There are a couple of acceptable long crack repair methods. The one I use is called the capillary method. In this, first stop-drill and pop a mini-bullseye at the end of the crack, and cover this site as well as the impact site, with electrical tape to block UV rays from prematurely curing any resin that might migrate into them. Set up crack the expander(s) on the inside of the glass. Then beginning at the lower end of the crack, apply the crack resin and curing tape as the resin is wicked into the crack and flows upward to within about an inch of the top end of the crack. Then remove the electrical tape, and with the bridge-injector assembly, fill the impact site and the min-bullseye, cure well and finish as usual. Please note: be careful not to lean on the windshield during this procedure. It important not to cause uneven stresses on the crack.

Techs using other methods will have to explain to you what they do.

Whichever method you decide is the best one for you, you should practice, practice, practice before offering crack repair to the general public. Get you a scrap windshield from a replacement shop and practice this until you are comfortable and confident that you can do the process efficiently and seemlessly.

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