As the laws of physics may have escaped me, how does this work without cracking windshields? Is the water around 15-20c or is it warmer. I have broken(cracked) windshields by pouring hot water on them.

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Owen

87 300TD 603 I-6
94 Jeep XJ I-6 4.0 (see the pattern)
89 750il
seventy-two hundred feet above sea level (kinda cold up here)