New insights into the beginnings of iron processing
Freiburg, 06/02/2026
Researchers at the University of Freiburg examined the microstructure and hardness distribution of a 2,900-year-old iron chisel and proved that blacksmiths deliberately cooled individual sections of tools faster than others in order to consciously control the steel material. The results demonstrate a gradual adaptation of Bronze Age working techniques to iron, which was a new material back then. They also deepen our understanding of the technological transition from the Bronze Age to the Iron Age and the early transfer of knowledge.
An international study on metalworking in prehistory, led by Dr. Ralph Araque Gonzalez of the Institute of Archaeological Sciences at the University of Freiburg, shows that steel tools were already being heat-treated in the 9th century BC. Dr. Bastian Asmus, also from the Institute of Archaeological Sciences and head of the Laboratory for Archaeometallurgy in Kenzingen, analysed samples from the cutting edge and shaft of an approximately 2,900-year-old iron chisel. Using light and electron microscopy, chemical analyses and Vickers hardness measurements, he precisely determined the microstructure, composition and mechanical properties of the samples.
The analyses show a clear functional difference within the tool: while the shaft remained relatively soft, the cutting edge, which was deliberately cooled more quickly, has a significantly finer microstructure. The slag residues, which are waste products from iron production that were also examined, prove that iron was produced at the site where the chisel was found in Rocha do Vigio in the south-west of the Iberian Peninsula.
“We were able to demonstrate for the first time that early blacksmiths made targeted use of the thermal properties of steel, even though modern alloying and hardening concepts were not yet available to them. This shows that technological change did not occur as a result of a sudden breakthrough, but rather through the further development of existing craftsmanship skills.”
Dr. Bastian Asmus
Research assistant at the Institute of Archaeological Sciences, Department of Prehistoric Archaeology, University of Freiburg
The results suggest that blacksmiths in the Bronze Age gradually adapted the working techniques they knew to the new material iron and successfully transferred their experience with heat, shaping processes and material behaviour to steel. “We were able to demonstrate for the first time that early blacksmiths made targeted use of the thermal properties of steel, even though modern alloying and hardening concepts were not yet available to them. This shows that technological change did not occur as a result of a sudden breakthrough, but rather through the further development of existing craftsmanship skills,” says Asmus. “Future reference data in materials science should be more closely aligned with the chemical properties of historical steels, as we believe that modern comparative values can be misleading.” The results were published in the Journal of Materials Research and Technology.
Further information
Original publication: Asmus, B.; Araque Gonzalez, R.; Mataloto, R. et al. Negotiating between iron and bronze traditions: The impact of a tool – The chisel from Rocha do Vigio. Journal of Materials Research and Technology, Volume 41 (2026), pages 1615–1629. DOI: 10.1016/j.jmrt.2026.01.091
Dr. Ralph Araque Gonzalez heads the project ‘The Iberian Steles of the Late Bronze Age: Visual Art, Technology and Knowledge Transfer between the Atlantic and the Mediterranean’ (DFG project number: 446739573), funded by the German Research Foundation (DFG), at the Institute of Archaeological Sciences, Department of Prehistoric Archaeology at the University of Freiburg.
The analysis of the iron chisel was carried out as part of the above-mentioned project.
Further research findings
Articles on further research findings from the project “The Iberian stelae of the Final Bronze Age: iconography, technology and the transfer of knowledge between the Atlantic and the Mediterranean”: