Warming Windshields

[jonnyques]

Well the weathers getting colder and so I need a lesson on warming up a windshield. Ive learned that air on full defrost can crack one out in the summer. Can heat on full defrost do the same? What meathods do you use to keep the outer layer of glass warm when doing a cold weather repair. I have a heat gun, but I cant see how that would keep it warm for 15min or so. I was thinking of a electric warming pad, anyone tried one? Should I look at thinner resins? All input would be great!
Thanks

[glassdoctor]

As for running the vehicle's defrost, you only need to use comon sense and monitor the glass temp.

1. Start the engine and turn the heat on high/defrost. This way the heat comes on gradually as the engine temp comes up.

2. If the damage is near the heat vents, be careful that the glass doesn't get too hot... turn it down once the car/glass is warm enough.

My normal method is to use a propane torch to warm the entire area and work effeciently. I would recomend this only when you are very experienced and know how long a particular repair will take, at what temp, etc.

As you alluded to, the glass will begin to cool once the heat source is removed. So it's better to have a constant source of heat if the repair will take some time, or if you don't know how long, etc....

One more thought... there is no ONE perfect method. What works great for 50 degree weather probably won't do it when it's 10 degrees. The vehicle defrost is not so effective for a repair at the top of the w/s, or when the car won't start, etc...

[screenman]

I use a propane torch but be careful.

I also think the previuos post was spot on.