Abstract
In antiquity, Pb was a common element added in the production of large bronze artifacts, especially large statues, to impart fluidity to the casting process. As Pb does not form a solid solution with pure Cu or with the Sn-Cu alloy phases, it is normally observed in the metal matrix as globular droplets embedded within or in interstitial positions among the crystals of Sn-bronze (normally the phase) as the last crystallizing phase during the cooling process of the Cu-Sn-Pb ternary melt. The disequilibrium Sn content of the Pb droplets has recently been suggested as a viable parameter to detect modern materials [Shilstein, Berner, Feldman, Shalev and Rosenberg (2019). STAR Sci. Tech. Archaeol. Res. 5, 29-35]. The application assumes a time-dependent process, with a timescale of hundreds of years, estimated on the basis of the diffusion coefficient of Sn in Pb over a length of a few micrometres [Oberschmidt, Kim and Gupta (1982). J. Appl. Phys. 53, 5672-5677]. Therefore, Pb inclusions in recent Sn-bronze artifacts are actually a metastable solid solution of Pb-Sn containing 3% atomic Sn. In contrast, in ancient artifacts, unmixing processes and diffusion of Sn from the micro-and nano-inclusions of Pb to the matrix occur, resulting in the Pb inclusions containing a substantially lower or negligible amount of Sn. The Sn content in the Pb inclusions relies on accurate measurement of the lattice parameter of the phase in the Pb-Sn solid solution, since for low Sn values it closely follows Vegard's law. Here, several new measurements on modern and ancient samples are presented and discussed in order to verify the applicability of the method to the detection of modern artwork pretending to be ancient.
Original language | English |
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Pages (from-to) | 700-706 |
Number of pages | 7 |
Journal | Journal of Applied Crystallography |
Volume | 57 |
Issue number | Pt 3 |
DOIs | |
Publication status | Published - 1 Jun 2024 |
Funding
We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III beamline P02.1. Beam time was allocated by an in-house contingent. Historical samples of metals (sample set 3) were kindly made available by Professor Massimo Vidale; they pertain to the set of historical metals gathered by the late Maurizio Marabelli of ICR, Rome. Jacopo Nava and Marco Favero assisted in SEM and XRPD data measurements, respectively. Publisher Copyright: © Carneiro Neto et al. 2024.
All Science Journal Classification (ASJC) codes
- General Biochemistry,Genetics and Molecular Biology