DIY Kitchen Appliances

June 21, 2011

Living up in the mountains with the nearest road a good ten minutes walk along a steep forest path it is quite extraordinary that we have mains electricity. I imagine that nowhere else but Japan would a utility company go to such lengths to get a house on the grid. Its true this connection allows us some modern comforts – well, three at least: laptop, lights and a refrigerator (whose days are definitely numbered) – but, had we been the original occupants we probably would have opted to stay off the grid. Right from the time we first moved here we have discussed options for generating electricity ourselves, at first in the context of long-term plans but following events at Fukushima these discussions have gained some urgency. Reasons for generating our own electricity are hopefully too obvious to warrant comment but why detach from the grid altogether? Our grid is owned and operated by Tepco (the Devil itself!).

Although the micro-hydro system we would like to have generating the few kilowatts of electricity we need might still be a little way off we have been working on some super low technologies to better align our energy use with our circumstances and needs.

The previous occupant of our house seems to have done most of her cooking by gas. Convenient if you live in a city, or village, or just if there is a road nearby, really. Far less convenient when the gas bottles have to be carried on your back up in to the mountains. Also when you live in the midst of a forest there tends to be an abundance of fuel, everywhere. And, of course, you gotta pay for the gas (and which friendly neighboorhood corporation will be taking your money this time?).

Rice Cooker

To reduce overall fuel consumption the first cooking appliance we built was a heat retention cooker (HRC). These brilliantly simple devices – sometimes referred to as ‘haybox cookers’ due to the insulation material originally used or by us as our ‘rice cooker’ due to what we mostly use it for –  are certainly one of the most effective energy-saving cooking devices around. Using the gas rice cooker that we inherited with the house it took around 35 – 40 minutes of fuel usage to cook one days supply of rice plus another 10 or so minutes each time we wanted to reheat the rice. With the heat retention rice cooker it takes around 10 minutes of fuel usage to generate enough heat to cook the rice and 3 – 5 minutes to reheat it (the HRC will keep the rice warm for the best part of a day but we avoid doing this due to the risks of bacterial growth in a constantly warm environment). Keep in mind the times I have given are for fuel usage not cooking time [see below].

The principle of the HRC is simply that you heat food in a pot then place the pot in the HRC (an insulated container) which traps the heat emitted from the food in the pot and uses this heat to cook the food. Essentially it’s a sort of slow cooker so can be used for anything you might cook in a slow cooker such as grains, beans, stews, casseroles etc., or anything you might  use an insulated box for such as making yoghurt or keeping food warm.

A couple of cardboard boxes, wood ash, a sheet of styrofoam-like material backed with a reflective material (used in Japan for covering bath tubs to keep the water hot), tape, a bag of batting an old blanket.

We used wood-ash as an insulator because we have it but other insulating materials could be corrugated cardboard, old blankets, polystyrene type packaging materials… As most of the heat escapes from the top of the box this must be insulated well hence our two layers of corrugated cardboard covered with the reflective material, the batting inside a plastic bag (preventing it from becoming moist and smelly) and the old blanket over the lid of the cooker (added mainly to hold the lid down but gives one more layer of insulation to the cooker). It is well worth lining the inside of the box with some sort of reflective material as this will reflect the heat emanating from the pot back at the pot.

The model we designed and built might seem a little over engineered but it works so well I would say the little extra effort and materials  really paid off. Before making our HRC we had read that brown rice would require 10 to 15 minutes boiling then 2 hours in the HRC. We boil our brown rice for 5 minutes and after one hour in the HRC it is perfectly cooked (this is only 15 to 20 minutes more than most electric rice cookers!). It’s true that our cooking time is improved because we sprout the rice before cooking but no matter how you cook it brown rice should be soaked for a long time or, better, sprouted.

The Macrowave

Another simple device we have built is a solar box cooker.

Two boxes, a sheet of glass, some aluminium foil, wheat paste, tape and a blackened pot.

We completed the solar cooker just as we entered the rainy season so we haven’t had many opportunities to use it yet. But on the rare sunny days that we have had over the past month it has performed reasonably well. Putting a pot of water on in the morning we have boiling water for morning tea. Nothing but beautiful rays of sunshine…

The dimensions of our solar cooker were determined by the piece of glass we had and it is a little smaller than ideal. Not shown in the photograph is a ‘splash plate’ of aluminium painted flat black that sits under the pot. It’s critical to use blackened pots in solar cookers as they make an immense difference to the cooking time.

For the low down on all things solar cooking including plans: solarcooking.org

The Rocket

Our latest DIY cooking appliance is a little rocket stove. With just a handful of sticks it burns really hot producing very little smoke. Since we introduced the rocket stove to our kitchen set-up we have almost entirely ceased using the gas cooker. [Update, June 2012. Shortly after this post was written we did cease using the gas cooker entirely. It has been in storage for around 10 months and not missed at all.]

An old commercial size soy sauce can, a length of stove-pipe, a stove-pipe elbow bend, a tin can, wood ash.

A rocket stove maximizes combustion and heat transfer efficiency. In a well built stove all the volatile gases released as the wood gets hot will be combusted. This occurs when there is sufficient temperature. To attain the necessary temperatures the stove is insulated with low mass, heat resistant materials (wood ash, again, in our case). The complete combustion of the volatile gases results in virtually no smoke being emitted – a cleaner, more efficient use of wood as cooking fuel.

Rocket stove before the addition of wood-ash insulation

Although our little rocket stove works brilliantly we’re planning a new improved model already: multiple burners with high, medium and low heat, raising it to table top height… At present we use ‘risers’ to elevate our pots above the flame when we need to ‘turn the heat down’ and when we want to turn it right up we have a ‘skirt’ that fits snugly around the pot and directs the heat vertically up the sides of the pot increasing efficiency. [June, 2012. We never did get around to making that fancy new improved model. Instead we learned how to cook well on a single burner. Having the HRC in combination with the rocket stove has worked well as we can keep a dish warm in the HRC as we prepare the next dish on the rocket.]

Video tutorial on making a rocket stove

The Rocket Stove Principle

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4 Responses to “DIY Kitchen Appliances”


  1. This is a really neat post! My son made a solar cooker a few years ago that looked like a radar hood as a science project, though yours looks more practical. We are thinking of adapting your design using more waterproof materials, and fitting one on our deck. Thanks for posting!

    • dion Says:

      I think a more water proof or moisture resistant version of the solar cooker is a good idea for Japan. The cardboard makes it nice and light so its easy to move around and keep out of the rain but the humidity here in Japan is a problem. The cooker shown in the post has been slowly falling apart just from the humidity!

      Here is a technique for waterproofing a cardboard cooker using glue, wax and fabric.
      (Scroll down to the ‘General’ section.)

      If you are going to keep it in the same place all the time then making it from sturdier materials is a good idea.

      The plans for the cooker in the post.

      I also made a UFO – a parabolic solar cooker – but I found that it was very unstable and I nearly blinded myself every time I went near it!

      I’ve been really enjoying the posts about the Jomon on your blog. I look forward to exploring the rest of it.

  2. Craig B Says:

    Can you use the rocket stove indoors? If so, any special ventilation requirements?

    • dion Says:

      Craig,
      if you want to use a rocket stove indoors it is best to use a flue. For this the stove design featured in my post would need to be modified slightly.
      Although there is little smoke once the fire is going a fair amount can pour out while getting it started. Also, visible smoke is not the only thing you need to be concerned about so either a well ventilated space or a modified design with a flue is necessary.


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