No abstract

Reactive lignin nanocapsules catalyze a pigmentation reaction to furnish an innovative type of sustainable polyvalent bioink. In this nanodevice, the pigment, vehicle, binder, and additive are included in a single confined spherical space. Bioinks with different shades of color, black, gray, yellow-like, pink-like, and red/brown hues, have been prepared by selecting the reactants and the pigmentation process. Lignin nanocapsules play multiple functions in the support and activation of the enzyme necessary for the synthesis of pigments. Lignin nanocapsules protected the melanin pigment from alkaline and UV-degradation treatment.

The aim of this work has been to test the application of a new multispectral imaging system, named Hypercolorimetric Multispectral Imaging, on two little 17 th oil paintings on copper in order to support the restoration activities. Hypercolorimetric Multispectral Imaging is a non-invasive, rapid and diagnostic technique that allows in-situ accurate and reproducible spectral reflectance measurements between 300nm and 1000nm to obtain seven monochromatic very high spatial resolution images (36 Megapixels starting from RAW format). The acquired images are transformed into radiometric and colorimetric measurements, consisting in 7 monochromatic images of spectral reflectance and one colorimetric image. All these calibrated images constitute the base for further processing performed through a dedicated software that implements a number of functions. In the present study a subset of those functions has been used, specifically: Principal Component Analysis, spectral clustering, spectral mapping, multiband contrast enhancement and edge detection. Combining calibrated images of different spectral regions acquisitions, it was possible to extract relevant information about the state of conservation of the two copper paintings and further significant details were readable compared with the data coming from each single acquisition.The Hypercolorimetric Multispectral Imaging acquisition process revealed to be fast allowing to be performed during the cleaning stage of the paintings. The imaging nature of the analysis allowed to compare and map different areas of the surfaces producing degradation maps of the painting layers, which represent a precious decision-making tool for conservators.

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.

The famous Persian illustrated manuscript's page called "Humay meets the Princess Humayun" from Louvre Museum was investigated using multispectral imaging, X-ray fluorescence mapping and Raman spectroscopy for a deepen study of its constitutive materials and painting techniques and to evaluate the state of conservation of the artwork. Cross image treatments were also performed in order to extract further knowledge from the artwork. Due to the extreme fragile nature of the object and its outstanding value in the collection of Louvre's Department of Decorative Arts, noninvasive and contactless diagnostic methods were chosen. Hypercolorimetric Multispectral Imaging (HMI), a portable 7-band multispectral system and its native digital image processing (DIP) software for image treatment, was used to integrate X-ray fluorescence (XRF) imaging mapping to multispectral and colorimetric dataset. It allowed to study the rich color palette, identify original materials and restoration interventions and eventual degradations of both pictorial layer and ancient paper. Punctual Raman spectroscopy was performed to confirm hypotheses of pigments characterization made on infrared and ultraviolet false color images (IRFC, UVFC). Image treatments crossing multispectral data and analytical punctual techniques investigated possible correlation between datasets providing interesting and easy-to-read distribution maps for chemical elements, which are characteristic for pigment identification. In particular, pigments not detectable through XRF for light-element limit of detection as ultramarine blue (lapis lazuli) and organic dyes were successfully identified and mapped. This integrated approach of multisource imaging data is a valuable tool for restorers and conservators, encouraging new protocols of noninvasive diagnostics for cultural heritage.