Hot box, wonder box, straw box, or thermal cooking

Hay box cooking without the hay or a box

Hot box, wonder box, straw box, or thermal retention cooking

I discovered an old-fashioned, low-tech method of “cooking” that I was hesitant to try at first. It sounded too good to be true. Cook your food part way, then put it in a simple contraption, walk away, and it would finish cooking and never burn.

What? As in: no need to keep stirring, no need to stick around, no need to pay attention to it?


So I began to do some research. Thank the gods for the internet, and online video. Whatever did we do without it?

The method is called hot box, wonder box, hay box, thermal or heat retention, or thermal cooking. I found articles and videos and even really old books that described various methods, tips, and tricks. I’ll summarize them for you here.

First off, you can use anything. Of course, commercial products are available, from stainless steel cookers with insulated carry bags, to filled cushions (polystyrene beads, or cedar shavings from the feed store) and draw-string pouches. Then there are homemade versions of the commercial products.

One old method was to line a box with hay; thus the name, hay box. Another method is to dig a hole, put your pot in it, and cover it with soil or sand, which would insulate it.

And then there are the low-tech, jerry-rigged things that I prefer, because you get to use your creativity and figure out what works with what you already have. Cost = free. Gotta love that!

A box, laundry hamper, or cooler, with blankets, newspaper, cardboard inside–put your pot in that
Bury your pot in a hole in the ground
Wrap your pot with blankets, sleeping bag, pillow, towels (no box needed)

Second, understand the principle:
Heat escapes from around a pot when you are cooking on the stove. If you can preserve that heat and keep it around the food and the pot, cooking will continue, without adding more heat. So use insulating material, which traps air around the pot.

Low-tech, hot box cooking

How to use thermal cooking:

Get a large box, cooler, or laundry hamper. Put a blanket or sleeping bag inside it, opening it up fully. I fold my blankets in half or fourths, just to make handling easier, then put a second blanket, aligning it perpendicularly to the first, like a cross, so I can wrap from all four sides. (See the diagram).

Place several sheets of newspaper, opened up, and then pot holders in the bottom, to prevent scorching. This also helps prevent fumes from synthetic blankets and reduces the chance you’ll melt it or other insulating material.

Start cooking your food normally, on the stove.

Turn off the stove.

Place your pot of food, with a tight-fitting lid on, inside your nest of blankets, etc.

Fold the blankets or sleeping bag to fully cover and envelop the pot.

Leave it as you go about the rest of your business.

The first time I tried this, my food did not cook all the way through. So more internet search lead me to the following…

Important details, tips and tricks:

  • Let your food come to a boil and cook on the stove until it’s at least halfway cooked. This will ensure it cooks all the way through. Otherwise, you may come back and open your pot, expecting a ready-to-eat dish, but it ends up being not fully cooked.
  • Keep the lid on your boiling food for several minutes prior to putting it into your thermal cooking setup. If you lift the lid to check the contents, you will let out all the heat.
  • Make sure your lid is tight fitting.
  • Set up your hay box/blankets/etc. near the stove, so it’s easy to move your pot to it. BUT, keep this well away from the stove or burner, to prevent a fire.
  • Place this somewhere your pets or other animals cannot get into it. Also, keep it out of reach of children. Make sure there is nothing that they can pull on.
  • A thicker, heavier pot will maintain heat better than a thinner one.
  • Use this to cook soups and stews, which can be overcooked and not suffer in quality. Something like pasta doesn’t work as well, although it is possible. Things that work in a slow cooker tend to do well.
  • To figure out timing, estimate that you will need between double and triple the time remaining. In other words, if your recipe calls to cook your soup 30 minutes, or until the carrots are soft, and you cook it for 15 minutes, then put it into the thermal cooker, you would need another 15 minutes of stovetop cooking. But double or triple that, so estimate 30 or 45 more minutes, and you should be good.
  • Food will stay very hot for many hours. Be careful when you open your thermal cooker. Use pot holders.
  • Insulation material can be anything that traps air. Corrugated cardboard, newspaper, either flat or crumpled, hay or straw, dried leaves, packing peanuts, dirt, sand, wool, fur, feathers.
  • You are trying to trap air, so multiple small pockets of air work best. Also, place the insulating material right up next to your pot. Do not leave large air spaces. If you are putting a small pot in a very large container, have pillows and blankets, or even towels, to fill the gaps between pot and container.
  • Beware when using synthetic materials that they do not give off toxic fumes when heated. Also, be sure they won’t melt next to your pot. I use those few layers of newspaper between my fleece blankets and the pot and have not had a problem.
  • Presoak and drain dried beans if you are cooking them. But because they generally require very long cooking times, I prefer to cook them in a pressure cooker instead of using thermal retention cooking.
  • You can use this if you cook with a solar cooker, but the weather changes, and you don’t want to resort to stovetop cooking. Put the food into a thermal cooker to retain heat and finish cooking.
  • You can also use this just to keep hot foods hot until serving time. For example, some people put finished casseroles in a thermal cooker, to stay hot and transport to a party or gathering.
  • Preppers, take note: this works well in a grid-down situation, or when you have to limit the use of fuel you use. You need enough fuel to boil your food a few minutes, and then it can finish cooking in your retention cooker.
  • I’ve not tried it yet, but I also have heard you can do this to keep cold or frozen foods cold, because it keeps cold air close to the food. This might be a good idea for transporting groceries home in the car…
  • Note: moisture will collect in the insulation material, so be sure to air it out and let it dry after use, to prevent mold.

Useful links
Here are some websites and videos to help you.
Has some general information, plus recipes, info on a few different types of cookers
Some methods to try, plus a plug for a commercial cooker
Long but very comprehensive video, with various examples
How to make a homemade wonderbox
Another one
Sewing a segmented, drawstring-type wonderbox
A jerry-rigged cooler
How to make a wonderbox, plus tips for baking and several different foods

I use this whenever I can, especially when it’s hot. Give it a try, and see if it works for you. Please leave a comment if you’ve discovered any other tips and tricks. Happy thermal insulation cooking!

…that doesn’t sound as fun as “Happy hot pot cooking!” does it? Haha.

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