Polychromic structures and pigments in Guangyuan Thousand-Buddha Grotto of the Tang Dynasty (China)

This paper presents a multi-analytical study of the polychromy in the Guangyuan Thousand-Buddha Grotto. Samples taken from 15 locations in No. 512 and No. 689 caves are prepared as cross-sections for the analysis by optical microscopy (OM) and scanning electron microscopy coupled with backscattered electron imaging (SEM-BSE). The cross section analysis indicates that some paintings were repainted in the past. The chemical composition of each painting layer is obtained by scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX). The main pigments for 15 samples including green, red, blue, white and black paint layers, are identified by the combination of polarized light microscopy (PLM), Fourier Transform infrared spectrum (FT-IR), Raman spectroscopy (RS) and X-ray diffraction (XRD) analysis. The integrated analytical results reveal that the green pigments are malachite and atacamite; the red color is attributed to minium, hematite and cinnabar; the blue pigments are lazurite and organic blue materials; the white color is ascribed to anglesite and gypsum; and the black surface of polychrome is the accumulation of longtime smudging by folk burning incense in the devotional practice or the soot deposition resulting from burning bonfires in the caves. Some arsenic-containing pigment is detected in the green samples. This case study also demonstrates the advantages and the limitations of every analytical technique for the pigment identification, confirming the necessity of the integrated analytical techniques approach. The present results are not only useful to assist in the authenticity of the used pigment materials and history of the polychromic in the past, but also aimed at guiding the conservation scientists in taking into account materials and methods utilized in the past.     

TRACES OF ANCIENT COLOURS ON TRAJAN'S COLUMN*

Recent restorations of Trajan's Column uncovered two marble fragments bearing traces of pigments, bright red (minium, hematite) in one case, and yellowish-orange (minium, hematite, clay minerals) in the other. Both were applied to the marble surface on a plaster underlayer. The presence of an underlayer and of surfaces coloured according to subject tells us that the colours were applied deliberately. Although the use of minium plus hematite is confirmed by archaeological finds, there is only a good probability that the colours were applied on the column at the time of its completion.     

四川广汉龙居寺中殿壁画制作材料与工艺研究

广汉龙居寺中殿壁画为四川地区明代建筑壁画中精品。为了解该壁画制作材料与工艺,采用显微观察、激光粒度仪分析、X射线衍射、拉曼光谱、酶联免疫等方法,对样品结构形态和材料组成进行了分析。结果表明:该壁画载体为编竹夹泥墙结构。地仗层泥土颗粒矿物成分主要为石英、钠长石,颗粒组成墙体壁画以粉粒为主、砂粒次之,垫拱板壁画粗泥层比细泥层砂粒含量偏低、粉粒含量偏高;加筋材料粗泥层为稻草秸秆、谷壳等,细泥层为棉或麻纤维。颜料层显色成分为古代壁画常见矿物颜料,红色为朱砂、铅丹,绿色为氯铜矿、副氯铜矿,白色为方解石、滑石,黑色为炭黑,蓝色为石青,黄色为针铁矿,胶料为动物胶或蛋清。该壁画在四川地区明代建筑壁画制作材料与工艺上具有典型性,主要体现在载体结构类型、地仗层材料组成、颜料层显色成分等方面。研究成果不仅可为该壁画后期保护修复提供依据,而且丰富了对四川地区明代建筑壁画的认识。     

Consideration on the construction process and the sandstone quarries during the Angkor period based on the magnetic susceptibility

