I've used hot water mainly to loosen the ice blockage in the cowl area
where the wiper drop into. Pouring hot water on the glass could crack
it.

On real heavy ice I use one of those brass edge ice scrappers. Its
worked fine for over 20 years.

We had an ice blizzard Dec 1 in the Joliet, IL. area. The direction the
rain & ice was blownig froze over the driverside doors and we had to get
in throght the passengerside. Took 15-20 minutes of warming the car up
before the ice come off the windshield & two fron windows. The backs I
didn't bother with. The rear defroster took careof the rear window.

Next morning the Buick LF tire was flat - cut in the inner sidewall.

harryface

91 Bonneville 310,897
05 Park Avenue 64,123

Define considerable difference. I understand that under some very specific
conditions you can freeze hot water faster than cold. I've even seen it
domonstarted. And while this is true for carefully controlled conditions, it
is definitely not the case for hot water poured on a windshield.

Usually there are several reasons cited for this apparent contradiction -
cold water doesn't develope significant convection currents, so it tends to
freeze at the boundry, slowing heat transfer to the rest of the water; hot
water evaporates at a signnificantly higher rate, both cooling the remoning
water and reducing the amount to be frozen; hot water includes less air,
improving heat rransfer. None of these factors apply to hot water poured on
a windshield. In that case you are dealing with a thin layer, not a pot of
water.

Try this - take two identical glass jars with tops. Fill one with 40 degree
water. Fill the other with 60 degree water. Seal the tops and place the jars
in freezer. See which one breaks first. I'll bet you it won't be the one
that started with 60 degree water. If you use open aluminum pots instead, I
won't bet you.

Ed

Ed

Hot water does start cooling quicker.  Thermal transfer is
proportional to the current temperature difference.  The bigger the
difference, the more the thermal flow.

However, as soon as the hot water has cooled to being as cold as the
cold water, then it cools at the same rate as the cold water cooled.
But by this point, the cold water has cooled for a while already, so
it's colder. The hot water never catches up. The cold water freezes
first.

So the first part of the statement above is true. The second part is
nonsense.

"In some specific circumstances, hotter water freezes faster
than colder water":http://en.wikipedia.org/wiki/Mpemba_effect

I can see that - things tend to move faster at the extremes!  The hot
water will plummet from 200-whatever degrees fahrenheit to freezing
faster than 70 degree water.

-CC

Uh, no.

What happens in most "home experiments" involving putting a tray of hot
water in the freezer and a tray of cold water in the freezer is this:
The tray with hot water initially melts the thin coating of ice on the
freezer's shelf, which then re-flows and forms a good bond to the bottom
of the ice tray allowing faster cooling of the try by conduction. The
tray of cold water does not get this benefit and rests atop the thin
layer of ice on the freezer shelf, and is forced to cool only by cold
air flow. If you place your hot and cold water trays in the freezer on
*dry* towels which eliminates cooling by conduction, the tray of cold
water ALWAYS FREEZES FIRST. You canna change the laws of physics, you
can only misinterpret them.

Utter nonsense.  For water to freeze heat has to be extracted and it
has to be brought to a freezing temperature.  Hot water has a lot more
eneregy to be extracted and that will take longer than cold water.
Unless you are living in some parallel universe with it's own set of
physics laws.

As a test place water that is one degree above freezing and water that
is one degree below boiling into equal containers.  Leave them in a
freezing compartment or outside in zero degreee weather and time.