Cooking technique question…

[Laurence Daniels]

I’m into losing weight in my pack and everything, and my base weight is about 12lbs, but for cooking, I’m having trouble visualizing a good flame from Esbit tabs and their stoves. I currently use a pocketrocket, but feel awful about waste re: partial canisters and environmental damage from these things…can you really cook(boil water) for a 4 night trip, say, with this type of setup. Thanks!

[Jim Colten]

Esbit stoves work very well cooking for one person if you are using the boil and soak cooking method. My longest solo outings have been 3 nights but I didn’t come home thinking that esbit cooking would work less well on longer trips. My only issue has been lack of variety in menu but Travel Light, Eat Heavy has lots of recipes that appear worthy of a test drive.

I’m editing this response to add that all my esbit experience has been in cooler conditions, heating (already liquid) water for breakfast with air temps in the 25F-35F range and 40F-50F for the evening meal.

[Glenn Roberts]

I spent about half a season using the Esbit stove. One think I learned quickly was that the performance is very good with a windscreen, and very lousy without one. You don’t have any BTU’s to spare (like you do with, say, a Whisperlite), so you need to focus them all on the pot in order to get one tab to boil a pint or more of water. I cut down an MSR Whisperlite windscreen to an appropriate height and circumference to fit my pot (leaving about an inch all the way around, for circulation.) I also found I needed to cut some small holes in the bottom edge, to let some air in. Used that way, the Esbit performed just as well as any other stove.

The only features that made me give it up were that it was only really useful with a mug-type pot, and the fact that you can’t conveniently extinguish and store unused fuel. I sometimes wanted to cook a larger meal than I could in a mug (MSR Titan Kettle), and when I boiled less than a pint, I needed less than one tablet. Great performance, but I’d waste part of a tablet, which kind of grated on me.

However, with the advent of the titanium esbit and windscreen…

[Jim Colten]

My experience closely matches Glenn’s, right down to using a cutdown MSR windscreen with air holes punched out.

But I’ve found it works nice with medium sized pots (5.5-6″ diameter) on a folding wing stove (just like those sold at BPL and Thru-hiker).

Some folks report success cutting or breaking the tablets for use heating small amounts and even extinguishing a burning tablet but I have no first hand experience with that since I tend to heat enough water that I use an entire tablet for each cooked meal (extra warm water for pot and personal cleanup).

[Vick Hines]

Seconds on the limitations of Esbit as well as the advice to use a windscreen.

However, if you limit the job to boiling a cup or two of water at a time, Esbit works well. The tablets are scored into fourths, and each fourth will heat (and maybe boil) a cup of water PROVIDED that you use an appropriate pot with a support that keeps it the tablet 1 to 1.25 inch or so below pot and an adequate windscreen. If you split tablets to the proper size there is no need to extinguish the unburned portion, but a small square of foil will smother a burning tablet if there is enough worth saving.

Small pots seem to work best for some reason. I use a large Sterno can with the top cut out and a 22 gauge wire bail. It holds about 9 ounces which works for my meals ‘cooked’ in a Ziploc. The pot weighs 0.3 oz. A simple pot support and tablet holder of expanded aluminum gutter screen weighs 0.3, and fits in the ‘pot.’ I just ordered one of BPL’s folding titanium Esbit burners. I’ve had a steel one for years, but retired it in favor of lighter alcohol burners. The ti burner almost matches the weight of my alcohol burner/pot suport, so I want to give it a try as an option.

A windscreen can be as simple as a 12 to 15 inch strip of oven liner cut 3 to 3.5 inches high with notches cut out of the bottom side for ventillation. ***There is no need to punch holes; its a lot of trouble, and a few notches do a better job. *** The idea is to make the strip long enough to give the pot 1/2 to 1 inch space all around. With the pot on the support, the windscreen should go about 1 inch up the sides. Approximately, more or less.

If you master cooking with one small pot or cup, Esbit is the lightest ‘stove’ you can carry, and will work fine for moderate conditions (above freezing). The hitch is the smell and snarky residue left on the pot. Doesn’t bother some folks.

[Laurence Daniels]

…all for your help.

[John S.]

Vick, when you say the tablet should be 1 to 1.25 inches below the pot, where are you measuring?

What is the smallest distance, in your opinion, from the bottom of the esbit holder/esbit tablet (not top of tablet) to the bottom of the cookpot that can be recommened?

The Esbit pocket stove at either height puts the tablet base under 2 inches from the pot base, so I imagine anything between 1 and 2 inches may be okay. The Thru-Hiker comparison doesn’t mention when the tablet may be too close to the pot base.

[Vick Hines]

John,
I remember someone doing a thorough study to find the ideal Esbit height – from the tablet to the pot. Which is th emeasure I use. Unfortunately, I don’t remember where or what the exact results were except maybe 1.25 to 1.5 – maybe. I just ballpark it somewhere in there. That range seems to give the cleanest burn for my particular rig. Less that about an inch and you will start to get smudge and a deposit of white hexamine crystals on the pot due to incomplete combustion. Esbit requires oxygen, and the pot can smother it if too low.

