Study of a XVIII century hand-painted Chinese wallpaper by multianalytical non-destructive techniques

In this work, hand-painted wallpaper belonging to a private Portuguese collection was analyzed in order to identify the pigments used. The analyzed artwork was an extraordinary XVIII century Chinese wallpaper that depicts exotic birds and flowers, which was painted with considerable accuracy and expertise. Thorough, in situ, X-ray fluorescence analyses were performed on nearly all the wallpaper. Since the elemental content of several colors was consistent for the four papered walls, strategic micro-samples were taken and analyzed by confocal Raman spectroscopy to further identify the pigments used. Pigments such as yellow ochre, lead white and barium white, vermilion, carmine, azurite and malachite were identified. Optical microscopy was used to analyze the fibers in the paper support, and fibers such as kozo, ramie and hemp or linen were identified.     

Noninvasive and nondestructive NMR, Raman and XRF analysis of a Blaeu coloured map from the seventeenth century

A complete multianalytical study of a hand-coloured map from the seventeenth century is presented. The pigments atacamite, massicot, minium, gypsum, carbon black and vermilion were determined by means of XRF and Raman spectroscopy. The state of conservation of the cellulosic support was monitored by means of unilateral NMR. The analysis was nondestructive and noninvasive, and thus several spectra were collected from the same areas, yielding more reliable results without damaging the artwork. The role of copper pigments in the oxidation processes observed in the cellulosic support is discussed, as well as the possible provenance of atacamite as a raw material instead of as a degradation product of malachite.     

Improvements in the wallpaper industry during the second half of the 19th century: micro-Raman spectroscopy analysis of pigmented wallpapers

Scientific studies of the pigments used in the manufacturing process of some pigmented wallpapers are presented in this work. Non-destructive micro-Raman spectroscopy was selected for this purpose, and provides important information about how the 19th century wallpaper industry incorporated new materials in their works and designs. At the same time, analysis can help to date the samples of uncatalogued wallpapers. Chrome yellow, burnt Sienna, Prussian blue, ultramarine blue, red lead, carbon black, calcium carbonate, red iron oxide and a red organic pigment were identified. According to the palette used, as well as to the manufacturing process, the wallpapers in this study can be dated to the second half of the 19th century.     

Multispectral and hyperspectral image analysis of elemental and micro-Raman maps of cross-sections from a 16th century painting

Spectroscopic imaging is well suited to the study of micro-samples from artworks, where the sample material is limited and the maximum amount of information needs to be obtained. In this study, a new approach to imaging elemental data from energy dispersive X-ray analysis maps was used in conjunction with micro-Raman spectroscopic imaging to characterise the paint layers within micro-samples. Cross-sections from the 16th century painting Portrait of a Youth were found to contain vermilion, lead-tin yellow type 1 and a blue-green pigment consistent with terre-verte. The mid-preparatory layer (imprimatura) contains a high proportion of elements and mineral inclusions that indicates a clay-type composition. The ground layer was identified as anhydrite with large gypsum inclusions. The pigments and composition of the preparatory layers are consistent with those used by Italian Renaissance artist Dosso Dossi.     

Surface-enhanced Raman spectroscopy analysis of house paint and wallpaper samples from an 18th century historic property

Conservation efforts for heritage buildings require a substantial knowledge of the chemical makeup of materials that were used throughout the lifetime of the property. In particular, conservators are often concerned with the identification of colorants used in both interior and exterior wall treatments (paint, wallpaper, etc.) in order to gain perspective into how the building may have appeared during a certain time period in its existence. Ideally, such an analysis requires a technique that provides molecular level information as to the identity of the colorant as well as other sample components (binders, fillers, etc.), which is useful for dating purposes. In addition, the technique should be easily applied to paint layer samples which can be extremely thin and fragile. Herein we report the surface-enhanced Raman spectroscopy (SERS) analysis of paint and wallpaper samples taken from exterior and interior surfaces of a historic building. Several pigments were identified in the samples, which ranged from early inorganic pigments (lead white, barium sulfate, calcium carbonate, anhydrous chromium(III) oxide) which have been used in house paints for centuries, to a more modern pigment (phthalocyanine blue), developed in the middle of the 20th century. This analysis highlights the usefulness of SERS in such a conservation effort, and demonstrates for the first time pigment identification in house paints and wallpaper using SERS, which has far-reaching implications not only in the field of conservation, but also in forensics, industrial process control, and environmental health and safety.     

