I'm not a chemist either, but this is more a job for a materials scientist. And there's only one way to find out really- go and make a mess out of my gas stove. Here goes, I'll go get back to you.

OK, here's what I found out.

With thin sandwich bags, forget it. They started blowing holes just about right away. Also, if they weren't full, the heat goes around the water, and melts the plastic above the water.

With a full quart freezer bag, I started to get somewhere- but where there were little wrinkles on the bottom of the bag, it started blowing pinholes.

So, I tried a quart bag on it's side, where it's smooth. Really tricky to hold that way, without getting burned. It never sprang a leak, but the zipper part started melting with the heat going around the bag, and I was losing the hair on my hands, so I quit.

Conclusion: it might be possible still, if you can manage to hold the bag in such a way that only smooth plastic with water on the other side is in contact with the heat. But damned if I can figure out how to do it in the comfort of my kitchen with a reliable gas stove. In a survival situation, no way.

Goatrider:

Maybe using a heavy aluminum foil base which is in contact with the bag that has water in it, but with the aluminum having a wide diameter so that flame and heat spilling around the edges would not directly affect the parts of plastic not having water in them might work.

If you decide to try it, give us the results.

Thanks!

Bountyhunter

That might work. But one of the problems I had was I left the stove running when I filled another bag, and when the bag touched the metal part of the stove it blew open right away. What I'm worried about is that the alumninum foil would also get the same sort of hot spots, which would melt into the bag. But it's worth a try, of course. Work is nagging me this afternoon, so I might not get to it right away if someone else wants to try it.