[Brent Deines]

I agree with with using the car's heater when possible, but I also use the defroster while warming the outside of the glass with a hair dryer. It requires a great deal of heat from the inside to warm the glass, so warming from the outside, or both the inside and outside is preferable. On a cold day you can heat the inside to the point that it is too hot to touch, but the outside will barely even be warm, and will cool immediately after the heat is removed. Maybe I've just been lucky, but in 20 years I have not cracked a windshield using by using the defrosters, although as I said, I almost always heat from the outside as well. 12V hair dryers are available at Camping World and other RV stores, but the quality is poor so I prefer a 115V model whenever possible. However I still recommend keeping a 12V model on hand for when you don't have access to AC, unless of course you have a generator or converter, which I also recommend in cold weather areas. It's kind of nice to have a portable heater to help keep you comfortable and there are many great ones to choose from these days.

If you use a hair dryer it is not too difficult to figure out a way to attach it to the glass so you have constant heat throughout the repair process. I have used a pump style or flip lever vacuum cup with a strip of Velcro attached to hold the dryer in place and pointed where you wanted.

As GlassStarz said, you don't want to warm it too quickly, but keeping the heat consistent once you have obtained the proper temperature really helps make your winter time windshield repairs go much better. Small hair dryers will even fit under the bubble dome which keeps an 18" area of the windshield warm, not just the spot you are working on, and also helps keep your injector and hands warm during the repair process.

In Montana we did not always have the luxury to stay home on days it was snowing, and in Oregon staying home when it rains is definitely not an option if you want to make any money in the windshield repair business.