As we flip the calendar to the winter months and temperatures begin to drop you could do everything right in getting the glass warmed up, but then as the resin is injected —POP! —the windshield cracks out. This could happen if the resin injected is too cold. By too cold we mean if there is more than 10 degrees difference between the resin and glass temperature.
If your windshield repair resin is stored in an unheated shop or vehicle tool box the resin will likely be at or below the ambient temperature. Knowing this, it’s best to store your resin in a location that keeps it reasonably warm. If the resin temperature is not within 10 degrees of the glass temperature, warm the resin and the windshield at the same time. An infrared thermometer can be used to quickly check both glass and resin temperatures. It is best if you can store your entire windshield repair system in a climate controlled environment. If that is not possible you should also warm up your injector prior to injecting resin as the temperature of the injector can change the temperature of the resin. While wearing nitrile gloves for protection, both the resin and the injector can be warmed up by simply rubbing them in between your hands.
Say no to crack by paying attention to both glass temperature and resin temperature before you begin any repair this winter.