Bronze production in Southwestern Iberian Peninsula: the Late Bronze Age metallurgical workshop from Entre Águas 5 (Portugal)

Abstract

Archaeological works at Entre Águas 5 (Portugal) uncovered a seasonal LBA settlement with significant metallurgical remains (crucibles, moulds, prills and a tuyere) related to bronze production. Radiocarbon dating ascribes an occupation period (10th–9th century BC) previous to Phoenician establishment in Southwestern Iberia. In spite of the proliferation of metal artefacts during LBA, the production of bronze alloys is still poorly understood. An integrated analytical approach (EDXRF, optical microscopy, SEM–EDS, micro-EDXRF and Vickers microhardness) was used to characterise this metallurgy. Crucibles show immature slags with copious copper nodules, displaying variable tin content (c. 0–26 wt.%), low iron amount (<0.05 wt.%) and different cooling rates. Certain evidences point to direct reduction of oxide copper ores with cassiterite. Scorched moulds with residues of copper and tin indicate local casting of artefacts. Finished artefacts also recovered at the site have an analogous composition (bronze with ∼10 wt.% Sn and low amounts of Pb, As and Fe) typical of coeval metallurgy in SW Iberia. Some artefacts reveal a relationship between typology and composition or manufacture: a higher tin content for a golden coloured ring or absence of the final hammering for a bracelet. An uncommon gilded nail (gold foil c. 140 μm thick; 11.6 wt.% Ag; ∼1 wt.% Cu) attests the existence of evolved prestige typologies. This LBA settlement discloses a domestic metallurgy whose main features are typical in Iberian Peninsula. Finally, it should be emphasized that a collection as comprehensive and representative of a single workshop has rarely been studied, enabling a deeper understanding of the various operations involving the bronze production and manufacture of artefacts.