Esbit burner testing

[Richard May]

So, with the discussion surrounding the BGET burner and the Esbitmizer I thought I'd share what my humble popcan does.

I don't know if my popcan does any better than those but someone may find it interesting.

Comparing notes with other burners would be cool.

I decided to just look at burn time in an exposed windless environment (my kitchen stove) since screens and pots just add more variables. Boiling water depends on too many variables to easily compare notes unless the same cook kit is used.

Goal: To see how long an Esbit tab burns and how much useful residue is left behind.

Procedure: One cube of Esbit was burned, fully exposed without a windscreen or pot.

Result: The Esbit tab burned for 16 minutes until the flame extinguished itself.

Here are some pictures of the burn:

There was a useable flame to 9min 44sec 57

By 11:22:44 the flame started to really slow down.

At 12:56:53 it was just a puff of flame:

The flame hanged on, barely, to 16:26:26

A previous test showed that some fuel was left unburned at the bottom of the can. That test had been done with the windscreen shown.

Edit: Grammar and the post wasn't pulling the pictures from Flickr. A more complete series of images starts on my flickr account here: https://flic.kr/p/ryWCLn

[Dan Yeruski]

Thank you Richard for starting this thread. I hope recent test results in my esbitmizer thread will be posted again here for future use.

It would be nice to jam this thread full of test results.

[Bob Moulder]

Good timing, Richard!

As I indicated in the Esbitmizer thread (getting a bit OT, oops) I'm interested in bringing 4 cups to boil with Esbit.

I bought some 14g tabs recently and was able to do some testing this morning. Not a lot of time and my thermometer probe quit working, and I accidentally crumpled the cone and had to use another pot, and it started raining in my laboratory (my deck) so not a lot of data. But interesting and encouraging results all the same.

Using the Ti Caldera cone and Flat Cat Gear Focus Fire 14, one 14g tab brought 3 cups very close to a boil. Hot enough that I'd be quite happy—probably 200°F. I had some .005" Ti foil stock with which I made a base to get the burner the correct height as described in the FF14 instructions.

Next, I split a tab in half, using 1-1/2 tab in the burner, just stacking it in there. Not per spec, but it worked fine. I lit a top corner of the 1/2 tab piece figuring that the top-down burn would keep it slow enough. Got a full boil of 4 cups of water in a little more than 17 minutes, and it even continued to burn for a short while after that. It was out almost completely around 18 minutes… as you've observed, it does continue to dribble on uselessly for a while before flickering out…

After that I tried a 1-1/2 tab burn with the Gram Cracker, also with the 1/2 tab piece just stacked on top. It also brought 4 cups to a boil, but just barely and not with as much vigor as the FF14, and it took a whopping 22 minutes with the flame continuing to burn weakly up to the 23-1/2 minute mark!

Bottom line: 1.5 tabs is enough for 4 cups, with the edge going to the FF14 set-up.

Using an older Evernew Ti pot, with my rumpled Ti cone… somewhat worse for the wear.

FF14 with my Ti foil stand to get the burner height to Flat Cat Gear spec.

1.5 tabs stacked like this for use with the FF14.

A real, by-gosh boil with the FF14.

Tab-and-a-half stacked for the Gram Cracker.

It took a while, but a legitimate boil was eked out with the Gram Cracker.

edit: for clarity

[Dan Yeruski]

Bob, I used my last 14gram esbit in a DIY BGET and almost got the boil of 4 cups. I used an Antigravity Gear, Caldera Cone for the 12cm Imusa Mug which holds 4 cups. If the pot was 1/2 closer to the tablet it may have gotten the boil. I have to wait for my supply of esbit arrives to do further testing. For sure, If I use one 4gram tablet with the 14 gram, I will get the 4 cups to boil.

[Adam Kilpatrick]

Richard, what is the weight of the pop-can stove?

Could be interesting if people compare weight of their esbit stand before and after the burn (before, clean, after, with residue). I realize many won't have scales with enough precision for this task. But this could be a non biased method of comparing residue.

I completely forgot about the Focus Fire 14. I've got one, yet to be folded, stashed away somewhere. What a dill.

[Bob Moulder]

Dan, what was the start temperature of your water?

I'm more than a little bummed that my thermometer quit working because at the very least I like to have that base reference. Our tap water gets pretty cool this time of year and in previous tests the water was measured at around 42-44°F. I let the tap run a while to get consistently colder water between stove burns, so I can say without fear of exaggeration that it was certainly colder than 50°F.

