A spider-web crack on your windshield consists of a midpoint with smaller cracks branching out of it. This can be a difficult type of crack to fix; however, depending on the thickness of the crack, its size and whether there are any air pockets in it, you may still be able to reduce the spider-web crack's visibility, if not eliminate it. Visit your local auto shop to purchase an injectable crack filler. Most fillers include all the necessary tools for the job.
Hold a rag over the opening of a can of acetone. Turn the can over to dampen that section of the rag with acetone. Lightly wipe the damp rag over the spider-web crack to clean the affected area of the windshield. Allow the windshield to fully dry.2
Peel off the supplied adhesive strip's paper backing. Center the strip over the spider-web crack. Rub it firmly onto the windshield with your fingernail, then peel off the paper backing on the side facing up.3
Place the supplied fitting onto the adhesive and use your fingernail to rub it in place. Adjust the fitting so it sticks as straight up as possible.4
Remove the resin syringe's cover and insert the tip into the fitting. Hold onto the syringe with one hand and pull the syringe's handle all the way up with the other hand. This creates a vacuum seal between the adhesive strip and fitting and sucks any air bubbles out of the spider-web crack. Wait for about 1 minute.5
Let go of the syringe's handle. The pressure from the vacuum will pull the handle down and shoot resin into the spider-web crack. Pull the handle back up and wait another minute before letting it go again. Repeat an additional four or five times to ensure you filled as much of the spider-web crack with resin as possible.6
Pull the syringe out of the fitting and gently peel both the fitting and adhesive strip off the windshield. Allow the resin to cure according to the manufacturer's directions. Use a bit of rubbing alcohol to remove any adhesive stuck to the windshield.