Biodeterioration of Incralac used for the protection of bronze monuments

Outdoor bronze sculptures are highly susceptible to corrosion in many environments and organic coatings are widely used for their protection. The purpose of this study was to determine the susceptibility of the commonly used coating Incralac to biodeterioration by microorganisms. A yeast was isolated from a bronze statue treated with Incralac and its ability to degrade Incralac was determined using growth curves, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The organism grew slowly on Incralac in liquid culture, but SEM images demonstrated its ability to adhere to Incralac coated metal. Additionally, the yeast caused a rapid drop in the low frequency impedance of Incralac coated metal that was not observed under sterile conditions, indicating that the organism accelerated deterioration of the coating. The potential for microbial growth to accelerate deterioration of Incralac should be considered when developing a maintenance strategy for the protection of outdoor metal monuments.     

Study of silica nanoparticles – polysiloxane hydrophobic treatments for stone-based monument protection

The growing interest in the conservation of historic buildings encourages the development of water-repellent materials and methodologies to consolidate and/or protect stones. Recently, particular attention was devoted to composites of inorganic oxides nanoparticles and hybrid siloxane or silicone polymers. Here we present a study on the water repellence of a thin protective coating obtained through sol-gel process starting from Glymo and Dynasylan 40®, and loading the silicate matrix with nano-sized silica particles (Aeroxide LE1® -Degussa-Evonik). The coatings were applied to limestone, sandstone and granite samples. The silica nanoparticles have been characterized by XRD, the siloxane matrix through micro-Raman spectroscopy, while the surface morphology was examined by SEM. The efficacy of the treatments has been evaluated through static contact angle measurements and capillary water absorption. The optical appearance of the coatings was evaluated by colorimetric measurements. Nanoparticles at suitable concentration gave high values for the static contact angle (up to ∼ 150°), for all stone species even for four months exposure to atmospheric conditions. The coatings, in the water capillary absorption tests, however, behave as expected only for granite even if the long-term water direct contact reduces the hydrophobicity.     

Effects of wax-based anti-graffiti on copper patina composition and dissolution during four years of outdoor urban exposure

The protection against graffiti has become a serious problem in most cities. Unfortunately such form of vandalism does not save the cultural heritage. The use of anti-graffiti coatings is a common treatment that can also temporary protect the surface from degradation due to interactions with the environment. Aspects that have not yet been sufficiently investigated from a metal artefact perspective are whether the presence of the anti-graffiti coating will influence the patina composition and reduce the degree of patina dissolution. Long-term (four years) effects of wax-based anti-graffiti coatings on bare copper sheet and pre-patinated copper exposed to urban atmospheric conditions are presented and discussed in terms of changes in patina dissolution rates, barrier properties and composition. The investigation is based on a multi-analytical approach combining chemical analysis, analytical and electrochemical tools (stereomicroscopy, FTIR, XRD, SEM/EDS, AAS, EIS, colorimetric measurements). Results are believed to provide important information related to the long-term applicability of such coatings to preserve the Cultural Heritage.     

Use of ZnO nanoparticles for protecting oil paintings on paper support against dirt,fungal attack,and UV aging

Zinc oxide nanoparticles were prepared and used for surface treatment of oil paintings painted on paper supports. The prepared coating mixture containing 2% of ZnO nanoparticles showed excellent transparency. The effect of coating on protecting the paper support and paintings against microbial attack by Trichoderma reesei and Aspergillus niger, dirt accumulation, and UV aging was studied. Coatings containing ZnO nanoparticles enhanced the durability of linseed oil-based paintings toward UV aging regarding the change in color. Coatings containing ZnO nanoparticles improved resistance to microbial attack when subjected to inoculums containing T. reesei or A. niger fungi. In addition, coatings containing ZnO nanoparticles reduced accumulation of dirt on oil paintings when left in open air for 6 months; cleaning of paintings was quite easy compared to the non-coated paintings or those coated with the varnish without ZnO nanoparticles.     

