ANALYTICAL CHARACTERIZATION OF ROMAN PLASTERS OF THE ‘DOMUS FARINI’ IN MODENA*

The paper refers to the analytical characterization of Roman painted plasters dating back to the second century ad . The following techniques were used: optical microscopy (OM), scanning electron microscopy (SEM–EDS), micro‐Raman and Fourier transform infrared spectroscopies (µ‐Raman and FT–IR), X‐ray diffraction (XRPD), colorimetry and thermal analyses (TG/DTA). The investigation analysed the chemical composition and structure of the plasters, the chemical composition of the pigment layers, the use of binders and any chemical alteration of pigments as well as deterioration of the samples. Stratigraphic analysis of plasters allowed identification of their individual components, which proved helpful in finding out more about the mural painting technique employed.     

ARCHAEOLOGICAL,STYLISTIC AND SCIENTIFIC RESEARCH ON 11TH–13TH CENTURY AD PAINTED FRAGMENTS FROM THE SAN GIOVANNI BATTISTA CHURCH IN CEVIO (SWITZERLAND)

The painted fragments collected during the archaeological excavation campaign in the San Giovanni Battista church in Cevio represent a unique patrimony of Romanesque wall painting in Tessin, Switzerland, having a strong stylistic linkage with the Lombardic art of the same period. The archaeological and stylistic research allowed the fragments to be dated between the 11th and 13th centuries ad and to group them in three chronological phases. The scientific research (p‐XRF, OM, SEM–EDS, FTIR and XRD) was aimed at characterizing the pigments and the pictorial techniques used. Important changes occurred in terms of some pigments used during the 11th and 12th centuries: in particular, azurite was used to decorate the earlier wall paintings while lapis lazuli was used for the 12th‐century ones. During the second period, lead‐based pigments (lead white and minium) were introduced into the palette. The use of natural yellow and red ochres and green earth was common for the three periods. The fresco technique was generally used, except for the application of azurite and lead‐based pigments, where the a secco technique was adopted. The integrated research is a contribution to the knowledge of Romanesque art in the Insubric Region.     

PREHISTORIC WALL PAINTINGS: THE CASE OF THE DOMUS DE JANAS NECROPOLIS (SARDINIA,ITALY)*

The Domus de Janas (Home of the Fairies, or Home of the Witches) are Neolithic hypogea located throughout Sardinia (Italy) and decorated with red and black wall paintings. The objective of this study was to define the painting technique through the analytical characterization of the pigments and binding media. Samples of painting film from different graves have been examined by means of various analytical techniques. XRD, Raman and SEM–EDX analyses identified the red and black pigments respectively as red ochre rich in hematite and carbon black, while GC–MS analyses characterized the organic binder as egg.     

STUDY ON THE PIGMENTS IN THE CRUCIFORM GALLERY OF ANGKOR WAT,CAMBODIA

In the cruciform gallery of Angkor Wat in Cambodia, red, orange, white and black pigments were widely painted on the surfaces of pillars, walls and friezes. The application sequence of the pigments is different from area to area. The following substances were confirmed from the pigments: hematite (laterite), minium, calcium oxalate hydrates (whewellite and weddellite), Pb–Cl compounds (cotunnite, laurionite and blixite), calcium phosphates (whitlockite), gypsum, hydrocerussite, calcite, anglesite, lead dioxide, azurite and carbon black. The orange pigment (minium) underlies the red pigment (hematite). The former may have been applied at the time of the foundation (the Angkor Wat style period), and the latter in the Bayon style period or later, but mainly before the early 17th century of the current era.     

山东青州龙兴寺部分北齐佛造像石材及朱砂颜料分析研究

山东青州龙兴寺窖藏佛教造像出土于1996年,造像雕刻技艺精湛,数量多,贴金彩绘丰富,展现出一种特殊的佛教造像艺术特征。一些佛像由于长期掩埋和历史上遭到破坏,彩绘发生了褪色、变薄、起翘等现象。为了弄清佛造像彩绘颜料和结构,本研究采用三维视频显微镜、显微拉曼光谱分析、扫描电镜-能谱、偏光显微镜等仪器分析颜料的结构和化学组成。分析结果表明,龙兴寺佛造像红色颜料为辰砂(Hg S)与铅白(2PbCO_3Pb(OH)_2)混用;地子主要为铅白,经过对该批出土佛造像残碎的石块做薄片处理做偏光显微分析,得到造像石材的主要矿相为含菱铁矿、生物碎屑、白云石的泥晶灰岩(灰岩即石灰石)。     

