The first in situ Raman spectroscopic study of San rock art in South Africa: procedures and preliminary results

Southern Africa has a rich heritage of hunter‐gatherer, herder and farmer rock art traditions made by using both painted and engraved techniques. Until now, there have been only a handful of studies on the chemical analysis of the paint, as all previous types of analysis required the removal of pigment samples from the sites a practice which has been avoided. Raman spectroscopy is an ideal techniques to analyse the paint non‐destructively and also offers the possibility of in situ work with portable instruments. This article describes the procedures and reports the preliminary results of the first in situ Raman spectroscopic study of rock art in South Africa (also a first worldwide), where we, first, evaluate the capability of a Raman portable instrument in very difficult conditions, second, analyse the paints in order to contribute to a better knowledge of the technology used and, third, evaluate the possible contribution of in situ analyses in conservation studies. The paintings from two different rock art sites were studied. The instrument proved to be highly suitable for in situ analyses in physically very challenging conditions. Most of the pigments and alteration products previously detected under laboratory conditions were identified, thereby giving information on both the pigments and conservation state of the paintings. A layered structure of alteration products and pigment was identified in situ for the first time by controlling the laser power, thereby obtaining the same results as in mapping experiments of cross sections of paint. Copyright © 2010 John Wiley & Sons, Ltd.     

The first Raman spectroscopic study of San rock art in the Ukhahlamba Drakensberg Park,South Africa

San rock art sites are found throughout southern Africa; unfortunately this unique heritage is rapidly being lost through natural weathering processes, which have been the focus of various studies conducted in the uKhahlamba Drakensberg Park since 1992. It has recently been shown that the ability of Raman spectroscopy to identify salts on rock faces on a micro, as well as nano scale, can make a contribution to these projects. In order to test the feasibility of undertaking on‐site analyses, a small rock fragment with red and white pigments still attached, which had weathered off the rock face, was analysed with Raman spectroscopy under laboratory conditions, using a Dilor XY Raman instrument and a DeltaNu Inspector Raman portable instrument. A small sample of black pigment (<1 mm²), collected from a badly deteriorated painting and a few relevant samples collected on site, were analysed as well. It was possible to identify most of the inorganic pigments and minerals detected with previous XRD and EDX measurements including whewellite and weddellite coatings, which could be a tool for carbon dating purposes. Two carotenoid pigments were detected for the first time in San rock art pigments. Animal fat was also observed for the first time on both red and white pigments, on the rock face adjacent to the paintings and in highest concentrations on the back of the rock fragment. The spectra quality makes successful on‐site measurements a good prospect. Copyright © 2008 John Wiley & Sons, Ltd.     

Joaquin Sorolla's pigment characterisation of the paintings ‘Vision of Spain’ by means of EDXRF portable system

In this work, portable energy dispersive X‐ray fluorescence (EDXRF) spectrometry was employed to the characterisation of the palette used by the Spanish artist Joaquín Sorolla (1863–1923) in the paintings ‘Vision of Spain’, a set of 14 oils on canvas painted by Sorolla between 1911 and 1919 by order of Mr Archer Huntington to decorate the library of the Hispanic Society of America (HSA) in New York. The analyses, sponsored by BANCAJA and provided by the HSA, were carried out in situ, prior to the cleaning and restoration process, while the paintings hanging on the walls of the library of the HSA. The results revealed that the paintings were made over different priming layers containing, respectively, lead white, zinc and barium compounds, lead white mixed with zinc white or lead white mixed with zinc and barium compounds. The EDXRF analyses of coloured zones identified up to 29 inorganic pigments and, in some cases, the probable use of organic pigments. Sorolla used traditional pigments as earth pigments, lead white, vermillion, etc., and modern pigments as cadmium yellow, zinc white, cobalt‐based blue, chromium‐based green, manganese‐based violet, etc. These results provide valuable information about the Sorolla's palette during the last stage of his life. Copyright © 2011 John Wiley & Sons, Ltd.     

