Pizza Oven! December 31, 2007
Posted by Graham in : Food, Green Building , trackbackI am proud to present the brand new Earth Oven recently completed at Derryduff.
Just last night Sherry and Andy joined me for the first trial run pizza making session, which was a great success and resulted in much happy chomping. We also enjoyed sitting around the ultra-hot oven for some hours afterwards and watching the remarkable patterns of the flames inside curling around the oven while discussing the finer points of Quantum Theory.
I had actually begun construction of the oven last summer at the 10-day permaculture course here, when we made the shelter and began the stone base. More progress was made during visits here in the autumn from Kinsale students, but the main driving force behind its completion was Sherry who kept at me to complete the project and did loads of the work, so many thanks Sherry!
The main source of information on earth ovens is Kiko Denzer’s Build Your Own Earth Oven which has easy to follow instructions which I followed fairly closely for this oven. Once the stone base is made and the firebricks set in place as above, the next stage is to make form or “void” of moist sand which the oven is built over and then excavated later. My sand was very course and would not hold together well until I mixed in some clay; however, maybe i used too much clay as it had set quite hard and took 2-3hours of hard hacking to actually remove from the oven! Finer sand for the void is recommended, but you could just use earth which would be much easier to work with.
The void is covered with moist newspaper and then the fire layer is constructed. This is just a mix of clay and sand. I used bagged powdered pottery clay for this layer, at a mix of 4 1/2 parts sand to 1 part clay, in the recommendation of Saul, who has made several ovens. However, the inside of the oven has got some cracks already; maybe less clay would have been better. Ianto Evans suggests 7:1; maybe I would try 6:1 on the next oven (!).
Next comes the cob layer, which has some straw in it.
We also decided to put a chimney in the from of this oven. but it seems it is not wide enough so most of the smoke comes out the door anyway. A 4″/ 10cm diameter flu pipe would be better I think.
The outside of the oven gets fairly hot; having used the oven now I am inclined to add a third, insulating layer, that could be a clay-straw mix, mainly straw. This could then be finished with a clay or lime plaster. Since the oven stays hot for some hours if insulated, it is possible with one firing to bake first pizzas, then bread, then scones perhaps; maybe even yogurt as it cools down! The oven does take 2-3hours of heating and most of a barrow load of firewood, so it is important to use them as efficiently as possible. Ideally of course the oven would generate heat inside the building. This could be achieved if it was constructed with a proper chimney and stove door with vent so smoke doesnt come inside. All ideas for future projects. One thing is for sure: there is really nothing quite like fresh pizza!
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We have built our own oven with 2 layers of cob over the fire layer of mostly clay. The second cob layer has lots of straw in it and acts as an insulation layer. It works very well, and the outside of the oven never gets more that barely warm. The inside, though, stays warm for a long time, over a day, and though I hadn’t thought of making yogurt in it, I think it would work (let us know if you try!).
Also, we didn’t put a chimney, and while it makes the oven a little more difficult to light (belows are handy there), once it is going, the smoke comes out of the door just fine.
Our oven actually saved the day when we had a 7 hours power cut last Monday, just as we were starting to cook new year’s dinner for 20 people. They all enjoyed the freshly baked pizza!