Revealing Roman Silverwork: Technology and Archeometallurgy of the Marengo Treasure (Second Century, Italy)

The Treasure of Marengo, a unique piece of art composed by 28 kg of Roman silver artifacts, was studied from a scientific point of view. In this paper, a comprehensive method of analysis of archeological metallic materials is proposed, allowing to determine: i) the gilding techniques used in antique; ii) the production techniques of the silver objects; iii) the Roman soldering composition; iv) the restoration techniques used at the beginning of the XX century; and v) the degradation state of the artifacts. In the proposed method, information obtained from different nondestructive techniques (i.e., energy–dispersive spectroscopy, X–ray fluorescence spectroscopy, scanning electron microscopy, optical and stereo microscopy) was combined with microstructural and compositional studies either on microsamples or on artifacts without sampling. The information obtained on the Treasure allowed to determine that the artifacts are embrittled due to an intergranular corrosion due to the presence of copper and lead precipitates at the grain boundaries in the as–solidified alloys. The presence of lead makes it possible to attribute silver extraction to cupellation processes. Gilding can be attributed to a leaf gilding for all the findings examined, except one for which fire–gilding technique was confirmed by the presence of mercury.