There used to be a wilderness legend that 3 inches or so was the best. The test was to debunk that idea. It did. Google on Esbit; maybe you can locate it.

[Glenn Roberts]

There’s an article on the thru-hiker website.

By the way, I also just remembered that I also used a heat reflector underneath the Esbit; can’t remember whether I cut a square out of the windscreen material, or cut down an MSR reflector. Didn’t do any tests with and without the reflector to see if it made a difference.

[Vick Hines]

The reflector can’t hurt, and helps save shelter tables and floors, not to mention preventing slow-burning fire in the leaf mold that can creep under your tent during the night. And so on.

[John Chan]

I’ve read sporatic remarks on the smell of unburnt esbit… that it has a “fishy” smell. Is this from trimethylamine coming from the fuel? Also, does anyone venture a guess at how much ammonia is evolved from the combustion of hexamine?

TIA

[Glenn Roberts]

Well, I suppose I must first admit that I just received my titanium Esbit wing stove, Ti foil windscreen, and a box of Esbit tablets from BPL – so it looks like I’ll be giving them another try, just because I have no will power! (There’s also the fact that stove, pot, and fuel for 6 days only weighs about 8 – 10 ounces.)

As far as smell: I don’t recall any particular odor when it was burning and I was merely sitting beside it (my face a couple feet away – the same safe distance as I would any other lit stove.) Having heard that comment before, I do vaguely remember once leaning close to it, but can’t remember if I got any particularly noticeable odor.

I do, however, notice a fairly noticeable ammonia odor from the box of 12 tablets. It’s not overpowering, but it is noticeable enough that I put the box, stove, and windscreen into a ziploc bag. That blocked the odor (though I still get a sniff when I open the bag.)

This is all very minor, and not a problem in the field.

[Vick Hines]

JC,
I have only seen one chemical analysis of the combustion products of hexamine, the one you cited elsewhere from Sgt. Rock’s site, I think. Don’t make me look it up. Unfortunately, it cites formaldehyde as a combustion product. I think that is not correct. Sometimes, you just have to trust your own perceptions, and I don’t perceive formaldehyde when burning hexamine although I am very familiar with it. What I do smell with both unburned and burned hexamine are free amines ( a general organic group, non-toxic but stinky). Amines give fish the ‘fishy’ odor and dominate the odor of unburned hex. There is little if any ammonia in hex combustion products. Interestingly, hexamine is made from ammonia and formaldehyde. You can make it at home with household concentrations of both chemicals. Just mix them and collect the precipitate. Lots of trouble, though.

What I DO notice producing formaldehyde fumes is trioxane which is a polimer of formaldehyde and releases some due to incomplete combustion. Trioxane is the purple solid fuel in OD foil packets now commonly found in military surplus emporia. (Note: formaldehyde is an alcohol – a little more complicated than ethyl and methyl.) The other place you will smell formaldehyde is during incomplete combustion of methyl alcohol. So you might catch a whiff when using denatured in an alcohol burner.

One answer to your queston: “does anyone venture a guess at how much ammonia is evolved from the combustion of hexamine?” is, hex is about 1/2 ammonia. More or less true, but misleading.

[Vick Hines]

> Used right, 1/2 an Esbit tablet (or .25 ounce) is more than enough to boil a cup under mild conditions. 1/4 is not quite enough.

>Therefore, extinguishing a tablet can save on fuel for those times that 1/2 may not do the job.

> And remember, 180 F is enough for most jobs… so

> You can snuff Esbit with a little foil cap. I use a oval of oven liner – one side 1 inch long for a handle, the rest bent over a fresh Esbit tablet to form a cap.

The Esbit will continue to give off a gas that will immediately precipitate on the inside of the foil cap as white crystals. Don’t worry about it. Just let the remainder of the tablet cool enough to put away – about 5 minutes.

[John Chan]

VH

With respect to your statement that “formaldehyde is an alcohol, a little bit more complicated than methanol or ethanol” I respectfully disagree.

Formaldehyde is an oxidation state of methane and ranks as the second last oxidation state (formic acid being the last).

So goes CH4 (methane) –(O)–> CH3OH (methanol) –(O)–> H2C=O (formaldehyde) –(O)–> HOC=OH (formic acid). If hexamine is synthesized from formaldehyde and ammonia one can venture that formaldehyde will not be a combustion product as combustion is oxidation (you are correct in that regard) but the evolution of ammonia from hexamine is of interest to me because nitrates and ammonia are among the most vigorous combustibles known… driven by the evolution of nitrogen gas which has a very low free energy. The observation that ammonia is evolved from hexamine during combustion perhaps alludes to the possibility that ammonia might be trapped as an impurity in the fuel and simply liberated as a gas when combustion occurs (without oxidation).

