Application of field portable EDXRF spectrometry to analysis of pigments of Levantine rock art

The results of the analyses of elemental composition of red and black pigments of Levantine rock art from La Saltadora rock shelters (Valltorta gorge, Castellón, Spain) are presented in this paper. Nondestructive analyses were carried out using a portable energy dispersive X‐ray fluorescence (EDXRF) spectrometer developed for in situ analysis. The results revealed the strong presence of calcium in all the analyzed locations due to the contribution of the underlying calcareous bedrock and the overlying crust. Iron is the main element detected in red pigments and manganese in black pigments. Iron and calcium ratios have been found indicative of the degree of preservation of the pictorial layer. Trace elements detected in the pigment composition confirm the use of different raw materials. Therefore, this work illustrates the potential of the portable EDXRF spectrometers for in situ analysis of rock art paintings. Copyright © 2010 John Wiley & Sons, Ltd.     

On‐and off‐site Raman study of rock‐shelter paintings at world‐heritage site of Bhimbetka

Rock‐shelter paintings of Bhimbetka world‐heritage site near Bhopal, India have been investigated using a portable Raman spectrometer. These paintings in the rock shelters belong to periods starting from pre‐historic to the 19th century AD (Gond period). In addition, tiny fragments of pigments (100–200 µm in size) extracted from some of the artworks were also studied in laboratory using a micro‐Raman spectrometer and analyzed using energy‐dispersive X‐ray analysis for elemental composition. Based on the Raman spectra and the elemental analysis mineral‐based pigments such as calcite, gypsum, hematite, whewellite, and goethite could be identified. A comparison of the spectra recorded on‐site using a light‐weight portable spectrometer with those using laboratory equipment is also made and discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

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.     

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.     

西藏扎什伦布寺壁画的科学研究

壁画是寺院建筑的重要装饰元素,也是藏传佛教艺术的重要组成部分。扎什伦布寺始建于明正统12年（公元1447年）,作为后藏最大的寺院,寺内保存了大量精美壁画,这些壁画对研究藏传佛教及佛教艺术具有重要意义。扎什伦布寺自建寺起一直为传播佛教文化服务,经历了频繁的大规模修建。为了解扎什伦布寺壁画的制作材料与工艺,为今后壁画的保护及修复提供重要的参考及科学支撑,选取寺内强巴佛殿四层北壁、吉康扎仓南殿西侧的典型壁画,共采集8个样品。采用超景深三维视频显微镜观察壁画的制作结构,显微激光拉曼光谱仪对有机与无机颜料的成分信息进行表征,偏光显微镜根据晶体的光学信息鉴别拉曼光谱相似的颜料颗粒,X射线衍射仪用于测定地仗成分,扫描电镜/能谱仪则对微观数据进行确认和补充。通过分析研究,壁画由地仗层、准备层、颜料层构成。颜料包括矿物及人工合成颜料,其中红色颜料为朱砂与颜料红14,绿色颜料为块铜矾、酞菁绿,黑色颜料为碳黑,黄色颜料为雌黄,蓝色颜料为合成群青。颜料红14与酞菁绿为有机合成颜料,合成群青则为无机合成颜料。块铜矾作为矿物颜料,在欧洲曾用于架上画、壁画、手稿等艺术作品中,但在国内还未曾发现其使用历史,这一发现扩展了对绿色颜料的认识。壁画的地仗层依据藏式壁画制作传统使用了阿嘎土,准备层则由黄土制备。研究结果表明,壁画制作时以阿嘎土打底,刷一层黄土找平壁面,以胶调和颜料绘制于黄土层之上。壁画除了使用一些常见的传统藏式壁画材料,还发现了一些近代人工合成材料,说明扎什伦布寺强巴佛殿四层北壁及吉康扎仓南殿西侧壁画曾经历过重绘或补绘。该研究结果不仅弥补了扎什伦布寺壁画的研究空缺,也为扎什伦布寺修缮历史的补充及完善提供了重要证据。     

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.     

