I cracked my first one today.

[SanAntonioWindshield]

Heat will do that Here in S. Texas we have lots of hot days and sum cold. If there is no shade or cold, I run the a/c or heat defending on weather (not on defrost) for 5-10 minutes. So the temp change is gradual. Another benefit to using there HVAC is sitting in there perfect climate controlled vechile during repair cycles while monitoring the repair.

Also be careful with Delta's moisture evaporator tool. I have had to windshield crack out using it twice. Just had one last week. I avoid at all cost but sometimes I take the risk. I've had more success. But I've had failures, so I try to avoid it. Never did understand the tool considering we know how sensitive heat is on the windshield cracks. I've also used Delta's heat exchanger tool to cool down the windshield and caused a crack out. So I'm convinced all temperature changes must be gradual.

Therefore my personal opinion on any tool that causes temperature changes is risky. And I try to avoid using them. That's my preference.

[kennycrane]

I personally would hate not having those tools, the moisture evaporator is genius for getting moisture out of a break, which by the way is crucial for a good repair. That cooling tool works great for me, I use them everyday and never had any trouble with glass cracking. Granted I do use caution. I try and not heat the glass any longer than 20 seconds in one spot. If it is a larger break and I am moving it around a little to heat all of the area I might go a little longer or even just repeat the process making sure the moisture is gone. Then the cooling tool I use gingerly also, but wow how it cools the glass down so that I can quickly go to work.

[johnnyone]

It has been a while so I decided to start my repair business up. I was feeling very confident on my repairs coming out good then it happened, a horizontal inward crack on the star I was repairing, didn't want to see that. It was about a inch long on both sides of the star. I relived the pressure and it did't travel. It was a warm day and i was working under the bubble. As far as the repair it filled up in the center. I contacted the owner and advised her that the repair failed and no charge.

[Dave M]

I have never liked using the moisture evaporating tool. It has been in a box since the year I bought it. I prefer using a mini torch going in a circular motion starting around 4 inches in diameter and working inward toward the break. The aluminum heat exchanger tool I touch the break for about 3 seconds and remove, repeating this process until cool. Have never had a w/s crack out using this process! Good luck

[johnnyone]

I have never cracked one out in over 15+ years. Here is what happened, let me know what you think?

You did it right for 15 years and 1 crack out? That is a fantastic record! I had one crack out just last week, seems to happen 1 out of 30 repairs and heat is always a factor.

[Jtmac]

Did you use a drying tool to dry the break? As mentioned above, Could have been moisture in the break that caused the crack when pressure was applied to it.

[Glass Patch]

I can only remember one windshield that broke out on me. I should of just said unrepeatable for any touch would send out a crack. But as a young repairer in the 80's I was convinced I could repair any damage. LOL It cost me a windshield for as a Glass Saver we had a replacement policy if we failed. I was a little bit more intelligent after that. There are those that can't be fixed as well.