Earthen Oven Part II
Welcome to part II of earthen oven. This second part will take you step-by-step through the earthen oven construction. The components to the earthen oven are simple, and for the most part easy to find. You will need firebrick, sand, clay, newspaper, and straw. We went to our local masonry shop to obtain the firebrick and clay. The clay from the riverbank will work fine but is harder to tote and difficult to get the proportions right when mixing with the sand. This is the list of exactly what we used building the oven:
- 40 Firebrick
- 700 lbs. All- Purpose Sand (approx. 290 lbs. for the form, 400 lbs. for the oven, and another 10 lbs. to finish the mouth).
- 200 lbs. (dry weight) Fireclay
- One or two days of Newspaper
- About a quarter bale of Straw or the like
Note: You will also need and a tarp to mix the materials.
This is how we built the earthen oven:
- Form a firm base for the oven. Flatten out a spot of ground or build a sturdy foundation to build it on. Lay the firebrick out on the working surface. Try to get the surface as flat as possible because this will be the floor of your oven. We had enough thin and thick firebricks to make a second layer. This will further help to insulate the oven that much more, and clean up are yard at the same time. The oven we built is 32’’ x 45’’ which equals out to 8 bricks wide by 5 bricks deep.
- After the base is set, the next step is to build the form. Start by drawing out the general shape of the oven with chalk on the brick. Tie a piece of string to the chalk and pivot it around the base, making three circles. The first circle should touch both of the outer edges and back of the floor of bricks. Follow it by drawing another circle 3’’ closer in and then a final one another 3’’ in. This will be your template for the dome and the two layers involved. Draw a mouth to your template by centering two lines 4’’ from the edge with chalk. Them draw another pair of lines, each coming 3’’ closer to the center. Stop each line about 7’’ from the front edge. You will need that space later. So, the inside circle for your oven should be 20’’ and the mouth approximately 12’’.
- And now for the fun part, the building of the form with sand. This is where the shape of the oven takes place. You will need to do this the same day you build the first layer of your oven or the sand will start to dry and blow away. This tests your sand castle skills from your childhood. Add water to the sand until just wet and form a mound in the shape of the oven. Basically go as to a desired height, but follow this one ABSOLUTELY NESSASARY RULE: the height of the dome to mouth ratio must be between 60-65%. If the mouth is to high, the oven will not carry heat properly, and if the mouth is too low, the smoke will not draw and the fire will not burn well. We built our dome and mouth around 16’’ and 10’’ respectively. It is a good idea to place a board at the mouth of the oven to keep the front straight and square.
- Cover the form in strips of wet newspaper. This will make it easy to remove the sand later.
- Now it is time to play in the mud! Spread out a tarp or canvas and place sand and clay atop. It should be 2 parts sand to 1 part clay. Add water and start incorporating the mix with your feet. Get the kids out to do this, they’ll love it. The consistency you are looking for is something very workable, not sloppy and not crumbly.
- Start piling the mud on the sand form. Bring the mud nearly to the “second” chalk line, anticipating settling as you build up. Treat the mud like bricks, keeping the mud square and stacking it. After you complete the first layer, let set for a day or two.
- Now for the second layer. Scratch the surface of the first layer so this layer will adhere well. Mix the mud as before, but this time add some hay to the mix. This will act as rebar and strengthen the mud. Layer the same way as the first layer. After completion, again let set overnight before finishing the mouth of the oven.
- Remove the board from the front of oven. Mound the remaining sand to continue out another couple of inches. Place newspaper as before and then create a nice round mouth to your oven with some more mud mix.
- After the oven has stiffened some (around a week) dig out some of the sand from inside. Watch for cracking. Wait a couple more days if any form. Continue to remove a little over several days until empty. After the sand is out, the oven should start drying more rapidly.
10. Let dry before using it, this will probably take around 4-6 weeks, depending on the weather.
12. Before you bake your first loaf of bread, start a fire in the oven to get rid of the remaining moisture. Don’t be tempted to bake a loaf of bread in it (believe us, we know); the oven will simply not hold the heat with the remaining moisture.
13. After the first fire, cracks will appear on the oven. Don’t be alarmed. SImply rub some of the mud mix into the cracks.
You are done! The oven, though, as hard and durable as it feels, is literally made of mud and straw and will need to be covered from the rain by a tarp or some other source.
In part III of earthen ovens, we will show how to bake bread from it.