Alan wrote:
You shouldn't use hot water as this will re-freeze faster than cold
water would(and for all of those people who don't believe me, go and
try it).

Have a think about the physics of that for a minute.

Hot water will never re-freeze faster than cold water. To freeze water
much reach 0deg. Water which is 10 deg will freeze faster than water
which is 40 deg given the same surface temperature of the windscreen etc.

When using warm/mildly hot water, you may get it re-freezing sometimes
simply because the energy stored within the hot water applied isn't
sufficient to raise the window temp above 0deg, but it will have raised
it a little. Just keep putting more and more warm water on it until the
temp has increased above 0deg and it stops freezing.

D