Make a Wooden Fuelless Cooker or Hay-box Using Scrap Wood and Hemp Wool.

The Hay-box or fuelless cooker was a very popular item around the turn of the 19th to 20th century, particularly during the World Wars and the Great Depression when people were often displaced and the price of fuel rose steeply and/or was rationed. Many cookbooks of the period had a chapter on recipes suitable for this type of cookery, so it's well worth a visit to a secondhand bookshop to see what you can find!

For anyone unfamiliar with this cooking method, the hay box or fuelless cooker uses residual (or retained) heat after the food has been initially heated to a rolling boil on a conventional stove, open fire, solar cooker or as we do - woodstove.

The best choices of meal for this type of cooker were/are stews made from cuts of meat which were cheaper and needed slow, low temperature cookery and which with hikes in coal and coke prices and the short supply of fuel, paradoxically had become expensive to cook. During the Wars there was also the problem of food rationing, which made it ever more important to avoid spoilage and waste. Hay-box cookers used less water and as the precious foodstuffs were cooked at an even temperature and by residual heat, this meant the food had no chance of burning nor becoming tough and inedible. There was also an added and even more important factor, in that nutrients were retained through longer cooking times and lower temperatures, thus even smaller amounts of meat, eggs, milk, fruit and vegetables for example, gave maximum nutritional value.

The popularity of hay-boxes and fuelless cookers however went much further back in history to a time of the great emigration periods of the early and mid 1800s, when people travelled vast distances and often only had time to light fires and cook in the evening and before they started their journey each morning. The slow-cook method using residual heat allowed them to get their stews and crockpot meals ready in the morning and cook them throughout the journey so as to have a hot meal at mid-day. Some years ago I made a cardboard box version of the fuelless cooker you can find that here: https://www.instructables.com/Cardboard-Cooker/ This version is fine as a 'quick fix' or an emergency back-up. In this Instructable I'm sharing how to make a more robust model which you can keep to hand in the kitchen or, as we show in the film, take in a car to provide hot, nourishing food on a journey.

There are two ways you can use a fuelless cooker, firstly you can use it to cook a whole meal, this was the way it was used in previous centuries both for men and women working in the fields and long distance travellers and how we used it in the film. Secondly, you can use it in your kitchen, to save energy when cooking a stew or similar dish, which requires slow cooking. We actually did this too with our cassoulet when we returned home in the evening, taking it from the box, where it was still quite warm and transferring it to our wood cooker. I have to tell you that after several years of making and eating this dish it was the best we had ever eaten! Furthermore we had saved on four hours of fuel.

UPDATE: There's also a third way, as quite recently I've seen an article on an ecological kitchen where a hay-box is incorporated into a kitchen drawer, so as to be a daily choice.

A wonderful 1940's instructional film showing how to make oatmeal porridge using a hay box. It was produced by Verity Films for the Ministry of Information. The hay box cookery starts at 1.34 but the whole film is just a brilliant insight into life in wartime Britain.

Our wooden box sits next to the telephone and is robust enough to act as a comfortable low seat. It was made using pallet wood and 10mm (⅜") thick pine cladding. This latter was left over from when I made our chicken coop last year. The insulation was 45mm (1¾") thick organic hemp and vegetable fibre, purchased in a 1250mm x 600mm (4' x 2') sheet for about $5.00. There are many other choices of natural insulation you can use including those shown above, which, from top to bottom comprise: organic alfalfa straw, organic triticale straw, organic vegetable fibre, organic hemp and linen, "Holzflex" wood fibre and organic sheep's wool. Many of these can be purchased directly from local farms and with such a small amount will be of minimum cost. Others such as Holzflex and Sheep's wool sheets are sold in alternative/ecological building suppliers for wall,roof and floor insulation.

I based the design of the box around our largest saucepan and for ease of loading when hot, the lower portion of the box was not much higher than the two handles on the side of the pan (as seen above). The box lid was deep enough to fit over the portion of the pan standing above the box rim.

Both the base and the lid were made in the same way, that is the vertical sections that made up the inner and outer walls were stapled to an upper and lower square frame, the width of the frame was the thickness of the insulation. 

