Don’t risk your life by having your screen replaced!
How could the glass industry allow a practice that did such damage as to seriously compromise a windscreen’s ability to support the roof and retain the passenger-side air bag as the car manufacturer designed it to?
Close cut, or short cut, means removing a windshield by cutting as close to the glass as possible, leaving the original bead of urethane in place. The installer then puts a new bead of urethane on top of the original, and installs the new glass.
Full cut means removing almost all the original bead of urethane after the glass is removed, cutting as close to the pinchweld as possible and leaving a very thin layer of the original bead intact. Then a very much larger bead of new urethane is applied, and the new glass installed. Most major car manufacturers support and endorse the full cut method; some flatly reject close cutting.
The Rust Problem
On all installations, it’s critical to re-prime every scratch and every bare area of steel that results as installers remove a windshield and prepare the pinchweld for installation. Only re-priming can seal the body and provide the best possible surface for bonding again. Any exposed, unprimed area is a potential rust site. Unfortunately, many installers are too rushed to properly follow the strict guidelines required for close cutting.
The most common cause of rust is running a utility knife around the perimeter of a windscreen to ease the cutout knife’s passage through the old urethane. This scores the metal all around the perimeter and leaves an entire circumference of potential rust problems. Using a utility knife is a terrible practice that saves only seconds on the removal.
It takes only a couple of minutes to re-prime an exposed surface, but, again, many installers don’t take the time, just don’t care, or weren’t properly trained in the first place. Many installers who think they’re doing proper close cut installations are actually doing “fast-track” or “quickie” installations, again due to lack of training or lack of caring.
Bottom line: rust is due to very poor workmanship, no matter what the installation method.
An example of rust that caused the screen to pop out on impact and eject the driver from the vehicle.
Second, a “decking” problem may occur with close cutting. When you stack urethane on top of urethane, the glass inevitably sits “higher” off the pinchweld. This, too, can induce stress breakage due to the fact that many vehicles’ doors now close tightly to the windshield moldings at the A-pillars.
Third, urethane compatibility requires never close cutting on top of a previous close cut, because you’re combining potentially dissimilar urethanes with no crash test data to assure that you’re returning a vehicle to its original crash worthiness.
There are many ways to scratch the pinchweld down to bare metal when removing a windshield; realistically, it’s almost unavoidable, but re-priming restores the bonding surface and restores the rust protection that was provided by the manufacturer. It is one of the single most important aspects of glass installation for the body of the car and the glass.
Article By Mark Rizzi