"But all flasks I have seen have those wretched seams at the bottom ... I suppose they're fine for storing beverage, but I don't want to fuss with heating them. Soldering melts at pretty low temperature."

Okay... what about casting something seamless?

Sue

I was actually comtemplating casting one this morning...an awful lot of work for a one-off product. Useful if you really really want something custom, but I don't really care--I'm a USGI canteen & cup combo guy.

I've fond several kitchen coffee containers ( flour, sugar, coffee sets for the counter) that are a good size for a kit and come with lids - most about 1 quart or 15cm high.

For my BOB I have a SS cup that fits around my water filter bottle. It's a hybrid Sport Berkey. I just replaced the Nalgene bottle with a SS Kleen Kanteen bottle so in a pinch I can remove the filter and lid and use that to boil water. For my full backpack I have the GI cup and also other nestable pots and pans and for car camping there is also my Dutch oven which has to be the greatest thing ever if you don't have to lug it far.

However, like many of you I am seeking something collapsible , really small and light weight better for my on body kit (OBK?).

Right now I have a piece of very heavy duty aluminum foil from a very old air force survival kit which seemingly was designed to be able to be folded and then unfolded and used to boil water and then refolded - but I confess I have not tried it. I am concerned that it will spring a leak and AFAIK there is no way to patch it in the field.

As a kid (a very long time ago) I had a collapsible aluminum cup that was a series of ever smaller rings of aluminum that fit together and held water fairly well (at least it did according to my now failing memory). But even if i could now find something like it, I doubt it could be used for heating as the rings would expand at different rates and in any case is larger than what I am seeking.

But I was looking at the collapsible silicone cups. They say they cannot be used on direct flame, but I was wondering if they could be used inside a aluminum foil shield which would then not need to be water tight. But since silicone is used for pot holders, I am wondering if heat would transfer to the water.

If not slicone, what else might work within a aluminum foil wrapper? (I know it's possible to boil water in just a paper bag.)

I keep meaning to try -- as a workable in-a-pinch patch -- high-temperature aluminum foil tape ( here). Might even work to apply to bottom of improvised container before cooking use to protect/reinforce against puncture. A one-foot length, wrapped around a soda straw, would weigh next to nothing and take little room in a kit.

According to data sheet, flame resistant and performance range "to over 600°F." Uses clear silicone adhesive. I wouldn't want to have a meal of the adhesive, but seems like the miniscule amount that might be released through pinhole or small tear repair in improvised foil cooking container could be tolerated, particularly in an emergency situation.

The data sheet does say that "adhesive does gradually thermoset in high temperatures [and] as it thermosets the adhesive mass becomes firm ... but will continue to hold the tape in place."

I'm no chemist or engineer. Wonder if this means even less would migrate into improvised foil cooking container?

Edit: Just noticed price/quantity on link I provided. Here's more reasonable source.

cigar hip flask...I'm not a cigar smoker so not sure if I have the correct name, but I've seen an aluminum or stainless hip container for 3 cigars that may be close to the desired size, and not sure of the amount of open space between the tubes...regards

Thanks for the info on the high temperature aluminum foil tape. That just might work. Maybe I'll give it a try. If the hole in the aluminum is small, I'm thinking putting the tape on the outside - that way the adhesive would just be thru a small hole whereas if you put it on the inside some could seep along all the edges.

I was also thinking about putting water in a plastic oven bag inside a (leaky) aluminum foil container or even just on top of a sheet to heat up over a fire - the aluminum would shield the plastic from direct flame. The question I have is although oven bags are designed to be used in microwaves would heating the bag cause chemicals to leach into the water?

Reynolds used to have aluminum foil cooking bags among their products. My sketchy memory thinks they were rated around 400°F and, necessarily, fairly heavy-duty foil But believe I've read they discontinued the product line (and couldn't find any sources online). Probably competing products out there. If plastic bag could be made workable, as you suggest, then foil cooking bag should do even better.

Hey,

I used that aluminum foil tape (I think it was muffler repair tape?) to strengthen a container made from an aluminum mini-loaf pan. I never tested it over a fire but boiled water in it on an electric stove. It was fragile but it did work. This small, light "pot" was then used as the liner for a Lock & Lock plastic container, which held one version of my PSK.

Mike

I personally do not use anything not made to cook in to...well cook in. A lot of metal cans and such have either paints or liners to prevent rust or advertise whats in them as well. Even some metal water bottles have liners sprayed into them so yeah they cant be trusted either.