Phthalocyanine identification in paintings by reflectance spectroscopy. A laboratory and in situ study

The importance of identifying pigments using non invasive (n.i.) analyses has gained increasing importance in the field of spectroscopy applied to art conservation and art studies. Among the large set of pigments synthesized and marketed during 20th century, surely phthalocyanine blue and green pigments occupy an important role in the field of painting (including restoration) and printing, thanks to their characteristics like brightness and fastness. This research focused on the most used phthalocyanine blue (PB15:1 and PB15:3) and green pigments (PG7), and on the possibility to identify these organic compounds using a methodology like reflectance spectroscopy in the UV, visible and near IR range (UV-vis-NIR RS), performed easily through portable instruments. Laboratory tests and three examples carried out on real paintings are discussed.     

敦煌壁画绘画材料多光谱图像标准数据库的建立和应用

多光谱摄影图像调查技术,基于不同物质对不同光谱吸收与反射的差异及不同波段单色光谱有相应的灰度偏向,以单色光谱灰度图像经伪彩色强化,可作为一种绘画材料普查方法。这种方法的应用首先需要建立相关遗址绘画材料多光谱图像标准,以此为基础才可以通过多光谱伪彩色等图像对壁画中漫漶壁画、相近色相颜料及无法观察的有机材料做前期普查,为后期高精度仪器的进一步调查提供参考。采用已知敦煌壁画中常用29种绘画材料制作标准颜料色板,通过规范多光谱拍摄程序和优化多光谱拍摄条件,在250～1 300 nm之间获取各种颜料在不同光谱区域的反射及荧光图像,再经过后期科学的图像校正及红外、紫外反射伪彩色图像合成,初步建立敦煌壁画颜料多光谱图像标准数据库。对真实壁画进行多光谱拍摄,将获取的可见反射、红外反射伪彩色和紫外反射伪彩色图像与标准数据库图像进行交叉对比,并采用便携式显微镜、便携式X荧光、近红外光谱等分析技术验证所获取的多光谱分析结果,表明壁画颜料多光谱图像标准数据库的建立,作为一种新型无损检测辅助方法,可通过多光谱图像对敦煌壁画颜料前期鉴别、推断绘画材料属性以及获取颜料分布状况等信息。绘画材料光谱图像数据库的建立可提高常见绘画材料类别及范围的前期调查效率和可靠性,是一种有效的颜料面集调查辅助方法。     

In‐situ and laboratory Raman analysis in the field of cultural heritage: the case of a mural painting

The present work exemplifies, over a mural painting from the 14th century, the advantages of an initial exhaustive research using latest generation hand‐held spectrometers (Raman mainly) in order to perform the characterization of valuable objects of cultural heritage. These in‐situ techniques (meaning on‐site and non‐destructive) are very useful to study the pigments and materials, to identify the nature and causes of some of the main sources of deterioration and to examine past repaints. In addition, the in‐situ measurements are of great importance in the selection of micro‐samples for the laboratory analyses. In this particular case, the combination of these results with the chemical imaging analyses in the laboratory (such as Raman and energy dispersive X‐ray spectrometry imaging) allowed the characterization of the mural painting, including, the identification of all restoration works applied in the past. Copyright © 2014 John Wiley & Sons, Ltd.     

Pigment analysis of Portuguese portrait miniatures of 17th and 18th centuries by Raman Microscopy and SEM‐EDS

Seventeen Portuguese miniature portraits on copper support from the Évora Museum collection (Portugal) were analyzed in situ and nondestructively by Raman microscopy (RM), SEM‐EDS, and stereomicroscopy. This work constitutes a great breakthrough in the study of miniature paintings from the 17^th and 18^th centuries, since the chemical information known about this unique kind of paintings are still scarce, and in particular, this exclusive collection was never been subjected to any physicochemical study. In this work, each portrait was examined in detail in order to characterize the pigments palette used by the miniaturists. The μ‐Raman analysis, in particular, guaranteed an exceptional visualization and good individual identification of small grains of pigments and other constituents of the pictorial layer. Using this technique, 19 compounds were identified, including bluish black covellite, a pigment rarely found in oil paintings. SEM‐EDS was used as an important complementary technique to confirm the chemical nature of some pigments and to identify shell gold (gold dust) in some portraits. Overall, the pigments identified in this large set of old paintings are broadly consistent with those mentioned in the painting treatises of that time or reported in other more modern bibliographic sources. Copyright © 2014 John Wiley & Sons, Ltd.     