CHEMICAL AND MINERALOGICAL ANALYSES OF GALLO-ROMAN WALL PAINTING FROM DIETIKON,SWITZERLAND

Around 90 samples of Roman wall painting dating from the first to the third century AD were analysed using different analytical techniques: X-ray diffraction, X-ray fluorescence, infrared spectrometry, scanning electron microscopy, energy dispersive spectrometry, optical microscopy and physico-chemical tests. The identified pigments are: ash, calcite, carbon black, celadonite, cinnabar, Egyptian Blue, glauconite, goethite, hematite and red lead. Pigment mixtures were used to get other colours such as brown, pink or purple. Three types of plaster were used: a first, and most dominant, with river sand, a second with crushed tile for damp places and a third, to which cinnabar was exclusively applied, was prepared with crushed calcite crystals.     

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。     

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.     

ELECTROCHEMISTRY AND AUTHENTICATION OF ARCHAEOLOGICAL LEAD USING VOLTAMMETRY OF MICROPARTICLES: APPLICATION TO THE TOSSAL DE SANT MIQUEL IBERIAN PLATE

An essentially non‐invasive electrochemical methodology addressed to the authentication of archaeological lead is described. The method is based on the record of the voltammetric response of nanosamples from the archaeological artefact mechanically transferred to a graphite ‘pencil’ electrode in contact with aqueous buffers. Three diagnostic criteria for authentication are described based on the appearance of: (i) oxidative dissolution signals for trace metals like copper, arsenic, antimony and, often, tin and silver accompanying stripping peaks for lead, (ii) peak potential shifts for reduction peaks for patination products, and (iii) the presence of reduction peaks for PbO₂. The method is applied to the authentication of an Iberian lead plate from the Tossal de Sant Miquel (Llíria, Spain) site using a series of genuine and false pieces from different provenances in the Valencian region (Spain).     

DISCOVERY,PRODUCTION AND USE OF TIN‐BASED OPACIFIERS IN GLASSES,ENAMELS AND GLAZES FROM THE LATE IRON AGE ONWARDS: A REASSESSMENT*

Tin‐based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries bc , and then again throughout the Roman and Byzantine Empires from the fourth century ad onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century ad , and subsequently in enamels applied to Islamic and Venetian glasses from the 12th century ad onwards. A selection of published analytical data for the tin‐opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X‐ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin‐based opacifiers in the second to first centuries bc , and for the switch from antimony‐ to tin‐based opacifiers in the fourth century ad are suggested, and the possible contexts in which tin‐based opacifiers might have been discovered are considered. The introduction of tin‐opacified glazes by Islamic potters in the ninth century ad is discussed in terms of technological transfer or independent invention.     

Vietnamese (15th Century) Blue‐And‐White,Tam Thai and Lustre Porcelains/Stonewares: Glaze Composition and Decoration Techniques*

EDS, X‐ray fluorescence, Raman spectroscopy, thermal expansion–shrinkage measurement and scanning electron microscopy were applied to determine the elemental components, structural phases and glazing temperatures of the transparent glazes, blue underglaze and overglaze tam thai (including gold‐like lustre) decorations from the 15th‐century Vietnamese porcelains/stonewares found at the Chu Ðâu–My Xa kiln site and in the Cù Lao Chàm (Hôi An) cargo. The ancient technology for colouring the glazes is discussed. The various blue tones in the underglazed décor result from cobalt‐containing manganese ore, with the intentional addition of iron oxide. The overglaze copper‐green and the gold‐like lustre were obtained by dispersing copper in lead‐based glass. The red colour was made using hematite dispersed in lead‐rich flux.     

