoid. What makes a crack different to a star break? What is the best technique? What resin should be used? All good questions which I will address in this article.

Star Break

First of all a typical star break is mostly underneath the surface of the top glass layer. A very easy repair to make with your bridge and injector. A long crack actually is open at the surface for the entire length of the crack. So the repair requires a different technique than a star repair. Because the crack is open at the surface, a device called a crack expander is put on the inside of the windshield under the crack. The expander is used to open the crack up so resin can be easily injected or applied with a syringe on the outside of the windshield.

A thicker, higher viscosity crack resin is required to repair and permanently fix the crack. The repair starts at the tip of the crack and you work your way back towards the crack’s origin…which is usually near the edge of the glass. It is very important to maintain even pressure from your crack expander when sliding along the crack. Not doing so may cause trapped air in the crack. Keep sliding the crack expander along the inside of the windshield, following your progress. You can see the crack filling from the side of the crack at glass level. Along the way, you will place 3″ curing strips on top of the crack. When the crack is filled, remove the crack expander from the inside of the windshield.

When working indoors, you will need to cure the resin with your ultra violet light. Place over curing strips for approx. 5 minutes. Move light as needed to cure entire crack.

When working outdoors, it is imperative that you keep your work completely covered with a fender mat, securing it with your aluminum bridges. When working outdoors with the fender mat on windshield, use a “peek-a-boo” style not to expose the resin to ultra violet light. You may need to move the vehicle so that sun light will not come from around the edges of the mat.

Allow the resin to completely cure in direct sunlight for approximately 5 minutes. Remove the curing strips. Holding a razor blade at a 45 degree angle, scrape off the excess hardened resin. Wipe clean with a clean paper towel. Your finished repair will look like a fine scratch on the windshield.

Additional tips:

  • Make sure that the crack is free of moisture before the repair. If there is any water present, it will prevent the resin from filling the crack and will cure with air pockets once the water evaporates.
  • Keep sunlight off of the crack while it is being repaired.
  • Never drill the end of the crack to try and stop it. This is not necessary and will make for an obvious mark on the windshield.

With a little practice you will be repairing long cracks just as easily as any other windshield repair.