The challenge with spider cracks versus a simple bullseye is that the radiating legs are often incredibly thin—sometimes thinner than a human hair. Air is trapped inside them, and surface tension can prevent resin from flowing all the way to the tips.
Fixing a spider crack doesn’t “melt” the glass back together. Instead, it involves injecting a specialized (usually a polymer with a refractive index very close to glass) into the cracks. The resin fills the air voids, restoring structural support and preventing further cracking. Once cured with UV light, the resin bonds to the glass. can you fix a spider crack in windshield