In building this prototype mud oven I (Bo Frick of Sweden) have basically been following the excellent instructions by Kiko Denzer in his “Build your own earth oven” book.
This oven is being built on wheels, to enable Falster Farm to show it in burning action at different markets, baking artisan breads, pizzas and all manner of gourmet foods.
I will here give you a resumé of the building process.
Step 1: Making a concrete slab and running two iron bars through it, this to enable future movement of the oven on and off the trailer. The slab was poured onto a round piece of plywood with a 5″ tall ring of wood, securing the slab. Chicken wire was added as reinforcement.
Step 2: Building a stonewall base that will house empty wine and beer bottles which will capture heat and hold it in suspension for the baking.
The stones are layered with a lime mortar consisting of ¼ lime and ¾ play sand. The reason for not using concrete is that it doesn’t breathe. The lime/sand mortar becomes rock hard but allows the moisture to travel in and out of the oven, releasing the construction of stress.
Step 3: Insulating the core of the base.
Clay was mixed with sand and sawdust producing a mushy
mixture that, after drying; was light and an air-holding insulation material, with the bottles in it.
Step 4: Brick baking floor and the opening arch of the oven in place.
Step 5: Making play sand “casting dome” that the clay layers will be resting against until completed when the sand is removed, creating the oven cavity.
Step 6: Laying the first dense clay layer that will exposed to the actual fire. This process had to be redone with cleaner clay, creating the right texture. The clay was mixed with sand and water and worked in a mixer.
Who said clay wasn’t fun!?
Step 7: Top plaster is applied of a clay/straw/water combination.
Step 8: The sand mold is removed leaving the Oven in a good smooth interior condition. It is much like the lost sand casting method. The moist sand once holds the clay “cob” in shape until such time as it is set-up. Then the sand is scooped out leaving the fire chamber.
The oven is being dried slowly with multiple small fires, this to minimize the amount and size of cracks.
Building the Clay Oven was fun and very fulfilling. When I get back home to Sweden, I will be using theis and so much more of what I have learned on Falster Farm in my business and farming ventures – new adventures!