Make a Thermos Cooker

[TWP]

There are commercial units available and many people make these using fabric and insulation.

This design uses cardboard boxes and bubble wrap insulation.

You will need a pressure cooker for this.  It might work with a simple lidded pot, but the pressure cooker allows for much higher starting temperatures, which effects cooking time.

https://survivalblog.com/a-homemade-thermos-cooker-by-m-p/

The article also includes some recipes and detailed instructions on cooking time calculations for this particular design.

DO NOTE the inverse relation between the amount of food used and the cooking time.  It may be counter-intuitive, but more food means LESS cooking time.  Read the article for an explanation.

[230gr]

Retained hear cooking is an important part of my food preparation planning. I will use stock pots fitted into cardboard boxes lined with 1" styrofoam using spray foam insulation to "round the corners". The pots will be placed in plastic bags first so they won't stick. Oatmeal, rice and various grain porridges or gruels are boiled and poured into the cookers the night before to be ready for a hungry crew in the morning.

Also for cooking beans and keeping meals hot for the night security and other personnel who may not be able to attend regular meals.

Wood is a labor intensive resource that must be used wisely and this is one way to do it. 

[TWP]

I note that using a pressure cooker will mean that the pot can easily be hotter than the boiling point of water (212 F - 100 C ).

Some plastics will melt at fairly low temperatures, so a test run is a good idea, before you have to scrape melted plastic off the outside of the pressure cooker...

This is less of a problem with Non-pressure cooking, ie. the max temperature will be (usually) the boiling point of water.

If you forget and boil the pot dry before inserting into the "thermos" you could still melt some plastics...

[230gr]

   
My understanding is that Polystyrene melts at 410 to 480 °F although it softened at around 284 °F. So sheets should be ok but a few thicknesses of cardboard or old paneling would protect them. Temperature will drop to 100 to 120 oF after 12 or 14 hrs anyway (just right to eat) and stock pots are much cheaper than pressure cooker and much lighter to handle too.

[TWP]

You're correct and I misunderstood, thinking that you had plastic in direct contact with the pot.

The cardboard lining is a good solution and should last for many uses.

Reading the original article, the author seems to be saying that the pressure cooker lets you reach higher internal temperatures and hence shorter cooking times and, perhaps, use less fuel for the initial heating cycle.

I would need to practice this, using a real wood fire, and the apartment managers and owners have problems with me building campfires.  They're not preppers, what can i say?

[230gr]

pressure cooker lets you reach higher internal temperatures and hence shorter cooking times and, perhaps, use less fuel for the initial heating cycle.

Was not thinking of short term cooking as such because, one the wood stove is fired up it, stays hot during the pressure cooker's run.  My thinking was for the low and slow cooking overnight and as a way to keep food hot enough to not spoil between meals.