R.E. Taylor Poster Award at ISA - Julia Montes-Landa

The effect of socio-economic dynamics in the selection of tin-bronze alloying techniques: A case study from Iron Age Iberia

J. Montes-Landa1, E. Pons Brun2, C., Rovira Hortala3, M. Martinon-Torres1

1Department of Archaeology, University of Cambridge

2Museu d’Arqueologia de Catalunya-Girona

3Museu d’Arqueologia de Catalunya-Barcelona

There are three main techniques to produce a fresh tin-bronze. Co-smelting combines mineral Cu with cassiterite (SnO2), cementation mixes metallic Cu with cassiterite, and co-melting involves metallic Cu and Sn. Several techniques often co-existed at the same production contexts (e.g. Farci et al., 2017; Murillo Barroso et al., 2010; Rademakers et al., 2018a, 2018b; Renzi, 2013), but the factors affecting selection are unclear.

Selection can be conditioned by the performance characteristics of a technique and/or by the socio-economic dynamics related to bronze production in an area. Performance characteristics are cross-cultural and easier to establish, but the role of socio-economic dynamics can only be explored through archaeological case studies. This poster aims to start approaching the role of socio-economic dynamics in alloying techniques selection.

A case study from IA Northeast Iberia is offered. Slags from two adjacent, indigenous sites were analysed: Mas Castellar de Pontós (MC), and Ullastret. Ullastret unites two oppida that are part of the same community: Puig de Sant Andreu (PSA), and Illa d’en Reixac (IR) (Casas et al., 2004; Codina et al., 2008; López Melcion and Toledo Mur, 1999; Martín et al., 1997; Museu d’Arqueologia de Catalunya-Girona, 2002; Pons et al., 2018; Rovira Hortalà, 1993; Rovira, 1993; Toledo Mur and López Melcion, 1999)Moreover, Emporion, the first Iberian Greek colony, is ~20km away. The choices observed at Emporion’s assemblage, published elsewhere (Montes-Landa, 2017), were compare to the indigenous ones too. pXRF, OM, and SEM-EDS were used to relate the slag microstructures and compositions to specific alloying techniques (Fig. 1). 

Figure 1. Some microstructures relevant for slag characterisation (Scales left to right, top to bottom = 300µm, 30µm, 1mm, 25µm, 300µm, 100µm).

Results are summarised on Fig. 2. Cementation was favoured at IR, but PSA (and MC) preferred co-smelting. The different choices at IR and PSA (part of the same community) allow to rule out environmental factors and performance characteristics as forces affecting decision. Both oppida are 400m apart, and it is expected that metallurgists had a broadly similar understanding of techniques, skills, and recipes. 

Figure 2. Summary of results

Cementation was also conducted at PSA and MC, but Cu was not smelt at either site. Metallic Cu in PSA might have been acquired from the nearby IR. However, it is likely that metallic Cu arrived to MC through exchange instead, what indicates a certain dependence on exchange networks for technique selection. 

Absence of co-melting at the indigenous contexts contrast with its presence at Emporion, where metallic Sn was acquired through Mediterranean Sea networks. Avoidance of co-melting in indigenous contexts might indicate cultural preferences (as other Greek innovations had been accepted, de Prado, 2010), and/or different positions in exchange networks that prevented access to Mediterranean metallic Sn.

Thus, the observed choices are dependent on socio-economic dynamics. Therefore, the presented data preliminary supports that socio-economic dynamics are the main factor affecting decision when selecting a technique. The role of performance characteristics is secondary. 

Our on-going project expands the chronology and geographical scope of this case study and introduces experimental archaeology to clarify performance differences between techniques. Its aim is to better understand technological choices concerning bronze alloying techniques, and how they can inform us about past societies beyond the selected area of analysis.


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