Detailed magnetic susceptibility measurement was conducted on the sandstones used for the Angkor monuments constructed in the period spanning the Preah Ko and Angkor Wat styles, and the construction process of the buildings and quarries of the sandstones was considered. Combined with the previous study on the sandstones of the Bayon style [Uchida, E., Cunin, O., Shimoda, I., Suda, C., Nakagawa, T., 2003. The construction process of the Angkor monuments elucidated by the magnetic susceptibility of sandstone, Archaeometry 45, 221–232], the magnetic susceptibility measurement revealed that there were 7 sandstone quarries corresponding to Stages I, II, III, IVa, V, VII and VIIIb during the Angkor period. The sandstones used for the monuments belonging to Stage I show average magnetic susceptibility values ranging from 1.1 to 2.3 × 10⁻³ SI units. In the Bakheng style period (Stage II), the average magnetic susceptibility of the supplied sandstones decreased gradually from around 10 to 1 × 10⁻³ SI units over time. The magnetic susceptibility range of the sandstones used for the monuments of Stage III was from 2.3 to 3.0 × 10⁻³ SI units. In the early Angkor Wat style period (IVb), the average magnetic susceptibility of the supplied sandstones increased over time, reflecting the supply of the sandstones from two different quarries, that is, the quarry corresponding to the Khleang and Baphuon style monuments (Stage IVa), with low average magnetic susceptibilities of 1.1 to 2.4 × 10⁻³ SI units, and the quarry corresponding to the main Angkor Wat style monuments (Stage V), with high average magnetic susceptibilities ranging from 2.8 to more than 4.3 × 10⁻³ SI units. The sandstones of Stage VII show low average magnetic susceptibility around 1 × 10⁻³ SI unit. The sandstones of Stage VId is a mixture of sandstones of Stages V and those of Stage VII. The sandstones with high magnetic susceptibilities are found in the monuments belonging to Stage VIIIb, reflecting the supply from the new sandstone quarry.     

新疆阿斯塔那唐墓出土彩塑的制作工艺和颜料分析

新疆阿斯塔那古墓群出土了大量的彩塑,为了解其制作工艺与彩绘颜料成分,采用显微激光拉曼光谱,结合剖面观察和能量色散X射线荧光光谱等科技手段,对出土于唐墓的6个样品进行了分析鉴定.结果表明,泥胎表面先用硬石膏做打底层,再施以彩绘,且彩绘颜料厚薄有异.所使用的红、黄、黑、白和绿色颜料有铅丹、密陀僧、朱砂和土红、雌黄、炭黑、硬石膏及氯铜矿等无机颜料,而粉色彩绘是由铅丹(或铅丹和密陀僧的混合物)与硬石膏调和而成,且密陀僧作为彩绘颜料在新疆是较早的发现.其最为重要的发现是蓝色彩绘为植物性染料——靛蓝.这一研究结果,为进一步的彩塑修复与保护方案的制订提供了有价值参考.     

Chemical and mineralogical characterization of Aguada Portezuelo pottery from Catamarca,north-western Argentina: PIXE,XRD and SEM-EDS studies applied to surface pre- and post-firing paints,slips and pastes

Particle-induced X-ray emission (PIXE), X-ray diffraction (XRD), electron microprobe analysis (EDS) and scanning electron microscopy (SEM) analytical techniques were used to characterize surface paints in pre- and post-fired Aguada Portezuelo decorated pottery. Surface paintings in black, white, red, brown, burgundy and ochre were analysed. Major, minor and trace elements were detected by PIXE, whereas XRD and SEM-EDS gave information on the main mineral phases and the characteristic morphology for each analysed pigment. The results obtained indicate that the main colour groups can be easily discriminated by PIXE, and they are characterized by only one pigment for each colour: hematite (red) and manganese mineral oxides (black), respectively, whereas white pigments are characterized by calcite, ghelenite and gypsum.     

The Construction Process of the Angkor Monuments Elucidated by the Magnetic Susceptibility of Sandstone*

The Angkor monuments in Cambodia are mainly constructed of grey to yellowish‐brown sandstones. No differences in the constituent minerals and in the chemical composition of the sandstones have been confirmed among the monuments. However, we have found their magnetic susceptibility a useful parameter by which to distinguish them. The principal monuments of Angkor Wat, Ta Prohm, Preah Khan, Banteay Kdei and Bayon, constructed from the Angkor Wat period to the Bayon period (from the beginning of the 12th century to the beginning of the 13th century ad ), were investigated in detail using a portable magnetic susceptibility meter. We succeeded in dividing the periods of construction into stages. This elucidated the enlargement process of the monuments and correlated their construction stages.     

