Windshield Repair Information
Different Kinds of Glass
Ordinary window glass, like you have around the house, is pretty amazing stuff. It's clear, strong and cheap. But it's also brittle, shattering into long, dangerous, wickedly sharp shards when overstressed. Plastics would be as strong, but not nearly hard enough to resist scratching and remain clear enough for a car window – just look at any plastic-glazed outdoor bus stop or phone booth, with its patina of fine scratches. For the side windows of cars, automakers have come up with a good compromise: tempered glass. It's stronger than standard, but more importantly, when it does shatter it breaks up into small granules. These granules are still sharp, but should do less damage than the long shards of un-tempered glass. However, for a windshield, constantly bombarded by pebbles, tempered glass would have a short life span.  So, many years back, the car manufacturers switched to a laminated glass sandwich for the windshield. It's a simple process. Two thinner sheets of glass are fused to a PVB (polyvinyl butyral) inner layer. The tempered-glass outer layers are then independent of each other. The rubbery center sheet provides damping to any shock waves from errant stones, reducing the probability of breakage. And if the glass is hit by an object smartly enough, odds are that only the outer sheet will break, as is the case with most stone chips. If a really big piece of debris hits the glass hard enough to break both inner and outer layers, the tough membrane prevents it from winding up in your lap. Even better, the shards of glass from the inner lamination wind up stuck to the membrane, keeping them from spalling away from the windshield at a high velocity, causing great havoc.
What is Windshield Repair
The windshield repair process officially began in 1972 with the introduction of the first equipment and chemicals that were specifically designed to repair impact damages on laminated windshields.
Since 1972, the development of more sophisticated tools and superior resins has enabled windshield repair to become an economically, environmentally and physically sound process which, when properly performed by a trained professional, can restore structural integrity and visual clarity to your windshield.
Windshield repair is a permanent process that removes air from the break and fills it with a curable, optically matched resin. Like human fingerprints, every windshield damage is unique. Often, repairs leave a mark no larger than a pencil point. Others, particularly those allowed to collect dirt and road debris, may be more visible. Most repairs performed by a qualified repair technician will result in 80% -95% improvement in visibility depending on the initial damage. Professional repairmen use high quality equipment capable of removing air in the damaged area and replacing it with a high quality glass resin that will prevent further damage and improve the finished look of the repair. The process bonds the glass together, restores strength to the windshield, improves the break’s appearance and prevents the break from spreading.
As previously noted windshields and safety glass are made from a "sandwich" of plastic laminate between two layers of glass. An impact strong enough to damage the hard outer layer can cause an infinite variety of chips, cracks, crescents, stars, or combination breaks. Often, the imperfection is tiny at the surface and expands into the familiar bulls-eye shape as it spreads toward the center layer. Most insurance companies will waive your deductible and pay for your repair. They do this to help avoid costly replacement of your windshield should the damaged area spread to the point where repair is not recommended.
Steps to Repair Windshield
- The windshield is cleaned and visually inspected by the technician. Any loose glass is removed from the impact point. If necessary a small hole is drilled into the break to allow access for the resin.
- A Bridge & Injector assembly is mounted over the break.
- Using hydraulic pressure, a polymer resin is injected into the break where it cures and bonds the separated glass. A series of polishing and buffing steps restore the clarity and structural strength to the glass. The resins are optically matched to a refractive index of 1.51, matching that of glass and harden with a bond as strong as the original glass.
- The resin is cured by ultra-violet light, restoring the original strength to the glass.
- The impact point, or drill hole is filled with pit filler, and also cured. Any excess pit filler is removed, and the windshield is thoroughly cleaned.
Quality windshield repairs exhibit the following characteristics:
- Damaged area is clear and difficult to locate - 85% cosmetic restoration.
- No visible air in the repaired break.
- No shiny black cracks in the impact area.
- Little visible distortion. Good optical clarity.
- Smooth outer surface area.
Reasons NOT to repair a Windshield:
- Damage penetrating both layers of laminated glass.
- Damage with three or more extended long cracks.
- Damage or crack contaminated by chemicals which inhibit repair.
- Damage or crack on the inside layer of glass.
- Damage or crack that is dirty.
- Damage or crack in a heated wiper rest area.
- Damage or crack in a fully heated windshield.
- Damage with pit size larger than 3/8 of an inch (9.525 mm.).
- Damage with pit depth to the laminate.
- Cracks that run through the acute area of the windshield.
- Edge cracks that intersect more than once with an edge.
- Stress cracks.
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