Non-destructive in situ determination of pigments in 15th century wall paintings by Raman microscopy

Raman microscopy has been applied to the study of 15th century wall paintings in a chapel of St. Orso Priory palace (Aosta, Italy) in view of their restoration. The use of a transportable instrument has made it possible to work non-destructively in situ without sampling. The main inorganic pigments used by the unknown artist, namely mercury sulphide, azurite, white lead, red and yellow ochre, carbon black and lead tin yellow type I have been identified, and the presence of organic substances and of some decay products (calcium sulphate and oxalate) has been observed.     

Identification of lead pigments in nanosamples from ancient paintings and polychromed sculptures using voltammetry of nanoparticles/atomic force microscopy

Voltammetry of nanoparticles coupled with atomic force microscopy was used to identify lead pigments in nanosamples proceeding from works of art. Upon mechanical attachment of few nanograms of sample to a graphite plate, well-defined voltammetric responses were obtained for lead orange, lead yellow, lead white, litharge, minium, Naples yellow, and tin-lead yellow, allowing for an unambiguous identification of such pigments. Atomic force images provide evidence for the occurrence of pigment-characteristic reduction processes accompanied by metal deposition on the graphite substrate. Electrochemical parameters are used for pigment identification. Application to the method for identifying lead pigments in different model binder + pigment specimens and pictorial samples from the canvas painting collection (anonymous, 17th century) of the Saint Joseph Church in Taormina (Italy), the frescoes painted by Antonio Acisclo Palomino y Velasco (1698) in the vault of the Sant Joan del Mercat church in València (Spain) and an anonymous polychromed sculpture (16th century) representing a Martyr Saint from Alacant (Spain) is described.     

Analytical contributions to the evaluation of painting authenticity from Princely church of Curtea de Arges

The present study contains the analyses performed for pigment samples taken from the Princely church of Curtea de Arges, one of the oldest churches in Romania. The results of our investigations have shown the source of these samples, thus being identified the pigments: natural ultramarine, cinnabar, red earth, and calcium carbonate in the painting from the 14th century, the pigments: lead white, zinc white, and Prussian blue in the repainting from the 19th century and the pigments zinc white, titanium dioxide white, bone white, yellow ochre, red ochre, green earth, artificial ultramarine, and mars red in the interventions carried out in the 20th century. The analyses consisted of light microscopy (LM) and microchemical tests, as well as energy dispersive X-ray (EDX) analysis. This system of analyses allows one to precisely determine the authenticity of certain pigments, thus avoiding the dating errors for different interventions carried out on the original mural painting from the Saint Nicholas Princely church of Curtea de Arges.     

Analysis of pigments from Roman wall paintings found in Vicenza

The analysis of about 60 samples of wall paintings was carried out using different chemicophysical techniques: optical microscopy, scanning electron microscopy (SEM) equipped with an EDS microanalysis detector, X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The identified pigments were cinnabar, hematite, red ochre, celadonite, cuprorivaite (Egyptian blue), yellow ochre, goethite and carbon. Only in one case some lead white was found instead. In general, the mortar preparation did not correspond to the complex structure suggested by Vitruvius (De Architectura), but it generally showed a porous layer, with crushed grains under the pigment layer. In certain cases two superposed pigment layers were found: yellow superimposed on both red and pink, black on pink, green on black.     

In situ investigations of vault paintings in the Antwerp cathedral

X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy have been used to examine 15th century mediaeval and 16th century renaissance vault paintings in the Our Lady's Cathedral (Antwerp, Belgium) in view of their restoration. The use of mobile instruments made it possible to work totally non-destructively. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the pigments. For the 15th century vault painting the pigments lead–tin yellow (Pb₂SnO₄), lead white (2PbCO₃·Pb(OH)₂), vermilion (HgS), massicot (PbO) and azurite (2CuCO₃·Cu(OH)₂) could be identified. The pigments used for the 16th century vault painting could be identified as red lead (Pb₃O₄), hematite (Fe₂O₃), lead white (2PbCO₃·Pb(OH)₂) and azurite (2CuCO₃·Cu(OH)₂). For both paintings the presence of the strong Raman scatterer calcite (CaCO₃) resulted in a difficult identification of the pigments by Raman spectroscopy. The presence of gypsum (CaSO₄·2H₂O) on the mediaeval vault painting probably indicates that degradation took place.     

Argentinean prehistoric pigments’ study by combined SEM/EDX and molecular spectroscopy

Composition of the prehistoric pigments’ (from Carriqueo rock shelter, Rio Negro province, Argentina) has been analysed by means of molecular spectroscopy (Fourier transform infrared (FTIR) and micro-Raman) and scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDS). Red and yellow pigments were recognized as red and yellow ochre. The matrix of the pigments is composed of one or more substances. According to the matrix composition yellow and red pigments were also divided into two groups—i.e. those containing kaolinite or sulphates. Green pigment was detected as green earth, made up of celadonite as a chromophore.     

