Car Glass Repair Information

How to Fix a Windshield that Has Been Cracked


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Learning how to fix a windshield when it has sustained one or more small chips or cracks can save you money. The required materials and tools are readily available at most hardware and automotive supply shops. Many of these shops carry complete windshield repair kits.

Causes of Windshield Cracks

Modern windshields are made out of a "sandwich" of specially treated safety glass and plastic that can normally withstand hits from projectiles such as small pebbles thrown up by other vehicles on the road. However, when pieces of debris have adequate mass and hit the windshield fast enough, a crack may result from the impact. These damages can be round or "bull's eye" cracks, star-shaped cracks or long cracks. Long cracks may result when the glass is subjected to a sudden change in temperature. The heavy closing of doors and vibrations from regular vehicle operation also contribute to the formation of long cracks.

Windshield Repair Procedure

It's possible to patch up windshield cracks with the use of DIY repair kits. These kits make use of resins for filling up breaks. Besides the resin filler and resurfacer, a kit will include a resin applicator. Depending on the type of windshield crack repair kit, the resin applicator may either be a simple syringe or a "bridge", which is an applicator that latches onto the windshield using suction cups. The latter is the better type because they offer stability and can be used to repair a cracked window. A car window presents a vertical, more challenging work area when compared to a windshield. Therefore, a bridge or suction type resin injector would be most ideal for such repairs.

Step 1: Preparation

To prepare the crack for repair, it first has to be cleaned and cleared of dirt and excess glass and then made into a bull's eye crack, if it's not already one. This is done to contain individual cracks and prevent their further widening and spreading. Bull's eyes are also created at the ends of long cracks to stop them from spreading. Use a pointed, metal probe for cleaning (and creating bull's eyes). Gently and lightly tap on the metal probe so as not to damage the middle plastic layer of the windshield.

Step 2: Resin Injection

After loading the specified amount of resin into the injector, position the bridge so that the injector is directly above the crack. Secure the bridge in place and proceed with operating the injector to force resin into the crack. Alternately use the pressure and vacuum controls of the injector to suck out air from the crack and force resin in. After the crack has been completely filled, remove the bridge.

Step 3: Curing

The resin used to repair windshield cracks is an anaerobic substance which means that, instead of air, it requires ultraviolet or UV light to dry and harden completely. The vehicle may be moved outdoors for curing, or a UV lamp can be used for indoor repairs.

Step 4: Resurfacing and Finishing

After the filler resin has finished curing, apply a sufficient amount of resurfacing resin directly to the repaired crack. Cover this with a cellophane patch (usually supplied with the repair kit) and cure using a UV lamp or direct sunlight. After the resurfacing resin has finished curing, scrape off the excess with a blade to level it out with the rest of the windshield glass. Wipe the area clean afterward with glass cleaner.

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