Towards a new history of bronze making: Explaining the selection of tin bronze alloying techniques across prehistoric N.E. Iberia (2100-200BC)

Copper-tin bronzes can be obtained through different techniques (i.e. natural alloying, co-smelting, cementation, co-melting and recycling). This paper presents a methodology and theoretical framework to contextually explain the logic behind the selection of bronze alloying techniques in different contexts, avoiding deterministic, aprioristic and linear narratives. To do so, we selected Northeast Iberia as a case study and present comparative results of slag and slagged technical ceramics from four sites (Minferri, Vilars, Mas Castellar and Ullastret) dated between 2100-200BC. Materials were analysed using pXRF, OM, SEM-EDS, and ICP-MS to characterise technological choices through time. Patterns of choice are considered in relation to the technical affordances of each alloying technique and contextualised within the relevant environmental and socioeconomic parameters. The results show that bronze-making technique choices were primarily dependent on (1) the (in)stability of raw material procurement networks, and (2) the existent selective pressures on performance characteristics for which each technique offered different trade-offs. Discrete combinations of these two variables can explain instances of different techniques co-existing (e.g. Minferri, Mas Castellar, and Ullastret) and cases of commitment to a single one (e.g. Vilars).

This is the first diachronic study of bronze alloying practices investigated through direct analyses of bronze-making residues for a given area. The analytical framework employed and the derived behavioural rules can be applied to other case studies to collectively build a multi-path history of bronze alloying development. This will be fundamental to understand the link between bronze alloying technique selection and social change, to better contextualise metal finds within their production and exchange networks, and to requestion existing models of bronze production organisation and technological diffusion across the world.