View Full Version : Converting a Thermos to a cook in water bottle

2012-03-27, 06:14
Bloffy from Australia here,
Need some science brains here if I can.
I recently picked up a stainless steel vacuum flask from a second hand store for $4 AUD (We commonly call them Thermos')
The Thermos holds about 750ml of water, has a perfect, wide mouth spout etc which I want to turn into a water bottle which I can also use for cooking with.
I know I can't boil it while there is a vacuum still (two reasons - ever put a tin of baked beans in a fire (Wohoo) and, because of the vacuum, it would take umpteen years and litres of metho to transfer enough heat through the vacuum.)
SO... (and I am getting to a point, eventually), I drilled 24 holes in three concentric circles in the base, removed some aluminium type insulation using dental picks from between the inner and outer skin and thought I was on a winner.
My theory being that the heat would rise up inside,have nowhere to go and therefore transfer quicker into the water.
Added my standard two cups of water, lit my metho stove and stood back. Fuel burnt out, finger dipped the water. Just tepid. More fuel, same drill, only moderately warmer. Double the fuel, stood back, no major improvement. Took it inside, put it on the gas stove for five minutes. Bottom outer layer was literally red hot but when I tipped it out, the water was hot but nowhere near boiling.
SO...(yeah,yeah I know, get to the point) my question is, do I need to drill some holes near the top of the vacuum so the heat passes up between the two walls and gets transferred that way?
Any ideas gratefully accepted. I know this is long winded but hopefully one of you smart bugas can shed some light on my dilemma.


Hog On Ice
2012-03-27, 09:30
I would say yes - drill some holes near the top - the hot air/combustion gases need a place to go after they have transferred some of their heat to the inner bottle so as to make room for new/hotter gases coming from the flame

2012-03-27, 13:24
I agree. So do the gurus at Hammock Forums.
Drilling the holes tomorrow . Should be good.Someone said it's like a Kelly Kettle in reverse. Hope the holes work. I'm thinking they will need to be big.
Cheers Bloffy

2012-03-27, 13:59
I wonder if you could turn a thermos into a stove/ water carrier. could the thermos itself be made into a stove by pouring the alcohol into the space in between and a few stragically placed holes.

2012-03-27, 18:26
Part of the problem is that stainless steel sucks when it comes to heat transfer.

Hog On Ice
2012-03-27, 18:31
yeah but its not as bad as titanium

Nearly Normal
2012-03-27, 19:46
or a fuckin thermos

SGT Rock
2012-03-27, 20:57

Sounds sort of like this idea.

2012-03-27, 21:04
except a used thermos cost $4 AUD. :argh:

2012-03-28, 08:28
OK, I came down with a cold today and stayed home. I got bored so I thought I would try and finish this off.
Now, let's get this straight. I am an ideas type person rather than a tradesman so no hanging the brown stuff on the quality.
I drilled the eight top holes and put it on my metho stove. Four cap fulls (not sure what that measure is) and there was a marked improvement on the water temp.
Drilled four breather holes around the bottom and noted a marked improvement but still no boil. Put it on the gas stove and noted that where I drilled the holes in the bottom was glowing red but the heat did not seem to be hitting the water container. Out with the angle grinder (any excuse will do) and lopped out all but the outside ring (very rough but who's looking).
Back on the stove and wohoo what an improvement. Added another four breather holes around the base, put it back on the metho stove and added a lid over the opening. Less than three cap fulls and I had a wonderful rolling boil.
Next step, I lit a very little hobo fire from twigs around the garden (it's out of fire season here and big fines apply) and in only a couple of minutes had water warm enough for a coffee but didn't push my luck as my neighbours might have got funny about the smoke.
So now I have a sealable stainless steel water container which will allow me to cook on open fire, gas and metho. Pretty cool huh? Gotta love backyard, home made R and D...
Alright, I know the rules. No pix no product. Here we go...
The first shows the height complete. The second is of the sealable two part lid, a rough coathanger bail and the tin lid I used while heating water. The third shows my dodgy, rough-as-guts work with the angle grinder. Note the blackened bottom from the hobo fire, yet no real discolouration to outside.
Sorry for yet another saga-length entry but hopefully someone finds it interesting.

Nearly Normal
2012-03-28, 17:26
Hobos don't have a little fire. We burn the woods down....and tote guns.

2012-04-01, 08:33
Had a few days to test and adjust this.
Knocked up a cobra weave shoulder strap using hootchie cord, which makes it comfortable to carry (and an interesting skill to learn, as well as giving me maybe 200ft of cordage if I could be bothered unknotting it). This has a couple of fish swivels on steel rings which means they are quick to release from the small extra holes I drilled above the top holes. In addition, I got busy with the angle grinder and tidied up the bottom (might even tidy it up even more but it's much better even now.)
I salvaged the original plastic bottom off the thermos from out of the bin and it now snugly holds a Pepsi Can stove and the small tin lid for when I am cooking.
I am thinking of making a hacksaw blade knife to store between the inner and outer liner and adding a small fishing kit with a few hooks, some line, trace wire, a few small split sinkers and some crimps etc, as well as into this area as well, maybe in a small cotton bag which can be used for char cloth if necessary. I will look to add a fire steel probably to the strap. A further refinement I am considering is to design a silnylon shelter into a cover for the water bottle (need a better name for this - any takers). My Ever Loving But Long Suffering Wife is rolling her eyes already.
So that would give me cordage, (water) carriage, cutting, cover, cooking, catching and combustion. Add a button compass, a small button torch and a whistle and I would have a pretty basic but handy kit all contained in or around one container.
Another tome, sorry.

2012-04-02, 00:30
Cooked lunch in the container yesterday after kayaking for a couple of hours. Just two minute noodles with some meat sticks and followed by a bit of scroggin. Very filling. Used my Smiggles metho stove. Not quite a full boil but hot enough to cook the noodles. Getting to like this kit.
Cheers Bloffy

2012-04-02, 12:58
for those of you (like me) who don't know what scroggin is:

2012-04-02, 17:02
for those of you (like me) who don't know what scroggin is:

deciphering scroggin had me scratchin my noggin.

SGT Rock
2012-04-02, 17:06

2012-04-02, 17:07
and listening to earl scruggs and cloggin'.

2012-04-03, 06:36
At least someone's paying attention.....