Complementary use of the Raman and XRF techniques for non-destructive analysis of historical paint layers

The portable XRF spectrometer has been applied in situ for the non-destructive elemental mapping of the pigment components of the XV c. mural painting and frescos of the Little Christopher chamber in the Main Town Hall of Gdańsk, Poland. For a sufficiently large data collection the principal component analysis (PCA) was applied in order to associate the most intense lines of the elements Ca, Cu, Fe, Pb, and Hg in the XRF spectra with the palette of colors: white, brown, green, blue, red, yellow, and black observed in the painting. This allowed to limit the number of extractions of the micro-samples for the complementary Raman measurements thus assuring the practically non-destructive character of the entire analysis. The reliable identification of the pigment compositions was based on coincidence of the XRF, PCA and the Raman results which confirmed the presence of the chalk, malachite, azurite, red lead, mars red, mars yellow and candle black in the historical paints, except of the carbon-based black pigment being out of the XRF detection range. Different hues of the green paint were specified and the variety of the red and brown ones was ascribed to compositions of the Pb- and Fe-based red pigments (Fe₂O₃ and Pb₃O₄) with addition of the vermilion (HgS) and carbon black, in agreement with literature. The traces of elements: Ba and Sr, Sb and Mo, and also Cd, were ascribed to the impurities of Ca, those of some ochre pigments, and to the soluble Cd salts, respectively.     

A study on red lead degradation in a medieval manuscript Lorvão Apocalypse (1189)

The mechanisms of red lead degradation were studied in a medieval Portuguese codex, Lorvão Apocalypse (1189), by Raman microscopy (µ‐Raman) and micro‐X‐ray diffraction (µ‐XRD). The range of pigments found for the illuminations is mainly limited to vermilion, orpiment and red lead. Micro‐Fourier transform infrared spectroscopy (µ‐FTIR) determined that the pigments were applied in a proteinaceous binding medium. In the red and orange colours, arsenic (As) was determined, by micro‐energy dispersive X‐ray fluorescence (µ‐EDXRF), to be ranging 1–4% (wt %). For those colours, lead white and calcium carbonate were found as fillers whereas orpiment was applied as a pure pigment. Raman microscopy identified, unequivocally, the degradation product of red lead as galena [lead (II) sulphide, PbS]. To determine the main factors affecting red lead degradation, a set of accelerating ageing experiments was designed to assess the influence of extenders and of the two other pigments, vermilion and orpiment. The experiments were followed by µ‐Raman, µ‐EDXRF and XRD. Raman microscopy results for the simulation of degradation of red lead, in the presence of orpiment, are in agreement to what was found in the Lorvão Apocalypse, galena being the main degradation product; also in common is a Raman band at ca. 810 cm⁻¹, which was attributed to a lead arsenate compound. It was concluded that in Lorvão Apocalypse, the degradation of red lead was a result of its reaction with orpiment. Copyright © 2009 John Wiley & Sons, Ltd.     

Non‐destructive, ‘in situ’, characterization of pigments in Minoan pottery at the stratigrafical museum of Phaistos (Crete)

This paper presents preliminary results of measurements of chemical composition of pigments on the Middle Minoan pottery coming from Festos and Hagia Triada excavations. The measurements were carried out ‘in situ’ with the use of the PIXE‐alpha spectrometer, with Po‐210 radioisotope as a source of sample excitation, built at Laboratorio Nazionale del Sud. The method of measurements is described in detail and the limits are discussed. The preliminary results confirm the use of the reduced iron technique to obtain the black slips and of the talc to produce the white ones. Similarly, the presence of Manganese in some orange pigments can be associated with the use of red ochre mixed to talc, the latter being used as whitening material. Copyright © 2010 John Wiley & Sons, Ltd.     

In situ energy dispersive X‐ray fluorescence analysis of rock art pigments from the ‘Abrigo dos Gaivões’ and ‘Igreja dos Mouros’ caves (Portugal)

A portable energy dispersive X‐ray fluorescence spectrometer was used to obtain the elemental composition of Neolithic rock art paintings of the ‘Abrigo dos Gaivões’ and ‘Igreja dos Mouros’ caves. These caves, located in the Esperança parish, Arronches' county, in the San Mamede's mountains (Portugal), belong to a group of spread shelters just next to the western Spanish border. Results show the strong presence of iron in bare rock, and this element can be clearly detected as the main component of the red paintings. No evidence of manganese was detected in either the brownish or the black paintings, contrary to other Neolithic paintings in the Mediterranean area. Copyright © 2011 John Wiley & Sons, Ltd.     

