Molecular characterisation of the tempera painting on canvas 'The Martyrdom of Gorcum'.

The artwork under investigation was presumably painted in the 18th century, the author, from the Neapolitan school, still remains unknown. The artefact comes from the storerooms of the Ente Morale Suor Orsola Benincasa and is an important historical-artistic testimony, as it is one of the very rare representations of a martyrdom involving various ecclesiastical orders, which took place in 1572 in the locality of Gorcum, by Calvinistic Gheusians, who were protesting in a bloody manner against papal authority [1]. From an initial examination, given its extremely precarious state of preservation, the work is in 'first cloth', i.e. without any conservation interventions. Only limited and localised pictorial interventions are visible under ultraviolet fluorescence, exclusively on three small points in the upper part of the panel. The work presents a considerable problem related to the degradation of the paint film. We can in fact note that some colour fields have undergone two different degradation processes within a few millimetres of each other, where the most evident alteration is the strong whitening of the surface. In order to be able to understand the cause of this problem, a multidisciplinar diagnostic approach was performed: to physically analyse the stratigraphy of the painting, we used microscopy whilst final varnishes and repainting were detected thanks to a Wood's lamp. To identify the type of binder in the paint layer, an initial FTIR analysis was carried out, which allowed the hypothesis of the presence of protein material; confirmation of this hypothesis was obtained by LC-MSMS analysis. Finally, analyses were carried out using XRF, ICP-MS to characterise the pigments present. Our results show a different concentration of metals (even in the same colour field) thus suggesting that the different degradation phenomena could be related to this characteristic.