I like to test with colder water because that is what I will encounter out in the woods… at least around here. As we all know, there's the lab and then there's the real world, and I will not be denied my 4 cups of hot! :^)

The Gram Cracker — which isn't hugely different from the BGET — raised the temperature of 4 cups of cold water (~43°F) very consistently up to 180°F with a pretty efficient setup. I'd be mighty impressed if someone came up with a way to corral the wasted heat and transfer enough BTUs to boil cold water with one 14g tab.

Already, there was so little waste heat coming out of the top vents of the cone that I thought the flame had gone out on the tab.

[Dan Yeruski]

I didn't check the tap water for temp accept with a dip of my finger into it LOL

It was medium temp. I was primarily interested in seeing how close to a boil I could get with the tray and an "old" esbit.

The BGET has very little residue left and it's in the form of powdery soot, miniscule amount. I think it may have something to do about the thermal feed back of the .002 stainless steel. I have Trail Designs Gram Cracker and will do tests next week to compare length of burn time and remaining residue.

I'm in a mind set that esbit is to be left in the tray to completely burn away. No saving little pieces. It's not worth the fiddle factors ;) Penny wise and pound foolish…..right?

[Richard May]

Adam, I have no idea how much it weighs—I've got one of those uber-cheap spring loaded scales that is very temperamental. I could very well be carrying around a lot less (I like to think) than I realize!

Regarding residual fuel and residue, it seems variable. Sometimes there's a little drop of fuel left at the bottom but it's usually just hard ash. The ash gets scraped out with a knife; any fuel gets burned at the next meal.

My cook setup isn't very efficient at the moment. The windscreen/stand system is rather in-efficient. As I've got the day off I think I'll build myself a cone to fix that.

[Richard May]

>> The BGET has very little residue left and it's in the form of powdery soot, miniscule amount.

Makes me curious about hard ash, often clumpy but thoroughly black trough-and-through, at the bottom of my burner.

[Bob Moulder]

I'm in a mind set that esbit is to be left in the tray to completely burn away. No saving little pieces. It's not worth the fiddle factors ;) Penny wise and pound foolish…..right?

Totally agree — I hate fiddling with stuff.

I thought about putting in 2 tabs, getting the water to a boil for dinner, blowing it out and leaving the remnant in the burner and then adding another full tab in the morning for breakfast. But it probably wouldn't burn efficiently with the fresh tab lying on the lumpy remains of the burned tab.

Nah, 1.5 tabs for a reliable boil in real-world conditions, complete burn and done. Much simpler.

[Bob Gross]

The next thing that we will hear is that the government will be requiring catalytic converters on these.

–B.G.–

[Dan Yeruski]

You're drifting :)

[Dave Heiss]

Apologies in advance if this leads to a thread drift, but I've always wondered why there isn't a pot that uses increased surface area to boost the transfer of thermal energy – from esbit, or alcohol, or any other BP fuel.

Jetboils and similar designs try to maximize heat transfer with fins to increase the surface area exposed to heating, and Caldera Cones provide a boost in heat transfer for the sides of a pot, but other than the Backcountry Boiler/chimney kettle configurations I don't think I've seen anything that modifies the shape of the pot itself. Pots are always…pots. What if a pot looked something like this (maybe with the top cone closed)?

I've pondered it for years and just thought this thread might be a good place to ask the question. A pot shaped like this and used with a Caldera Cone might set records for boiling efficiency.

[Dan Yeruski]

Dave, that design will not allow heat to go up inside the cone. I experimented with pot of that type. It was a DC electric coffee pot of the small type. I thought that was going to be the mother of all pots LOL it failed miserably. Better off with the Kelly Kettle design.

[Jameson Tisch]

I figure I'll copy over my information in case people missed it, while also adding some pictures of the testing that I did. Once the BGET gets to me as well as the Esbit wing stove more testing will be done.

From the mini esbitmizer thread: "So I was able to go out this afternoon and run a couple tests on the mini esbitmizer – one with (2) 4g tabs and one with (1) 14g tabs.

It was 50F outside, but very windy (about 16MPH), and both tests were conducted with 2 cups of 60F water in a 600ml short/wide titanium Evernew pot, a 2in high stainless steel mesh pot stand, titanium windscreen, and the baseplate supplied with the mini esbitmizer.

The test with the two 4g tabs never came to a full rolling boil unfortunately, plenty of crab eyes, but no boil and ran out at 14 minutes.

The test with the one 14g tab came to a full rolling boil at roughly 12 minutes and 15 seconds (I left the pot lid on due to the wind so I'm not sure of an exact time) and ran out at 19 minutes.

The 4g tabs lit up very easy whereas my 14g tabs were very difficult to light, but maybe I just had bad tabs. The 4g tabs also left only a small amount of soot on the pot compared to the 14g tabs which left noticeably more. The 4g tabs also burned much cleaner meaning they left much less residue in the mini esbitmizer after burning, with the 14g tabs leaving a much larger amount of residue left after burning down.