Analysis on Mural Structures and Components of the Tombs in Liao Dynasty (A.D. 907–A.D. 1125)

The compositions of plaster, pigments, and binding medium were identified using micro-Raman spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray, and gas chromatograph-mass spectrometer. The results show that the plaster was calcium carbonate; the red color was ascribed to hematite; the blue pigment was ultramarine; the black pigment was carbon; and the yellow pigment was litharge. Animal glue as the binding medium was mixed in the pigments. Dissolved salt (mirabilite) was confirmed on the tomb passage. The mural detachment was detected with portable infrared thermal imager, and this damage resulted from the soil layer. This will serve as the basis for repairing the murals and reliable methods for identifying ancient murals.     

Application of the backscatter fundamental parameter method for in situ element determination using a portable energy‐dispersive x‐ray fluorescence spectrometer

The backscatter fundamental parameter (BFP) algorithm was adapted and modified for the use with a portable energy‐dispersive x‐ray fluorescence (EDXRF) spectrometer system. The method utilizes coherently and incoherently scattered peaks of primary radiation to estimate the ‘dark matrix’ of the analysed sample. A so‐called ‘full fundamental parameter’ model was implemented in the algorithm, allowing a simple calibration of the method using only one standard sample. To improve the accuracy of the method, the differential mass scattering cross‐sections were used. The algorithm also takes into account the secondary excitation effects. The method was applied to element determinations in various matrices with minimum sample preparation. It was tested in the laboratory with homogeneous samples prepared from standard reference materials and was also successfully applied to in situ element determinations in soil. The analyses were performed using a portable XRF spectrometer equipped with a ¹⁰⁹Cd radioisotope source and an Si‐PIN photodiode detector. The BFP algorithm was found to perform well for the analysis of loose powder samples containing an unknown fraction of ‘dark matrix,’ and therefore it is regarded as suitable for in situ element determinations. Copyright © 2003 John Wiley & Sons, Ltd.     

Analysis of paintings from the nineteenth century Brazilian painter Rodolfo Amoedo using EDXRF portable system

The pigments used in four of the most representative paintings of the Brazilian artist Rodolfo Amoedo were characterized by means of the EDXRF technique. The analyzed paintings were ‘The Last Tamoyo’ (1883), ‘Study of a Woman’ (1884), ‘Bust of Mrs. Amoedo’ (1892) and ‘Bad News’ (1895). EDXRF measurements were carried out with a portable system developed by the Nuclear Instrumentation Laboratory, consisting of an x‐ray tube Oxford TF3005 with a W anode, operating at 25 kV and 100 µA, and a Si‐PIN XR‐100CR detector from Amptek. Several spectra were obtained in each color and distinct hue of the paint layer, with an acquisition time of 300 s and a beam collimation of 2 mm. Some pigments used by the artist were zinc white, lead white, ochre, umber, vermilion, Prussian blue, cobalt blue, cadmium yellow, black iron oxide and manganese violet. In the painting ‘The Last Tamoyo’, titanium white was identified in some alteration areas, which were restored during the twentieth century. These results—together with computed radiography analyses—will be used to create a database about the nineteenth‐century collection of the National Museum of Fine Arts, in order to assist restorers, conservators, art students and researchers in the field of archeometry. Copyright © 2009 John Wiley & Sons, Ltd.     

PIXE‐alpha non‐destructive and in situ compositional investigation of black gloss on ancient pottery

