Subsurface vs. Surface Cracks in Windshields: How to Identify and Repair Them

Not all windshield cracks are the same. One common distinction? Subsurface cracks vs. surface cracks. Windshields are made up of two sheets of glass held together by a thin plastic interlayer, creating laminated safety glass. Lamination increases the glass’s durability because, when the glass breaks, it bonds to the tough, tear-resistant plastic layer inside. This layer also preserves visibility, as it stays clear even after the windshield is damaged. When a rock or other debris strikes the windshield and causes a chip or crack, the damage is typically contained to the outer glass layer, leaving the inner layer intact.

What Is a Subsurface Crack?

A subsurface crack usually forms at the point where a small rock or road debris hits your windshield. The result is often a bullseye chip—a circular impact mark below the outer layer of the glass.

These types of cracks are often less than an inch wide and don’t break through to the surface. But they’re still dangerous—because over time, vibration, pressure, and temperature changes can cause micro-cracks to spread into long surface cracks.

If not treated early with a quality windshield repair kit, they can compromise your windshield’s structural integrity.

What Is a Surface Crack?

A surface crack happens when the damage has extended to the top most layer of the windshield glass. These cracks are usually visible on the surface and may feel rough or raised if you run your finger over them.

Surface cracks are harder to repair and more prone to spreading across the glass. If you see one forming, it’s important to act fast with the right windshield crack repair kit before it gets worse.

How to Tell Which Type You Have

Here’s a quick and simple method:

  • Take a flat-edged tool like a razor blade.
  • Gently glide it over the damaged area.
  • If you feel a bump or ridge, it’s a surface crack. If it feels smooth, you’re likely dealing with a subsurface crack.

The Importance of Using the Right Windshield Repair Kit

Not all windshield repair kits are the same. A high-quality kit—like the ones offered by ClearShield Supplies—can handle both subsurface and surface cracks effectively. Look for a kit that includes:

  • Miniature drill-to clean and prepare rock chip for repair
  • Metal injection bridge to precisely inject repair resin
  • Top quality repair resins to provide a repair that lasts and looks great
  • Curing strips and razor blade to smooth out the repair and restore the windshield’s smooth surface. 
  • Step-by-step repair instructions or video tutorials

Why Use a Windshield Crack Repair Kit?

  • Prevents cracks from spreading
  • Restores visibility and strength
  • Saves money when compared to full replacement
  • Easy to use with no experience needed

Repair Both Types of Cracks with One Kit

Our professional-grade windshield crack repair kits are built to repair both surface and subsurface cracks safely and quickly. Whether you’re fixing a fresh chip or stopping a crack from spreading, ClearShield has you covered.

Tip : Always repair cracks as soon as possible. Delaying a fix can lead to full windshield replacement, which costs significantly more.

Final Thoughts

Whether you're dealing with a minor chip or an expanding surface crack, identifying the type of damage is the first step toward a successful repair. Using the right windshield repair kit can prevent small issues from turning into big problems.

  • Don’t wait for the crack to spread.
  • Choose a reliable windshield crack repair kit.
  • Follow our step-by-step repair guide or training videos for best results.

Ready to repair your windshield the right way?
Browse our best-selling kits at ClearShieldSupplies.com and get back to a clear, safe view of the road.

Frequently Added Questions:

1. What is a subsurface windshield crack?

Ans - A subsurface windshield crack is damage that lies below the outer layer of the glass, typically caused by a direct impact like a rock chip. It often appears as a small, circular bullseye.

2. What is a surface crack on a windshield?

Ans - A surface crack extends through the top layer of windshield glass, often growing from an untreated subsurface chip. These are visible and can be felt when you run a blade over the area.

3. How do I choose the right windshield repair kit?

Ans - Choose a windshield repair kit that includes a miniature drill to prepare the chip, a metal injection bridge for precise resin application, and top-quality resins for a clear, lasting repair. Make sure it also has curing strips, a razor blade to smooth the surface, and clear step-by-step instructions or video tutorials for easy use.

4. Can one repair kit work for both surface and subsurface cracks?

Ans - Yes. ClearShield’s windshield repair kits are designed to repair both subsurfaces.

5. What happens if I ignore subsurface or surface cracks?

Ans - Ignoring cracks can cause them to spread due to temperature changes, road vibrations, or moisture. This weakens the windshield, reduces visibility, and may lead to costly replacements.

6. How much does it cost to repair a cracked windshield?

Ans - Repairing minor surface cracks usually costs less than a full replacement, often between $50–$150. Subsurface cracks may require more advanced repairs or even a full windshield replacement, which can cost $250–$500+.

7. Can subsurface cracks spread faster than surface cracks?

Ans - Yes. Since they weaken the inner glass layers, subsurface cracks often spread more quickly under stress from driving, heat, or cold.

8. How can I prevent cracks from spreading before repair?

Ans - Avoid sudden temperature changes (like blasting hot air on a cold windshield), keep the glass dry, and drive carefully over rough roads until repairs are made.

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