The painting of the Etruscan “Tomba della Quadriga Infernale” (4th century BC), in Sarteano (Siena, Italy): technical features

This work presents the results of an investigation of the painting technique used in the Etruscan tomb “Tomba della Quadriga Infernale”. This tomb was discovered in Sarteano (Siena, Italy) in October 2003 and dated back to the second half of the 4th century BC. Red, dark red, pink, yellow, white, black, and grey colours were used in the tomb in order to create paintings, which now represent a very precious record of the Etruscan art of wall painting in a hypogeal environment. The technical features of the painting were revealed by stratigraphy using optical and electronic microscopy. The components and preparatory layers of the painted areas were characterized using Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray microanalysis (SEM-EDS), X-ray diffraction (XRD), and gas chromatography/mass spectrometry (GC/MS). XRD, SEM-EDS, and optical microscopic techniques were also used for mineralogical analysis of the rock substrate. The SEM-EDS and FTIR analyses showed that red and yellow ochre, calcite, and vegetable charcoal were used to paint the walls of the tomb: the pigments, either alone or mixed together, were utilized to produce pure colours (red, yellow, white, and black) and intermediate tonalities (pink, dark red, and grey). SEM-EDS, FTIR, and XRD highlighted that the painting was made on a preparatory layer of calcite, applied onto a levelling material made up of calcite, clay minerals, quartz, and iron oxides. GC/MS analyses revealed that egg was used as an organic binder to disperse the pigments.     

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.     

The production and technology of glazed ceramics from the middle ages,found in the saepinum territory (Italy): a multimethodic approach*

A collection of ceramics from the Middle Ages found in Altilia and Terravecchia (the Saepinum area, Campobasso, Italy) were characterized by using different mineralogical analyses to investigate their provenance and production techniques. The body ceramic was investigated using Rietveld phase analysis of X‐ray powder diffraction patterns, X‐ray fluorescence spectrometry and scanning electron microscopy. The chemical compositions of the coatings were measured by scanning electron microscopy and their mineralogical compositions were determined using a particular technique of X‐ray small‐angle scattering (SAS) optimized for studies of thin films. Moreover, the material used for decoration was studied using micro‐Raman spectroscopy. The archaeometric results confirmed the distinction into two different ceramic classes, already individuated from archaeological analysis: the Altilia objects belong to the protomajolica class, whereas the objects from Terravecchia are RMR (ramina‐manganese‐red) ceramics. A comparison between the chemical and mineralogical compositions of good‐quality ceramic objects and those of waste products indicated local production of the ceramics. A sharp distinction was found in the chemical composition of the coatings: the Altilia products have tin‐opacified lead glazes, while the Terravecchia ones have transparent high‐lead glazes. Among the Altilia products, the unsuccessful process that produced a large quantity of discarded materials was attributed to the high lead content of the glazes. In fact, the principal advantage of the high lead content was to make the preparation and application of the glaze suspension easier, but the risk of reduction of lead oxide to metallic lead was greatly increased. Using micro‐Raman spectroscopy, the following minerals were identified as pigments: pyrolusite for the dark colour, malachite for green, lepidocrocite for yellow and hematite for red.     

THE CHARACTERIZATION OF PAINTS AND WATERPROOFING MATERIALS FROM THE SHIPWRECKS FOUND AT THE ARCHAEOLOGICAL SITE OF THE ETRUSCAN AND ROMAN HARBOUR OF PISA (ITALY)*

This work presents the results of a diagnostic survey on the shipwrecks from the archaeological site of the ancient harbour of San Rossore (Pisa, Italy). The original waterproofing, caulking and painting materials were characterized by Fourier transform infrared spectroscopy (FTIR), gas chromatography – mass spectrometry (GC–MS), energy‐dispersive X‐ray microanalysis (EDX) and X‐ray diffraction (XRD). The major constituents of the waterproofing and caulking materials detected on the planks were tricyclic abietanes showing a high degree of aromatization. These compounds are indicative of a pitch obtained from the wood of trees of the Pinaceae family. The analysis of the organic components of the paint samples revealed diterpenoid acids characteristic of Pinaceae resins together with linear long‐chain alcohols and fatty acids, highlighting the presence of beeswax. Noticeably, the characteristic odd carbon number alkanes that are normally present in beeswax were not detected. The EDX and XRD analyses showed that hematite, calcite, cerussite and kaolinite were employed as pigments to paint the ships’ hulls.     

