🚀 go-pugleaf

Chris Townsend >
> And black is currently very popular - most soft shell clothing seems
> to be black.

That sucks <g>

> I can't say though that I've really noticed the difference 
> between pale and dark coloured clothing in terms of warmth. 

I guess Chris means in winter. Being cold or warm
depends on so many factors that it's difficult
to notice the relatively minor effect of exterior colour. 
However, if you check with a thermal imager, you'll notice 
a marked difference. Silvery stuff, such as those mylar 
bags, is actually pretty good at stopping radiative 
heat loss due to the very low emissivity of the
material. Mylar is good as thermal camo too, btw, when 
you really don't want those SAR people to find you... ;) 

In summer, in sunshine, the difference in "hotness"
of black vs white is so obvious that I'm sure everyone 
is familiar with it. It's easy to notice when wearing 
eg woodland camo: the black spots feel much more hot 
than the dark green and brown ones and the light green 
is even less hot.

> I suspect "technical" clothing doesn't come in white or 
> silver often because it shows the dirt.

This, of course, is yet another reason why it should be 
white or silver. It's useful that the dirt shows. Dirt 
typically degrades performance (like breathability or
insulation) and if the dirt shows clearly, it's easier 
to judge when the stuff needs to get washed. 

> I like black sleeping bags - they absorb heat and dry fast 
> when damp.

Sure. But only if you have a significant source of thermal 
radiation visible, like sunshine or fire. In midwinter 
cold-camping (eg above treeline or environmental policy) 
you have neither. And, that's presicely when bag warmth 
really matters. Moreover, you should be using a VB liner 
in such conditions, and thus, hopefully, have much less 
need for drying the insulation of the bag.

Agreeably, radiative heat loss isn't that much of an 
issue with bags, as one usually uses the bag inside 
a confined space, like a tent. Moreover, if 
the bag is warm enough, it's exterior temperature 
is close to ambient, which again reduces the 
relevance of the emissivity. Otoh, if you'll forced
to use the bag without a shelter or cover, and the 
bag isn't warm enough, it's exactly the conditions 
where the radiative loss is biggest. And, also, it's 
the conditions where you could do without any extra
heat loss... (These are qualitative comments though,
one would have to do calculations and measurements in
order to check the relevance of the quantitative 
difference.)

Nevertheless, I agree that it's mostful if the bag
is black with open fire or sunshine available. Imo,
however, it's sufficient that the _inside_ of the 
bag is black, as it's typically turned inside out
for drying. I'd like a winter bag to be silver or
white (added benefit of being visual camo too) on 
the outside and black on the inside. The only winter 
bag that comes to mind with silver colour is 
Stephenson's Warmlite Triple, the VB of which
is silver coloured on the _inside_ of the tops. As
far as I can see, silver on the inside isn't very
useful - it's actually just the exterior colour that 
matters - ie the emissivity of the outermost layer
wherefrom the thermal radiation escapes into cold
space (see eg Glen Randall's 'Cold Comfort').

Otoh, silverized insides of shelters is useful,
especially in case of tarps used with a fire in 
front. Acts as a thermal mirror. 

Oh well, I seem to have got carried away...