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 Automotive design and technology have undergone a major revolution during the past decade, and auto glass is no exception. Today's window glass is thinner, covers a larger area, and contributes to both the structural integrity and safety of the vehicle. Even the glass itself is hi-tech. Some windshields today have only two layers instead of the traditional three-layer glass-plastic-glass construction. The inner layer of glass has been replaced with plastic to reduce weight, so installers must use care when working on one of these because the plastic can easily be stretched if the installer is not careful. Some windshields are also electrically heated for rapid defrosting and have a thin conductive coating between the inner and outer layers of glass (Ford) or on the passenger side of the inner glass (GM). But the most significant change that's taken place has to do with the way in which the windshield and back glasses are held in place. Starting in the early 1980's, vehicle manufacturers began using high-strength urethane adhesive to bond windshields, back windows and quarter glass in place. The type of urethane adhesive that's used has a shear-strength rating of about 600 pounds per square inch! Bonding with this type of adhesive allows the glass to help support the roof of the vehicle so it can meet federal rollover and roof crush standards (FMVSS216). Bonding also improves the windshield's ability to act as a safety net to help retain the vehicle's occupants in a severe crash, which further contributes to overall vehicle safety. This, too, is covered under another federal safety standard (FMVSS212). The latest change is that the windshield now plays a role in air bag deployment in vehicles with passenger-side air bags. Many passenger-side air bags are designed to deploy upward and outward, deflecting off the windshield as they unfurl. The windshield helps "aim" and support the air bag during deployment, so a strong bond is absolutely essential. If the windshield is not held in place securely, it could pop loose and defeat the life-saving features of the passenger-side air bag system. With these in mind, it should be obvious that windshield replacement isn't the simple job it once was. It takes a certain amount of know-how as well as ability to replace one of today's hi-tech windshields. Special glass removal tools are also required, along with the know-how to use them. Anybody who installs auto glass must also be familiar with the adhesive systems that are used and use prescribed installation procedures to assure maximum adhesion strength. Because of this, training and specialized knowledge is necessary for anyone who installs auto glass. |