ELEMENTAL ANALYSES OF A GROUP OF GLAZED TERRACOTTA ANGELS FROM THE ITALIAN RENAISSANCE,AS A TOOL FOR THE RECONSTRUCTION OF A COMPLEX CONSERVATION HISTORY*

A group of Italian glazed terracotta sculptures, attributed to the della Robbia workshop of Florence, is partly displayed in the Louvre Museum. Analyses of the apparently homogeneous sculptures by techniques such as PIXE, SEM, ICP/AES and ICP/MS have identified differences in the materials used. The data provide a subdivision of the sculptures, which is compatible with what is known from historical documents and artistic considerations, and suggest a date for this ensemble at the end of the 15th century, when the della Robbia family was involved in the decoration of the San Frediano church in Florence.     

MICRO‐RAMAN SPECTROSCOPY CHARACTERIZATION OF DELLA ROBBIA GLAZES*

Micro‐Raman spectroscopy and the laser‐induced transformation technique were used for systematic study of five coloured glazes on Saint John the Baptist (29 inch tondo), a majolica terracotta relief attributed to Luca Della Robbia and on permanent exhibit in The John and Mable Ringling Museum of Art. We suggest that ions in a lead silicate matrix, called ‘lead ultramarine’, could contribute to the famous Della Robbia blue colour, in addition to the effect of Co atoms as suggested previously by Pappalardo et al. (2004 ). The original yellow glaze contains lead(II) antimonate. The green is a mixture of the yellow and blue pigments, the brown contains hematite, and the white glaze contains tin dioxide as an opacifier. The use of lead oxide as a main fluxing agent is confirmed by laser‐induced micro‐crystallization.     

A STUDY ON LATE MEDIEVAL TRANSPARENT‐GLAZED POTTERY AND ARCHAIC MAJOLICA FROM ORVIETO (CENTRAL ITALY)*

Nineteen samples of medieval transparent‐glazed pottery and archaic majolica from Orvieto (central Italy) were studied. They were classified by archaeological criterion as follows: five transparent‐glazed fragments with green and brown decorations (first half of the 13th century), eight green transparent‐glazed fragments (13th century) and six tin‐glazed fragments with green and brown decorations (second half of the 13th century). SEM–EDX, XRD (the Rietveld method) and XRF were used to characterize the chemical and mineralogical compositions both of the bodies and the coatings. In all of the samples, the paste is Ca‐rich with CaO contents as high as 13–20 wt%. The mineralogical composition is compatible with a firing temperature of about 950°C, which is the typical temperature reached in a wood kiln. No difference was observed between the bodies of transparent‐ and tin‐glazed pottery. In the case of transparent glazes, the burial conditions lead to heavy weathering of the samples. However, on the basis of the analyses carried out in non‐weathered areas, the typical composition is PbO 55–65 wt%, SiO₂31–35 wt%. In tin glazes, the tin is scattered on the mass of the glaze as SnO₂crystals with a concentration of 7–14 wt%. Concerning the decorations, it is established that the green colour is due to the presence of copper, while manganese is responsible for the brown colour. These pigments, which represent the typical colours of ‘archaic majolica’, are spread through the glaze homogeneously, apart from one case in which there is clear evidence of manganese oxide crystals.     

初版与再版邮票的质子激发X荧光鉴别法

报道用质子激发X荧光（PIXE）法分析我国初版与再版纪念邮票和特种邮票的实验结果。实验表明,初版和再版邮票所用印刷油墨颜料的化学元素的成分是不同的,因而PIXE方法可以用来实现初版和再版珍贵邮票的无损鉴定。这一方法也可以应用到对某些重要纸质文献或艺术品真伪的鉴定。     

ON THE EMBALMMENT OF S. FRANCESCO CARACCIOLO

The Italian saint Francesco Caracciolo died in June 1608 and his body was transported from Agnone in the Abruzzo region to the city of Naples, where he was interred. According to written sources, his body was embalmed, but the embalmment method is unknown. In the present work, four samples of the remains of S. Caracciolo have been analysed for traces of embalmment. No organic compounds usually used for embalmment were found using GC with MS detection. Only low background levels of As were measured using CV‐AAS (Cold Vapour Atomic Absorption Spectroscopy). In two samples analysed by CV‐AAS, however, very high concentrations of Hg (12.7 μg g^?1 and 4.9 μg g^?1) were measured, these being 100 to 1000 times more than the background Hg levels found in bone tissue of other medieval and Renaissance individuals. Two interpretations seem viable: (1) the high Hg levels are caused by embalmment using Hg‐containing compounds; (2) the excess Hg originates from a medical treatment that S. Caracciolo received in his youth, when he was cured of leprosy, or in connection with his illness just prior to his death. The case of excess Hg in the remains of S. Caracciolo has distinct parallels with those of other Renaissance burials.     

Characterization of archaeological obsidians from Lagartero, Chiapas Mexico by PIXE

Obsidian samples from the archaeological site of Lagartero, Chiapas, Mexico and other samples from Mexican and Guatemalan sources were analyzed by proton induced X-ray emission. Statistical treatments such as principal-component analyses were applied to the data set. Obsidians from Lagartero were identified as coming from two obsidian sources in Guatemala and one in Mexico, thus indicating that there was contact between people of Lagartero and other Mayans or Mesoamericans.     