Use of Raman microspectroscopy to characterize wallpaintings in Cerro de las Cabezas and the Roman villa of Priego de Cordoba (Spain)

The analysis by Raman microscopy of several wallpainting fragments found at an archaeological site in Fuente Tojar and in the Roman villa of Priego de Cordoba, both in southern Spain, revealed that the most abundant colours in them were obtained from the usual pigments of the time. Thus, red corresponded to red ochre, which consisted of hematite mainly. Also, yellow came from yellow ochre (goethite), blue from Egyptian blue, and grey hues were obtained from mixtures of coal and calcite occasionally also containing gypsum. The components of some pigments were confirmed by X-ray diffraction spectroscopy. The two spectroscopic techniques were additionally used to examine the mortars and the preparatory layer present in the fragments.     

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.     

Non-invasive and non-destructive micro-XRF and micro-Raman analysis of a decorative wallpaper from the beginning of the 19th century

Non-destructive and non-invasive micro-Raman fibre optic and micro-XRF analyses were performed to study a wallpaper from the beginning of the 19th century. The complementarity of these two non-destructive techniques is shown in this work. The analysed artwork is considered one of the most beautiful wallpapers ever manufactured according to the catalogues and books; it is known as Chasse de Compiègne, manufactured by Jacquemart, Paris, in 1812. During the analysis, an unexpected pigment was detected by both analytical techniques: lead-tin yellow type II. This pigment was used until ca. 1750, when other yellow pigments replaced it, thus it is very difficult to find it in paintings afterwards. Together with this pigment, red lead, Prussian blue, brochantite, yellow iron oxide, calcium carbonate, vermilion, carbon black of animal origin (bone black), lead white, and raw and burnt sienna were also determined by combining the analytical information provided by both techniques. A possible degradation of brochantite to antlerite is also discussed.     

Composition of prehistoric rock-painting pigments from Egypt (Gilf Kébir area)

The composition of rock-painting pigments from Egypt (Gilf Kebia area) has been analyzed by means of molecular spectroscopy such as Fourier transform infrared and micro-Raman spectroscopy and scanning electron microscopy coupled to an energy dispersive X-ray spectrometer and X-ray fluorescence analysis. Red and yellow pigments were recognized as red and yellow ochre with additional rutile.     

Raman spectroscopy as a means for the identification of plattnerite (PbO2), of lead pigments and of their degradation products

The Raman spectra of plattnerite [lead(IV) oxide, PbO2] and of the lead pigments red lead (Pb3O4), lead monoxide [PbO, litharge (tetragonal) and massicot (orthorhombic)], lead white [basic lead carbonate, 2PbCO3.Pb(OH)2] and of their laser-induced degradation products were recorded using a range of different excitation lines, spectrometer systems and experimental conditions. The degradation of PbO2 is more extensive along the pathway PbO2-->Pb3O4-->PbO (litharge)-->PbO (massicot) the shorter the wavelength of the excitation line and the higher its power. The Raman spectrum of PbO2, which is black and of the rutile structure, is particularly difficult to obtain but three bands, at 653, 515 and 424 cm-1, were identified as arising from the b2g, a1g and e(g) modes respectively, by analogy with the corresponding modes of isostructural SnO2 (776, 634 and 475 cm-1). A further oxide was identified, PbO1.55, the Raman spectrum of which does not correspond to that of any of the laser-induced degradation products of PbO2 at any of the wavelengths used. The Raman results are critical to the future use of Raman microscopy for the identification of lead pigments on artworks.     

Micro-Raman analysis of coloured lithographs

Raman micro-spectroscopy was chosen for analysis and identification of the pigments present in four nineteenth-century hand-coloured lithographs, as this technique has several advantages over others for this purpose. The possibility of performing completely non-destructive analysis without any sampling is probably one of its most favourable qualities for art analysis. Raman spectroscopy can also be used to determine some pigments that cannot be detected using FTIR, such as vermilion, carbon blacks, cadmium pigments, etc. Among others, Prussian blue, ultramarine blue, carbon black, chrome yellow, yellow ochre, red lead, red iron oxide, burnt Sienna, indigo blue, chrome orange, phthalocyanine green, and some other organic pigments, were determined in the specimens. The results obtained have led to doubts about the age of the lithographs.     

Investigation of roman age pigments found on pottery fragments

This work deals with the study of the physico-chemical characteristics of pigments found on pottery fragments from an excavation in Vicenza (Contrà Pedemuro S. Biagio). The examined pigments were: a blue colour on a terracotta fragment; an olive green on a black pot bottom; yellow traces on a red depurated terracotta; an olive green plate bottom with an amaranth “a fresco” test; a deep red on a depurated terracotta; a white trace, again on a depurated terracotta. The techniques used were optical microscopy, scanning electron microscopy (SEM), equipped with an energy dispresive (EDS) microanalysis detector, X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Most of those techniques were non-destructive and able to provide the required results. All the pigments belonged to the group of basic colours, we did not find “precious” pigments. They have many similarities to those discovered in other European sites in France and Switzerland, witnessing the active trading exchange in which X^a Regio, Venetia et Histria played an important role.     

