Long crack repairs are often approached with caution, but why is that? How is a crack different from a star break? What’s the best repair technique, and which type of resin is ideal? These are key questions, and in this article, I’ll walk you through the answers.

A typical star break is mostly contained beneath the top glass layer, making it relatively straightforward to repair using a bridge and injector. However, a long crack is exposed along its entire length, requiring a different approach. Since it’s open, a tool called a crack expander is positioned inside the windshield, directly beneath the crack. This expander gently widens the crack, allowing resin to be injected or applied with a syringe from the outside.

For this repair, you’ll need a thicker, higher viscosity resin specifically designed for cracks. Start at the crack’s tip and work backward toward its origin, often near the glass edge. Maintain steady pressure on the crack expander as you move it along to avoid trapping air. As you progress, keep the expander sliding along the inside of the windshield, monitoring the resin filling the crack from the side at the glass level. Place 3-inch curing strips over the filled crack and, once complete, remove the crack expander.

If working indoors, cure the resin with a UV light for about five minutes over each curing strip, adjusting as needed to cover the entire crack.

When working outdoors, shield the repair area with a fender mat, securing it with aluminum bridges. Use a “peek-a-boo” technique to prevent sunlight from curing the resin prematurely, and reposition the vehicle as needed to block any sunlight from entering under the mat’s edges.

Allow the resin to cure in direct sunlight for about five minutes, then remove the curing strips. Scrape away any hardened resin excess with a razor blade held at a 45-degree angle and clean the area with a paper towel. The finished repair should resemble a faint scratch on the windshield.

Additional tips:

• Make sure the crack is fully dry before beginning the repair, as any moisture can prevent proper resin filling and may lead to air pockets as it evaporates.
• Avoid exposing the crack to sunlight during the repair process.
• Do not drill the end of the crack to stop it; this step isn’t needed and will leave a noticeable mark on the windshield.

With practice, you’ll see that repairing long cracks can become as manageable as other types of windshield repairs.