By
Ignacio Montero Ruiz (presenter)
Raquel Vilaça (contents author)
Summary
Tin bronze alloyed with lead to get leaded bronze is a step forward in the development of metallurgical technology. This alloy is the result of the mix of three different metals in order to get a new one with properties previously unknown. The proportion of each metal is the key to change such properties. It is generally accepted that the addition of lead lowers the melting point and increases the metal fluidity. Thus the casting is much better. However, high percentage of lead (> 20 %) makes the metal almost impossible to use if high mechanical stress is needed because the large areas of lead interspersed among the bronze form regions of weakness.The use of high leaded bronzes is associated in the NW of Iberia to a specific types of axes (double looped palstaves). Given the contexts they appear (large hoards showing careful positioning of the objects) the aspect of unfinished tools (axes keeping up the casting jet and metal excrescences) or/and the structure (axes having a lead core), a non-functional (ritual or premonetary) use is frequently attributed to these objects.The identification of Cu-Pb ingots circulating in Iberia at the same period when these high leaded bronzes are produced suggest that a cementation process with a Cu-Pb metal and casiterite was used to prepare this alloy. Elemental analysis(XRF) of objects confirms that the lead added is not related to the need to replace or saving copper or tin in the alloy.Lead isotope analysis identifies the production of Cu-Pb ingots in the southern area of the Iberian Península, so this research tries to confirm if the provenance of the lead used in this high leaded alloys in the NW region is the same than in the ingots. This study will contribute to our understanding of the mass production and deposition of metal, paying particular attention to the impact of the Phoenicians on the trade networks.
Keywords
Archaeometallurgy. Archaeometry. NW Iberia. Lead.