For the first time, archaeologists at the University of Gothenburg have discovered a complete plano-convex ingot in Sweden, marking a significant milestone in the understanding of metallurgical artifacts in Northern Europe. These ingots, recognizable by their distinctive shape featuring a flat bottom with a convex top, have traditionally been linked to the Bronze Age and are often composed primarily of copper or bronze. However, the Swedish ingot has challenged longstanding assumptions due to its unique alloy composition, indicating a more complex historical narrative than previously understood.
The initial excitement surrounding the find quickly deepened when isotopic and chemical analyses revealed that the ingot is made of a copper-zinc-tin-lead alloy—a metallurgical signature closely associated with the Iron Age and subsequent periods rather than the Bronze Age, to which its shape seemed to belong. This unexpected result prompted a broader investigation into trade and cultural exchanges during the Nordic pre-Roman Iron Age, suggesting sophisticated metallurgical knowledge and long-distance interaction networks across the Baltic region.
Plano-convex ingots have been a common feature in archaeological assemblages, especially throughout the Mediterranean basin, continental Europe, and the Atlantic coastline. Their shape was not merely functional for transport but also emblematic of the technological stage and cultural milieu of the communities that produced and used them. Traditionally, these ingots’ copper or bronze content has provided vital clues about the technological capabilities and trade routes of their time. The discovery of an alloy mixture involving zinc, tin, and lead in the Swedish sample is therefore a remarkable indicator of metallurgical evolution and regional trade complexity during the Iron Age.
Given the ingot was found in isolation and lacked direct archaeological context, traditional dating methods were untenable. This limitation necessitated an interdisciplinary approach, combining archaeometallurgical analyses such as lead isotope and trace element profiling with comparative studies of metal artifacts from other regions. Notably, a coalition of experts from Poland collaborated with the University of Gothenburg researchers, identifying striking compositional parallels to rod ingots recovered from the Iława Lakeland in northeastern Poland, thus expanding the contextual framework beyond a strictly local perspective.
The lead isotope analysis employed in this research serves as a powerful investigative tool in archaeometallurgy, enabling the tracing of metal origins back to specific ore processing regions. By comparing the isotopic signatures of the Swedish ingot with known mining areas, the researchers could hypothesize not only about the geographical pathways of metal procurement but also about the complex trade networks operating across Northern Europe during the Iron Age. This multilayered understanding is instrumental in reconstructing the movement of raw materials and finished products over vast distances, underscoring economic and cultural interconnections.
Alongside isotopic profiling, trace element analysis further illuminated the ingot’s metallurgical composition, confirming the presence of copper alloyed with zinc, tin, and lead in proportions indicative of an advanced metallurgical technique. This complex alloying reflects purposeful metallurgical choices aiming to modify the ingot’s properties, such as hardness and malleability, which would have been crucial for its intended applications in tools, weapons, or other functional items.
The collaboration between Swedish and Polish archaeometallurgists was pivotal to this breakthrough. By cross-referencing the composition of the Särdal ingot with rod ingots from northeastern Poland, the team highlighted a robust pattern of shared metallurgical traditions and trade routes in the Baltic arena. This finding fortified previously tentative hypotheses about cultural and technological exchanges during the Nordic pre-Roman Iron Age and revealed the intricate web of contacts connecting disparate communities across the Atlantic to the Baltic Sea.
This study underscores the necessity of a multidisciplinary and cooperative approach in archaeological research, especially when confronting isolated artifacts that defy simple categorization. The integration of natural scientific methodologies with archaeological theory allowed the research team to transcend local interpretational limits, producing a comprehensive historical framework that sheds light on the complexities of Iron Age metallurgy and trade.
Moreover, the findings challenge the traditional chronological assignment based solely on artifact morphology, demonstrating that shape can be an insufficient or misleading indicator of temporal placement. The Särdal ingot’s composition clearly reflects a metallurgical phase beyond the Bronze Age, revealing that ancient metalworkers possessed sophisticated alloying knowledge and were participants in far-reaching exchange networks much earlier than previously recognized in the region.
The revelation also amplifies understanding of the social and economic structures sustaining metal production and distribution during the Iron Age. The strategic use of diverse metals within the alloy possibly indicates not only technological advancement but also resourcefulness in utilizing available materials, reflecting adaptive strategies in metallurgy influenced by ecological and economic factors.
Published in the Journal of Archaeological Science, this research not only enriches the corpus of archaeometallurgical knowledge but also sets a methodological precedent for future studies of isolated metal finds. The work exemplifies how combining scientific analyses with detailed archaeological contextualization can unravel the historical narratives embedded within metal artifacts, fostering a nuanced appreciation of past human behaviors and intercultural dynamics.
As the first complete plano-convex ingot from Sweden subjected to such rigorous investigation, the Särdal ingot now occupies a central place in the discourse on Iron Age metal trade across Northern Europe. It compels scholars to reconsider established timelines and encourages further exploration into the technological and cultural intersections that shaped the metallurgy of the Baltic and Atlantic regions.
Serena Sabatini, a lead researcher in the study, emphasizes the transformative power of international cooperation in archaeological science. She notes that without the collaborative spirit and data sharing among researchers across borders, such intricate patterns of ancient trade and metallurgy might have remained invisible, underscoring teamwork’s critical role in the advancement of historical understanding.
Subject of Research: Not applicable
Article Title: Iron age metal trade between the Atlantic and the Baltic Sea: new insights from the first complete plano-convex ingot found in Sweden and ingot rods from the Iława Lakeland in northeastern Poland
News Publication Date: 28-Jul-2025
Web References:
https://www.sciencedirect.com/journal/journal-of-archaeological-science-reports
http://dx.doi.org/10.1016/j.jasrep.2025.105312
References:
Analysis based on lead isotope and trace element methodologies in archaeometallurgy, collaborative research publications by University of Gothenburg and Polish scholars.
Image Credits: Not provided
Keywords: Archaeometallurgy, plano-convex ingot, Iron Age, isotopic analysis, trace element analysis, Baltic trade, metallurgical alloys, Nordic pre-Roman Iron Age, copper-zinc-tin-lead alloy, metal trade networks