ANALYSIS OF NASRID POLYCHROME CARPENTRY AT THE HALL OF THE MEXUAR PALACE,ALHAMBRA COMPLEX (GRANADA,SPAIN), COMBINING MICROSCOPIC,CHROMATOGRAPHIC AND SPECTROSCOPIC METHODS*†

The pigments, binders and execution techniques used by the Nasrids (1238–1492) to polychrome carpentry in the Hall of the Mexuar Palace at the Alhambra (Granada, Spain) were studied using optical microscopy, scanning electron microscopy with EDX analysis, selective staining techniques and gas chromatography – mass spectrometry. This pioneering investigation presents the first results of a research project devoted to filling gaps in the knowledge of Nasrid art, traditionally approached by stylistic studies. Moreover, it is essential for the polychromy conservation of the studied artworks, and will help to clarify historical and painting uncertainties in the Alhambra monument. The palette consists of a limited range of colours: white (lead‐base pigment), red (cinnabar and red lead), blue (lapis lazuli), black (carbon‐based) and false gold (golden tin). Tempera grassa was the painting technique identified. Two types of grounds were used: (i) gypsum in calligraphy decoration for the false gold technique, and (ii) synthetic minium in geometric drawings in carpentry. Organic insulating layers of linseed oil were used between paint strata. Artists applied synthetic minium to protect the wood (Juglans regia and conifer) against attack by xylophages. To lighten the surface darkened by this ground layer, powdered tin was added to achieve a metallic lustre.     

Iron isotope analysis of red and black pigments on pottery in Nasca,Peru

The Nasca culture of the south coast of Peru developed during the first millennium ad and is known internationally for its elaborately decorated polychrome pots. Despite decades of iconographic analysis, little is known about the more technological aspects of Nasca pigment production and application. We present results from a pilot study on iron isotopes as a potential line of inquiry into the differences between red and black pigments in Nasca pigments. As well, we conduct a small firing experiment to examine potential changes in isotope composition. Our analyses show three significant results. First, firing does not change the isotopic ratios of Fe in pigments. Second, red and black pigments show differences in their iron isotope composition, which relate to differences in the minerals used to make the different colors. Third, naturally available hematite samples show greater isotopic variation than pigment samples, suggesting that people selected a limited range of iron oxides to produce pigments.     

铅丹、朱砂及其混合物紫外光致变色的电化学及光谱研究

铅丹(Pb₃O₄)和朱砂(HgS)是古代壁画和彩绘上常用的红色颜料,它们的变色是文物保护工作者、策展人和艺术史学家长期关注的问题。但由于其所处环境复杂,影响因素众多,这些颜料的变色机理的研究较为困难。为了探究紫外光照对这些颜料的影响,采用电化学方法和控制环境的紫外老化模拟实验研究了铅丹、朱砂及其混合物的光降解过程,并利用拉曼光谱和X射线光电子能谱(XPS)对实验样品进行分析。电化学实验中铅丹受405 nm激光照射出现还原电流,朱砂出现氧化电流。紫外老化实验确认了铅丹在光照下的还原反应,反应产物为碳酸铅(PbCO₃)和碱式碳酸铅[Pb₃(CO₃)₂(OH)₂]。因此,光照会引起铅丹发生还原反应,引起朱砂发生氧化反应,两种颜料表现出典型的半导体性质。另外,光化学反应动力学结果显示,掺杂朱砂可能会加快铅丹的光降解过程。     

Characterization and origin of black and red Magdalenian pigments from Grottes de la Garenne (Vallée moyenne de la Creuse-France): a mineralogical and geochemical approach of the study of prehistorical paintings

Pigments sampled from wall paintings and from crayons taken on the floor, at the Grottes de la Garenne (Saint-Marcel – Indre, France) have been analyzed and characterized by infrared spectroscopy, Raman micro-spectroscopy, X-ray diffraction, ICP/MS and analytical TEM. The red pigment used for the wall paintings is mainly composed by hematite, clays, carbon matter and carbonates. Results on the red pigments show that the compositions of the paintings are similar to that of some crayons. Regarding these analyses, their origin is compatible with local siderolithic facieses. Analysis of black pigments shows that they are made of cryptomelane, pyrolusite, clays, carbonates and carbon matter. It shows also that paintings and some crayons compositions are compatible. On the contrary of red pigments, the origin of black pigments is probably allochtonous. Indeed, the traces of thallium detected in cryptomelane, the cerium anomaly and the absence of iron are not compatible with local facieses or other sites from the French Massif Central.     

