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Fair winds!

Dave and Anke
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Monday, February 20, 2012

Haybox aka Thermal or Retained Heat Cookers

Drawings from Aprovecho

Cheap energy ain't so cheap, anymore.

A friend, who suffered from arthritis and heated with wood, once told me, "I want the best return in BTUs on calories invested." Mmm. There's a deep thought!

It's become much more common, recently, to consider efficiency in terms of  insulation. But our crafty forebears applied it to cooking, upping that return on investment of which my friend spoke.

The general concept of a haybox is an insulated container, closely fit to a lidded pot. Anything with lots of air spaces trapped within it (hay, newspaper, foam, wool, etc.) may be used... 4 inches all round the pot being a good working minimum.

Historically, hay was a choice insulator. It would be chopped coursely and, while damp, packed firmly around a dedicated pot. Once dry, it would retain the pot's shape in a tight fit. Hence the name haybox. They were common by land and sea. Soldiers used them to cook rations in the field.

Bring the contents of the pot to a solid boil, put it in the container and close the lid. No more fuel necessary! Cooking continues at a simmer for hours. Recipes are similar to those for crock pots.

Piping hot soup on deck in the wee hours! WOO-HOO!! Don't even have to wake the cook (and a cook awoken is a grumpy cook).

Additionally, a thermal mass (brick, stone, shaped concrete plug) may be heated on the side, and inserted with the pot for dry baking. A metal liner is a safety feature for this method, as the thermal mass can reach scorching hot temps if not watched carefully.

A notable refinement is to line the container (outboard of the insulation) with a reflective layer of foil or equivalent. Tristan Jones (I seem to remember from One Hand for Yourself, One for the Ship) spoke of layering foamboard cut to fit a pot. Nomex cloth?

Here are some pics of various DIY solutions, and commercial thermal cookers (vacuum insulated). Search for any of the title terms under images for a quick overview, or go straight to any of the many excellent articles posted online.


Looks like a Sailor's work!

How easy can it get?

Lanny Henson Green Pail Cooker

Here's a row from Africa.


Here are a couple just to get the flavor... can be very spendy. Many claim advantage over a straight, retained heat cooker by enabling convection cooking vs. straight simmering. Anyone out there got one and care to comment?

Watch out for thin bottomed inner pots, which don't heat well. Some complain of warm spots and heat loss around the lids, especially but not always in cheaper models.

Thermos Shuttle Chef Thermal Cooker by Nissan
Thermos Thermal Cooker by Thermos

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  1. I cook rice and other dishes in a wide mouth thermos. Rice is dead simple. Measure in the rice, pour in the boiling water. Put the cap on. Shake it up a bit and lay the thermos on its side.

    When I boil water for breakfast tea or coffee, I make sure there's enough for the rice dish. Then I've got hot food for lunch without having to start the stove.

    1. Hi Sixbears,

      Yes, indeedy! Thanks for adding Thermos Cooking into the discussion. I'd totally spaced that they're the simplest and very flexible RHCs that most already have on-board.

      We like wide-mouth thermoses (vacuum bottles) for cooking.

      In addition to your procedure, we preheat the bottle (add about a cup of boiling water, cap, and let stand a minute or so... dump water, then continue as you describe) and wrap loosely in sleeping bag. We tend to wrap 'em, even when it's just hot water... will be coffee hot after 24+ hours.

      I've had poor luck with just about every model but those made by Nissan (which have been consistently excellent). Just haven't held their heat (if you can feel warmth or warm spots, it's a lemon). We probably could have traded in on guarantee, but aren't organized enough. A small haybox or bag will up the capacity of a poor quality thermos, if necessary.

      Thermoses often come rated for heat retention. You'll want the one with the highest (longest) rating available.

      Whatever model, do look for metal liners. The glass ones can shatter spectacularly, or worse, they sometimes heat splinter without being obvious.


      PS. Nissan makes a vacuum insulated French Press. It keeps coffee nice and warm on cool days. FPs have the advantage that one can keep adding grounds and water to keep coffee going for guests without a dedicated pot on the stove. Good for crowd pots of loose leaf teas, too.

  2. Ahoy!

    A really great combination is an insulated container, and a pressure cooker. I kept a batch of 'Glop' going for a year or so, when out in the 'bush'. I took one meal a day out of it, and NEVER opened it between.

    When I opened it and stirred the contents, and heat it for the meal. After I had finished the meal, I would add something to bring the level back up, and heated it to 'ripping hot'. This not only started the cooking process; It sterilized the contents. Then I just put it on the back of the stove, later in a insulated container, until the next day. Putting it in the box not only insured cooking, it kept idiots from opening it and introducing potentially dangerous contamination. Be sure you have "Sailor Boy" pilot crackers to go with it!

    Cheers, AK. Dave

    1. Hi AK.Dave (Are we me? Better pinch myself!),

      Good point! And the pressure cooker also helps protect from spills should the box or bag get knocked.

      I'm curious, do you stopper the vent once the pressure's down?


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  4. Here's another good portable solution: a drybag of the right size carefully packed with Reflectix aluminized bubblewrap insulation with a cardboard liner to keep the hot pot from direct contact with the plastic (and judicious use of duct tape to construct everything and keep it neat) inside of which fits a bailed "bushpot" style covered stainless steel cooking vessel...

    Firebox Stove sells a good pot of the kind, along with other... interesting... stuff.

    A good book about cooking this way is: _The Fireless Cookbook_.

    1. Hi Peter,

      Good idea... I'd be curious if the light plastic wouldn't wither in the heat, cardboard or no. We've had some trouble with bottle plastics melting in water tolerable for handwashing. If you try it, let us know!

      Love those Firebox Stove containers... very well thought out and a good range of sizes.

      Dave Z

    2. A sufficient layer of cardboard between the Reflectix and the pot in the construction prevents much change in the aluminized bubble wrap insulation.