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This paper reports on the evaluation of a polyvinyl alcohol (PVA) “twin-chain” polymer network (TC-PN) combined with an oil-in-water nanostructured fluid (NSF) for the removal of a polyvinyl acetate (PVAc) varnish. Small Angle X-ray Scattering, Confocal Laser Scanning Microscopy, and Fluorescence Correlation Spectroscopy showed that the structure of the gel and the NSF are only minimally altered by loading the fluid into the gel. The NSF is partially free to diffuse through the network, but also interacts with the gel walls. During the cleaning, the dynamics of the fluid at the gel-substrate interface are controlled by the osmotic balance taking place among the interconnected pores. These features grant effective and controlled cleaning performances. The case study identified for this research is Pablo Picasso’s The Studio (L’Atelier, 1928), one of the masterpieces in the Peggy Guggenheim Collection, Venice (PGC). In 1969 the oil painting, originally unprotected, was wax-lined and then varnished using a PVAc varnish. Over the years, the white shades of the painting have been compromised by the yellowing of the varnish and soiling of deposits. On painting mock-ups, the NSF-loaded hydrogels allowed the swelling and softening of PVAc varnish and wax layers, which were then removed with gentle mechanical action. Effective varnish and wax removal at the micron scale, and the absence of residues from the cleaning system (gel and NSF), were confirmed by Fourier Transform Infrared Spectroscopy (FTIR) 2D imaging. The effective and safe removal of the aged PVAc varnish and wax layer from the surface of the painting was then carried out using the same cleaning protocol successfully tested on the mock-ups, setting the NSF-loaded PVA TC-PNs as robust and reliable tools for the cleaning of sensitive works of art.

Laser‐induced graphene (LIG) has been so far obtained from polymer precursors and proposed for numerous applications, including various types of sensors and energy storage solutions. This study examines a radically different class of new precursors for LIG, distinct from polymers: inks and dyes. The identification of specific organic dyes present in commercial markers demonstrates that the aromatic structure, in conjunction with high thermal stability (residual weight > 20% at 800°C), are key factors for laser‐induced pyrolysis. Eosin Y is identified as an excellent LIG precursor, comparable with well‐known polyimide. The unique properties of dyes allow for dispersion in various media, such as acrylic binder. A dye concentration of 0.75 mol L−1 in acrylic binder results in a conductivity of 34 ± 20 S cm−1 for LIG. The composition and microstructure of LIG from dyes are thoroughly characterized, revealing peculiar features. A versatile “Paint & Scribe” methodology is introduced, enabling to integrate LIG tracks onto any wettable surface, and in particular onto printed and flexible electronics. A process for obtaining freestanding and transferrable LIG is demonstrated by dissolving acrylic paint in acetone and floating LIG in water. This advancement offers novel avenues for diverse applications that necessitate a transfer process of LIG. Dyes are identified as a new class of precursor for Laser‐Induced Graphene (LIG). The conversion via laser‐induced pyrolysis and resulting LIG are systematically characterized. A new methodology called “Paint & Scribe” is introduced which allows the functionalization of any wettable surface with LIG and an integration with printed and flexible electronics.

The conservation of textiles is a challenge due to the often fast degradation that results from the acidity combined with a complex structure that requires remediation actions to be conducted at several length scales. Nanomaterials have lately been used for various purposes in the conservation of cultural heritage. The advantage with these materials is their high efficiency combined with a great control. Here, we provide an overview of the latest developments in terms of nanomaterials-based alternatives, namely inorganic nanoparticles and nanocellulose, to conventional methods for the strengthening and deacidification of cellulose-based materials. Then, using the case of iron-tannate dyed cotton, we show that conservation can only be addressed if the mechanical strengthening is preceded by a deacidification step. We used CaCO3 nanoparticles to neutralize the acidity, while the stabilisation was addressed by a combination of nanocellulose, and silica nanoparticles, to truly tackle the complexity of the hierarchical nature of cotton textiles. Silica nanoparticles enabled strengthening at the fibre scale by covering the fibre surface, while the nanocellulose acted at bigger length scales. The evaluation of the applied treatments, before and after an accelerated ageing, was assessed by tensile testing, the fibre structure by SEM and the apparent colour changes by colourimetric measurements.

One of the main problems connected to the conservation of street art is the selective removal of overlying undesired graffiti, i.e., drawings and tags. Unfortunately, selective and controlled removal of graffiti and overpaintings from street art is almost unachievable using traditional methodologies. Recently, the use of nanofluids confined in highly retentive pHEMA/PVP semi-interpenetrated polymer networks was proposed. Here, we report on the selective removal of acrylic overpaintings from a layer of acrylic paint on mortar mockups in laboratory tests. The results of the cleaning tests were characterized by visual and photographic observation, optical microscopy, and FT-IR microreflectance investigation. It was shown that this methodology represents a major advancement with respect to the use of nonconfined neat solvents.

