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Colloid science is contributing solutions to counteract the degradation of artifacts, favoring their transfer to future generations. Advanced materials such as nanoparticles, coatings, gels and microemulsions have been assessed in conservation, spanning from archeological sites to modern and contemporary art. We give an overview of the fundamental milestones and latest innovations in conservation science, targeting solutions and tools for remedial conservation based on green nanomaterials and hybrid systems. Future perspectives and outstanding challenges in this exciting field are then outlined. [ABSTRACT FROM AUTHOR]

This paper describes a cleaning method for removing ingrained carbonaceous dirt from lime-based wall paintings by utilizing hydrogels in combination with aqueous cleaning liquids. Nanorestore Gel® Peggy 6 has a number of advantages over traditional cleaning methods, and it is capable of holding large amounts of liquid, but it limits liquid penetration into the substrate. Cleaning action occurs only at the interface, without affecting the surrounding area or leaving residues. Furthermore, its viscosity makes it an ideal tool for treating irregular, vaulted surfaces. Laboratory experiments conducted on limewashed model tiles were decisive in the design of in situ experiments on fifteenth-century wall paintings. The cleaning efficiency of each method was assessed and quantified using colorimetry, 2-D FTIR mapping and image analysis using Cultural Heritage ImageJ. SEM-EDX was used for seeking residues. Results of both the model and in situ cleaning tests show a significant reduction of ingrained dirt when comparing Nanorestore Gel® Peggy 6 to traditional methods. Best visual results were obtained when cleaning with hydrogel loaded with 5% triammonium citrate was following by swabbing with a wet sponge. However, using water alone with the gel yielded almost as good a result in situ, making cleaning possible without any risk of residues. [ABSTRACT FROM AUTHOR]

Aged pressure sensitive tapes (PSTs) can compromise the integrity and readability of drawings and paper artworks. Typically, PSTs on contemporary artifacts are difficult to remove owing to degradation processes and to the intrinsic sensitiveness of paper, inks and dyes to the solvents and tools used in the traditional conservation practice. Alternatively, we provide here a critical overview and expansion on the use of two recently developed methodologies for the removal of PSTs, based on the confinement of cleaning fluids in retentive gels. Various combinations of PSTs backings and adhesives were addressed on paper mock-ups containing different types of artistic media (inks, dyes), monitoring the ability of a hydrogel and an organogel to gradually exchange, respectively, an oil-in-water microemulsion or diethyl carbonate through the PSTs backings, swelling the adhesive layers and enabling safe PST removal. It was shown that the two methodologies are complementary as they target the removal of tapes with different components. In all cases, selective tape removal was carried out without uncontrolled bleeding of inks or transport of dissolved matter through the paper matrix, thanks to the retentiveness of the gels. The two cleaning systems were then assessed on four completely different artworks on paper, where they proved to be versatile tools to remove aged PSTs, or re-adhere detackified tapes that were part of the original artwork. Overall, the two methodologies complement each other and allowed overcoming the limitations of traditional cleaning approaches. [ABSTRACT FROM AUTHOR]

Abstract: Aqueous nanostructured fluids (NSFs) have been proposed to remove polymer coatings from the surface of works of art; this process usually involves film dewetting. The NSF cleaning mechanism was studied using several techniques that were employed to obtain mechanistic insight on the interaction of a methacrylic/acrylic copolymer (Paraloid B72) film laid on glass surfaces and several NSFs, based on two solvents and two surfactants. The experimental results provide a detailed picture of the dewetting process. The gyration radius and the reduction of the Tg of Paraloid B72 fully swollen in the two solvents is larger for propylene carbonate than for methyl ethyl ketone, suggesting higher mobility of polymer chains for the former, while a nonionic alcohol ethoxylate surfactant was more effective than sodium dodecylsulfate in favoring the dewetting process. FTIR 2D imaging showed that the dewetting patterns observed on model samples are also present on polymer‐coated mortar tiles when exposed to NSFs. [ABSTRACT FROM AUTHOR]

The article focuses on the use of nanomaterials for conservation of artefacts. It states that microemulsions, due to their huge interfacial area, can be used for better cleaning of artefacts and are less toxic as compared to organic solvents such as aliphatic and aromatic hydrocarbons. It discusses the use of amphiphilic formulation, containing ethyl acetate, propylene carbonate and a surfactant, for the removal of aged acrylicâ€vinyl copolymers from historic murals.