Testing a fluorinated compound as a protective material for calcarenite

A polyfluorinated compound was studied as a material for the specific protection of calcarenite. Water capillary absorption and vapour permeability measurements were carried out in order to evaluate efficiency as a protective agent. Particular attention was given to characterising its resistance against bio-deterioration induced by microorganisms such as blue and green algae. Chemical surface modifications were induced by UV-irradiation in a specially designed climatic chamber and were investigated through comparative tests on untreated and artificially weathered samples using X-ray photoelectron spectroscopy (XPS). This paper discusses the potential use of the compound studied as a specific coating material for the protection of calcarenite.     

Self-cleaning materials on Architectural Heritage: Compatibility of photo-induced hydrophilicity of TiO2 coatings on stone surfaces

Titanium dioxide (TiO₂) can be used to realize transparent self-cleaning coatings on stone surfaces as an active and preventive protection system, limiting cleaning and maintenance actions, reducing their costs in Architectural Heritage. This self-cleaning ability is due to photo-induced hydrophilicity on treated surfaces. The aim of this investigation is to analyze this effect, since it could bring to a greater water absorption, a potential source of damage for stone surfaces. Titania sol, obtained by sol-gel and hydrothermal processes, was deposited on travertine by spray coating, in two different ways. Water absorption by capillarity, static contact angle and a specific surface water absorption analysis were assessed before and after the TiO₂ treatments. The effects of deposited amount of titania on the characteristics of treated surfaces were evaluated. It was shown that there were no evident changes in the substrate reactivity without ultraviolet (UV) light exposure, while it seems that hydrophilicity due to UV light does not lead to higher water absorption, thus encouraging the use of TiO₂ coatings in the field of Architectural Heritage. However, before widely applying this conservative treatment, some further researches are recommended in order to better assess its durability and sustainability.     

Smart surfaces for architectural heritage: Preliminary results about the application of TiO2-based coatings on travertine

The development and application of self-cleaning treatments on historical and architectural stone surfaces could be a significant improvement in conservation, protection and maintenance of Cultural Heritage. In this paper, a TiO₂-based coating has been investigated in order to evaluate its possible use as a self-cleaning treatment. This coating was obtained by a sol-gel and a hydrothermal (134 °C) processes and then it was applied on travertine (a limestone often used in historical and monumental buildings) in two ways, obtaining a single-layer and a three-layer treatment, respectively. In order to verify its potential use in the field of Cultural Heritage, the maintenance of appearance properties of the treated travertine surfaces was monitored by colour and gloss analyses. Besides, de-pollution and soiling removal tests were carried out under ultraviolet-light exposure to evaluate photo-induced effects and self-cleaning efficiency. Results seem to allow the use of TiO₂-based treatments on historical and architectural surfaces made up by travertine, where de-pollution and self-cleaning photo-induced effects are well evident, maintaining their original visual appearance. Anyway, before applying TiO₂-based coatings as conservative treatments, further tests are needed especially on their durability, that is mandatory for Cultural Heritage applications. On-site test in an urban environment and accelerated test by weatherometer are currently under way.     

Effectiveness of antigraffiti treatments in connection with penetration depth determined by different techniques

The elimination of spray paint using traditional (chemical and mechanical) methods inevitably entails altering surface characteristics. Hence, the impact and deterioration caused by graffiti in heritage buildings and monuments have led to the development and application of preventive systems in the form of antigraffiti coatings (which prevent paint from seeping into the pores of the surface material and facilitate cleaning). The effectiveness of two of these treatments, a commercial product (fluoroalkyl siloxane, protectosil, marketed by Degussa) and a hybrid organic-inorganic material (Ormosil), was evaluated in five construction materials (limestone, granite, cement mortar, lime mortar and brick), in terms of their penetration into the substrate. A number of techniques were used to determine the penetration depth (SEM/EDX, micro-Raman and LIBS), because a comparative analysis showed that none was universally valid for all types of treatments. The results show that the presence of the coating on the surface of less porous materials only ensures effective cleaning when the surface is fairly smooth. In granite, for instance, the CF₃ terminals in the fluorinated treatment hinder spray paint bonding more effectively than Ormosil, but not efficiently enough to ensure complete removal of the paint from granite surfaces.     

