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We have already told you the story of Maurizio, the “furnace man”. We stopped at the working and “construction” of the artefacts. When all the material was ready to be baked, Maurizio began to stuff the cooking oven which was formed by a hearth of masonry and an uncovered cylinder, 10 meters high and 5 meters wide.
The ﬁrst operation consisted in putting in the rocks to be cooked and to continue the arc of the hearth in order for the ﬂames to penetrate the 2 or 3 meter tall mound, making sure to form ﬁreplaces so that the heat reached the top.
Above this layer of stone was put crude bricks, in order for them to be lapped by the ﬂames, thus covering the sheets with the extra bricks. The adventure began with the lighting of the furnace, when the heat reached the approximately 1.000 degrees centigrade necessary for a proper baking.
Usually it took about a week of continuous ﬁre with fagots of wood that the woodsmen (back then, there were men who worked in the woods for a livig) made, collecting remains of cut trees and wood left in the cleaning of the underbrush.
It was an ugly job, narrated in the story of bricks that Brunelleschi “cooked” in Impruneta for the building of the Duomo of Florence. If all went well, (pyrometers and thermometers did not exist), the ﬁre went out and they waited for a few days for the heat to lower before being able to extract the material and check the result.
It was difﬁcult for the material to be burned (like what happened in oil burners in the early tunnel furnaces). If the rocks weren’t cooked when they were put in water, they remained rocks.