The chemical characterization of the black gloss on ancient pottery is, since several years, the object of different scientific investigations. Among the different typologies of black gloss, the Attic one is the most refined, because it is prepared by using a fine suspension of an illitic clay applied on the surface of the clay body so that, after an oxiding‐reducing‐oxiding firing cycle at high temperature (800–950 °C), it reaches the typical shiny black aspect. Red figure vases were largely produced in South Italy often reaching a high artistic level. This is the case of the Sicilian red figure vases, sometimes called ‘Sicelioti’, whose production began in Sicily around the end of the fifth century BC and continued until the beginning of the third century BC . The aim of this work is to submit and compare a selection of data related to the chemical composition of the surface black gloss of some Attic and Sicilian red figure vases: This has been investigated, and a chemical‐based discrimination has been proposed. The non‐destructive particle‐induced X‐ray emission‐alpha portable spectrometer was used. The results, carried out in situ at the ‘Paolo Orsi’ Archaeological Museum in Syracuse (Sicily), together with the ones recently obtained in similar analyses at the Archaeological Museum of Catania University, confirmed the compositional stability of Attic vase black gloss and indicated that in a well‐defined time period, the chemical composition of the Sicilian black gloss decorations is very stable and superimposable with that of the contemporary Attic artifacts. Copyright © 2016 John Wiley & Sons, Ltd.     

Testing of Raman spectroscopy as a non‐invasive tool for the investigation of glass‐protected pastels

Five French pastels and a sanguine drawing dating from the 17th to the 20th century were studied by Raman spectroscopy. Different operative conditions were used: the pastels were investigated through their protective glass, and the results obtained were compared with those obtained after removing the glass and after sampling a micrometric particle of pigment. Different parameters (wavelengths, powers of excitation and objectives) were tested in order to assess the optimal procedure of analysis for this fragile work of art. The results obtained for black (carbons), yellow (chrome/cobalt yellow), red (lead oxide, vermillion, orpiment), brown (red lead and chrome yellow), blue (Prussian blue, lapis lazuli/ultramarine), green (mixture of above blue and yellow pigments) and white (calcite, lead white, anatase) pigments are presented and the consistency of the pigments' period of use with the dating proposed for each pastel is evaluated. In one of the pastels, the blackening of the carnation colour made of an unstable mixture of lead white, red lead and vermilion was studied. Copyright © 2010 John Wiley & Sons, Ltd.     

景德镇釉上彩绘瓷器釉上彩的Raman与EDXRF分析

釉上彩绘瓷器是我国古陶瓷中重要品类之一,具有极高的艺术价值和科学价值。采用拉曼光谱和能量色散X射线荧光分析等无损技术手段,对陶瓷釉彩的元素组成和物相组成综合分析,探讨了人们广为关注的景德镇元、 明和清代釉上彩绘瓷若干典型颜料种类的组成配方及其相应的呈色机制。研究发现景德镇古代红绿彩、 五彩、 粉彩等标本中的深红釉上彩料为赤铁矿着色,黄彩为铅锡黄着色,胭脂红彩则由含量不到0.1%的金所着色,绿料皆为二价铜离子着色。研究结果也进一步说明了Raman和EDXRF这两种无损、 微区分析技术的有效结合可以在深化陶瓷类文物的分析研究,尤其是针对图案交错复杂的多种彩绘颜料研究方面起到重要的作用。     

Characterization of a Namban folding screen from the Edo period by means of EDXRF,SEM‐EDS and Raman spectroscopy

In this work, a multianalytical approach is employed to characterize the materials used in a Namban folding screen that depicts the arrival of the Portuguese to the port of Nagasaki. Portuguese sailors reached Japan in 1543 and initiated what was to be known as the Namban trade. This interaction between Portuguese and Japanese was meticulously recorded by artists in the form of valuable and rare folding screens. The present screen, attributed to the Edo period (~1603–1868), is what we could consider a second‐generation screen, a copy of scenes and characters that appear in screens from the Momoyama period (~1573–1603) but in increased scale and minor detail. The materials used in the screen were identified by means of in situ energy dispersive X‐ray fluorescence. Complementary results were obtained by Raman and scanning electron microscopy coupled to energy dispersive spectrometry analysis of microsamples taken from the screen. The palette used in this artwork resorts to gold, malachite, azurite, vermillion, red lead, white oyster shell, and carbon black. Differences were found, when compared with previously studied screens, i.e. the use of mixtures of pigments, namely vermillion with red lead in an orange shade of red and also the mixture of vermillion and carbon black to obtain a brown color. Special emphasis was given to the characterization of the golden areas and study of techniques of gold application. Copyright © 2013 John Wiley & Sons, Ltd.     

