Originally Posted by
fietsbob
you Want a wet cotton tube sock over your water bottle to cool it .. by evaporation ..
Yup, this will bring the bottle down to wetbulb temp.
Meaning, if it's 100° dry bulb day, you put a wet sock on most anything, and if it's got a good breeze across it, then the sock will cool down to wet bulb temp (78-82 on a hot, humid day in Iowa).
But I'm not even going to guess if that's enough to actually cool the water (alot of mass there) to where we mere hoo-mans could feel it.
EDIT: I don't know weather conditions in dry states - it's possible that with 100° dry bulb and low humidity, that wet bulb could be around 60? 65? That might make a difference you could feel!