Starting out?

> so boiling a pint from cold gives around 40 Kcal

You're under-selling it...

Say we start with water at 0C, and heat it to boiling, 100C.

deltaH = 567 * 100 = 56.7kcal.

I'd suggest it would be hard to drink anything hotter than 70C, though, which hits your 40kcal bang on...

cirrus wrote (see)

Another one to think about, stick your camera inside the tent - possibly even at the bottom of your bag because the batteries on most of them hate getting really cold.

If you get your camera nice and warm inside your jacket, sleeping bag etc then take it out into the cold your lens fogs up preventing you catching that "blink and you miss it" shot.

Better to stick the batteries inside to keep them warm then put them into the camera which is already at the same temp as the outside. If it's really, really cold have two sets of batterries and rotate them.

> If you get your camera nice and warm inside your jacket

...it will probably fill with condensation and totally knacker it.  A common cause of mobile phone failures, too.

Cap'n - I was told some time ago that 60 degrees C is the upper temperature limit for contact with hot surfaces or liquids. COuld be proven wrong but that releases 34kcal.

But how can you rate the psychological effect of a hot drink? I am sure that is probably worth a good few psychological kcals IMO.