On Fri, 13 Jan 2017 08:49:02 -0000, NY wrote:

Thermal shock of boiling water on glass that is at around zero degrees.

Screen exposed to clear skies and it will be a lot colder than 0C,
could well be 10 C or more below what ever the air tempertaure is. So
air temp of -10, wndscreen -20 or lower.

Laminated windscreens are pretty damn tough but I'd still not throw
near boiling water over one. Far easier to start the engine, press
"defrost". By the time the side windows have been squirted and
cleared even frozen on snow will just slide off the heated front and
rear screens. B-)

--
Cheers
Dave.