Approaches to interrogate the erased histories of recycled archaeological objects

Abstract

Any archaeological artefact made from recyclable material may have been recycled before deposition. Three approaches are presented which have identified recycling in the archaeological record: (1) the application of log ratio analyses to investigate compositional data indicates that Roman glass was recycled and reapplied as a glaze on Parthian pottery, thereby suggesting that the paucity of Parthian and Sasanian glass in the archaeological record is due to recycling;(2) linear mixing lines on plots that combine compositional and isotopic data suggest that most silver found in the Iron Age hoards of the southern Levant was mixed, with vertical mixing lines indicating that some of it was melted down hastily in times of unrest; and(3) histograms of compositional data provide evidence of recycling accompanied by dilution of cobalt-blue glass in New Kingdom Egypt, potentially because the colourant was not available in later periods, thereby questioning the accepted provenance of the cobalt source. It is considered that application of these approaches can contribute to a better understanding of the motivations behind recycling in prehistory.

Identifying episodes of recycling in the archaeological record

“…This fits well with the narrative that glass was not produced in significant amounts after c. 1250 BC (Shortland 2016, 95), with glassmakers reducing the levels of cobalt through dilution with a base glass to the point where the colour was still effective. Recycling is also supported by broad distributions of PbO and Sb 2 O 3 , which indicate unintentional mixing due to the failure to separate all the white opaque glass (calcium antimonate) as well as yellow glass (lead antimonate) from cobaltblue glass during recycling (Wood 2022). Essentially, the compositional data suggests recycling and dilution (and its associated accidental introduction of contaminants) rather than a deliberate reduction in the amounts of cobalt added to new glass in this later period.…”

“…However, examination of continuous data, such as chemical and isotopic data, can be used to identify mixed signatures associated with episodes of recycling. Nonetheless, despite being common in the archaeological literature, care must be taken with bivariate plots of elements and compounds used to identify mixing lines, as their application can lead to erroneous interpretations (Wood 2022).…”

Crisis? What crisis? Recycling of silver for Roman Republican coinage

“…With several sources of silver contributing to the production of Republican Roman coinage, each with different chemical signatures, the issue of mixing and recycling becomes potentially significant (Wood 2022). It is proposed here that decreases in lead emissions around the same time as silver coinage becomes the major currency of the Roman Republic (Fig.…”

New scientific analyses reveal mixing of copper sources in the early Iron Age metal production at Ili, western China

“…However, we argue that provenance studies targeted on any Xinjiang metal group should be placed in a wider geological and social context, primarily because of the highly mobile lifestyle favoured by local people that leads to higher chance of long‐distance movement of metal objects as well as mixing and recycling. Very few scientific approaches could provide direct evidence for identification of mixing and recycling of ancient metal (see papers in this Special Issue, e.g., Berger et al, Wood, 2022). The most effective method so far is still combination of lead isotopic ratios, trace elements, and alloying composition (particularly lead concentration, Pollard & Bray, 2015).…”