Thermal Cooking—What It Is and How It Works

My friend Shawn was teaching a class on food storage and preparedness a couple of months ago, and for her first class she chose to demo a thermal cooker.  These units are running between $60 and $200 on Amazon right now.  They’re definitely out of my price range, and besides, I’d rather spend the money on food and medical supplies, especially when a thermal cooker is easy enough to make at home.  However, the DIYing will be left to another post.  Today we’ll cover the process of thermal cooking itself.  Then you can decide whether you want some kind of thermal cooker.

What is Thermal Cooking?

Thermal cooking means “cooking with heat,” and if you are like me, you think of a little something sarcastic to say, like “Isn’t all cooking done with heat?”  So a little more helpful explanation might be that a thermal cooker works like a slow cooker, but without electricity or any other form of energy.  It sounds like just the kind of thing we may need as energy costs skyrocket and the powers that be wish to control our energy consumption.

While playing along with their agenda is that last thing I’d ever want to do, it’s always a good idea to have different options for cooking food.  And thermal cooking was a common practice during World War II, when energy had to be conserved.  It’s a practice that may become popular again as our energy costs soar.  Thermal cooking can be used to prepare a meal without heating up the kitchen in summer and saves about 80% in fuel costs.  It saves another estimated 60% in water consumption, which is critical if water is in short supply.

In addition, there are a couple of other advantages to using a thermal cooker:

·       No burned food.  Once the food is in the thermal cooker, it can’t burn. 

·       Like with a slow cooker, the food can cook while you do other things.  You can even leave home without any concerns about a fire breaking out or food burning.

·       If you are cooking with firewood, you don’t need anywhere near as much.

There are a couple of cons to using a thermal cooker, but they’re not huge.  The first is that food takes a lot longer to cook, up to several hours.  The second is that some foods just can’t be prepared in a thermal cooker—things like cookies and sautéed vegetables.  And recipes that involve thickening sauces or gravies have to be adjusted. 

How Does It Work?

The food is boiled on the stove for 2-20 minutes depending on what it is and then covered and placed in the thermal cooker.  (See table.)  Thermal cooking is ideally suited to preparing stew, chili, and soup.  It makes incredibly tender meat.  A thermal cooker can also be used to bake bread or culture yogurt. 

To use a thermal cooker, cook the food on the stove for the amount of time indicated in the table below, choosing a pot or pan that is just large enough to hold all the food without boiling over or spilling.  You want as little airspace as possible in the pan.  Place a large potholder inside the thermal cooker (if your chosen cooker recommends it), and put the hot pot on top.  Close the thermal cooker as directed.  Then walk away and let the thermal cooker work its magic. 

A good thermal cooker will cook the food and keep it hot for several hours.  In all cases (except when making yogurt), the food should be cooking at or above 135°F.  Once the temperature drops below 135°F, it must be consumed or refrigerated within 2 hours.  Otherwise, you run the risk of incubating bacteria and creating ideal conditions for the development of food poisoning. 

As previously mentioned, with a thermal cooker there is no loss of moisture, unlike with conventional cooking.  As a result, sauces and gravies will not thicken, and so it is necessary to either reduce the amount of moisture used in preparing the meal, or flour or another thickener will need to be added. 

 

Thermal Cooker Cooking Times
Food	Time on stove	Time in thermal cooker
Chicken	15 minutes	3 hours
Beans, dry (soaked)	10-15 minutes	3-4 hours
Other meat	20 minutes	5 hours
Potatoes, whole white	5-10 minutes	1-2 hours
Rice, white	2-5 minutes	1 hour
Rice, brown	10-15 minutes	2 hours
Soups, creamed	2 minutes	1 hour
Vegetables	5 minutes	1 hour
Yogurt*	Begin at 120°F	4 hours

 

Links to related posts:

Global Sun Oven  

References:

https://www.amodernhomestead.com/wonderbag-non-electric-slow-cooker/

https://prepschooldaily.blogspot.com/2022/08/make-wonder-bagwonder-oven-thermal.html

Recipes:

https://www.wonderbagworld.com/recipes/

https://www.livinglekker.com/wonderbag-favorites

https://www.youtube.com/watch?v=4GuCj9CpjxU

https://www.youtube.com/watch?v=UIvB_qZmH4A