Virtues of Giambologna from Grimaldi Chapel Archaeometric Characterisation Part II: ‘Artistic’ and Natural Patinas

The scientific investigation on metal artwork is meant to expand the knowledge regarding the technical skills developed by artists in sculpture manufacturing. Moreover, all the gathered data support the speculation about the motivations behind the choices of certain material or a specific casting and/or finishing method (e.g., aesthetic, economic or technical reasons, or both) and give fundamental information for planning adequate restoration interventions. The subject of this study is the Virtues sculptural group made at the end of the XVI century by Giambologna to decorate the Grimaldi Chapel in the church of San Francesco di Castelletto (Genoa, Italy). Six life-size statues depicting Charity, Justice, Hope, Fortitude, Faith, and Temperance (i.e., the artwork discussed in this article); seven bas-reliefs; and six winged representations of putti are what remains of the original monumental project. Different micro-invasive analytical techniques (scanning electron microscopy and energy dispersive x-ray spectroscopy, SEM–EDS; micro-Raman Spectroscopy, μRS; gas chromatography–mass spectrometry, GC–MS) were applied to determine the chemical nature and the state of conservation of the “artistic” and natural patinas visible on the Virtues surfaces. Some patination tests were performed taking into account the collected analytical data and the indications provided by the scientific literature and the historical documents. The combination of the results obtained through the scientific investigations and the experimental work allowed for supposing the materials and the patination technique selected by the artist to adorn the sculptures and providing indications for the correct conservation of the six sculptures.