An experimental reconstruction of ancient iron production took place on the 8th of September 2020 in collaboration with R.C. ‘Athena’, Xanthi Division and was hosted at the premises of the Institute in Xanthi, Greece. The experimental approach is an integral part of project ME.Tech.NAS. carried out at CReA-Patrimoine, Universite Libre de Bruxelles and is an ideal way to understand technical details and gestures by experiencing the making of metals. The whole attempt was video recorded and was attended by several scientists while the products and by-products were sent for analysis at N.C.S.R. ‘Demokritos’ in Athens.
Initially the iron ore was collected from an idle mine in the region of Palaia Kavala that was exploited in antiquity by underground and surface mining. The last exploitation phase was conducted by the mining corporation IPAMCO LTD in the 1970s. Analyses undertaken during this time revealed iron oxide contents in the order of 40-60% and was thus selected as a rich raw material appropriate for our experimentation as it was also extracted by ancient miners.
In total 45 kg of iron ore were collected for the needs of the experimental simulation. Crushing was conducted by using a stone anvil and a hammer. During this process losses in mass were calculated between 4 and 9%. Therefore, from the 45 kg of unprocessed ore we ended up with 42 kg of crushed and treated ore out of which 30 kg were used for smelting.
The second stage involved building of the furnace for which clay containing chamotte ideal for stoneware was utilised. Straw was added to the clay paste and kneaded together in order to increase its refractory capacity. Initially a square pit (40 x40 cm) was dug to a depth of 10 cm and was then lined with clay. The superstructure was built out of small bricks of the clay paste and was raised at a height of 15 cm with a wall thickness of 7 cm. A hole was left at the back side to allow for the tuyère insertion at a later stage. From this point upwards the chimney was raised with a wall thickness of 4 cm leading to a total furnace height of 40 cm. The frontal side was left open and a door was built out of the same clay paste that was attached during the smelt. The furnace was then left to dry for two weeks and was pre-fired with wood as a fuel for two hours one day before the experimental smelting.
The last stage was that of smelting the iron ore. After a second two-hours preheating stage the smelting started. Air was supplied by an electric blowing device that was used to imitate the hand driven bellows of an ancient metallurgist. It was connected to the furnace via a long tuyère and operated at a low wind speed of 4 in the Beaufort scale. Every ten minutes 1 kg of ore was added followed by 3 kg of charcoal filling up the furnace to its rim. This process was repeated until all the ore was added for a duration of 5 hours. Temperature readings were taken every 20 minutes using a Type K thermocouple allowing us to have the profile of temperature fluctuations during the smelt.
Once the smelt was over the frontal door was opened and the product, that is the iron bloom encased in slag was removed. The upcoming analysis of the bloom and slags will throw light on the efficiency of this simulation and will provide excellent reference material to compare with ancient metallurgical residues that are under study in the framework of project ME.Tech.NAS.
Overall, it was a successful attempt that attracted the attention of local archaeologists and scientists promoting a fruitful discussion on the practicalities and difficulties associated to producing metals in antiquity while stressing the ingenuity of ancient craftsmen. At the same time the educational value of such an attempt has been acknowledged and has paved the way for future collaboration with R.C. ‘Athena’ on similar attempts open to schools’ visits and performances to wider audiences.
Acknowledgments
We would like to thank warmly Dr. Despoina Tsiafaki (Director of Research Head of the Culture & Creative Industries Department ‘Athena’ Research Center) for coordinating and promoting the action to a wider public. Many thanks to Maria Arapaki and Yannis Nerantzis for help in building the furnace, Yannis Mourthos for help during the smelt, Dr. Vasilis Evangelidis and Natasa Michailidou for help in the organisation.
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