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The ability to observe traces of biological material on buildings and stone artworks is of particular importance in understanding how to best deal with them and maybe, in the future, even make use of biofilms for conservation science. We have identified hyperspectral imaging as a viable method for the efficient analysis of such biological materials. Thanks to the high throughput of our approach based on an interferometric method based on Fourier Transform, we were not only able to detect traces of biofilms on stone samples, but also to map in which areas these were found to have higher biological activity.

Street Art is an artistic expression in constant development, whose interest has grown in recent years among society, public administrations, conservators, and heritage scientists. This growing awareness has given rise to a series of debates between professionals with the intent to expand the knowledge relating to conservation practices and possible protection solutions. Additionally, the paint materials used by contemporary artists are in constant development; therefore, difficulty has emerged in the identification of their degradation processes when exposed to environmental conditions and in the consequent selection of a specific protection system. This review presents an overview of the recent literature and experiences in the field of knowledge and preservation of Street Art, focusing on the type and nature of paint formulations, the main deterioration processes of painted artworks in outdoor conditions, and the most recent advances in materials and methods for the conservation and protection of Street Art. This review aims to emphasise how the approach to the challenge of preservation of Street Art is complex, aspiring to the need for optimised diagnostic protocols for the development of innovative and effective protective coatings. This paper is a starting point to provide suggestions and indications for the development of further research projects within the framework of preservation and protection of contemporary muralism. [ABSTRACT FROM AUTHOR]

The Colossus of San Carlo Borromeo, named San Carlone for its large dimensions, represents a unique opportunity to study the long-term effects of atmospheric corrosion on patina formation on historic copper sheets. The sculpture's large dimensions, complex geometry, direct visitor interaction, and exposure conditions generate different microclimates. The purpose of this study is to understand how and to what extent these microclimates affect the formation of the copper patinas. The results show that microclimates play a key role in patina formation: in external surfaces exposed to rain, the main constituent is brochantite, whereas a wider variety of corrosion products have been found in sheltered and internal surfaces, such as antlerite, atacamite, copper oxalate, posnjakite, and anglesite. [ABSTRACT FROM AUTHOR]

The study of characterisation and production of artificial patinas plays a key role in the field of cultural heritage. In particular, artistic patinas should be considered as an integral part of the artworks, as they are deliberately produced by artists and metalworkers as a part of their artistic design. Therefore, it is important to achieve a good knowledge of their composition and corrosion behaviour in order to setup and perform optimal conservation strategies for their preservation. In addition, the possibility of realising laboratory patinas that are as representative as possible of natural corrosion layers is important for the realisation of laboratory specimens which can be used as reliable model systems (mock-ups) for the study of degradation mechanisms and conservative treatments. For this work, both artistic and laboratory patinas have been considered and investigated. In particular, six different artistic patinas produced by Fonderia Artistica Battaglia were characterised. Moreover, a series of laboratory patinas was produced according to chemical procedures adapted from those already reported in the literature. The patina morphology was evaluated by stereomicroscopy observations, their composition was analysed by means of FTIR and XRD analysis and their corrosion behaviour was evaluated by LPR and EIS measurements. Finally, the LPR and EIS analysis have pointed out the low protection provided by the corrosion layers of artistic patinas. In regard to laboratory patinas, the optimized procedures of production were found to be effective for the realization of the main corrosion products of copper-based surfaces. From an electrochemical point of view in particular, quite different electrochemical behaviours were observed on artificial corrosion layers with the same chemical composition. [ABSTRACT FROM AUTHOR]

In the past decade, the usage of soft materials, like gels, has allowed for a better control of the water release process into the substrate for cleaning interventions. Agar—a natural polysaccharide harvested from algae—has been used to perform cleaning of stone materials, gypsum works, and paintings with remarkably positive results. Agar presents the great advantage of being cheap, easily available, fast to produce and not toxic, allowing for more sustainable conservation works. More recently, a new type of agar fluid, agar foam, promises further control of the water release and ease of application on delicate surfaces. In the present study, this new type of agar, CO2 and N2O foams, has been characterized and compared with the conventional sol/gel agar system. Moreover, the cleaning effectiveness of the agar foam was tested both in laboratory conditions and in two case studies: a historical gypsum from the porch framing of the Abbey of Nonantola, and the 20th century gypsum cast of the Pietà Rondanini by Michelangelo, located in the Sforza Castle in Milan. The obtained results show that foaming changes the sol-gel transition temperature of the agar gel as well as incrementing its dissipative behavior. When freshly applied, the foams flow with a reduced velocity, thus allowing a better control and ease of application. Once gelified, they act as a soft solid-like material, as shown by their rheological properties. Moreover, it was found that CO2 foam slightly reduces the water release to the surface, while maintaining the moldability and ease of application. The study allows for the conclusion that agar foam offers an interesting alternative for delicate surfaces, with a non-coherent mineral deposit, and with complex geometries that often represent a challenge for the conventional agar applications [ABSTRACT FROM AUTHOR]

A system for advanced fluorescence investigation of works of art has been assembled and integrated in a characterization procedure that allows one to localize and identify organic compounds that are present in artworks. At the beginning of the investigation, fluorescence lifetime imaging and spectroscopy address a selective microsampling of the artwork. Then analytical measurements of microsamples identify the chemical composition of the materials under investigation. Finally, on the basis of fluorescence lifetime and amplitude maps, analytical data are extended to the whole artwork. In such a way, information on the spatial distribution of organic materials can be inferred. These concepts have been successfully applied in an extensive campaign for analysis of Renaissance fresco paintings in Castiglione Olona, Italy. Residue of various types of glue and stucco left from a restoration carried out in the early 1970s was localized and classified. Insight into the technique used by the painter to make gilded reliefs was also obtained. OCIS codes: 300.6500, 300.2530, 110.2970, 160.2540.

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