Biodeterioration is an increasingly widespread process of degradation in the context of the conservation of cultural heritage, which involves a combination of physical and chemical damages together with an aesthetic alteration of materials. For biological damage on monuments caused by pathogens, macro- and microorganisms, chemical treatments are generally used, most of the time dangerous for the environment and for the operator. In this context, new eco-friendly products represent necessary tools for the treatment of biologically deteriorated stone surfaces and represent a new challenge in the field of restoration and conservation of materials of cultural interest. A relatively new class of unconventional green solvents are deep eutectic solvents (DESs), which have peculiar chemical-physical characteristics such as being non-toxic, ecological, biodegradable, non-flammable, and stable in the presence of water. Furthermore, many DESs known in the literature have also been shown to have a biocidal action. All these characteristics make DESs very advantageous and safe, and they could be used as biocidal agents for the treatment of biodegraded surfaces of cultural heritage, being non-toxic for the environment and for the operator. So far, they are used in various fields, but they still represent a novel frontier in the cultural heritage sector. The present research aims at testing five different DESs for the first time in cultural heritage. In particular, DESs are applied to a mosaic located in the Ostia Antica Archaeological Park (Rome), and their efficiency is compared with a biocide product currently used in the restoration field, namely, Preventol RI50, through luminescence, bio-luminometry, and spectrocolorimetry analysis. The preliminary results achieved show the different behaviors of each DESs, highlighting the possibility of employing them in the field of cultural heritage. Further studies have been planned, some of which are already underway, to investigate the properties of DESs and indicate any improvements to make them more effective, both as solvents and as biocides, and easy to apply to various types of materials. The results obtained from this first study are very promising for the use of DES as a new green strategy for cleaning and conservation treatments of materials in the field of cultural heritage.

In this work, the consolidation efficiency of SiO₂ nanoparticles (synthesized in the Chemistry laboratories at the Tor Vergata University of Roma) was tested on Pietraforte sandstone surfaces belonging to the bell tower of San Lorenzo (Florence, Italy) and was fully investigated. Nanoparticles (synthesized in large-scale mass production) have been characterized by XRD—X-Ray Diffraction; Raman and FTIR—Fourier Transform Infrared spectroscopy; SEM—Scanning Electron Microscopy; while the Pietraforte sandstone morphology was examined by Porosimetry, capillary absorption test, surface hardness test, drilling resistance and tensile strength. The colorimetric measurements were also performed to characterize the optical modification exhibited by Pietraforte sandstones, especially after the SiO₂ treatments. Our results show that applying to the Pietraforte, the new consolidating agent based on SiO₂ nanoparticles, has several advantages, as they are more resistant to perforation, wear, and abrasion even long range (for long times of exposure and consolidating exercise against Florentine sandstone), compared to the CaCO₃ nanoparticles (tested in our previous paper), which instead show excellent performance but only close to their first application. This means that over time, their resistance to drilling decreases, they wear much more easily (compared to SiO₂-treated sandstone), and tend to exhibit quite a significant surface abrasion phenomena. The experimental results highlight that the SiO₂ consolidation efficiency on this kind of Florentine Pietraforte sandstone (having low porosity and a specific calcitic texture) seems to be higher in terms of water penetration protection, superficial cohesion forces, and an increase in surface resistance. Comparing the performance of SiO₂ nanoparticles with commercial consolidants in solvents such as Estel 1000 (tested here), we demonstrate that: (A) the restorative effects are obtained with a consolidation time over one week, significantly shorter when compared to the times of Estel 1000, exceeding 21 days; (B) SiO₂ nanoparticles perform better than Estel 1000 in terms of cohesion forces, also ensuring excellent preservation of the optical and color properties of the parent rock (without altering it after application).

Preventive conservation and restoration of mural paintings in hypogean environments is a significant challenge. These types of settings are particularly difficult to manage due to their peculiar morphological and microclimatic features. Since its foundation in 1939, the Central Institute for Restoration (Istituto Centrale per il Restauro—ICR) within the Italian Ministry of Culture has been engaged in the prevention and safety of these unique cultural heritage assets. Starting from a holistic analysis of vulnerability and hazards specific to hypogean environments, this study examines the main risks and corresponding conservation strategies. Particular attention is given to the impact of residual risk on restoration decision-making, with the aim of defining logistical and operational requirements to carry out sustainable and enduring interventions in these complex settings. The compatibility and durability of restoration materials under hypogean conditions are also examined. Furthermore, thanks to funding provided by the PNRR CHANGES project, a few research directions are proposed to address unresolved issues through the investigation and assessment of innovative products and methodologies. This review aims to lay the foundation for the development of guidelines incorporating protocols for the conservation and restoration of mural paintings in hypogean contexts, with particular attention to the needs and constraints imposed by these specific environments.

