Before starting the restoration of an artwork, good practice involves the evaluation of the item healthiness possibly carried out through non-invasive techniques. In the specific case of painting inspection, hyper- and multi- spectral techniques are commonly used to analyze the outer layers (varnish, pictorial, and drawing), while X-ray, tomography, and many others can be employed to investigate its inner structure. Although highly desirable, a single technique providing all the information about a painting is still not available. Thus, it is of great interest to define the analysis’ protocols that could optimally exploit the complementarities of a minimal set of techniques. To this aim, the present paper shows the combined use of the hypercolorimetric multispectral imaging and pulse-compression thermography on a 15th century wall painting attributed to the Italian artist Antonio del Massaro, also known as Pastura, representing the Madonna with the Child and the Saints Jerome and Francis. The capabilities and the complementarities of the two techniques, whose information can also be fused through post-processing, are illustrated in detail in this paper. In addition, a false-colour imaging approach is proposed to improve the readability and analysis of the thermography results.

In this paper, two different objects from the ethnographic collection of the museum of the Congregation of the Sacred Hearts of Jesus and Mary (Rome), a Polynesian barkcloth (tapa) and a Polynesian headdress in feathers (pa’e ku’a), were investigated to characterize the materials, to evaluate their state of conservation and address the restoration activities. Imaging methods such as multispectral imaging, 3D ultraviolet induced fluorescence and scanning electron microscopy have been integrated with analytical techniques such as X-ray fluorescence spectroscopy, Fourier transform infrared and surface enhanced Raman spectroscopy. Imaging investigations allowed us to differentiate constitutive materials and study their distribution, such as the yellow dye in the tapa used to trace the geometrical pattern and the psittacofulvins responsible for the feathers’ colors in the headdress. The combination of molecular spectroscopy, supported by observation under a scanning electron microscope, allowed us to propose a characterization of the organic painting materials (Morinda citrifolia, Curcuma longa) used for the tapa, and of the type of feathers (from Vini kuhlii bird) and vegetal fibers (Cocos nucifera L.) used to realize the headdress, as well as enabling the identification of degradation products and microorganisms affecting the artifacts before restoration. Fourier transform infrared spectroscopy detected the organic materials used as adhesives for the tapa and headdress: a polysaccharide, probably starch, for the tapa and a natural rubber from Cerbera manghas L. for the headdress. The results of the multi-analytic diagnostic campaign enabled the choice of proper restoration materials, compatible with the original ones, and helped us develop effective protocols for the artifacts’ conservation, such as laser cleaning of the feathers.

(1) Background. The aim of this work is to combine non-invasive imaging with chemical characterization analyses to study original and restoration materials of a late 16th-century painting on a canvas representing the “Coronation of the Virgin with the Saints Ambrose and Jerome”, preserved in the Diocesan archive of Orte, a town in the district of Viterbo (Italy). The diagnostic campaign was addressed to support the restoration activities and the choice of the most suitable cleaning operations. (2) Methods. Both traditional analytical techniques and innovative multispectral imaging were applied to solve the diagnostic issues and best address the restoration of the painting. Specifically, hypercolorimetric multispectral imaging (HMI), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FT-IR), optical microscopy, and gas chromatography coupled with mass spectrometry (GC-MS) were combined to obtain information on the general conservation state of the artwork and the characterization of pigments, organic binders, and superimposed materials, these last being particularly important to identify ancient and not-documented restoration intervention, enabling the correct choice of the most suitable and effective cleaning intervention. (3) Results. Multispectral data allowed us to differentiate and map original materials through infrared and ultraviolet false color images and spectral reflectance-based similarity maps, suggesting pigment attribution and focusing point analysis for characterization. This approach was particularly successful to identify and locate the presence of unaltered smalt blue in the first painting coat, which had been covered with other pigments, and to suggest the use of organic dye in mixtures with cinnabar and ochres. Spectroscopic and chromatographic techniques enabled us to identify the painting palette and confirm the use of oil-based binder for the pigments and characterize the altered top layers, made with a natural resin and an animal glue. (4) Conclusions. The characterization of the artwork’s materials was essential to select the most suitable methods and materials for the bio-cleaning, based on bacteria, experimented with during the restoration activities.