Effects of gamma rays on a restored painting from the XVIIth century

The subject of this study is a Peruvian painting from the 17th century, which has been recently restored and then contaminated by mould. It received different unsuccessful treatments. Therefore, radiation process was suggested as an alternative once it is an effective technology for decontamination and conservation purposes. The aim of this study is to investigate the influence of irradiation process on the original painting and on the products used in the restoration process. These products were irradiated with ⁶⁰Co gamma rays applying doses in the range of 6–25 kGy. The polymeric materials were characterized by thermal analysis techniques before and after irradiation. The colour of the pigments irradiated and non-irradiated were compared by spectrophotometric analysis. Small samples removed of the original painting were also irradiated and investigated. The results obtained until now allowed concluding that the irradiation with the appropriated dose of 6.0 kGy, according to the literature, will not damage the restored painting.     

Analysis by raman spectroscopy and XRF of glass beads from excavations in the harbor area of rio de janeiro,Brazil

In this paper, nine beads from excavations in the Valongo Wharf, located in the harbor area of Rio de Janeiro, Brazil that were utilized as ornaments by Africans and Afrodescendants during the 19th century were analyzed by Raman and X-Ray Fluorescence (XRF) spectroscopy. All samples in the analysis showed Raman spectra with two bands of maximum intensity around 1000 and 500 cm⁻¹ related to the maximum stretching (ν_max) and bending mode (δ), respectively, of the tetrahedral network of the SiO₄ present in the glass matrix. However, there is variation in the intensity and position of the bands that are directly associated with the burning process and the raw material utilized in the manufacture of the beads. Based on the polymerization index (I_p = A₅₀₀/A₁₀₀₀), it is possible to relate these two parameters. By establishing a correlation among the I_p and the ν_max band, the beads were classified into groups. The results reveal that the beads’ base paste exhibits differences, allowing their classification into groups according to the manufacturing process. Based on the combination of the elemental characterization and Raman spectroscopy results, it was also possible to conclude that European and Asian countries are the possible origins of the beads.     

Surface- and resonance-enhanced micro-Raman spectroscopy of xanthene dyes: from the ensemble to single molecules.

Surface-enhanced resonance Raman scattering (SERRS) spectra of various rhodamine dyes, of pyronine G and thiopyronine adsorbed on isolated silver clusters were recorded at the ensemble level and at the single-molecule level with a high-resolution confocal laser microscope equipped with a spectrograph and a CCD-detector. Comparing single-molecule spectra with ensemble spectra, various inhomogeneous spectral features, such as line splitting, spectral wandering, spectral diffusion and abrupt spectral jumps between different metastable spectral states, are revealed positions and the relative intensities of the vibronic bands. Resonance enhancement is investigated with respect to single-molecule surface-enhanced Raman scattering (SERS) spectroscopy and is found to be responsible for approximately three orders of magnitude in sensitivity. A significant influence of the substituents on the single-molecule SERRS sensitivity is found, showing that various chemical effects are responsible for surface enhancement in addition to the electromagnetic enhancement effect.     

Raman spectroscopic analysis of human remains from a seventh century cist burial on Anglesey,UK

Specimens from human remains exhibiting unusual preservation excavated from a seventh century stone cist burial at Towyn y Capel in Anglesey, UK, have been analysed using Raman spectroscopy with near-infrared laser excitation at 1,064 and 785 nm. Specimens of hair and bone provided evidence for severe degradation and microbial colonisation. The deposits within the stone cist showed that some microbially mediated compounds had been formed. Analysis of crystals found at the interface between the hair and the skeletal neck vertebrae revealed a mixture of newberyite and haematite, associated with decomposition products of the hair and bone. An interesting differential degradation was noted in the specimens analysed which could be related to the air-void and the presence of plant root inclusions into the stone cist. This is the first time that Raman spectroscopy has been used in the forensic archaeological evaluation of burial remains in complex and dynamic environments.     

Elucidation of molecular and elementary composition of organic and inorganic substances involved in 19th century wax sculptures using an integrated analytical approach

Wax sculptures contain several materials from both organic and inorganic nature. These works of art are particularly fragile. Determining their chemical composition is thus of prime importance for their preservation. The identification of the recipes of waxy pastes used through time also provides valuable information in the field of art history.The aim of the present research was to develop a convenient analytical strategy, as non-invasive as possible, that allows to identify the wide range of materials involved in wax sculptures.A multi-step analytical methodology, based on the use of complementary techniques, either non- or micro-destructive, was elaborated. X-ray fluorescence and micro-Raman spectroscopy were used in a non-invasive way to identify inorganic pigments, opacifiers and extenders. The combination of structural and separative techniques, namely infrared spectroscopy, direct inlet electron ionisation mass spectrometry and high temperature gas chromatography, was shown to be appropriate for unravelling the precise composition of the organic substances. A micro-chemical test was also performed for the detection of starch.From this study it has been possible to elucidate the composition of the waxy pastes used by three different sculptors at the end of the 19th century. Complex and elaborated recipes, in which a large range of natural substances were combined, were highlighted.     