I arrived at the box dimensions from the size of the saucepan. This size would be the minimum internal dimension of the box. To arrive at the outside wall height for the box base I had to add the thickness of the box bottom, the insulation and the thickness of the platform wood. I always tend to regularly check the measurements especially prior to cutting the wall material - better to be safe than sorry!

Four frames are needed (2 for the base and 2 for the lid). To ensure they are all exactly the same size I assembled them in a jig. I made this by screwing three straight pieces of wood in a 'U' shape to a piece of chipboard. The size of the U being the size of the frame and the corners at right angles.   

Select the pallet wood for the frames, cut to width (that of the insulation thickness) plane it smooth and cut to length.

Position the two vertical legs of the 'U' against the sides of the jig and check that they touch the bottom jig edge, apply wood glue (PVA) at the corners and put the third, horizontal part of the 'U' along the corresponding jig edge. Ensure that all 3 pieces are pushed firmly against their guides and staple or nail where they overlap. Turn the, now joined three wood pieces around in the jig so that the fourth, open side of the 'U' is sitting against the bottom jig edge. Once again glue the corners and position the fourth piece of the frame on top and staple or nail.

 The reason I used a 'U' shaped jig and not a complete square is that it is much easier to remove the frame by sliding it out rather than trying to lift it.

Repeat for the other three frames and then stack all four frames and clamp at each corner and leave to dry.

Each picture above corresponds to the paragraphs below:

The bottom face of the box has pallet wood planks nailed to the frame to form a solid support.

Turn the base over and cut and fit two extra pieces of wood to the frame. This is to furnish a vertical face to which the box walls can be attached.

The saucepan is to sit on an insulated platform made to fit into the square recess created in the previous stage. The platform is about 20mm ( ¾") smaller than this recess to account for the wall thickness and is deep enough to fit a square of the 45mm (1¾") thick insulation beneath it. Being removable it can be taken out and cleaned if there is any spillage.

Now comes the clever bit, I already know the height I need for the box base so I measure the internal wall height and include the height of the insulated base. Cut the 10mm (⅜") cladding to this length.

Use panel pins to attach the walls to the base. Ensure a good fit at the corners.

The base now looks like this. 

Prior to fitting the top frame to the base, attach two additional wooden pieces, so as to make a flat surface to the frames upper face.

Nail, or staple the top frame to the walls of the base. (two images)

The box now looks like this. The outside walls can be cut to length and the insulation cut to size for the walls and the insulated platform.

The insulation should be a good, close fit to ensure maximum efficiency.

Attach the outer cladding. I tend to use the stapler because it's less tedious but panel pins are fine.

Cut two carrying handles and fix to the box, screwed through the walls into the upper frame.

The insulated platform can then be dropped into the completed base.

The construction of the lid is similar to that of the base except that the top outer cover of the lid is put on last. I found that this makes it easier to attach the inside walls to the frames.

Again each image above relates to a paragraph below:

Firstly, cut the interior walls to length, which is the height of the pan and lid projecting above the box base plus the insulation thickness and the thickness of the cladding covering the insulation.

Fix the interior walls to the lower frame........

............and the upper.

To make the space for the insulation at the top of the lid cut two 45mm (1¾") wide pieces of wood to the internal dimension of the lid and wedge them in place at the top of the lid, with a few millimetres protruding above the uppermost face.

Cut cladding to fit to these two pieces and attach. The cladding must not overlap the edges.

Remove this assembly, turn it over and put it back into the lid top. (two images)

Tap it flush to the upper face of the frame..........

..........and attach to frame.

Cut insulation for walls and top, cut cladding and attach.

Cut and attach two handles, securing them, as before, by screwing them to the upper frame.

To ensure a snug fit of the lid to the base, cut four pieces of fruit crate wood (5mm - ¼" pine), to fit around the inside of the lid perimeter and chamfer one edge of each piece.

Staple, or nail these pieces to the inside wall of the lid, chamfer facing out and protruding about 10mm. This acts as a guide to align the lid to the base and produces a more effective seal to prevent heat escaping.

Now if you want to, watch the film of the construction and our road test at the sea side.

Cheers and Bon Appétit!

Andy