>>1065874at fifty bucks, they aren't even that expensive. I do know an alternative, but it's about 40 bucks unless you can get your hands on swiss surplus canteen (in which case it's about 20), so you don't save that much. Anyways, I've yet to try this myself and have only seen it done once, so don't rely on me to much.
Here's how it works: first, you need to get a stainless steel canteen (aluminium might work as well, but I wouldn't use it due to the risk of aluminium poisoning). The canteen should be as thin and high as you can find. You'll also need a cork (as in actual cork, not plastic or rubber) and a hobo stove tall and wide enough to put the canteen into it and still have space to the sides. If you'll do this more often, you might want to modify the stove so it keeps the canteen stable and at a constant height.
First you fill the canteen and loosely place in the opening (don't press it in to hard or the canteen might develop pressure inside), then light the stove. once the fire is going strong, place the canteen on top. The stove will guide the smoke and hot air to the sides of the canteen, making for more effective heat transfer while the cork limits the amount of escaping steam to the point where the canteen just barely maintains atmospheric pressure, minimizing heat loss. once the water comes to a boil, the cork should pop out (it'll rise slightly to let steam out, then fall back down) under the increased pressure.
Now as I said, I've only seen this done once, so I can't guarantee that my description is completely correct.