Gilding and pigments of Renaissance marble of Abatellis Palace: non‐invasive investigation by XRF spectrometry

Most of the artworks constituting the collection of Renaissance statuary of Abatellis Palace in Palermo (Sicily) show evidence of colour layers and fragments of gold foil that probably once covered the whole marble surface. The restoration of some of these statues has allowed to carry out archaeometric studies about the painting technique and to highlight the original materials and inclusion present on the precious marbles by two famous Italian sculptors of the Renaissance, Francesco Laurana and Antonello Gagini. The measurements have been performed in situ through the integrated use of two non‐invasive techniques: visible fluorescence stimulated by ultraviolet light and X‐ray fluorescence. The ultraviolet‐induced fluorescence analysis has provided additional information on the conservation status of marble surfaces by differentiating the pictorial materials and highlighting the presence of gilding and pigment traces through their characteristic fluorescence response. The observation in ultraviolet light has been used as valuable guide for the identification of the significant points to be analysed by X‐ray fluorescence to characterise the original materials. X‐ray fluorescence measurements have cast light about their chemical composition and stratigraphical structure. Pictorial layers were identified: vermilion for red layers, blue pigment based on copper for blue layers and pure gold leaf for gilding layers. Principal component analysis of the data was capable of clustering the different painting materials, discriminating through their chemical content. The results represent an important scientific support both to the hypotheses about the original look of the artworks and to the resolution of restoration and conservation questions still open. Copyright © 2012 John Wiley & Sons, Ltd.     

Scientific investigations of the Imperial Gates from the Petrindu wooden church,Salaj County,Romania

In order to preserve and restore the Imperial Gates from the Petrindu wooden church, Salaj County, Romania, (map location—latitude, longitude: 46.97, 23.19), the scientific investigation of the wooden support and painting materials (ground and pigments) was performed, employing Fourier‐transform infrared spectroscopy (FTIR), X‐ray fluorescence spectroscopy, and 3D scanning. FTIR spectroscopy offered information about the wooden degradation stage, whereas X‐ray fluorescence and FTIR spectroscopic methods were employed for structural painting materials characterization. The structural data can be correlated with the artistic, theological, and historical analysis of this religious patrimony object. After obtaining information about the wooden support and painting materials, the Imperial Gates were 3D digitized using state of the art laser scanning technology. The digital 3D model obtained was restored in a virtual environment and converted into an interactive 3D model that can be used for Romanian cultural heritage digital dissemination.     

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.     

太平天国侍王府壁画表面修复材料的原位无损FTIR分析

太平天国侍王府壁画是中国南方壁画的典型代表,具有重要的历史、文化和艺术价值。历史上曾对多幅壁画进行过化学保护,部分壁画表面形成了一定厚度的有机物涂层,分析研究壁画保护修复材料成分对于文物保护具有重要的理论和现实意义。由于文物的珍贵性与不可再生性,原位无损分析技术的研究和应用是未来文物分析的发展趋势,基于便携红外光谱仪的反射红外光谱技术是对文物表面材质较为理想的无损分析手段。利用反射傅里叶变换红外(FTIR)光谱对侍王府壁画的地仗层和表面修复材料涂层进行了现场原位无损分析,这在我国古代壁画及其保护修复材料分析中属首次。首先测试了无涂层壁画白色背景位置反射FTIR光谱,并与标准无机矿物光谱比对确定了壁画地仗层成分主要为方解石和生石膏。在此基础上,分析了无涂层和有涂层壁画表面的红外反射特性及地仗层化学成分对表面涂层反射FTIR光谱测试的影响,探讨了应用Kramers-Kronig(K-K)变换处理数据的可行性,确定了K-K变换的应用范围,分析了壁画涂层K-K变换后反射光谱与衰减全反射(ATR)光谱的差异,并通过显微ATR FTIR光谱和热裂解气相色谱质谱联用(Py-GC/MS)技术分析验证了原位反射FTIR光谱测试结果的可靠性,扫描电子显微镜(SEM)测量了涂层厚度,证明不同厚度涂层均能得到可解析的高质量反射FTIR光谱。最终确定侍王府壁画曾使用过聚醋酸乙烯酯、聚二甲基硅氧烷和三甲树脂三种高分子材料进行过表面加固,并得出壁画保存现状和修复材料及涂层厚度有较大关系。证明了基于反射模式的FTIR光谱技术能准确有效地获取文物表面有机物和部分无机物成分信息。该方法对表面有机涂层尤为敏感,是壁画类文物较为理想的无损分析方法,在壁画保护研究领域具有十分广阔的应用前景。同时,该研究弥补了我国壁画类文物表面有机物原位无损分析的不足,为该领域研究提供了一条新思路。     