Abstract: Past restorations performed with acrylic and vinyl polymers showed detrimental effects to wall paintings that lead to the complete disfiguration of the painted surfaces. The removal of these materials performed with the traditional solvent-based methodology represents a real challenge to conservators and usually achieves very poor results. This review reports on the new palette, nowadays available to restorers, based on microemulsions, micellar systems, physical and chemical gels specifically formulated for the cleaning of cultural heritage artefacts. These systems have been developed in the last twenty years within the cultural framework of colloids and surface science. [Copyright &y& Elsevier]

Abstract: This paper reports on the application of Soft Condensed Matter to the Conservation of Cultural Heritage and is manly based on the conversation that one of the authors (Piero Baglioni) had with Pierre Gilles de Gennes during his last visit to Florence. [Copyright &y& Elsevier]

Cultural Heritage is a crucial socioeconomic resource; yet, recurring degradation processes endanger its preservation. Serendipitous approaches in restoration practice need to be replaced by systematically addressing conservation issues through the development of advanced materials for the preservation of the artifacts. In the last few decades, materials and colloid science have provided valid solutions to counteract degradation, and we report here the main highlights in the formulation and application of materials and methodologies for the cleaning, protection and consolidation of works of art. Several types of artifacts are addressed, from murals to canvas paintings, metal objects, and paper artworks, comprising both classic and modern/contemporary art. Systems, such as nanoparticles, gels, nanostructured cleaning fluids, composites, and other functional materials, are reviewed. Future perspectives are also commented, outlining open issues and trends in this challenging and exciting field. [ABSTRACT FROM AUTHOR]

The removal of hydrophobic materials from a porous support, such as wax stains on wall paintings, is particularly challenging. In this context, traditional methods display several drawbacks. The limitations of these methods can be overcome by amphiphile-based aqueous nanostructured fluids, such as micellar solutions and microemulsions. In this study, a microemulsion for the removal of wax spots from artistic surfaces was formulated. The nanostructured fluid includes a non-ionic surfactant, i.e., Triton X-100, and two apolar solvents, namely p-xylene and n-nonane. The solvents were selected on the basis of solubility tests of three waxes in several organic solvents. The nanostructured fluid was characterized by means of small-angle X-rays scattering (SAXS) and the information about micelle structure was used to understand the interaction between the microemulsion and the selected waxes. The microemulsion was then tested during the restoration of the frescoes in the Major Chapel of the Santa Croce Basilica in Florence, Italy. After some preliminary tests on fresco mockups reproduced in the laboratory, the nanostructured fluid was successfully used to clean some wax deposits from the real paintings, hardly removable with traditional physico-mechanical methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nanostructured fluids are used to remove polymer coatings in art conservation. • Polymer films are either dewetted or swollen depending on their composition. • Surfactants have an important role in swelling polymer films. • Polymer swelling depends on the polymer glass temperature change induced by surfactants interaction with polymer films. • Nonionic are more efficient than zwitterionic/ionic surfactants in lowering the T g. Nanostructured fluids (NSFs) based on water, organic solvents and surfactants are a valid alternative to the use of neat unconfined organic solvents for polymer coatings removal in art conservation. The physico-chemical processes underpinning their cleaning effectiveness in terms of swelling/dewetting of polymer films were identified as key in this context. The role of surfactants on polymers' dewetting was considered to be mainly restricted to the lowering of interfacial tensions. However, recent experiments evidenced that surfactants have an important role in swelling polymer films. Five different amphiphiles were selected, namely: sodium dodecylsulfate, dimethyldodecyl amine oxide, hexaoxyethylene decyl ether (C 9-11 E 6), pentadecaoxyethylene dodecyl ether (C 12 E 15), and methyoxypentadecaoxyethylene dodecanoate (C 11 COE 15 CH 3). They were combined with a carefully selected organic solvents' mixture (1-butanol/butanone/dimethyl carbonate) to formulate new NSFs, differing for the surfactant only, and used to perform cleaning tests on surfaces coated with Paraloid B72® and Primal AC33®. Here for the first time, polymer swelling induced by surfactants was quantified and correlated with the glass transition temperature of the two polymers by differential scanning calorimetry, before and after the exposure to the fluids. Confocal laser scanning microscopy and small-angle X-ray scattering provided additional insights on the interaction mechanism. Nonionics were proven more efficient than zwitterionic/ionic amphiphiles in the polymer swelling, and, overall, methyoxy pentadecaoxyethylene dodecanoate resulted the most effective among the selected surfactants. A direct relation between the effect of surfactants on the polymers' glass transition temperature and cleaning capacity was established. This finding, fundamental to understand the interaction mechanism between NSFs and polymer coatings or paint layers, is key to achieve a selective, effective and complete removal of polymer coatings, as recently shown in the removal of vandalism and over-paintings from street art. [ABSTRACT FROM AUTHOR]