This paper presents an overview of a research line developed at the Istituto Centrale per il Restauro within the CHANGES (Cultural Heritage Active Innovation for Next-Gen Sustainable Society) project, funded under the Italian National Recovery and Resilience Plan. The research was developed in different phases: a first one dedicated to the study of the deep background and the state of the art in the ICR background: history, methodologies and research in the field; a second phase was dedicated to the selection of a specific urban art mural, as a key study with conservation problems connected to some of the principal preservation treatments related to the outdoor context; the mural was also identified as a beloved icon in the public space with a profound socio-cultural meaning for the community. Nido di Vespe, created in 2014 by the artist Lucamaleonte is part of a broader artistic project called M.U.Ro-Museum of Urban Art of Rome, an open-air public art museum located in the Quadraro district in Rome, designed by the artist Diavù. A third phase focused on the research in ICR laboratories, specifically addressing: cleaning, reintegration, and protection strategies adapted to dynamic outdoor environments. A multi-step cleaning system based on polyvinyl alcohol-borax semi-interpenetrated hydrogels loaded with nanostructured fluids was developed to selectively remove spray-paint vandalism while preserving the chemically similar original pictorial layers. The reintegration phase investigated acrylic and urea-aldehyde resins as binders to produce compatible, reversible, and UV-traceable retouching and infilling materials. For surface protection, multilayer coating systems incorporating nanoparticles with antimicrobial, photocatalytic, and UV-stabilizing properties were formulated to enhance durability and chromatic stability. Laboratory tests on mock-ups simulating typical street and urban art materials and morphologies showed satisfactory results, while diagnostic investigations on Nido di Vespe provided the reference data to calibrate the experiments with real mural conditions. Cleaning tests demonstrated promising removal efficiency, influenced by the chemical composition, thickness of the overpainted layers, and surface roughness. The reintegration system met the expected performance requirements, as the tested binders provided good results and allowed the development of compatible, reversible, and distinguishable solutions. Protective coatings showed good results in terms of chromatic stability and surface integrity; however, the long-term behavior of both reintegration, cleaning, and protection systems requires further evaluation. The results achieved so far support the development of sustainable and flexible conservation strategies for the conservation of contemporary street and urban murals and will guide the future application of the selected materials and methodologies in pilot conservation interventions on the mural chosen as a meaningful case study within the broader research.

This paper presents the results of non-invasive diagnostic investigations performed on the canvas oil painting depicting the Marian iconography “Mater Boni Consilii”. The painting, whose author and origin are unknown, was found in an old shop in Florence following the overflowing of the Arno River in 1966. In order to define the importance of the artwork, a multianalytical analysis was performed on the painting, using multispectral imaging, X-ray fluorescence (XRF), and Fourier Transform Infrared Spectroscopy (FTIR-ATR) for the definition of materials, with a particular focus on the identification of pigments. The results allowed for the drawing up of a color palette, composed mainly of ochre and earth pigments, cinnabar, lithopone, lead white, and ultramarine pigments. After cross-referencing the acquired information with other findings, it was possible to place the painting in the period between the end of the XIXth and the beginning of the XXth centuries.

Consolidation treatments are essential for the conservation of wall paintings affected by decohesion and disintegration phenomena. In hypogean environments, high relative humidity, limited ventilation and elevated biological risk impose particularly stringent performance requirements. Under these conditions, consolidants must ensure chemical compatibility, effective distribution within water-saturated substrates, long-term stability at high relative humidity and low toxicological impact. Calcium-based nanomaterials, especially nanolime dispersions, are widely employed as reference consolidants. However, their performance is strongly influenced by the dispersing medium, environmental conditions and substrate characteristics. This study addresses the lack of comparative assessments of currently available calcium-based consolidants by testing four products—two alcohol-based nanolimes (Nanorestore Plus^® and CaLoSil^®), one aqueous nanolime dispersion (Nanolaq^®) and a laboratory-formulated aqueous nanocalcite—applied to painted mock-ups. For the first time, the effectiveness of these treatments was investigated under both high relative humidity and water-saturated conditions through a multi-analytical approach. Colorimetric variations, water vapour permeability, water absorption and consolidant distribution within the pictorial layers were evaluated. The results provide a comparative assessment of consolidant performance as a function of the hygrometric regime of the substrate, with differentiated responses under high-humidity conditions and attenuated differences under water-saturated conditions. Overall, the effectiveness of the consolidant appeared to depend significantly on the combined influence of the dispersing medium, the imbibition state of the substrate and its chemical nature, highlighting the need for selection criteria and evaluation protocols based on simulating realistic conservation conditions.