Methyl–modified hybrid organic-inorganic coatings for the conservation of copper

A simple sol-gel technique for the preparation of methyl–modified silica coatings for the protection of the external surface of copper has been used in this study. Tetraethylorthosilicate (TEOS) has been used as a precursor to prepare nanosilica coatings on the surface of copper. The methyl–modified silica sols were obtained by mixing of 3% SiO₂ sol solution with trimethylchlorosilane (TMCS) or hexamethyldisilozane (HMDS) as basic materials. For comparison, the copper substrates were also coated with commercial polymers (Paraloid B 72, Plexisol P 550-40 and polyvinyl butyral (PVB)). The surface morphology changes of uncoated and coated specimens were investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The hydrophobicity of surfaces and photochemical ageing effects were evaluated by contact angle measurements. Potentiodynamic measurements were obtained in order to compare corrosion parameters of the coatings.     

The funerary klinai of tomb 1 from Amphipolis and a sarcophagus from ancient Tragilos, eastern Macedonia: a physico-chemical investigation on the painting materials

Optical and SEM-EDS microscopy, X-ray powder diffraction and micro FT-IR spectroscopy investigations of the funerary klinai (couches) of Tomb 1 from Amphipolis and a stone sarcophagus from ancient Tragilos—two painted monuments made by Macedonian craftsmen of the Early Hellenistic period—identified the original materials and painting technique, as well as synthetic materials used as consolidants during past restoration treatments. The original organic binders and the superficial modern coatings have been identified by micro FT-IR spectroscopy applied directly to the sampled powders or tiny fragments and to their solvent—soluble fractions. The pigments identified on the couch of Amphipolis are: red and yellow ochre, cinnabar, Madder lake, paratacamite and antlerite, carbon black, calcium carbonate, kaolin and gypsum. The identification of egg and animal glue confirms the application of tempera and secco techniques. The detection of polymers such as polydimethylsiloxane, polyvinyl acetate and alkyd resins, is related to modern restoration products. The pigments attested on the paintings of the Tragilos' sarcophagus are: red and yellow ochre, Egyptian blue, malachite, carbon black, calcium carbonate and gypsum. The absence of organic binders combined with the constant presence of calcium carbonate in all the examined samples suggests the use of lime as the binding medium in the painted decoration of the sarcophagus. The presence of Paraloid B72 is related to recent conservation treatments.     

Teodelinda's tales at Monza Cathedral: A physico-chemical diagnosis of the pictorial cycle

The pictorial cycle “Teodelinda's Tales” at Monza Cathedral, painted by Zavattari and his sons in 1444–1446, has been investigated by optical and SEM-EDS microscopy and microFT-IR spectroscopy. Paint layers, gildings and other metallic decorations have been analysed to elucidate the execution technique, the state of conservation and the possible retouchings in consequence of deterioration processes. Organic binders, coatings and adhesives have been also identified especially by microFT-IR spectroscopy applied directly to the sampled powders or fragments and to their solvent–soluble fractions. The obtained data offer a correct and satisfactory knowledge of the original organic and inorganic materials and those used in the subsequent retouches and restorations, their state of conservation and the painting techniques (fresco, mezzo fresco and secco).The physico-chemical investigations allowed to identify the nature and sometimes the provenance of the employed materials (i.e. ultramarine blue pigments) and some decay markers, particularly useful in understanding and describing the cycle realised by the authors and the modifications suffered along the centuries, and also to propose an integrated methodology for the scientific study of the mural paintings.     

Assessment of synthetic polymeric coatings for the protection and preservation of stone monuments

The performance of five synthetic coatings for the protection of stone monuments of Hellenistic and Byzantine period has been evaluated. The selected coatings included four commercially available siloxane-, siloxane/acrylic- and perfluoroether-based compositions, as well as a new composition based on newly synthesized fluoro-organosilane. The coatings were applied onto petrologically different stone substrates, such as marble, travertine, sandstone and a newly baked brick compatible with Roman period bricks, used for the restoration processes in Galerius Palace, Thessaloniki, Greece. The coatings' protective efficiency was investigated by measurement of water–stone contact angles, water vapor permeability, and water absorption by capillarity. The optical properties of the applied coatings were also investigated and they were also ranked with regard to their optical characteristics.     

