If your car's windscreen is cracked or chipped, you don't want to put off getting it fixed; the windscreen protects your view, stops you from flying out of the car during an accident, and provides support for the roof of the car. You may also face a fine or citation for having a cracked windscreen! Since it's so important to keep the windscreen in good repair, note a few considerations you should keep in mind about trying to address this fix on your own.
Heat and condensation
If the windscreen of your car is very hot, the gel you use to fill a crack or chip may not set properly. This filler may also become too runny, so it won't fill the crack or chip and will simply run down the windscreen itself.
If the crack or chip in the windscreen has moisture or condensation inside it, this can also keep the gel or other repair material from setting properly. Professional installers will know how to evaluate the temperature of a windscreen, and they will use a commercial handheld dryer on the glass first to keep it dry but without making the material too hot.
Removing the patch
Most DIY kits will have a syringe for injecting a filler or gel and patches for the front and back of the windscreen, to help keep that gel in place as it hardens and sets. Removing this patch can be tricky; you need to ensure the gel or filler is properly set, and then scrape off the patch without leaving any residue behind. You might use a razor blade to remove the patch, but if you don't do this properly, you could easily scratch the windscreen. A professional repair technician will know when to remove this patch and will do so without damaging the glass.
Knowing when to replace
A windscreen that has been damaged is now weakened, and filler or gel may not restore its strength, even if that gel seems to fill in the entire crack or chip. A weakened windscreen is very dangerous, as it may actually shatter during an impact or even when you hit a heavy bump. In turn, you or your passengers could be hit by flying glass, or you might fly out the windscreen if you're not properly buckled in. An auto glass repair professional will know how to evaluate the strength of a damaged windscreen and will know when replacing it is a better option than repairing it.