[Vick Hines]

JC,
Yeah, John, you’re right, formaldehyde has the C=O bond, not alcohol’s -OH. I shot off too fast.

I suppose ammonia could be an impurity in hex, assuming the production process was so inefficient as to waste unreacted ammonia. Hex is made all over the world because it is such an important precursor material. What we use for fuel is simply a small amount diverted on its way to becoming either plastic or high explosive. One would assume, therefore, that hex production usually takes place in fairly sophisticated plants. I assume that Esbit production is European, but over time I have seen what seems to be Esbit from different plants, so the possibility exists that they procure it anywhere they can get it at the best price. Some producers use a little wax either for mold release or for surface binding and sealing. Others do not, and produce brittle tablets with the crystaline look of pure hex. Tablets from different production runs also have differing levels of amine outgassing. Don’t know why.

[John Chan]

VH,

I remember once in 3rd year synthetic organic chemistry a lab where we purified some large amines by rotovap using di-ethyl ether as the solvent. Presumably any gaseous by-products of synthesis that are trapped in the crystal structure of the impure hexamine will be liberated with the ether… but this is an expensive and “non-green” solution for getting pure product.

I’d venture a guess that sub-contractors producing hexamine for Esbit are cutting costs here for environmental/ bottom line reasons. Makes me wonder though how stringent Esbit’s QC are on their suppliers though. If you look on their website you’ll see them touting their proud heritage and unshakeable integrity in bringing to market the best, highest quality solid fuel… More marketing?

[Vick Hines]

When a guy spends much time talking about integrity, get your hand on your wallet.

What I was thinking about is the issue of introducing the right mole weights of this and that to get a complete reaction. Since hexamine precipitates out of the solution of formaldehyde and ammonia, it doesn’t interfere with continued reaction. Then its purity is a matter of proper washing… which might not be done right. The thing is, hex burning smells a lot like hex in my stove kit. I wonder if there are not some ‘room temperature’ oxidation products all the time.

[John Chan]

Well, if it occurs in solution then the ammonia is probably in the form of an ammonium salt (NOT ammonium nitrate… BANG!) so perhaps as the hexamine precipitates out of the reaction mixture the stochiometric ratios of reactants is altered as contaminants in the crystals (ie ammonium ??chloride?? is the bigger contaminant) and this impurity is liberated as ammonia gas when the hex is burned… otherwise only nitrates would be the final oxidation products after complete combustion and you’d have your own little acid rain storm in a poorly ventilated tent whenever you broke out the hex.

[Vick Hines]

Yeah, probably. You are way ahead of me on this. All I know if hex has a foul odor. I still use it for solo trips.

An interesting side issue: formaldehyde is made by a catalytic reaction of methane and water. I have detected it when methanol is burned in aluminum and brass burners and especially when incomplete oxidation can be suspected (in tent or at high elevation or both) I wonder if aluminum and brass (copper/zinc) catalyze it or if methanol combustion produces formaldehyde easier than methane.

[John Chan]

VH,

I think formaldehyde can be easily formed by burning methanol “rich”. I detect it in the priming cup of my open jet stove as well and essentially, the fuel in the priming cup is burning rich since all available oxygen (most) goes to the 16 surrounding jets. The same goes with acetaldhyde which is given off when ethanol is burned in the stove. Despite all the tweaking, the fuel in the priming cup will always burn rich unless the priming cup is eliminated (as in some of the Mini Bull Designs stoves).

Still, I’ve switched to ethanol (95%) for my alcohol stove now. Burns a little sootier but acetaldehyde is more easily metabolized by your liver than formaldehyde… and frequent use of the stove in enclosed places (tent) only exacerbates the problem.

[Vick Hines]

Yes, I first noticed it in 1977 when using a Trangia. So you’re burning what, Everclear?

[John Chan]

I’m burning lab grade 95% ethanol. Get it from work… too poor to afford everclear but being an academic does have its advantages.

[Vick Hines]

Thought so. Chemistry, right?

So have you designed a no-soot isopropyl burner yet? Preferably one that serves as its own pot support? Tinny claims to have done so (using a version of the old splash-plate burner, I think. That’s one way to get the temps needed to burn iso cleanly. ) Now, THAT would be a coup. Someone claimed not long ago on this site that iso had higher BTU than either ethyl or methyl. It is certainly cheaper and easier to find in more places.

[John Chan]

Close,

Functional Genomics (Molecular Biology).

The problem with isopro is the commercially available stuff is only 70-75% (rubbing alcohol) so already, you’re at a huge disadvantage in terms of calories needed to vaporize the water component. Isopropanol is actually a branched alcohol (CH3)2CHOH which makes it potentially higher in terms of liberated energy (C-C bonds) but harder to combust. I hardly see the point of making an isopro burner unless you can get the good fuel cheaply.

Fortunately for me, there’s lots of 100% isopropanol kicking around the lab should I decide to go through the esquisite mental torture of tinkering with a stove set-up and said fuel.

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