Understanding the selection and co-existence of tin bronze alloying techniques in Antiquity. An experimental and archaeological approach with Northeast Iberia as case study (2800-200BC).
From co-smelting through cementation to co-melting, there are different ways to make tin bronze. We can only tell these techniques apart through the analysis of production slag. Interestingly, archaeological evidence indicates that the oldest techniques were not replaced by more modern and ‘advanced’ ones, and that several techniques often co-existed in the same production contexts. This situation requires an explanation.
This thesis evaluates how environmental and socio-economic factors may have affected the selection of bronze alloying techniques in the past. To do so, it was firstly necessary to assess differences in performance between techniques through a set of field-based alloying experiments. The results suggest that, although the end-product was of comparable quality, different techniques offer alternative trade-offs during production. Secondly, to evaluate the impact of socio-economic and environmental dynamics in technique selection, a series of archaeological assemblages from Northeast Iberia dated between Chalcolithic and Iberian times (2800-200BC) are presented. Archaeometallurgical by-products of these collections were analysed using pXRF, OM, SEM-EDS, and LIA to characterise technological choices through time. These choices were considered in relation to their performance characteristics, and subsequently contextualised within the relevant environmental and socio-economic dynamics.
It was found that alloying technique choices were dependent on (1) the degree of instability associated to raw material procurement networks, and (2) the high or low selective pressures operating on the different performance characteristics of each technique. Socio-economic factors were generally conditioning both, but discrete combinations of these two variables can explain instances of co-existence of different alloying techniques, and examples of commitment to a single technique.
The study of selection patterns behind bronze alloying techniques is presented as a promising tool to re-question existing models of bronze production organisation, and technological diffusion across Europe and beyond. The approach developed can be easily adapted to study other instances of counterintuitive adoption, rejection, or discontinuation of innovations in other technologies.