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Principles of Auto Glass Installations

This article is published for the purpose of educating the reader on the techniques and principles of auto glass installations and explaining the Aftermarket Auto Glass industry, for the purpose of helping the reader to make an educated decision in choosing a quality professional to replace their auto glass. This article is written to explain the process of aftermarket auto glass installations and is not to be used as a teaching tool or to instruct the reader on windshield installations. Your windshield is a safety device and should only be installed by a qualified professional.

Obtain a replacement windshield for your vehicle. These can be bought new or reclaimed from a wrecker’s yard, in which case check the windshield for chips and cracks with your own eyes before handing over any money. If you are moving the detached windshield in your vehicle, use lots of cushioning such as blankets and duvets to prevent damage in transit. If second hand, the windshield will not be ready to fit. The existing urethane bead will need to be either removed or trimmed down to about 1mm in depth. This is quite easy using a razor blade and a sawing motion.

Remove the plastic surround side and top mouldings correctly. Don’t pry the clips that hold them on; these clips are small plastic pieces specific for the vehicle and its moulding. This saves time, but the result is that the moulding will need to be glued on if no replacement clips are on hand. Time saved ten minutes or more and about $5.00 for the clips. Most are simple and totally aesthetic in value and are just an inch of plastic which is attached to the windshield. They do nothing for the windshield except make it look nice. Some are extremely complex with plastic clips and clamps which hold the molding securely to the windshield.

Cut the urethane from the outside between the glass and the pinchweld, using a cold knife. Depending on tools used and experience, this can take anywhere from fifteen minutes to an hour. The urethane which holds the windshield in place is flexible but extremely strong; this allows the glass to move and not crack from every stress placed on it during driving.

Prepare the pinchweld. Clean away any visible dirt with a brush and then plain water. The old urethane needs to be trimmed down to about 3mm thick. Use a razor blade. Any rusty areas or areas with loose/damaged urethane will need to be taken back to the metal. Rust problems must be fixed. These areas of bare metal must then be primed.

Prepare the glass with a primer specially matched to the urethane adhesive. The purpose of the primer is to open the molecules of the frit band (the black band around the perimeter of the windshield) this is done to prepare the glass to accept the molecules of the urethane. If your installer is in a hurry, ignorant or just does not care if your windshield pops out he will skip this step. After the glass is activated, the molding is attached to the glass and the urethane is next.

Apply the urethane with an electric caulking gun. (Insert Picture) The best thing for the new urethane to adhere to is the old urethane. (Insert Picture of contaminated pinchweld under the molding) It must be clean and free from dirt, oil or other contaminants. A problem installers have is wind blowing dust onto the pinchweld before the urethane adhesive has been applied. This wind is caused from not only the weather conditions but other vehicles including the big trucks. The job can be done without an electric gun but it is much more difficult to get a consistent bead, making leaks likely.

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