Analysis of artist’s palette on a 16th century wood panel painting by portable and laboratory Raman instruments

Non-destructive analysis of the artist’s palette of ancient wooden panel paintings is a difficult task and studies are rare. Here we compare different methods of analysis of a wooden panel painting, dated to the early sixteenth century, mainly by Raman and infrared spectroscopies. Raman spectra were recorded on collected/sampled micrometric fragments using portable Raman instruments with laser excitation lines at 532 and 785 nm and transportable Raman instruments at 532, 633 and 785 nm; a fixed 1064 nm Raman spectrometer was also used. Infrared analyses were performed in Attenuated Total Reflection (ATR-FTIR) mode. Using the portable instrument, the Raman spectra evidenced white lead, calcite and vermilion only. Raman spectra recorded by transportable and fixed instruments enabled the identification of most of the artist’s palette: (i) white lead, calcite, gypsum and cerussite for white colour; (ii) vermilion, red lead, litharge, haematite for red; (iii) azurite, indigo and lapis lazuli for blue. IR spectra gave information on the organic binding media. XRF analysis on a brown pigment suggested an heterogeneous mixture of a red pigment (such as haematite and/or minium) and a green one as malachite. GC-MS analysis allowed identifying terpenic resin in the composition of the outer protective layer.     

Application of ATR–FTIR spectroscopy to the analysis of tannins in historic leathers: The case study of the upholstery from the 19th century Portuguese Royal Train

Tanning materials of historic leather samples collected from the 19th century Portuguese Royal train were analyzed by attenuated total reflection–Fourier transform infrared (ATR–FTIR) spectroscopy. Studied leathers were visually identified as morocco leathers, one of the most valued types of vegetable tanned leathers. In technical and historic literature, morocco leathers are described as a distinctive type of vegetable tanned leather, with a typical grain surface pattern, made from goat skins and sumac (Rhus coriaria) leaves.ATR–FTIR spectra of the Royal train leathers were investigated and compared with 10 reference tanning materials obtained from different plants in use in the 19th century, here described. Two different types of vegetable tanned leathers were identified. The obtained spectra allowed to confirm the presence of morocco leathers as well as to detect a different type of vegetable tanned leather, probably applied as a restoration material in a past intervention. This study shows the usefulness of ATR–FTIR to distinguish different types of historic leathers based in the spectroscopic characteristic IR bands of vegetable tannins used for leather production, which can be of great assistance for conservation condition assessments.     

Study of 19th century inks from archives in the Palazzo Ducale (Venice, Italy) using various analytical techniques

Inks and paper are the main materials and components of library and archive collections. Since the Third century B.C. there has been a continual succession of ink recipes from all over the world, with varying levels of documentation of the recipes used; however, it was only in the 19th century that Europe became the main producer and industrial leader in the discovery of new products. The aim of this study is to find out more about this last historical period, when new inks were created that had never been known or used in the past. In this study we chose four inks: they belong to documents preserved in the archive of the Superintendence Beni architettonici per il paesaggio e per il patrimonio storico artistico ed etnoantropologico (BAPPDAD) of Venice Lagoon, held in the Palazzo Ducale (Ducal Palace) of Venice.Fourier Transform Infrared Spectroscopy (ATR), Scanning Electron Microscopy (SEM-EDS) and pyrolysis coupled to a gas chromatograph with mass spectrometric detector (Py–GC–MS) allowed us to obtain a qualitative characterization of organic and inorganic elements in three different ink typologies.     

Analysis of a coloured Dutch map from the eighteenth century: the need for a multi-analytical spectroscopic approach using portable instrumentation

A Dutch map from the eighteenth century was multi-analytically analysed making use of energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), Raman and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS). The cellulosic support was characterised and its state of conservation was evaluated. Besides, paramagnetic impurities were detected together with copper metallic chips. The colours present in some areas of the map were also analysed. Vermilion, carbon black and organic pigments were found. Surprisingly, in the green areas, the rare presence of the mineral moolooite (copper oxalate) was detected. A possible biological attack is discussed in order to explain the presence of such compound. Almost all of the techniques used in the analysis were portable, non-destructive and non-invasive, which is very desirable when analysing objects belonging to Cultural Heritage. The need for a multi-analytical approach using portable instrumentation is also discussed.     

