Windshield Repair – How Does It Work?

by Don Elliott on January 31, 2012

Windshield repairs can be completed on windshields with minor damage. Many people are skeptical about repairing any glass that is broken or chipped, let alone in a critical automotive component like the windshield. How is it possible to “glue” broken glass back together in a permanent way?

The secret of windshield repairs is in the way windshield laminated glass is made. Two pieces of glass are bonded over an inner layer of Poly Vinyl Butyral (PVB). The bonded layers of glass and PVB make the glass able to withstand impact from foreign objects, preventing them from entering the passenger compartment. As an additional safety feature, it prevents objects and people from flying out of the car in the event of an accident.

Most minor chips, bullseyes, and cracks only break the outer layer of glass. In 1971, The 3M Company introduced a technique called “Scotch Weld” to remove the air from the crack and replace it with resin. Over the years, improvements have been made. Today, all major glass replacement companies also offer glass repair services. In fact, the windshield repair process has gotten so efficient that most insurance companies will pay for it to avoid the more costly windshield replacement service.

Not all chips, bullseyes, and cracks can be repaired satisfactorily. The Repair of Laminated Automotive Glass Standard (ROLAGS) was established in 2007. They recommend that the following types of damage can be repaired in lieu of replacing the windshield:

  • Bullseye: Diameter no larger than one inch
  • Combination Break: Diameter of the body of not more than two inches excluding subsurface cracks that emanate from the break
  • Crack: No longer than fourteen inches
  • Half Moon or Partial Bullseye: Diameter no larger than one inch
  • Star Break: Diameter of break not to exceed three inches
  • Surface Pit: Damage with a diameter of not less than one eighth of an inch

Windshield repair is not recommended if the break penetrates the inner layer of glass, if the plastic inner layer is discolored, or if the damage is in the driver’s primary viewing area. An experienced auto repair technician will be able to determine if the windshield repair will adequately remove enough of the damage to maintain the structural integrity of the windshield.

As mentioned above, most windshield repair is covered by the owner’s insurance policy. Reputable windshield repair shops are familiar with the paperwork and will generally make the claim on your behalf.

If your insurance policy does not cover windshield repair, it is possible to make the repairs yourself. Windshield repair kits are fairly inexpensive. Read the instructions completely before you begin. The surface temperature of the glass when inserting the resin is very important. If the surface is too hot or too cold, it will give you less than satisfactory results. It may be wise to just let the professionals handle it.

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