My guess is that one possible reason I could not get the 4g tabs to come to a boil is that the mini esbitmizer does not raise the tabs off the ground meaning there was probably around a 1 7/8" gap between the top of the tab and the pot which would have only increased as it burned down. The 14g tab would have been more of a 1 3/4" gap between the pot and tab. Overall though, more testing needs to be done with them as that was my first time working with the 4g tabs, and I feel like they are clearly superior to the 14g tabs if I can get a boil out of them."

"
This was after the 2 4g burn
After the 14g burn

[Richard May]

For the sake of S/UL I tasted my first Red Bull, ever. Yuck! Coffee for caffeine please!

But it was for science.

Turns out the little can is better than the regular can at burning Esbit 14g tabs (17m 51s). Which raises and interesting new set of tests: Esbit 4g and the Coughlans round tabs. Those I'll do later.

Also, since I'd seen some stoves could simmer I tried putting a simmer ring around the tablets. The result was a 39 minute, 44 second burn!

As a bonus even less residue was left behind in the burner.

These are the details:

Goal: Determine how long a 14g Esbit tab burns and how much residue and fuel remain.

Procedure: As above. Windless kitchen, fully exposed. Two modes: normal and simmer.

Normal Burn: 17 minutes, 51 seconds. This is an improvement over the regular pop-can. As is seen in the picture virtually all the fuel is burned. The residue is all thoroughly consumed.

Simmer Burn: 39 minutes, 44 seconds. This blew me away. All I did was make a ring out of the can to fit inside the burner. The ring is 21mm tall.

— FOR THE WIN: Iced water boil test —

Among my projects today was to make a Clone Cone for my Toaks 450ml cup. Trail Designs doesn't make one so I took matters into my own hands. It's good enough that I'll build it out of titanium.

Goal: Determine burn time and how long it takes to boil about 400ml of ice water using an aluminum foil cone and a single Esbit 14g tab.

Procedure: Fill cup with water that had been sitting in ice for several minutes to reduce temperature to near freezing. Assemble cone and heat water in both normal and simmer modes using the mini pop-can. Environment was around 70F, windless.

Exact boil times are ambiguous since I cannot see through the lid so I took the time when I could hear the rolling boil.

Normal Mode: water boiled at 8 minutes, 30 seconds. Flame extinguished at 16 minutes, 10 seconds.

Simmer Mode: Now this was really interesting. The water actually boiled at 20 minutes and the flame went out at 31 minutes. When I took the lid off the pot to see the boil in action it slowed and when I put the lid back on the boil started again—a full rolling boil with bubbles and water spurting out the bottom of the lid kind of boil.

edit: clarity and added an image.
edit2: I had previously stated the ring was 15mm tall when in fact it is 21mm tall.

[Adam Kilpatrick]

Great stuff Richard.

Just to check with the last test, that's with your minipopcan with the simmer ring?

[Richard May]

Yes, that last simmer test is with the ring. It's interesting that the burn time should be so much shorter in the cone. My first guess is that the temperatures in the cone are higher.

Has anyone else observed this or similar?

[Adam Kilpatrick]

Very interesting Richard.

Yes, maybe the air temp is higher in the cone, therefore speeding up the reaction process.

Also its interesting your ring vs no ring comparison. The times of both suggest to me that without the ring, perhaps the boiling capacity is greater as the ratio of time to boil to total burn time is better. An index for this kind of thing could be useful, eg;

Potential Boil Capacity Quotient= total burn time/time to boil

PBCQ (pop can)=1.90 (3 significant figures)
PBCQ (pop can with 15mm simmer ring)=1.6 (2 significant figures)

Potential Boil Capacity (PBC) = Volume Tested * PBCQ

PBC (mini pop can)= 760ml
PBC (mini pop can simmer ring)=620ml

Note the first one is impossible with your pot as it exceeds its capacity.

Note the relationship between PBCQ won't be linear as the heat output changes as the tablet burns down, and its also dependent on such things as how fast heat escapes from the pot, the windscreen used, pot dimensions and material, is pot insulated, etc. As many of these things are controlled in your test the metrics are potentially useful.

I got my new sidewinder in the mail last night, gram cracker, and starlyte (restricted). Still waiting on 4g esbit tabs, BGET and Starlyte XL (restricted). Once I get them, and have a spare day next weekend (Easter is for bushwalking!) I'll start doing some tests too to put up here. Kicking myself I didn't order an ezbitmizer for comparison purposes. I'll make pop can and mini pop cans with and without simmer rings too; great ideas Richard :-)

[Richard May]

Potential Boil Capacity Quotient= total burn time/time to boil

PBCQ (pop can)=1.90 (3 significant figures)
PBCQ (pop can with 15mm simmer ring)=1.6 (2 significant figures)

Potential Boil Capacity (PBC) = Volume Tested * PBCQ

PBC (mini pop can)= 760ml
PBC (mini pop can simmer ring)=620ml

I like this!