The infrared microspectroscopic and energy dispersive X-ray analysis of paints removed from a painted, medieval sculpture of Saint Wolfgang

A spectroscopic study of paints removed from a 15th century sculpture depicting Saint Wolfgang, which is housed in the Ball State Museum of Art, was performed. Infrared spectra on the minute paint samples were obtained using a microscope accessory in the transmission mode, and the spectra were compared to reference spectra of known art pigments and materials. In addition, energy dispersive X-ray spectra were obtained using a scanning electron microscope source. Although many of the pigments found are relatively modern pigments, the first application of paint is composed of materials consistent with the sculpture's medieval date. Pigments identified include brass gilding, calcium carbonate, China clay, lac dye, orpiment, Prussian blue, satin ochre, ultramarine blue and red, and zinc chromate. A zinc tungate finish was also identified.     

Multiwavelength Raman spectroscopy analysis of a large sampling of disordered carbons extracted from the Tore Supra tokamak

Disordered carbon often exhibit a complex Raman spectrum, with four to six components. Here, a large variety of disordered carbons, forming a collection of samples with a great variety of structures, are analyzed using multi-wavelength Raman microscopy (325.0, 514.5, 785.0 nm). They allow us to extend Raman behaviour known for nano-crystalline graphite to amorphous carbons, (dependence with the excitation wavelength) and other known for amorphous carbons to nano-crystalline graphite, (differentiation of the smallest cluster size probed using different excitation wavelengths). Experimental spectra were compared to simulated spectra, built using known laws, to evidence a new source of broadening.     

DFT study of the IR and Raman spectra of a fluorescent dendron built from cyclotriphosphazene core

Combined experimental and theoretical studies on molecular structure of the zero generation dendron, built from the hexafunctional cyclotriphosphazene core, with five OC₆H₄(CH₂)₂NHSO₂C₁₀H₆N(CH₃)₂ terminal groups and one oxybenzaldehyde group G₀ are reported. The Fourier transform Raman and IR spectra of G₀ have been recorded. Conformations of low energy isomers of G₀ have been studied at quantum-chemical level. The optimized geometry has been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. The theoretical geometrical parameters, harmonic vibrational frequencies, IR intensities and Raman scattering activities are predicted in a good agreement with the experimental data. It was found that dendron molecule G₀ has a concave lens structure with planar OC₆H₄CHO fragments and slightly non-planar cyclotriphosphazene core. Relying on DFT calculations the bands of the core and terminal groups were assigned. The frequencies of ν(NH) bands in the IR spectrum reveal the presence of the H-bonds in the dendron.     

A Histidine Residue and a Tetranuclear Cuprous-thiolate Cluster Dominate the Copper Loading Landscape of a Copper Storage Protein from Streptomyces lividans

The chemical basis for protecting organisms against the toxic effect imposed by excess cuprous ions is to constrain this through high-affinity binding sites that use cuprous-thiolate coordination chemistry. In bacteria, a family of cysteine rich four-helix bundle proteins utilise thiolate chemistry to bind up to 80 cuprous ions. These proteins have been termed copper storage proteins (Csp). The present study investigates cuprous ion loading to the Csp from Streptomyces lividans (SlCsp) using a combination of X-ray crystallography, site-directed mutagenesis and stopped-flow reaction kinetics with either aquatic cuprous ions or a chelating donor. We illustrate that at low cuprous ion concentrations, copper is loaded exclusively into an outer core region of SlCsp via one end of the four-helix bundle, facilitated by a set of three histidine residues. X-ray crystallography reveals the existence of polynuclear cuprous-thiolate clusters culminating in the assembly of a tetranuclear [Cu₄(μ₂-S-Cys)₄(Ν^δ1-His)] cluster in the outer core. As more cuprous ions are loaded, the cysteine lined inner core of SlCsp fills with cuprous ions but in a fluxional and dynamic manner with no evidence for the assembly of further intermediate polynuclear cuprous-thiolate clusters as observed in the outer core. Using site-directed mutagenesis a key role for His107 in the efficient loading of cuprous ions from a donor is established. A model of copper loading to SlCsp is proposed and discussed.     

Vibrational analysis of small species in the liquid phase by a combined density functional theory and polarizable continuum method

The vibrational frequencies of small organic molecules and inorganic ions were predicted both in vacuum and in the liquid phase at the B3LYP/6-311G++(d,p) level of theory, within the harmonic approximation. The solvent effect was introduced as an electrostatic influence of the bulk by means of the integral equation formalism of the polarizable continuum model. The results show that the application of this continuum solvation model can reduce the overall error in the theoretical predictions. In order to improve the quality of the results, two different scaling procedures were applied. The frequencies obtained for the continuum, when compared with vacuum calculations, show a better linear correlation with experimental data, which increases the efficiency of the scaling procedures. A further reduction of the errors is obtained by partitioning the overall set of frequencies according to the nature of the normal modes and the charge of the solutes. The quality of the theoretical predictions, especially for the stretching modes of vibration of nonionic chemical species, is here noteworthy.