Double-looped palstaves with casting jet from Western Iberia. An analytical approach

3rd International Conference on Innovation in Art Research and Technology

Parma. Italy
Conference. 2018

In this study, a collection of double-looped palstaves with casting jet from the Late Bronze Age (LBA)/Early Iron Age (EIA) (approximately the first half of the I millennium BC) of Western Iberia was analysed through a non-destructive analytical protocol which combined Energy Dispersive X-Ray Fluorescence (EDXRF) Spectroscopy with a Monte Carlo (MC) simulation algorithm named XRMC [1].

From an archaeological point of view, double-looped palstaves with casting jet present a strong morphological standardization. Even in most of cases they have unknown archaeological context, they are generally found in multiple and monotypological hoards which are a distinctive mark of the LBA/EIA from Northwestern Iberian Peninsula .

The palstaves selected for this paper have been analysed with a forefront analytical protocol combining EDXRF for the analysis of the artefacts and MC simulation for the data processing and quantification process. This protocol has already proven to be able to reproduce the chemical composition of the bulk alloy of a multilayered artefact, such as archaeological metals, with no need of removing or cleaning the more superficial layers [2,3]. This analytical approach has represented an undoubted advantage in the analysis of the selected palstaves, both because sampling of the artefacts was not allowed and for the possibility of analysing different points for each palstave in a completely non-destructive way.

According to previous studies, double-looped palstaves with casting jet are usually associated to a high-leaded tin bronze metallurgical tradition, being characterised by a high and unpredictable Pb concentration [4,5]. However, more recent studies have shown that double looped palstaves with casting jet with lower Pb concentration were produced as well [6,7]. The determination of the Pb concentration is a central issue for the archaeological interpretation of this type of artefacts, since Pb affects the mechanical properties of an alloy: indeed, higher Pb values led to the formation of segregations that make the metal weakness, thus theoretically not suitable for activities requiring high mechanical stress.

The preliminary results carried out on the double-looped palstaves with casting jet selected for this paper seems to support this trend, also confirming the reliability of the EDXRF/MC analytical protocol as a completely non-destructive approach able to determine the chemical composition of the bulk metal with no need of surface preparation, thus establishing itself as a reliable and non-destructive tool able to address and solve specific archaeological issues.