On 13/01/2017 11:48, NY wrote:
"The Natural Philosopher" wrote in message
news
On 13/01/17 08:49, NY wrote:
"The Natural Philosopher" wrote in message
news Why tepid? I run the hottest water I can from the hot tap and fling it
liberally on to the screen. Been doing it for oodles of years with no
problems.

Tim

I pour a just boiled kettle on it

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

yes. helps get the ice off

Don't want to crack my windscreen. Also, I'm not sure whether the rubber
of the wiper blades and the surround to the windscreen (between glass
and car body) would withstand boiling water.

I can assure you they all can*, but the water is down at around 20
degrees by the time it reaches them.

*black metal easily reaches 100 degrees in tropical sun.

Ah, maybe I'm being over-cautious, then. What about water at 100 meeting
glass at around 0 - isn't there a risk of the glass cracking? I've heard
of people that it has happened to in this situation.

Probably best to play safe and wait about 30 secs after the kettle
has boiled. by the time you get outside it should be well off of boiling.