A NEW SETTING FOR THE NORTHERN BORDER OF THE VENETI: METALLIC FINDS FROM THE VENETIC SITE OF MONTE CALVARIO,AURONZO DI CADORE*

In 2000 several bronze and lead objects were discovered at the Venetic‐Roman site (200 bc –ad 200) of Monte Calvario di Auronzo, in the Italian eastern Alps. They were mostly finished artefacts plus semi‐worked products. Analysis included SEM–EDS, EMPA, XRPD, TMS and AMS spectrometry. The compositional results of the finished artefacts suggest that the choice of the alloy had been made according to the decorative techniques to be used. A semi‐worked high‐leaded bronze object indicates the existence of a metallurgical production of cast artefacts at the site. TMS analyses of a lead ingot exclude local provenance, proving the existence of important trade routes.     

ROMANO‐EGYPTIAN RED LEAD PIGMENT: A SUBSIDIARY COMMODITY OF SPANISH SILVER MINING AND REFINEMENT*

Samples of red pigment from a group of seven Roman‐period Egyptian mummies, known as red‐shroud mummies, are investigated. Elemental analysis by inductively coupled plasma time‐of‐flight mass spectrometry (ICP–TOFMS) shows that the samples contain mostly Pb (83–92% by weight), along with 0.2–2.0% Sn. All of the samples are found to have similar trace element distributions when normalized to the continental crust, suggesting that they share a common geological origin. Lead isotope ratios are found to match the mixed lead sources typically associated with Rio Tinto, Spain – a site extensively mined for silver during the first century ad . Raman microspectroscopy identifies the major phase of each sample to be red lead (Pb₃O₄) with a minor phase of lead tin oxide (Pb₂SnO₄). Lead tin oxide does not occur naturally, and its incidental occurrence within the sample indicates that the material was heated under oxidative conditions at temperatures in excess of 650°C. In archaeological contexts, the high‐temperature oxidative treatment of lead is typically associated with metallurgical refinement processes such as cupellation. Based on this evidence, it is argued that the pigment was produced out of litharge associated with silver cupellation at the Rio Tinto site.     

X‐ray Diffraction and SEM Investigation of Wall Paintings Found in the Roman Temple Complex at Horvat Omrit,Israel

In the present study, the fragments of wall painting found in the Roman Temple Complex at Horvat Omrit were analysed for the first time using the non‐destructive techniques of X‐ray diffraction (XRD) and scanning electron microscopy (ESEM) equipped with energy‐dispersive X‐ray spectroscopy (EDS). The application of these methods enabled unambiguous identifications of the pigments and plaster components of the samples. Quantitative information on mineral composition, crystallite size and elemental composition of each studied paint layer and plaster was collected. Based on the results of the XRD and EDS analyses, the green pigment was identified as celadonite. It was revealed that the Egyptian blue pigment does not contain impurities of tin and lead, and this excludes the use of bronze scrap in its synthesis. Comparison of the mineral composition of the paint layers indicates that a wider palette of colours was obtained by mixing the available mineral pigments. The study of cross‐sections of painted specimens revealed the usage of slaked lime for plastering. The obtained results give a new insight into the wall painting technique employed by ancient artists at Horvat Omrit, in northern Israel.     

THE COLOURED TESSERAE DECORATING THE VAULTS OF THE FARAGOLA BALNEUM (ASCOLI SATRIANO,FOGGIA, SOUTHERN ITALY)

Twenty‐six tesserae (red, orange, yellow, light amber, green, blue and white) from the balneum of the villa at Faragola (Ascoli Satriano, Foggia) have been examined by colorimetry, ICP–MS, ICP–OES and SEM–EDS. Different types of calcareous sands have been used as the source of silica (network former), also providing the stabilizing agent. A natron‐type soda source served as the network modifier; however, the use of a sodium‐rich plant ash and the recycling process have been hypothesized for the production of two tesserae (FT 1 red and FT 3 orange). The colouring and opacifying agents were Cu oxide (cuprite, orange), metallic copper (red), Pb antimonates (yellow), Ca antimonates (white), a mixture of copper (Cu²⁺) and Pb antimonates (green), a mixture of cobalt (Co²⁺) or copper (Cu²⁺) and Ca antimonates (blue). The light amber tesserae should owe their colour to iron (Fe³⁺) alone or associated with sulphide (S^2?) and Ca antimonates. It is likely that the Faragola tesserae were locally produced in a secondary glass workshop.     

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.