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Now, its time to add the first layer of earth that actually forms the shell of the earth oven. This is "cob" without the straw. Various combinations of sand, clay, and earth were tried. I made several experimental mixes with different proportions. The best was made from “Farnsworth Redi-mix”. This was soil dug from the newly exposed soil along the edge of Farnsworth Road. Bulldozers had just reconstructed a section of road, widening it and exposing fresh subsoil along the edge. The soil was definitely clayey and sandy. It packed into a nice tight ball, with some plasticity, did not crumble and you could feel a good bit of gritty sand in it also. I collected 10 - 5 gallon buckets full of this soil. Right nearby along Farnsworth creek, I also collected some more fine sand and some fairly pure clay.
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The mix for the first layer of the dome was prepared by mixing 2 buckets full of Farnsworth redi-mix with the larger stones removed, and 1 heaping shovel full of sand. Half a gallon of water was added and the mix was kneaded and folded by foot power into a homogenous squishy glob of cob (without straw).
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We began building up a 3 inch to 4 inch thick shell of the earth mix over the sand core. We formed rough large turd-shaped pieces of cob and poked and prodded them together.
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As we built higher, it was apparent that the mix was a little too soft. It was bulging out at the bottom from the weight and compaction effort of the layers above. But we kept going, shaving off the excess bulging with a trowel to get a nice uniform dome. We found that you don’t want to pat the mix and smooth out all the joints as you build - this brings out the water and makes it softer so it bulges more. It worked better just to poke it together, and get the dome built up and not worry about the cracks and crevices between the cobs.
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After the entire sand core was covered, we used a board and rocked it back and forth, up and down over the dome and patted it by hand to make a smooth even surface and close up the cracks. We used the board to try to push some of the lower bulging mix up towards the top, to even out the thickness.
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