Early Islamic pigments at Nishapur,north-eastern Iran: studies on the painted fragments preserved at The Metropolitan Museum of Art

Pigments appearing on ninth–twelfth-century AD-carved stucco, wall painting, and terracotta friezes excavated at Nishapur in north-eastern Iran were investigated by optical reflectance spectroscopy, micro X-ray fluorescence spectrometry (μ-XRF), X-ray diffractometry (XRD), micro-Raman spectroscopy (μ-Raman), and scanning electron microscopy (SEM). Many of the pigments identified including vermilion, red lead, hematite, limonite, carbon black, atacamite, calcite, and gypsum have been identified in previous studies of pigments used in later Islamic periods. However, a series of unusual pigments such as wulfenite, pyromorphite, phoenicochroite, and jarosite were also found in the present study. The association of kaolinite and alunite with limonite and other Fe-bearing yellow pigments points to a local provenance for these pigments. In addition, the presence of orpiment in the vermilion may be indicative that the vermilion was artificially manufactured. These findings suggest that pigment use and manufacturing during the ninth to eleventh centuries in Nishapur was still in a trial-and-error stage and the palette known from the twelfth century onwards had not yet been systematized.     

延庆辽代墓葬壁画制作工艺及其颜料的物相鉴定

北京延庆发现一座辽代晚期的壁画砖室墓。为研究该墓室壁画结构和鉴定其颜料成分,运用拉曼光谱、X射线衍射和X射线荧光等多种方法进行了分析研究。结果表明该墓室壁画主要有灰泥层、白灰层和颜料层组成;红色颜料的呈色物相为α-Fe2O3,黑色颜料的呈色物相为炭黑。     

PIGMENT IDENTIFICATION IN GREEK POTTERY BY RAMAN MICROSPECTROSCOPY*

Raman microspectroscopy (RMS) is now established as a key technique for the identification of pigments of archaeological pottery that permits the in situ study of art objects by a non‐destructive procedure. The information obtained represents a great aid to restoration and conservation techniques. In this work, the chemical nature of the red, black and white pigments of five samples of Greek pottery from the end of the fifth century and the first half of the fourth century bc , exhumed from the Iberian necropolis of Cabezo Lucero (Guardamar del Segura, Alicante, Spain), has been identified. The black and the red pigments are found to be magnetite (Fe₃O₄) and hematite (α‐Fe₂O₃), respectively. The white pigment is found, for the first time, to be composed of alumina (α‐Al₂O₃ and γ‐Al₂O₃) probably yielded by the thermal decomposition of Greek bauxite.     

山东危山西汉墓出土陶器彩绘颜料研究

为研究山东危山西汉墓出土彩绘陶器颜料成分,采用偏光显微镜、显微拉曼光谱仪和扫描电子显微镜-能谱仪进行了分析。研究结果显示,危山汉墓陶器彩绘颜料有朱砂、铅丹、中国紫(汉紫BaCuSi2O6)、铁红、铁黑、白土等。中国紫颜料首次在山东省的发现,扩大了该颜料的使用区域,具有重要的考古学意义。另外,还在紫色颜料中分析出了BaCu2Si2O7蓝色晶体,这是继中国蓝中国紫之后的又一重大发现。     

甘肃泾川罗汉洞石窟壁画及制作工艺研究

罗汉洞石窟始凿于北朝,是泾川百里石窟长廊的重要组成部分。作为古代丝绸之路上的重要历史文化遗产,其赋存的石窟壁画内容丰富,制作工艺特殊,对于研究泾川佛教的发展及丝绸之路文明有着重要的价值。通过罗汉洞壁画材质组成、结构特征等综合分析,壁画主体结构由内到外依次为支撑体,粗泥层(添加有麦秸),细泥层(添加有棉花),白底层,颜料层。壁画多处可看出重层现象,内层早期壁画所采用颜料均为矿物颜料,其中红色颜料为朱砂,绿色颜料为氯铜矿,蓝色颜料为石青。而外层清代光绪年间壁画红色颜料为铁红,绿色颜料为巴黎绿,蓝色颜料为群青,橙色颜料为铁黄,黑色颜料为炭黑。通过对罗汉洞石窟壁画制作工艺进行诠释与解读,并与其他丝路沿线壁画颜料应用方面进行比对,以期促进这一丝路文化遗产的保护和利用。     

