35 of 234 days: Bronze cont.

I’m still sick and it is for the birds. I do feel I’m on the mend though. But I’ve caught up on emails for the most part and otherwise cleared the decks to really start crunching my data so far and then build this slide deck for the conference in Rome next week. I’m going to keep this short as time and energy are at a premium.

The following article really felt a game-changer for my understanding of what I’m seeing in the data. The lead authors are known to me from a number of their other publications which I often cite, but this one really got to the heart of the matter of intrinsic value. Back in 2006 they had already came to conclusions through their testing that I personally reached back in 2019 with my meteorological work on RRC 14, 18, & 19 (final text, I’ve seen proofs so it should be out later this year). This and their careful thinking about bronze recipes will really strengthen my initial report on my data to say nothing about what the next steps are.

Ingo, G.M. & De Caro, Tilde & Riccucci, Cristina & Angelini, Emma & Grassini, Sabrina & Balbi, S. & Bernardini, P. & Salvi, D. & Bousselmi, Latifa & Çilingiroğlu, Altan & Gener, Marc & Gouda, Venice & Al-Jarrah, Omar & Khosroff, S. & Mahdjoub, Zoubir & Al saad, Ziad & El-Saddik, W. & Vassiliou, P.. (2006). Large scale investigation of chemical composition, structure and corrosion mechanism of bronze archeological artefacts from Mediterranean basin. Applied Physics A. 83. 513-520. 10.1007/s00339-006-3550-z.



A large number of Cu-based archaeological artefacts from the Mediterranean basin have been selected for investigation of their chemical composition, metallurgical features and corrosion products (i.e. the patina). The guidelines for the selection of the Cu-based artefacts have taken into account the representativeness of the Mediterranean archaeological context, the manufacturing technique, the degradation state and the expected chemical composition and structure of the objects.
The results show wide variation of the chemical composition of the alloys that include all kinds of ancient Cu-based alloys such as low and high tin, and also leaded bronzes, copper and copper-iron alloys. The examination of the alloy matrix shows largely different metallurgical features thus indicating the use of different manufacturing techniques for producing the artefacts. The results of the micro-chemical investigation of the patina show the structures and the chemical composition of the stratified corrosion layers where copper or tin depletion phenomenon are commonly observed with a remarkably surface enrichment of some soil elements such as P, S, Ca, Si, Fe, Al and Cl. This information indicates the strict interaction between soil components and corrosion reactions and products. In particular, the ubiquitous and near constant presence of chlorine in the corrosion layers is observed in the patina of the archaeological Cu-based artefacts found in different contexts in Italy, Turkey, Jordan, Egypt, Spain and Tunisia. This latter occurrence is considered dangerous because it could induce a cyclic corrosion reaction of copper that could disfigure the artefact.
The micro-chemical and micro-structural results also show that another source of degradation of the bronze archaeological artefacts, are their intrinsic metallurgical features whose formation is induced during the manufacturing of the objects, carried out in ancient times by repeated cycles of cold or hot mechanical work and thermal treatments. These combined treatments induce crystallisation and segregation phenomena of the impurities along the grain boundaries and could cause mechanical weakness and increase the extent of the inter-granular corrosion phenomena.

In other news, I think I have my Nottingham dates to work on the Nemi material in May and my colleague Wayne Powell is coming with me and that means the science end of this work will be able to appear in a co author publication at some point to match my numismatic and historical approaches. He’s a bronze expert esp. tin isotopes among other things. Particularly awesome is his most recent publication on the Uluburun shipwreck and how it updates our understanding of tin trading and community connections. If you like that sort of thing you might check it out.

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