Silk artifacts constitute an invaluable heritage, and to preserve such patrimony it is necessary to correlate the degradation of silk fibroin with the presence of dyes, pollutants, manufacturing techniques, etc. Fourier Transform Infrared Spectroscopy with a Focal plane array detector (FPA FTIR) provides structural information at the micron scale. We characterized the distribution of secondary structures in silk fibers for a large set of South American historical textiles, coupling FTIR with multivariate statistical analysis to correlate the protein structure with the age of the samples and the presence of dyes. We found that the pressure applied during attenuated total reflectance (ATR) measurements might induce structural changes in the fibers, producing similar spectra for pristine and aged samples. Reflectance spectra were thus used for the rigorous characterization of secondary structures. Some correlation was highlighted between the age of the samples (spanning over five centuries) and specific changes in their secondary structure. A correlation was found between the color of the samples and structural alterations, in agreement with the chemical nature of the dyes. Overall, we demonstrated the efficacy of reflectance FPA µ-FTIR, combined with multivariate analysis, for the rigorous and non-invasive description of protein secondary structures on large sets of samples.

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.

Semi-interpenetrating (IPN) poly (2-hydroxyethyl methacrylate)/polyvinylpyrrolidone hydrogels were synthesized and used for the removal of adhesives from the back of canvas paintings. The high water retention capability and the specific mechanical properties of these gels allow the safe cleaning of water-sensitive artifacts using water-based detergent systems. The cleaning action is limited to the contact area and layer-by-layer removal is achieved while avoiding water spreading and absorption within water-sensitive substrates, which could lead, for example, to paint detachment. The use of these chemical gels also avoids leaving residues over the treated surface because the gel network is formed by covalent bonds that provide high mechanical strength. In this contribution, the physicochemical characterization of semi-IPN chemical hydrogels is reported. The successful application of an o/w microemulsion confined in the hydrogel for the removal of adhesives from linen canvas is also illustrated.

Gels are particularly useful for the cleaning of works of art, as they allow the controlled delivery of cleaning fluids on solvent-sensitive substrates such as easel paintings. Owing to the presence of covalent cross-links between the polymer chains, chemical gels exhibit mechanical properties that allow their easy handling and their residue-free removal from artistic surfaces after the cleaning intervention. Organogels based on the cross-linking of methyl methacrylate (MMA) can be prepared as loaded with solvents for the controlled removal of unwanted layers from the surface of canvas paintings. Here, we propose MMA-based organogels obtained by solubilizing MMA in pure organic solvents (e.g., ethyl acetate, butyl acetate and ketones) and using a dimethacrylate cross-linker. The uptake/release behavior of the gels has been investigated, and their mesoporosity has been characterized through small-angle X-ray scattering. Finally, the gels have been used for the removal of historical varnishes from canvas painting samples, checking the absence of gel residues with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).

The project Saving Oseberg is funded by the Norwegian State with the aim to preserve the Viking Age wooden objects from the Oseberg burial mound. They were excavated in 1904 near Tønsberg, Norway, and many have been treated in the past with alum salts (KAl(SO 4 ) 2 ·12H 2 O). Alum was widely used during the early 1900s as a treatment for archaeological wood to prevent shrinkage and impart strength. In the 1990s, conservators observed an alarming condition of the objects. Initial investigations showed that the alum treatment has initiated a slow but ongoing deterioration process, attacking the wood for over 100 years. Today, the artefacts are highly acidic and have significantly reduced mechanical strength. In the last decade, the use of non-aqueous alkaline nanoparticle dispersions has provided successful results for the protection of cellulose-based materials. Alum-treated archaeological wood samples from Oseberg, with a pH ≤ 2, have been treated with alkaline nanoparticle dispersions, and the effects of the treatment have been evaluated by thermal analysis (TG-DTG), infrared spectroscopy (ATR-FTIR) and X-ray microtomography (micro-CT) analyses. In this contribution, the preliminary results will be presented.

The cleaning of artifacts must not alter the original properties of the objects. While the use of free solvents is risky, their confinement into polymeric networks can allow the safe removal of unwanted layers from artifacts. Recently, a methyl 2-methylprop-2-enoate (MMA)-based organogel was formulated as loaded with butan-2-one (MEK), and used to remove aged varnishes from canvas paintings. However, this formulation is not enough retentive to allow its use on paper, where higher retentiveness is needed to avoid the uncontrolled spreading of MEK and dissolved materials. Here, a new PMMA-MEK gel was designed to overcome this limitation. The amount of cross-linker and monomer used in the synthesis of the gel were tuned to achieve optimal retentiveness. Differential scanning calorimetry (DSC), differential thermogravimetry (DTG), small-angle X-ray scattering (SAXS) and attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) provided information on the solvent content, release rate, and mesoporosity of the gel as compared to the previous system. The lower solvent release rate of the new formulation allowed the safe removal of wax that jeopardized a 19 century paper document. The removal was confirmed through optical microscopy and ATR-FTIR, which also highlighted the absence of gel residues on the treated surface.