Apr 19, 2014 at 10:14 am #1315838
@kentLocale: High Sierra
First I tried a MYOG experiment, and made a stove by cutting off the bottom of an Arizona Tea aluminum can, only to later learn of my "error" (occasionally, ignorance is bliss, maybe?) :)
It wasn't until a bit later that I read that you're not supposed to use aluminum with esbit since esbit burns about 200° hotter and melts alum.
Since the stove was already made, I thought I'd try it anyway. Well, after a good 20 or more burns, still no problems!
Does anyone know, and can explain, the physics/science behind why my aluminum can-bottom hasn't been destroyed yet? How is the heat being dissipated or how is the can being insulated, or…other…?
Details, if they matter/help:
The can bottom is used inverted so that the concave surface allows the esbit to properly form a small pool during the burn.
Wind screen is always used (around a FireLite 550 Ti pot).
The sides of the can are cut very short so that the tab height in my can stove closely approximates the height of the tab when it's in my Ti-wing stove. The can delivers a boil slightly faster than the Ti-wing.
The only thing I can see on the can is the esbit residue you always get.
Much appreciate your answers.
edit – reposition a text line & add: no additional heat shield is used under the stove.Apr 19, 2014 at 10:27 am #2094577
@funnymoLocale: Sunshine State
I experienced my original aluminum foil windscreen's rapid deterioration. My foil roasting pan screen, however, is still going strong after years of use. I attribute this to the thickness of the screen, since it is just as close to the pot as the original. That's part of it. The smarter-than-I types will explain why, but I always assumed the thicker the metal, the more it could handle.
Next, since heat rises, much of the heat goes up and away from your can so very little contact with direct flame actually takes place.
I'm interested in the better responses…Apr 19, 2014 at 10:49 am #2094581
Kent, I sometimes use that same setup. Off hand, I can think of two reasons why the aluminum doesn't melt:
1) The most intense heat from the burning Esbit is 0.5" above the aluminum tab holder, and it rises away from it.
2) Aluminum is very good at conducting heat, such that it really cools itself somewhat by spreading the heat throughout the can and then releasing it to the surrounding air.
Where is an engineer/physicist when we need one?Apr 19, 2014 at 10:49 am #2094582
@cobbermanLocale: Northern Colorado
Same reason you can boil an egg in a wax paper cup filled with water over a fire. Not a scientist but I believe the water diverts the heat from the paper cup/aluminum so that it does not reach the melting/burning point.Apr 19, 2014 at 12:02 pm #2094593
@millonasLocale: Santa Cruz Mountains, CA
If there is water in the Al container then the water buffers the heat and the container would stay at about the temp of boiling water. Also people are right about the heat getting dissipated from the bare Al. My guess is you might do some damage if you used enough esbit and put the empty Al close enough. But with water in there you are never going to have an issue. What is happening is that due to the very fast heat exchange between the metal and the water all of the thermal energy is going into helping the water molecules to escape their mutual molecular attraction – in other words potential energy – in other other words, turning from liquid to vapor. So the temperature (kinetic energy) of the water molecules and metal (mostly free electrons) does not have a chance to increase until the water boils off. So no melting, and perfectly safe to use if there is water in it.
Also, note that this kind of buffering effect does not work with windscreens sine they are not touching the water, though the air does have an effect.Apr 19, 2014 at 1:15 pm #2094606
Your description is a good one for use of an aluminum pot. But he is using a titanium one. He is questioning why the inverted aluminum can bottom, which he uses to hold the Esbit tablet, doesn't melt.Apr 19, 2014 at 3:32 pm #2094637
e is questioning why the inverted aluminum can bottom, which he uses to hold the Esbit tablet, doesn't melt
I am guessing that the ground is cooling the stove (heat sink)Apr 19, 2014 at 3:52 pm #2094645
@slammerLocale: Oklahoma Flat Lands
I use the bottom of a 12oz Red Bull can as an esbit holder.
Used over and over again with no sign of wear, I also us a 3" titanium disc under mine.
As Franco said it must be the ground acting as a heatsink. The draft of the windscreen bringing in cooler air into the bottom may have an affect as well.
It would be interesting if someone could get some temp measurements above and below the esbit holder.Apr 19, 2014 at 4:10 pm #2094648
@kentLocale: High Sierra
Thanks for all the replies.
Focusing only on the fact that burning Esbit is in contact with that thin, delicate aluminum, I kept thinking each time I'd use the stove, "this will be the time it burns through."
The ideas of the heat rising and the aluminum being able to quickly dissipate the heat have come to mind, but I've been assuming I was just wrong about something.
I had also forgotten about the paper cup scenario.
So, it does seem that multiple factors are working in my favor and that my little creation has a long life ahead.
Because of the miniscule weight penalty of a spare, I've been carrying the bottom half of a tiny Altoids "box", just in case. Perfect size for an Esbit tab!Apr 19, 2014 at 4:20 pm #2094653
I have used an esbit in an al stove with no issuesApr 19, 2014 at 7:32 pm #2094689
@b-g-2-2Locale: Silicon Valley
The responses so far are accurate. Aluminum is a very good conductor of heat from Esbit fuel or anything else. If you are simply boiling water, then the water cools the inside of the pot enough that the outside doesn't melt before the water boils. On the other hand, if you are cooking something with much less water content, then this can't occur quite the same way, so you stand a better chance of deforming the aluminum. Whether that happens or not depends also on the thickness and alloy of the aluminum, and how much time the aluminum will be in harm's way of the flames.
I had some bad experiences with this early in my backpacking career. So, since I seek more reliable solutions, I tend to use titanium pots instead. They are just a little more indestructible.
–B.G.–Apr 19, 2014 at 9:24 pm #2094709
@millonasLocale: Santa Cruz Mountains, CA
Yes heat sink is the answer in ether case. Especially if the stove is touching the pot, but also if the stove is touching the earth. If the surface to volume ratio is large enough even air might act as a semi-decent heat sink.Apr 19, 2014 at 9:54 pm #2094714
@richardcullipLocale: San Diego County
Interesting question and a wide range of answers, even if some folks were not answering the specific question you asked.
I believe the answer is that the open flame of the esbit isn't reaching any where near the max temperature of 1400C. It has to do with the type of flame. An open flame from burning esbit is a turbulent diffusion type flame. This type of flame doesn't reach the maximum temperature available in a laminar premixed flame (think Bunsen burner).
While I couldn't find a specific discussion about temperatures in an esbit flame I did find a good discussion about various flame types and temperature. As an example, Natural gas burned in a Bunsen burner produces a max temperature around 1250C in a laminar premixed flame. However, it only reaches 900C in a open turbulent diffusion type flame.
A discussion of various flame types and resulting temperatures can be found at
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