A hot lunch on a cold day with Esbit fuel.

ThermosDuring a break in our seemly endless series of Pacific Northwest winter rains/snows, I took a day snowshoe hike on a familiar ridge in Mt. Rainier National Park.  It seem like a good day for a stove experiment.  Normally on winter outings, I take along a 20 oz. capacity stainless steel thermos, fitted with a reflective foil insulating wrap.  At lunch, even in winter, it provides steaming hot water for instant espresso spiked hot chocolate drinks. On this trip, I opted to leave the thermos behind and take my small solo stove setup based on a Toaks 750 ml. titanium pot and windscreen to provide the heat.  That meant I could forgo the normal cold sandwich and have my favorite trail hot meal – Annie’s Microwave Esbit unpackedWhite Cheddar Mac & Cheese with some maple flavored bacon jerky bits thrown in for good measure, plus the normal mocha hot drink.  My little stove setup is designed to be fired either with alcohol or Esbit tablets, which were the choice for this trip.

As noted in past posts, lighting Esbits tablets is a little tricky.  My climbing partner who introduced me to Esbit always struck a stormproof match and set the resulting inferno down on the tablet to light it.  I settled on using a butane cigar lighter that produces a small blowtorch flame.  But since the lighter is butane fired, its performance in cold weather is a little finicky.  It is also 4 times heavier than a Bic lighter.  Recently I came across some discussion of using alcohol as an accelerant for lighting things.  The suggestion was for dipping a little Piezo lighter in alcohol and then hitting the sparker.  You get a brief flame out of the lighter tube.  Pretty cool, but it didn’t always work and my experience with these lighters is that they seem to have a very short life.  I have started to use a ferrocerium rod and steel striker for lighting alcohol stoves.  It does a good job.  So the next thing to try was dripping a little alcohol on an Esbit tablet and lighting the alcohol to start the tab burning.  It seemed to work and I could light the alcohol by striking sparks onto it.  I now carry a very small 1/2 fl. oz. dropper bottle of alcohol as part of my Esbit fuel kit.  So, of course, I needed to try all this out on my winter outing.

Winter EsbitWhen it was time for lunch, I had arrived at my viewpoint destination and cleared some snow off the log railing for a seat and table.  I packed a little snow on the log to make a level platform for the stove 20230308_120221and got to work.  I couldn’t get the ferrocerium sparks to light the alcohol.  Surprise, it was cold out and the energy content of the sparks weren’t enough to vaporize the alcohol for ignition.  Even though Indiana Jones is good with a bull whip, he carries a backup.  And so I did get out my Bic lighter to touch off the alcohol.  Then things went smoothly.  I heated water and made my hot drink in my insulated plastic mug.  With more water added to the pot, I added the macaroni to cook for about 3 minutes.  When tender, the sauce mix is added and stirred in with the jerky bits.  The whole process pretty much used up one Esbit tablet, but got the job done.  Pretty tasty.

PackedSo how does this all compare with the no-cook lunch approach for both weight and volume?  The bottom line is that the two options are actually pretty close.  The empty thermos and cozy comes in at just under 13 oz. and the stove setup, including my mug,spoon, and 2 Esbit tablets is just over 13 oz.  The thermos packed is 85 cu. in. in volume while the stove packed is a bit larger at 120 cu. in.  The water I used for lunch was about 16 oz.  I typically carry maybe 18 oz. hot in the thermos, but solo would only use about 8 for a hot drink.  I expect my uncooked lunch weighed about the same as the sandwich I would carry, but my plastic sandwich box would be another 3 oz. and another 35 cu. in. in volume.  I would carry my small folding plastic cup in both cases.  So basically weight and volume don’t favor either approach.  Certainly getting the stove out, heating water, cooking and cleaning up is more work than just having a sandwich and mixing a hot drink, but the hot lunch is definitely a nicer treat – your pick.

The final question is – what about water?  With the thermos, you are carrying that extra water, probably in addition to your daily water volume.  For cooking lunch, you need to have that much extra water as well.  Unless you were to melt snow for cooking.  My previous post looked at melting snow with a different pot, my cone windscreen and big alcohol burner.  That setup produced 18 oz. of melted water for 1 fl. oz. of alcohol (0.8 oz. weight).  How much water can I get per Esbit tablet with this trip’s stove package?

20230308_121419It took another trip to snow country to answer that question  and I was very surprised at the result!  I set up the pot and windscreen and melted snow, burning through two Esbit tablets.  I netted 5-1/2 cups of water, 44 oz., for 1 oz. of fuel by weight.  Compare that to last winter’s alcohol stove snow melting experiment yielding 72 oz. of water for 4 fl. oz. of alcohol (3.2 oz. weight), or 22.5 oz. water per fuel oz.  That’s almost twice the performance when burning Esbits.  And the alcohol requires a container to carry it, while the Esbit tabs have only a plastic wrapper.  However I got the 72 oz. of water with the wider pot, cone windscreen and Trangia alcohol stove in the same time, 1/2 hr., as it took to get the 44 oz. with the smaller pot and Esbit tablet and holder.  The Trangia alcohol setup was about 5 oz. heavier and slighter larger in volume, 134 cu. in.

Why the big difference?  Esbit tablets, made of hexamine, have a heat content of 30 kJ/g.  Alcohol “stove fuel” is a mixture of ethanol and methanol, about 30/70% giving a heat content of about 22 kJ/g.  That’s less than half of the observed performance difference.  The rest must be due to a better stove/pot heat transfer efficiency.  The Esbit tablet,s when melting snow, burned much more slowly – 15 minutes per tab – than in normal cooking use, typically 8-10 minutes.  The burning rate will be set by the rate of heat transfer to melt the hexamine for combustion.  With a cold pot right above and cold air coming in the air ports, the table temperature, the burn rate and heat output should be lower.  The hot combustion products then pass up the narrow annulus between the windscreen and the very cold pot walls, making for a great heat transfer environment. 

So score a big win for my little Toaks pot and homemade windscreen set up fired with Esbit tabs.  As packed, without the drinking mug and fuel (which will nest in the pot) it weighs in at less than 10 oz.!  Add as many Esbit tabs as you wish at 1/2 oz. each, and you have a killer back up winter outing stove as well as a very serviceable ultralight solo cooking kit.  It could make sense to bring along something like this to address the 10 Essentials issue of providing extra water on a day outing in snow where open water sources are not expected.

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