Portable XRF study of pigments applied in Juan Hispalense’s 15th century panel painting

Several medieval paintings and polychrome sculptures have been analysed in the frame of a collaboration between the Fine Arts Museum of Seville and the National Centre of Accelerators, dedicated to a non‐destructive study of artworks that belong to the wide museum’s collection. Among the oldest artworks in the collection is the panel painting Archangel St. Michael attributed to Juan Hispalense, one of the first painters in the 15th‐century Seville known by name. The panel was analysed by a portable X‐ray fluorescence (XRF) to get more information about the pigments applied and to identify possible later interventions. The results showed that the pigments were those commonly used in that period. Lead white was found in the preparation of the painting and in colour layers. For yellow colour, yellow ochre was used, while for the red one, the painter usually mixed red earth and vermillion. Blue pigment is azurite, while the copper‐based green one could not be determined more specifically by XRF. Brown colour is made with yellow ochre and organic black or, in some cases, umbra. Black pigment is probably bone or ivory black. Many decorative parts of the panel are gilded, which were confirmed by Au peaks. Later interventions were carried out on the base of Ti–Zn white mixed with earth pigments, while for green areas such as Archangel's wings also chrome green was applied. The research is part of a larger study which is still going on, whose aim is to gain more knowledge about the 15th‐ and 16th‐century Spanish painting and polychromy. Copyright © 2011 John Wiley & Sons, Ltd.     

In situ Raman microscopy applied to large Central Asian paintings

Procedures and versatile Raman instruments are described for the non‐destructive in situ analysis of pigments in large paintings. A commercial Raman microscope is mounted on a gantry for scanning paintings with dimensions exceeding 1 m². Design principles and the physical implementation of the set‐up are outlined. Advantages/disadvantages and performance of the gantry‐based instrument are compared with those of a mobile Raman probe, attached to the same Raman microscope. The two set‐ups are applied to Central Asian thangka paintings. The utility of the gantry‐mounted Raman microscope is demonstrated on a 19th century Buddhist painting from Buriatia, South Siberia. Surprisingly, three arsenic‐based pigments, i.e. orpiment, realgar, and pararealgar, are found all in the same painting. Pararealgar is used for painting the numerous yellow areas. Realgar is admixed with red lead for adjusting its orange tint. Finally, orpiment is blended with Prussian blue for producing green. Traditional malachite is used in addition as a non‐adulterated green pigment. The mobile Raman probe was employed for examining a Tibetan painting of the 18th century from Derge monastery in the Kham area of Sichuan. The highly unique painting could be dated well and its origin accurately located. In fact, the painter's workshop, where the thangka has been executed, is shown in great detail on the painting itself. The painter's palette of this thangka matches the canonical set of pigments used in Tibet for more than 10 centuries. Copyright © 2009 John Wiley & Sons, Ltd.     

A multi-analytical approach for the study of the pigments used in the wall paintings from a building complex on the Caelian Hill (Rome)

In the present study, shards from Roman wall paintings (from the end of the first century to the fourth century A.D.) decorating the domus below the Basilica of SS. John and Paul on the Caelian Hill (Rome), were analyzed in order to identify the pigments used. The analytical techniques employed for the characterization of the pigments were the scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDS) and infrared spectroscopy (ATR and micro ATR). While SEM-EDS allowed to perform a qualitative analysis of the material, by FT-IR chemical species have been identified. The pigments identified were those mentioned in the literature for the Imperial Roman fresco painting: different types of ochre (yellow and red), mixtures containing lead, green earths and precious pigments such as cinnabar and Egyptian blue. They were often used as mixtures and the use of the most valuable pigments (cinnabar and Egyptian blue) were found in the most ancient rooms.