Sunday, April 11, 2010
Earthwise Valley -- Earth Oven
I'm comfortable tackling a new project in the kitchen, or throwing chemicals at some paper in the darkroom, or deciphering a new knitting pattern.. but building is not my strong suit, if only for lack of experience. Building with anything... wood, bricks, metal.. I haven't been there and don't often go there. Nonetheless, I'm living in the valley now, in a country of DIYers, and it's time to learn to build!
As I'm most comfortable in the kitchen, I was put in charge of building our earth oven. An earth oven is made from mud, sand, mulch, and bricks. All the materials were found for free on the land. To prepare for our earth oven, Dave and the volunteers had to put together a stone plinth. It was also made with free materials. Yea!
Next step was making the bottom of our oven. We put a wooden pallet on our plinth for an even surface, and spread a thin layer of clay over the plinth to protect the wood from heat. This is not how i would recommend making an oven. I think next time we'll focus on the base as insulation. We used firebricks to make our hearth floor on top of the clay. Then we marked a circle for the oven and used a stick to measure the height and made a dome form out of sand.
We started the oven itself by making the sand dome which would become the oven interior when we'd dig it out later. It's a 70cm diameter and 40cm height. This will be big enough for a couple loaves of bread or one pizza tray.
Once our form was complete, we covered it with wet newspaper and had lunch. beware, the newspaper dries fast in the sun and blows away in the wind! Next time lunch will have to wait.
After lunch, we got our hands (and feet) dirty making the mix for the oven form. It was part clay, part sand. We mixed it on a tarp, using our feet mostly. I read that the recommended way of mixing was to do the twist, so we put on some appropriate music and did just that!
When we'd have a good mix, something that would stick together well, we made "muffins" (little round clay bricks) and began stacking them up around our sand form, kinda like building an igloo.
The first layer was about 7-10 cm thick. The second layer is for insulation and went on right after. It's the same thickness as the first layer, but made of clay slip (basically mud and water) and fiber (we used dried sticks and grasses). Our first bucket of clay was all gone, so we had to collect some from another location. It was a pretty pink hue!
The final layer is a thin layer of plaster. We used clay slip, sand and manure. There are rather troublesome cows that often invade the valley. Well, at least their shit isn't worthless! When the whole thing was finished, Jon ran down the road with a chainsaw to get us a door. It's made from a rata stump, which is a hardwood that should be able to handle the heat. Jon did a good job matching my requested door height, which is 25cm exactly and just wide enough for our pizza trays (36cm). Little John cut the door opening to match our door, and smoothed out the edges.
After it was finished, we let it wait about a week. The disadvantage of putting all three layer on at once is that it takes longer to dry out. Next time, I'd like to try putting the insulation and plaster on after the first layer has dried. After a week, we dug out the sand (actually, Dave dug out the sand) and started a fire in the oven to dry out the inside.
Our first fire didn't dry out the back of the oven, so we weren't able to bake in it. However, the second fire dried it all out and brought our oven to baking temperatures. The first products of the oven were two fine loaves of wholemeal bread, a couple kumara and an ear of corn. It lost heat fast though.
The third firing produced six pizzas (which were quickly devoured by eight hungry volunteers!) The oven seemed to hold its heat longer, though this time we left eh embers in it, pushed to the sides.
Check out Earthwise Valley's website