Developing a fireless oven for retained heat baking and roasting

The fireless oven is an extension of the haybox concept, except it strives to roast and bake via heat-radiating substances instead of boiling everything in a relatively large quantity of water.  In the 1910s, the heat radiating substance was soapstone.

Several months ago, I bought two soapstone fire bricks to experiment with but for prepping purposes, I didn’t have a sensible method of heating the bricks. That seems to have changed with the “free energy” rocket stove.

This morning with the outdoor temperature at 40F degrees and sunshine, I wrapped a room temperature soapstone brick (about 1 1/4″ thickness) in aluminum foil to prevent soot buildup and placed it on the cold rocket stove.

The 1913 book, The Fireless Cook Book by Margaret Jones Mitchell advises to heat new soapstone radiators slowly the first time, after which they are safe to heat more rapidly, so I built my little fire up in the stove accordingly.

The test to know when your soapstone brick is ready for baking is to sprinkle a wee bit of flour on the surface.  When the flour begins to brown, the brick is hot enough.

This occurred in 25 minutes of lighting the first twigs and gradually building the fire.  The top surface of the brick registered about 469F degrees.

The energy cost to heat the brick was zero. Possible downside is that you have to feed small fuel into the stove fairly continuously.  For me, that was amusement, not a downside.

Finishing this project won’t be particularly cheap as unlike the haybox or Wonder Bag, the insulation has to be non-combustible.  So for that I’ll go with ceramic wool furnace insulation, but it’ll take me awhile to get where I can actually bake with bricks!  I must say I am motivated!

One last note.  We have a cooking option that Ms Mitchell did not – Reynolds Oven Roasting Bags.  I put a 3lb chuck roast and veggies in a bag and submerged it in a large quantity of boiling water to make a pot roast in the haybox the other day.  The roast cooked in its own undiluted juices and came out perfect.

I checked the safety of the bags.  No toxic chemicals are released into the food from the nylon Reynolds bags.


  • Comments (5)

    • 2

      Awesome! Thank you for reporting on your tests with this — I look forward to hearing more experience as you are able to share it.

    • 1

      That’s a very cool concept. I think it will need to be very well insulated so the heat from the bricks can keep radiating into the food for a long period of time with as little wasted into the atmosphere. 

      Do you think that if you placed the brick into a haybox of shredded paper like the one I built, that it would catch the paper on fire?

      • 3

        The 1913 Fireless Cook Book instructions call for using asbestos for the insulation, with the cooking “chamber” being some sort of metal bucket nestled into the insulation.  I would say trying the hot bricks with any combustible or melt-able insulation would probably be dangerous.  That’s why I will use ceramic wool (such as Kaowool) to insulate the box.

    • 1

      What about an horno or earthen oven? If it can stay static, a small one might be able to do the same thing, collecting heat from a fire, then holding it for a long time to bake breads and things.

      They still use them out here in the southwest.

      It would be cool if they could be adapted to use alcohol stoves, small rocket stoves, and propane

      • 2

        I’m always looking for indoor cooking options.  For tonight, we’re expecting howling winds, zero-degree wind chills, followed tomorrow by snow and freezing rain (and wind) into Friday morning.  If necessary I could heat the bricks in the wood stove and never have to go outside to cook if the thermal oven is in the house. 

        Oh, and the lovely preps that are all staged for the upcoming weather and attendant power outages!  :o) Let ‘er buck!