The white illusion: archaeometric study and authentication of white decorations on bronze fibulae from Parre (BG)

The archaeological site of Parre, Bergamo province, is known for the discovery of a conspicuous bronze hoard at the end of the 19th century. Further excavations performed by the Superintendence of Lombardy uncovered an important Iron Age settlement (Poggiani Keller-Rondini, 2020). Among the numerous bronze artefacts from this archaeological site, 13 bronze fibulae with white decorations were selected for analyses. These fibulae belong to different types and display various linear and/or geometric decorations, marked by an unusually bright white colour. The presence of whitish decorations on bronze artefacts dating back to the Iron Age in Northern Italy is well documented, as in the case of leech fibulae with circular inlays (De Marinis, 2000). These latter fibulae, however, are generally filled with denatured red coral, nowadays bleached and displaying a dull whitish hue. The decorations of the archaeological finds from Parre, instead, show a much brighter hue with respect to the other artefacts of comparable chronology – even quite similar to the white ink often used in the marking of archaeological finds (white Indian ink). The 13 fibulae were thus analysed with a completely non-destructive, multi-analytical archaeometric approach – involving optical microscopy, µ-Raman spectroscopy, µ-X-ray diffraction and scanning electron microscopy with EDS – the same one used to study the bronze artefacts decorated with coral inlays (Berruto et al., 2023). This approach brought to an exhaustive characterisation of the raw materials used to produce these ‘brighter’ white decorations, allowing a check for what concerns their authenticity and chronological compatibility within the period in which these artefacts were made. In most cases presence of titanium dioxide (TiO2: white Indian ink) was unequivocally acknowledged: this material accounts for a modern intervention, presumably carried out with the aim of highlighting the decorations for a presumed public and scholarly use.