Curing large breaks present a number of challenges, especially large star and combination breaks. But with a little extra care, show the most dramatic cosmetic improvement upon completion.
One thing that is often overlooked is the fact that cracks may extend beyond the edges of a standard curing tab. This can cause a repair to fail. The problem is that even if the cracks are properly filled, they will not be properly cured if not completely covered before curing.
Obviously, the solution is simple. Use multiple curing tabs, or strips of curing film, to make sure cover every crack is completely. Run a little thin resin along the surface of filled cracks to help curing tabs stick and properly seal the surface of the crack. One drop every couple of inches is plenty if properly spread with an eye dropper or syringe.
The surface resin may cure in seconds. But it is important to cure for a full 5 minutes to ensure curing the resin all the way through. Remember, most windshield are made from a glass that blocks a percentage of the UV rays. These UV rays cure the resin, so reducing cure time may cause repair failure.
If the UV light covering the damage is narrower or smaller, be sure to move your light as many times as necessary to get a complete cure on every part of the break. Curing for 5 minutes each time the light is moved. Use long crack lights, dual bulb lights, or multiple lights to reduce the number of necessary light moves.