Specific data points that make comparing different setups meaningful — presuming we can keep the environmental elements fairly consistent.

To me an environment at around 70F (21.1C), windless and iced water are pretty easy to get. I think icing the water puts it at a consistent temperature and challenges a stove-kit to compensate for lack of wind and colder surroundings.

I look forward to seeing if you replicate the simmer burn.

Funny, I've been ticking off excuses to get an 850ml pot.

You just added one. :-P

edit: I corrected the height of the simmer ring. It's actually 21mm tall.

[Adam Kilpatrick]

replicating experimental conditions is always tough…but we can try. Room temperature is not too difficult (my house is pretty old, doesn't have a thermostat, so won't be precise), though I'd have to do burns on the stove top with the rangehood running so we don't choke on esbit fumes!

I'll have to dig up a couple of suitable thermometers too.

I will definitely try and replicate your simmer tests with popcans. Especially your observation of reduced burn times with/without cone. Its a very interesting observation.

[Jameson Tisch]

So I did some more esbit stove testing the past two weekends. As my last post stated I tried to get 2 cups of 60F water to boil with 2 4g cubes in the mini esbitmizer and was not successful. I've since read that 12g seems to be the magic number but I wanted to see how close I actually got.

So I tested the same setup indoors this time to eliminate the wind variable to see if that had any effect.

The cubes wound up burning out after roughly 12 minutes – down from the nearly 14 minutes outside and I measure the temperature of the water to hit 190F. Not that close to boiling but certainly hot enough to use for coffee/tea or with filtered water where you don't necessarily need a boil but of course YMMV.

I then tested the steel BGET that Zelph sent me (big thank you to him it was much appreciated!! Sorry it took this long to write up) with 2 4g esbit cubes. The BGET is definitely made for 1 14g gram cube and 2 4g cubes did not fit perfectly in the tray but with some determination I got it to work alright. To be clear, I laid them flat just as they would sit in the mini esbitmizer. I did not flip them on their side to make them fit.

Using the same setup as before except with the BGET I got a similar boil time of 12 minutes and 190F water.

The only difference I noticed was that the mini esbitmizer left a very small amount of residue on the bottom of the pot whereas the BGET left considerably more for some reason. Not sure if it's because the flame was getting choked from not enough oxygen or the cubes were packed too tightly in the tray, but I would say there was 2-3 times the amount of residue left on the bottom of the pot. Similar to, if not a bit more than, using a 14g cube.

[rmeurant]

Are you esteemed Esbit researchers taking account of heat loss vertically downwards, and appropriate counter-measures? I say this because I have quite an efficient homemade system, with reflective cylinder shield and reflective disk below; but when I substitute the miniEsbitmiser for the Esbit tripod, even though I'm using the Ti tray provided and an alu foil disk underneath that, the heat below scorched my Evernew burner sheet. That is clearly heat going to waste, as well as potentially damaging to tent floors etc. I'm thinking I should elevate the minEmiser to avoid this. There would be both conductive (through whatever support is used) and radiant heat loss ( depending on the configuration), even if elevated, but it ought to be able to be mitigated somewhat… I think also there might be a near ground effect with cold air…?

[rmeurant]

Perhaps BPL readers could get Esbit to sponsor a design competition – with good prizes – to optimize designs for custom Esbit burners for given quantities of water and agreed conditions?

[Bob Moulder]

One 14g tab for boiling 2 cups seems to be the accepted norm because it accounts for less than ideal conditions and somewhat less system efficiency, and things always seem to be less efficient in the field than in our backyards. There is always going to be some heat radiated/conducted out the bottom, and it is well established that narrow-bottomed vessels are significantly less efficient than pots with wider bases.

With the Evernew 1.3l/Caldera Cone/Flat Cat FF14 combo I was able to consistently boil 4 cups of cold (~43°F) water using 1.5 14g tabs, which obviously works out to 10.5g of fuel per 2-cup ration. Is it possible to equal or surpass this with any 2-cup system? I kinda doubt it, but then I don't have nearly as much Esbit experience as many of you.

Does anyone actually operate an Esbit stove inside a tent? The gases it gives off seem pretty noxious. I could imagine using it in a vestibule with good ventilation.

But alas I remain an Esbit virgin as I have never used it in the field. That will change next weekend because the weather is getting much nicer here and it looks like a good time to do a real hike and fire it up in earnest with a hot dinner hanging in the balance. :^)

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