How to make an Earth oven

There are different instructions on how to make an Earth Oven. Kiko Denzer has written a book about it but I wanted to make an Earth oven that would cost 0 yen, if it does not work than I will buy the book. 

I did some research online and found some useful information, I also talked to Ryo-san (my neighbor/landlord) about the Islands soil and history. The Island possesses a red clay looking dirt, some people have tried making an earth oven with it but it tends to crack. On my research I found out that sand is helpful to keep it together. I thought of using beach sand but it does not recommend soft sand, rather river sand which helps it keep together. 

Step 1

MAKE EXAMPLE BRICKS

 Mixing dirt and sand at different ratios. I made 3 tiny bricks with my hands and the dirt I had in my yard. 1) dirt only 2) dirt and tiny bit of sand 3) 2:1 of dirt and sand. Let it dry under the sun for days. The toughest looking one was the number 3. 

Step 2 

MAKE A BASE

You want your base to be at hip height so when you are cooking and making the fire you don't have to hunch every time. Use stones and dirt for the bottom of the base and on the top you want to have a bed of sand. It is important to keep the oven in a dry condition and that is what the sand is for. 15cm of bed sand will do, any kind of sand here. Make sure it is a parallel surface and it is not tilted. Layer red bricks or fire proof bricks. I couldn't find either so I used bricks made out of cement. 

Layer of stone, sand and bricks

Base

It took me a two days to make the base. The stones I had to bring from the beach on the car and then bring each of them from the parking lot down hill to our home. After doing this it took me weeks to gather the energy and finish it up. 

STEP 3

MAKE A DESIGN PLAN FOR THE OVEN

1) Based on the area that I could play with I designed the size of the oven . I did not have much space to play with so the oven was going to be small. For a beginner like me I think small is good, in case it goes bad than your hard work is less than if you had made a bigger one.  

The Diameter: 56cm

Height: 30cm

The height of the oven cannot be bigger than 2/3 the diameter of the oven. 

2) The oven has 3 layers. In the information I found there are many ways of making it but the more research I made the more it seemed that the thicker the layer the better it is for keeping the heat in the oven. 

Layer 1- The Dense layer- Thermal mass is made of mostly sand and a little clay. 3-4 inches

Layer 2 -Insulative layer - Helps keeping the heat, made of straw, sand and clay.

Layer 3- Structural strength layer - Similar to the first one but with straw. 

3) The door- The doorway cannot exceed 63% of the total height of the oven. 

4) Make a draft of your design and layering. Draw the layout on your base with a crayon to keep track of the layers as you build. 

I scaled it to see the real size and how big my pizzas were going to be.

Then I drafted the design on the base.

Step 4

MAKING A SAND CASTTLE

To be able to hold the shape of the vault you use the support of a sand castle. For this I used very thin sand from the beach. This is fun and easy. 

Once you are done with that you cover it with a plastic bag, this is to help you dig out the sand from the inside and also to be able to stick your finger while making the layers and making sure that all around it has the same thickness. 

Sand castle

Cover sand castle with a plastic bag

Step 5 

BUILDING THE EARTH OVEN 

1) Layer 1- Mix clay and sand. The proportions recommended were 2:1 sand to clay but as I was mixing the two it seemed too much sand so I turned the equation the other way around to 1:2 sand to clay and a bit of water. Spreading a plastic sheet on the ground and stepping on the mixture with your naked feet and dancing to some twist and salsa. Make sure you mix both ingredients well, pull the edges of the sheet and fold the clay and repeat that as many times as it takes. At first I intended to make the layer 6 cm thick but it ended up being 4cm thick. 

Clay mixture.

Cut the door with a knife or some other tool that is thin and sharp.

2) Layer 2 - Mix clay, straw and sand. It recommended to have equal proportions of 1:1:1 but I mixed in less sand this time too. I do recommend that you follow your instincts and feel the texture of the mixture, also if you want to test it, make balls and throw them to the ground from chest level, it should stay together. There is no straw in this Island so I used a local palm tree trunk material that was strong and thin. 

What I used instead of straw

layer 2

layer 2 finished

Layer 3- Similar mixture to layer one but with straw. I did the same mixture and didn't add the straw. I made enough to be able to design something around it. 

 Step 6 

HEAT THE OVEN

Once you have finished the oven than you can heat it. Now it is important to heat slowly and many times before you start baking. Also I think it is better to have a rook on top of it to make it last longer. I named mine the Wahippo Wahiki. Get inspired and create your own oven. It is also important to consider your environment when you build one. If you are trying to be an eco conscious person and the forest around you is being deforested than cutting more trees will not help. To heat an oven you will use a lot of wood. In this Island there are cutting down the pine trees because they are alien invasive species and therefor there is abundance of it. The oven also creates CO2. But if you are in good position to build it than it is a fun project to do with your friends, family and loved ones. It is not that difficult to make but it does require energy :)