Non-destructive analysis of pigments in a triptych by Marten de Vos

The Fine Arts Museum in Seville conserves an especially wide group of paintings from the 16th century Spanish art, among which one of the highest importance is a triptych attributed to Marten de Vos. One of the panels was recently restored, which opened a possibility for its material and technical analysis. For this research, only non-destructive techniques have been used: ultraviolet light, infrared reflectography, and X-ray fluorescence. The ultraviolet exam showed wide areas of later interventions, which were confirmed by X-ray fluorescence results. By infrared reflectography it was possible to observe under-drawings and some pentimenti. The X-ray fluorescence results identified inorganic pigments, common for that period of time: lead white, yellow, and red ochres, lead–tin yellow, vermilion, a green copper based pigment, azurite, smalt as De Vos’s basic blue pigment, umber, and an organic black pigment, probably bone black.     

Bronze Age and Iron Age gold torcs and earrings from the Iberian Atlantic façade: a non‐invasive multi‐analytical approach to the characterisation of the alloys and the corrosion

A group of Bronze Age and Iron Age gold torcs and earrings from the Iberian Atlantic façade, several with tarnishing, are studied with different X‐ray‐based techniques, including portable devices for in situ analysis. The construction of the complex objects is discussed, and information on the evolution of the alloys is provided. By comparing the elemental composition of the analysed objects with published data for Bronze Age and Iron Age jewellery from the Portuguese area and with data obtained and published for Chalcolithic objects from the Iberian area, the changes in gold supplies could be discussed, and this has led to suggest changes in the chronological attribution of three torcs, on the reuse without melting of one pair of earrings and on the origin of the so‐called gold ingots. The analysis of tarnished areas of the torcs and the earrings showed the presence of distinct corrosion products due to atmospheric corrosion, which could be in part identified. Copyright © 2015 John Wiley & Sons, Ltd.     

Non‐invasive approach in the study of polychrome terracotta sculptures: employment of the portable XRF to investigate complex stratigraphy

In the field of conservation science, in situ non‐invasive analytical techniques are widely used to investigate polychrome surfaces as frescoes, mural or easel paintings. Indeed, these techniques allow achieving information on materials composition and they often reduce the micro‐sampling. In this work, in situ non‐invasive techniques have been used to study a complex system, terracotta polychrome sculptures. The presence of the priming, the numerous painted layers and the ground layer spread on a porous material substrate are the main features of these sculptures; therefore, their study requires a scientific approach based on results obtained by different analytical techniques. In order to evaluate potentialities and limitations of the non‐invasive approach to this complex case, the results of energy‐dispersive X‐ray fluorescence (EDXRF), spectrophotometry and optical microscopy have been compared with the data achieved by laboratory analytical investigation as optical and scanning electron microscopy, energy‐dispersive X‐ray microanalysis and Raman spectroscopy. In particular, XRF data collected on several polychrome terracotta are here re‐examined on the basis of the results obtained by laboratory techniques. Even if, in some cases, portable XRF may induce to a wrong interpretation of the stratigraphy, it can be considered a suitable instrument for a preliminary diagnostic campaign of terracotta polychrome sculptures. Copyright © 2011 John Wiley & Sons, Ltd.     

FT‐Raman spectroscopy of pigments on a Hindu statue,Kali Walking on Siva

FT‐Raman spectroscopic analysis of eight pigmented specimens from an important Hindu statue group, Kali Walking on Siva, acquired in 1895 but of indeterminate age and now in the Horniman Museum, London, has revealed some interesting and unusual combinations of coloured pigments including cinnabar, minium, lapis lazuli and red ochre. Several specimens showed evidence of organic additives, which have been attributed to shellac resins commonly believed to have been used on this type of statuary. The Raman spectroscopic results confirm that the predominant black pigment on the Kali figure is lamp black or soot, in contrast to the SEM‐EDX data that suggests the origin of this pigment as from bone black or ivory black from the presence of phosphorus. An eclectic range of white pigments have been identified in this group including lead white, barytes, calcite and anhydrite; rutile and anatase found on one specimen on the jackal in this group have been ascribed to recent unrecorded restoration. Copyright © 2006 John Wiley & Sons, Ltd.