Apparently You Shouldn’t Try This Windshield Trick At Home

Putting boiling water on a frozen windshield will not cause the windshield to shatter. Vehicle windshields are constructed using laminated safety glass, which is a piece of polyvinyl butyral between two or more pieces of glass.

However; there is a good chance if your windshield has a small chip or crack, some of the vapour or liquid may seep into the opening and when refreezing happens the liquid will expand causing the glass to separate into a crack.