Tailoring new fluorinated acrylic copolymers as protective coatings for marble

The protective performances of two new fluorinated acrylic copolymers (based on the monomers 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDM) and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIM) are evaluated and compared with Paraloid B72, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA) and its partially fluorinated homologous 2,2,2-trifluoroethyl methacrylate/MA (TFEM/MA). The polymeric materials have been tested on Candoglia marble, a very low open porosity stone (<1%) used in Italian historical architecture (Milan Cathedral). The copolymers were tested according to UNI-Normal protocol. Measurements of capillary water absorption, static contact angles, colour variation and water vapour permeability were made before and after accelerated photo-ageing. FTIR spectroscopy and size exclusion chromatography (SEC) analyses were carried out on samples aged on inert substrate to assess the photostability of the copolymers themselves. The relationship between the protection efficacy and the fluorine content and distribution has been investigated. The results obtained show that the addition of a partially fluorinated co-monomer to the Paraloid B72 copolymer structure did not result in the expected improvement of the coating properties, while the fluorination of the copolymer side chain gave rise to encouraging performance.     

A visible and long-wavelength photocured epoxy coating for stone protection

An epoxy coating modified by PDMS hydroxyl terminated is presented in this paper in order to evaluate its potential use as a protective of a stone surface. With a view to its use in restoration sites, visible and long-wavelength photoinitiated cationic polymerization is proposed here. The system investigated is based on a crosslinking mechanism which shows remarkable advantages for stone protection, such as the low toxicity of the products and facility of mixture preparation. Furthermore, the visible light exploitation represents the most important advantage, because it is easy to apply in a restoration site, with or without irradiation instruments. Besides coating characterization through FT-IR, DMTA analyses and contact angle measurement on glass slides, analyses were also carried out on coated plaster samples. These analyses were performed in order to evaluate the effectiveness of the protective, in relationship to hydrophobicity (contact angle measurement, capillary water absorption) and morphology surface changing (SE/SEM observations, colorimetric measurements) before and after polymer application and UV aging test of coated samples. The overall characterization makes it possible to consider it a suitable coating for stone protection.     

A new family of high viscosity polymeric dispersions for cleaning easel paintings

The procedures for making and applying a new family of high viscosity aqueous polymeric dispersions based on poly(vinyl alcohol)-borax (PVA-borax) matrices are presented. A specific system of this type has been used to remove an oxidized varnish coating from the surface of “Coronation of the Virgin with Saints”, a 15th century egg tempera painting on wood by Neri di Bicci (Florence, 1418–1492). FTIR spectra showed that the oxidized varnish was constituted of highly aged shellac resin. Good cleaning performance was attained when the liquid portion of the dispersion consisted of a mixture of water and acetone. Rheological investigations indicate that the acetone content does not affect the mechanical properties of the polymeric dispersion. Those mechanical properties permit easy removal of the cleaning agent simply by peeling it from the surface by means of a forceps or spatula once it has carried out its cleaning function. Optical microscopic and FTIR investigations show that the cleaning agent is able to remove the oxidized varnish coating from the surface of the Neri di Bicci painting without leaving detectable residues.     

Nanocontainer aqueous systems for removing polymeric materials from marble surfaces: A new and promising tool in cultural heritage conservation

The present study dealt with the characterisation of marble surfaces coated by three kinds of polymeric material usually employed in stones conservation and with the evaluation of the removal of these coatings from the surfaces by means of new nanocontainer aqueous systems constituted of micellar solutions (MS) and oil-in-water microemulsions (MC). The polymeric coatings were also subjected to accelerated artificial ageing in order to detect possible effects associated to natural photochemical ageing. The aim of the work was the assessment of the performance of such nanocontainer aqueous systems taking acetone (Ac) as a reference “traditional” solvent for the removal procedure. The characterisation was carried out by means of Scanning Electron Microscopy (SEM) and Environmental Scanning Electron Microscopy (ESEM), Fourier Transform Infra-Red (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopies and the results obtained showed that the performance of these innovative methods based on nanocontainer aqueous systems can be considered highly promising in the view of a “green approach” to the conservation of cultural heritage.     

