The Chaîne Opératoire of Middle Kingdom smelting batteries and the problem of fuel: Excavation, experimental and analytical studies on ancient Egyptian metallurgy

Abstract In this paper, a solution is proposed to answer the problematic issue of the type of fuel used in the early Middle Kingdom smelting furnaces at Ayn Soukhna based on a strict experimental protocol. The protocol was repeated 17 times, for a total of approx. 1500 h of experimental work. In correspondence with the archaeological data obtained at Ayn Soukhna, the combined use of fresh acacia and donkey dung as fuel for smelting is proposed; the use of charcoal for smelting can be excluded. A holistic evaluation of experimental and archaeological evidence has shown that a combination of fresh wood and donkey dung was most likely the standard fuel choice at Middle Kingdom Ayn Soukhna. This is evidenced by the compatibility of results from experimental smelting using wood and donkey dung in terms of furnace lining impact and colorimetry, slag typology and deposition, ash and charcoal distribution, and raw copper shape and size. The use of charcoal systematically results in incompatible smelting results, as does smelting without donkey dung. In addition to green wood, donkey dung is required to regulate the temperature distribution inside the furnaces and to increase the production of copper prills. Green wood creates a favourable atmosphere for the smelting of copper carbonate ore. It heats the lining of the column less, allowing the furnaces to be reused over several campaigns. The dual fuel use of green wood and donkey dung, however, has resulted in the best agreement between experimental smelting results and corresponding archaeological evidence. This archaeometallurgical research in the Nile Valley is carried out by a team composed of Georges Verly, in charge of archaeology and experimental archaeology, and Frederik Rademakers, in charge of archaeometry, as well as numerous master students and a Maitre d’art, Hugues Paridans. Dialogue and interdisciplinarity are the assets of this project, dictating equality between its members, representing the sum of ideas and debates, building all research protocols and publications.