The identification by Raman microscopy and X-ray diffraction of iron-oxide pigments and of the red pigments found on Italian pottery fragments

The technique of Raman microscopy has been used to identify and characterise the pigments used in red shards of medieval and earlier items of pottery which have been found in various archaeological sites in the South of Italy. The research has led to the identification, on the basis of their characteristic Raman/resonance Raman spectra, of the red pigments as iron(III) oxide (e.g. Indian Red, Red Ochre or Venetian Red) and the yellow pigments as hydrated iron(III) oxyhydroxide (e.g. Yellow Ochre and Mars Yellow). X-ray powder diffraction experiments confirm the conclusions drawn above.     

Analysis of Roman age wall paintings found in Pordenone, Trieste and Montegrotto

The aim of the present work is the study of many fragments of wall painting from archaeological excavations in three different Roman age sites dating back to the I Century before Common Era: Pordenone (località Torre); Trieste (Crosada) and Padova (Montegrotto). The techniques used were optical microscopy, scanning electron microscopy (SEM), equipped with a EDS microanalysis detector, X-rays powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Fourier transform Raman spectroscopy (FT-Raman) and electron paramagnetic resonance (EPR) spectroscopy. The identified pigments were: cinnabar, hematite, celadonite, glauconite, cuprorivaite (Egyptian blue), yellow and red ochre, calcite, limonite, coal black.In general, the mortar preparation did not correspond to the complex procedure suggested by Vitruvius (De Architectura), but generally showed a porous layer, with crushed grains under the pigment layer. In some cases, two superimposed pigment layers were found: yellow superimposed on both red and pink, black on pink, green on black.The slight differences we found in the use of the pigments in the three studied sites might show that the same technology, culture and taste spread all over the Roman Empire in North Eastern Italy (X^a Regio Venetia et Histria).     

Byzantine wall paintings from Kastoria, northern Greece: spectroscopic study of pigments and efflorescing salts

This study concerns the investigation of pigments and efflorescence phenomena on the wall paintings of Kastoria, a rural, non-metropolitan Byzantine town. A large number of representative samples were collected from the murals of three churches, dated to post-Byzantine era (14th-17th c. AD). The identified pigments for the red colour were hematite (Fe2O3), cinnabar (HgS) and minium (Pb3O4), while brown and yellow colours were attributed to mixtures of ochres (Fe-oxides and hydroxides) and lime. The utilization of admixtures of iron, lead and mercury compounds was also attested in order to render specific tones on the painted surfaces. Black and dark blue hues were prepared using black carbon and Mn in some cases. Grey colours were assigned to a mixture of black carbon and lime. Green colour is rather attributed to admixtures of Fe-rich minerals and lime and not to the commonly used green earths. Baryte (BaSO4) was also evidenced as a filler or extender. Phosphorous was detected and connected to proteinaceous material and Mo and Sb were traced which are probably affiliated to Fe-oxides. Regarding efflorescing salts, the determined compounds are: calcite, dolomite, gypsum, halite, nitratine, natron and mirabilite, all of which are related to temperature and humidity changes and moisture fluctuations inside the wall paintings.     

Characterization of slate ornaments from Teotihuacan by nuclear and conventional techniques

Several ornaments named tezcacuitlapilli (coccyx-mirrors) are described and chemical analyses of raw materials (slate and pigments) were carried out by neutron activation, X-ray diffraction, scanning electron microscopy and radiography. Elemental and statistical analyses revealed that three different kinds of slate were used in their manufacture. The white pigment contains gypsum while ochre, yellow and red pigments contain iron oxide. These ornaments were identified as coming from the Cave of the Sun Pyramid of Teotihuacan. An attempt was undertaken to reconstruct the contexts of their manufacture and symbolic interpretation.     

A noninvasive complementary study of an Egyptian polychrome cartonnage pigments using SEM,EPMA, and Raman spectroscopy

Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were used to study pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 bc ). The surface morphology of each color region was examined using backscattering (BS) and secondary electron imaging. SEM X-ray energy dispersive spectrometry and EPMA wavelength dispersive spectroscopy provided semiquantitative chemical analysis of each pigment. Raman spectroscopy was used to identify the minerals associated with the pigments. This technique confirmed the presence of cinnabar (α-HgS) in the red part of the fragments. A mixture of orpiment (As₂S₃) and bonazziite (β-As₄S₄) and/or alacránite (As₈S₉) was detected in the yellow regions of the fragments. The orange pigment was confirmed to be a mixture of orpiment, uzonite (χ-As₄S₅), and pararealgar (As₄S₄). Egyptian blue (CaCuSi₄O₁₀) and Egyptian green ((Cu,Ca)SiO₃) pigments were detected from blue/green dark-colored regions of the fragments.