Evaluation of the effect of phase change materials technology on the thermal stability of Cultural Heritage objects

The use of phase change materials (PCMs) in civil buildings as an effective thermal energy storage solution has been well documented in literature and proven in the field. When applied to Cultural Heritage, PCMs’ technology needs to be adapted to specific requirements. Besides the important objectives of economic return and human comfort, the indoor microclimatic conditions have to be suitable for conservation purposes. The application of PCMs’ technology to Cultural Heritage has been investigated within the European MESSIB (Multi-source Energy Storage System Integrated in Buildings) project. Firstly, several methodologies of incorporation of PCMs in different materials were studied and tested. The thermal properties of gypsum panels and silicon coatings incorporating micro-encapsulated PCMs in the form of powder and emulsion were analysed in the laboratory. Then, PCMs incorporated in gypsum panels in contact with a wooden panel were tested and their effect on the thermal behaviour of the wooden panel was evaluated under thermal cycles in a climatic chamber. PCMs incorporated in silicon coatings in contact with a painting were also tested. Moreover, gypsum panels containing PCMs were tested in the S. Croce Museum in Florence, Italy, where the microclimatic monitoring has shown thermal conditions potentially dangerous for the works of art preserved. The research performed both in the laboratory and on the field confirmed the effectiveness of the PCMs as thermal storage solutions, but also gave evidence on an important drawback when the material incorporating PCMs is in direct contact with an object of art.     

Self-calibrated quantitative elemental analysis by laser-induced plasma spectroscopy: application to pigment analysis

A new laser-based spectroscopic technique, called calibration-free LIPS (laser-induced plasma spectroscopy), is proposed for fast and precise elemental analysis in the field of cultural heritage conservation and study. Quantitative stratigraphic results, obtained by CF-LIPS on ancient Roman frescoe samples, are shown. The application of this calibration-free procedure frees the LIPS technique from the need of reference samples or an internal standard. This characteristic, along with the intrinsic speed (the whole process of data collection and analysis takes a few minutes) and precision (of the order of a few parts percent) make the CF-LIPS a viable technique for in situ quantitative analysis of artworks.     

Detection of diagenetic alterations by Spectroscopic Analysis on Archaeological Bones from the Necropolis of Poseidonia (Paestum): A case study

Understanding the chemical and physical alteration in archaeological bones, occurred after burial, is very interesting for researchers. In this paper, we present a study on the diagenetic alteration of human archaeological bony tissues from Paestum (South Italy), by combining complementary spectroscopic techniques, such as solid-state nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and X-ray diffraction. In particular, ¹³C nuclear magnetic resonance–cross polarization-magic angle spinning (¹³C NMR CP-MAS) spectroscopy allows to identify and discriminate the adsorbed calcite, that is a diagenetic contaminant, from the structural one of apatite and ¹H NMR-MAS spectroscopy shows how the degradation of organic phase of collagen is related to the time. The NMR data are combined with crystalline index, measured by X-ray diffraction, and with the splitting factor obtained by infrared spectroscopy. Moreover, the evaluation of the relative content of biogenic structural carbonate and of diagenetic fluorine is reported.     

New cellulosic titanium dioxide nanocomposite as a protective coating for preserving paper-art-works

We investigate the TiO₂ role in the inherent protection of paper works of art to protect them against damaging effect of ultraviolet radiation, pollutant gasses, mold and bacteria. In this study a cellulosic nanocomposite of TiO₂ were used as protective coating on the surface of paper fibers. This layered nanocomposite can act as a consolidate materials too. Furthermore, to determine how well paper works screen objects from the damaging effects, two accelerated aging mechanisms due to light and heat are discussed. Results show good stability of papers with nanocomposite coating. Also, a good light stability was shown in the colored paper that treated with this nanocomposite. Furthermore, to demonstrate the degree of antifungal properties of coated papers, papers were treated with two common molds and the good preventive effect of coated paper against molds is described.