How to Build an Earthen Oven for Baking Pizza and Bread

An Earthen oven is easy to build but it may take some practice to make the perfect oven.

Simple Earthen Oven

The three basic steps for making an earthen oven are:

  • Prepare a pile of wet sand, and give it the shape of a hemisphere
  • Cover this shape with one or more layers of mud
  • Open a vent and remove the sand

If you dry it by lighting a fire, you can bake it tomorrow. To cook, light a fire in the oven without applying a seal over the mouth. Then, clean the oven of embers and ashes, bake bread, meat or vegetables, use something to close the mouth, and wash your hands for dinner.

The principle on which all the work is based is that clay is extremely common, being one of the main constituents of the earth's soils. In most soils there is a layer of clay just below the surface layer. So if you have a garden, and you feel like digging, you will most likely encounter a layer of clay, which you can use to build your oven. Clay is fairly easy to recognize.

Common earth, or organic matter is floury or crumbly.
It is often necessary to improve a clay soil if we want to grow vegetables, but to build an earthen oven, pure clay is what we need most.

Clay is sticky, slippery and vaguely greasy (and hard to dig even with a Backsaver Autospade). When it is wet it is easy, by rolling some between your hands, to create those little snakes that potters call columbines.

Where to find the clay to build an earthen oven

There are many tips on how to recognize, treat and use natural clay.

However, for those who don't feel like digging, or who simply don't have a piece of land, but only a barren boulder or paved yard, common potters' clay, mixed with sand, is an excellent substitute, almost as cheap and certainly less labor intensive to source. The average proportion is one part clay and two or three parts sand, depending on the quality of the clay.

Speaking of sand, even if you live near the sea, use the sand sold by building material distributors. First, because taking sand from the sandy shores is a crime, second because the quality of sea sand is not right (among other things, there is too much salt), third because building sand is really cheap.

Let's take a look at the construction process

Having created the base for the kiln according to the simple procedure described earlier (but for a quick test, you can also use a pair of sturdy trestles and a plank or sheet metal top) place refractory bricks on a light layer of sand.

Try to get a flat, smooth surface, without using mortar of any kind and without allowing sand to penetrate between the bricks. Refractory bricks generally have a smooth side and a machined side with an inscription or mark: the smooth side should remain visible, while the machined side will lodge in the sand, for greater adherence and to have a hob without roughness.

Next, with wet sand, create a hemisphere, a little wider than high, that has the dimensions of the inside of the oven you want to build.

You cannot build huge ovens with this system: about 24 Inches (sixty centimeters) in diameter is the maximum we feel we can recommend, for the first test.

With this diameter, the dome should be no more than 16-20 in (40 to 50 cm) high. The process is the same as that used to build sand castles or volcanoes on the beach, nothing difficult.

Only, care must be taken that the shape is as regular and smooth as possible. Once the sand dome is finished, do not let it dry too much, proceed immediately with the clay and sand covering.

It may be a good idea to arrange a few sheets of wet newspaper all around the sand dome: it will be useful, when you go to dig out the sand, to recognize the boundary between the sand and the lining clay, which is not entirely easy to the touch.

Next, proceed to lay down the first layer of clay. Some caution will need to be used here, lest excessive pressure deform or precipitate the sand form (which is quite strong anyway). Press the clay on itself, rather than toward the sand form.

For the thickness of the clay layer, adjust with the size of your palm. Carefully continue adding clay until you reach the ridge of the dome, and cover it completely. It does not matter if the outer layer is uneven or rough, the important thing is that the thickness is as uniform as possible and that it adheres well to the sand form. If the clay tends to run off, it means it is too wet; if it crumbles or separates, it means it is too dry.

Having completed the dome, you can move on to carving the vent. If the mixture of sand clay and water was right, you can also cut the mouth immediately.
When in doubt, it is better to wait, but not too long, otherwise cutting the opening will become difficult.

Mark the size of the hole's vent on the clay dome with any sharp tool, remembering that its maximum height should be about 60/65% of the total inside height of the kiln.
Start by opening a hole large enough to fit your hand through, and remove some of the sand. Digging an internal channel that is not too large will help dry the dough without too much compromising its stability.

Through the hole, assay the internal strength of the clay walls: if they are firm and strong, you can proceed further. If, on the other hand, removing the sand causes everything to collapse, don't worry: next time it will be easier...

To cut the opening you can use a sturdy metal knife or something similar. In any case, whether you decide to cut the spout right away, or to wait a while, your oven needs at least one more layer of lining. The layer you just made is the cooking layer, the one that will hold the heat from the fire and return it to the food being cooked. You now need a layer of thermal insulation, which will keep heat from escaping to the outside.

A mixture of clay and hay straw is often used for this coating layer, just to stay in the environmentalist tradition that traces the construction of this type of oven back to ancient civilizations.

If you have such enthusiasm, I invite you to knead mud and straw with your bare feet, as the ancient Egyptians did with their bricks; alternatively, a mixture of clay and vermiculite or perlite, or pure clay mixed with expanded clay, can be used.

If the first layer of your kiln is very smooth, score it with a fork or something similar to create a rough surface that will facilitate adhesion between layers. Proceed in the coating in the same way as for the first layer, but increase the thickness by at least a third, again taking care to spread an even amount over the entire surface.

If you feel up to it, at this point you can also shape the oven vent, creating a small invitation, or a tunnel that can be used to insert a chimney. These ovens, like all ovens moreover, can work just fine without a chimney, but its use makes the baker's work more comfortable.
If you have not already done so, completely empty the oven of sand, cleaning it away thoroughly.

The last layer of lining will serve to protect the kiln from the elements, and will allow you, if you feel up to it, to give vent to your sculpting inspiration. A thin layer of the finest clay and sand will form a kind of hydraulic plaster, which will give the kiln its final shape. If you want a smooth surface, wait until the last layer is almost dry, then work it in with a sponge or a freshly dampened rough cloth. If you want a very plastic material that you can work with to give artistic shape to your kiln, there are those who suggest mixing clay with dried manure from grazing animals, which contains plant microfibers that improve strength and workability.

Now you need to let it dry in the kiln, which can take up to several weeks. If you are impatient to cook, you can light small fires inside the kiln to speed up the dehydration and curing of the clay. Kilns can also be 'fired' very quickly without serious damage, but some cracking may occur. This is not a problem in itself; some fractures due to the expansion of the kiln during overheating are normal. If the fractures do not close again when the kiln is cold, they can be grouted with clay or refractory mortar. Only such fractures as will affect the stability of the kiln are to be avoided, so it is always best to proceed with small initial fires.

The entire operation just described takes no more than two or three days, depending on your skill and luck