甘肃泾川出土5件佛教造像彩绘分析及相关研究

运用显微观察、荧光拍照、偏光显微镜、X射线荧光光谱、X射线衍射及扫描电镜能谱分析手段,对#87北魏造像碑、#99隋代佛头、#54宋代残破佛头和2件泥塑佛像残块表面彩绘进行研究。结果显示,北魏和隋代造像红色为朱砂,绿色为石绿,白色为方解石;隋代造像面部肉色为硫酸铅和朱砂的混合物,眼黑为炭黑;宋代造像表面红色为铁红,白色为方解石;泥塑残块#1表面蓝色为石青和石绿的混合物,#2表面为朱砂,判断其制作年代不晚于唐代中期。白灰层主要成分为碳酸钙,并具有亮白色荧光反应,与碳酸钙粉末混合有机胶制成白灰层的荧光反应一致,判断古代样品白灰层中可能存在有机胶结质。在元素分析过程中,铅(Pb)一直存在,而在物相分析中并没有发现Pb的化合物。同样问题在早期关中出土墓葬壁画分析中同样存在,是否与彩绘工艺本身有关,值得引起关注。     

司马金龙墓出土木板漆画屏风残片的初步分析

为了解山西大同北魏司马金龙墓出土木板漆画屏风的颜料使用情况和制作工艺信息,利用Micro-Raman、FrlR、XRF、断面切片等技术,对屏风残片上的四种主要颜色(红,黑,黄,白)、红色漆底层、断面分层进行分析与鉴别,结果如下:(1)屏风所使用的颜料有朱砂、炭黑、雌黄、雄黄、石膏.(2)屏风的红色底层系由生漆与朱砂调和、结膜而成,其中可能未曾添加桐油.(3)屏风彩绘部分的颜料分层十分明确,各层的厚度相对均匀,反映出制作者较为高超的绘画技法.(4)在颜料层、木胎与红色漆底层之间的"过渡层"中,分别观察到一些白色物质.初步分析后认为,"过渡层"中白色物质为羟基磷灰石的可能性较大.颜料层中白色物质的成分和物相仍有待进一步的分析.     

Integrated Analytical Techniques for the Study of Colouring Materials from Two Megalithic Barrows

We have determined the composition of rock art pigments from two megalithic barrows located in the north of Portugal. The use of XRD, SEM–EDS and FT–IR spectroscopy confirmed the presence of hematite and kaolinite in the red pigments from the Eireira barrow, and kaolinite in the white pigment from the Leira das Mamas barrow. The organic composition of the pigments was studied by GC–MS, suggesting that the red sinuous lines and dots from the Eireira barrow were prepared with cooked or heated algae and/or aquatic plants, with egg as binder, while the white pigment from the Leira das Mamas barrow revealed a mixture of vegetable oils for kaolinite moulding, which could be stabilized by temporary exposure to high temperatures. The multi‐analytical approach used on this study of megalithic pigments allowed the recovery of important data about north‐western prehistoric communities, namely the way in which they exploited existing resources and their ability to transform them.     

Characterization of a black residue in a decorated Neolithic pot from Dikili Tash,Greece:an unexpected result

A black depositional layer on the inner surface of a Neolithic carinated vessel from the archaeological site of Dikili Tash in Eastern Macedonia was examined scientifically. The layer was initially considered as decomposed organic matter and interest was focused on identifying the original organic contents. The scientific investigation, which included FTIR spectroscopy, analytical SEM examination and optical microscopy, revealed that the black substance was not organic but a pure iron oxide layer deposited on the vessel’s inner surface, and reduced in places to black iron oxides, during a destructive fire. The conclusion is that this layer represents the remnants of the vessel’s original content, which was a red hematite pigment. This unexpected find provides, for the first time, a missing link in the evidence of pigments used in Neolithic times, previously attested to only by finished products.