Surface analysis on three examples of 'cuoridoro' from the 18th century in Sicily: From scientific investigations to conservation strategies

Abstract

This paper illustrates the results of diagnostic investigations carried out on three painted leather altar frontals, belonging to the decorative typology known as "cuoridoro" or "golden leathers", dating back to the 18th century. Due to their technical and compositional complexity, a multi-analytical approach was adopted, combining non-invasive and micro-destructive investigations. Non-invasive investigations, including Digital Optical Microscope (DOM), UV-Induced Visible Fluorescence (UVF), and infrared reflectography (IRR), provided valuable information on the decorative surface and preliminary data on deterioration. In addition, portable X-ray fluorescence (p-XRF) and Fibre-Optic Reflectance Spectroscopy (FORS) analyses were used to identify chromophores in the painted, silvered, and gold-plated layers. Further insights into the execution technique were gained through micro-destructive investigations on sampled materials, employing optical microscopy (OM) on polished and stratigraphic sections, along with Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray spectrometry (EDX). Finally, biological studies were carried out to characterize the leather support, integrated with entomological and microbiological analyses to identify any degradation phenomena due to biological activity. The results indicate that the three altar frontals faithfully reflect the typical characteristics of this artwork type. They also exhibit common degradation forms, such as the darkening of silver leaf, indicating their age and conditions over time. Moreover, the knowledge acquired has proven to be essential for the planning and implementation of restoration interventions. These efforts were carried out at the Centro Regionale per la Progettazione ed il Restauro dei Beni Culturali (C.R.P.R.) in Palermo (Sicily).