I discovered something entirely by accident that might be of use to others.
How to keep a frozen water bottle... frozen.
Rocket science it isn't.
When riding with my son, I carry quite a bit of extra water, in a rack-top
bag. What I'll often do is freeze a couple of bottles overnight, but they
would thaw out very quickly. But another time I had to use my camera
backpack, and to make sure the bottle didn't drip into the bag (Cytomax
wouldn't be good for camera gear), I wrapped the bottles with no more than
two layers of paper towels, and put them into a gallon-sized sealed baggie.
Amazingly, 7 hours later and the contents were still 80-90% frozen. Tried
the same experiment in the rack top bag, same thing again. Nearly totally
frozen bottles at the end of a long ride (yeah, sounds like I brought too
much stuff to drink!).
I haven't yet tried just wrapping one up and putting it into a regular
bottle cage, so don't know yet if that would work as well. Could be that
there's some insulative qualities to the bags which makes the difference
(even though bottles without any paper towels wrapped around them and placed
into a baggie thawed out very quickly). The easiest experiment might be to
just prepare one and leave it on the counter at home and see what happens in
a day.
It seems absurdly simple. Why it works is up to someone here to tell me. So
much for the idea you need to buy a special insulated bottle to keep things
cold!
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com