On Fri, 13 Jan 2017 13:59:44 -0000, charles wrote:

In article , Tim+ wrote:
Mark Allread wrote:
On Fri, 13 Jan 2017 11:48:04 +0000, 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.

Never mind heard, I've seen it happen when a visitor 'proudly' showed
us the trick as we were scraping our windscreen clean.

It cost him a new screen - it cost us a few minutes scraping.


I would still maintain that he was unlucky. An unmentioned benefit of the
hot water method is that if you use enough, you warm the glass enough to
reduce/eliminate condensation on the inside.

How often do you see folk driving off whilst still trying to wipe mist
off the inside? Not just inconvenient but dangerous.


Yesterday this mist formed when I'd got 100 yds down thew road.

Doesn't happen to me, mainly because I sit further back.

--
Snap-off parts, because it's French.