CERAMIC PRODUCTION,PROVENANCE AND USE—A REVIEW*

The contribution of the physical sciences to the reconstruction of the production technology (i.e., processing of raw materials, forming, surface treatments and firing methods) for earthenwares, stonewares, porcelains and stonepaste bodies are summarized. The organization of production and the reasons for technological choice are considered. Provenance studies based on both chemical analysis and thin‐section petrography are discussed, with the investigation of Minoan and Mycenaean pottery being taken as the case study. The approaches to determining how pottery vessels were used in antiquity are outlined. Finally, future developments in ceramic studies are briefly considered.     

The Improved Lns Pixe‐Alpha Portable System: Archaeometric Applications*

The possibilities presented by the improved portable PIXE system are discussed. Examples are given of applications in the cultural heritage field, and in particular in the characterization of pigments and silver patina on ancient Roman coins. The limitations of the system are also discussed.     

EVIDENCE FOR THE USE OF EGYPTIAN BLUE IN AN 11TH CENTURY MURAL ALTARPIECE BY SEM–EDS,FTIR AND SR XRD (CHURCH OF SANT PERE,TERRASSA, SPAIN)

The present study shows the analysis performed on pigment samples taken from Sant Pere (Terrassa, Catalonia, Spain), a remarkable church built in the Romanesque style. On the basis of the results obtained from the analysis, an interesting discussion arises after finding evidence of Egyptian blue in one of the samples, a discovery that was not expected due to the time period of the samples. The pigments were identified by the combined use of FTIR and SEM with an EDS facility. For the blue pigment, since the EDS and FTIR analyses suggested the possible presence of cuprorivaite, micro‐XRD experiments using synchrotron radiation were run.     

SYNTHESIS AND ACID RESISTANCE OF MAYA BLUE PIGMENT*

Maya blue is an organo‐clay artificial pigment composed of indigo and palygorskite. It was invented and frequently used in Mesoamerica in ancient times (eighth to 16th centuries). We analyse in this paper one of the characteristics of Maya blue that has attracted the attention of scientists since its rediscovery in 1931: its high stability against chemical aggression (acids, alkalis, solvents, etc.) and biodegradation, which has permitted the survival of many works of art for centuries in hostile environments, such as the tropical forest. We have reproduced the different methods proposed to produce a synthetic pigment with the characteristics of the ancient Maya blue. The stability of the pigments produced using either palygorskite or sepiolite has been analysed by performing acid attacks of different intensities. The results are analysed in terms of pigment decolouration and destruction of the clay lattice, revealed by X‐ray diffraction. Palygorskite pigments are much more resistant than sepiolite pigments. It is shown that indigo does not protect the clay lattice against acid aggression. We show that Maya blue is an extremely resistant pigment, but it can be destroyed using very intense acid treatment under reflux.     

一批中国古代镶嵌玻璃珠化学成分的检测报告

结合外束质子激发X荧光（proton induced X-ray emission,PIXE）和能量色散X射线荧光（energy dispersive X-ray emission,EDXRF）分析技术,对中国新疆、湖北、四川、广东出土的古代镶嵌玻璃珠的化学成分进行了检测.结果表明：新疆拜城克孜尔墓地出土的西周-春秋时期镶嵌玻璃珠为CaO-MgO-SiO2玻璃,战国时期中国境内的PbO-BaO-SiO2和Na2O-CaO-SiO2镶嵌玻璃珠是同时存在的.本文亦对相关问题进行了一些讨论,并提出了部分今后的工作建议.     

GEMSTONES FROM VIGNA BARBERINI AT THE PALATINE HILL (ROME,ITALY)*

This study investigates 25 gemstones (23 intaglios and two undecorated cabochon, used between the third quarter of the first century ad and the second century ad ) found in the archaeological excavations performed at ‘Vigna Barberini’, in the north‐east sector of the Palatine Hill in Rome. The analytical results obtained by means of SR‐XRD, Raman micro‐spectroscopy and PIXE measurements provided, in a totally non‐destructive mode, unambiguous characterization of the gemstones. The collection from Vigna Barberini consists of two colourless chalcedonies, 11 carnelians, one sard, three Cr‐bearing chalcedonies, two nicoli, two orange jaspers, one heliotrope, one almandine garnet, one peridote and one lapis lazuli. Given the lack of analytical data discriminating between different sources, the worldwide occurrence of all these gemstones makes it difficult to reconstruct preferential routes for their commercial trade. However, the methodological approach followed for this research should be of help for the identification of discrimination parameters for provenance investigation.     

中国出土的一批战国古玻璃样品化学成分的检测

对化学成分体系的确定是中国古代玻璃研究中很重要的一个方面,为此,用外束质子激发X荧光技术(PIXE)、电感耦合等离子体原子发射光谱分析(ICP AES)等方法,对新疆、湖北、河南和重庆等地区出土的一批战国时期的玻璃珠(包含镶嵌玻璃珠)、玻璃璧样品进行了检测。结果表明,战国时期中国境内同时存在PbO BaOSiO2、K2O SiO2、Na2O CaO SiO2三种硅酸盐玻璃,分布的地域范围从中国的新疆东部一直到长江、黄河流域,以及南方的四川、贵州等地区。中国古代的PbO BaO SiO2和K2O SiO2玻璃在技术发展上应该具有密切联系。结合文献资料对这些玻璃的产地等相关问题进行了简要讨论。     

THE OCCURRENCE OF PALYGORSKITE IN THE YUCATÁN PENINSULA: ETHNO‐HISTORIC AND ARCHAEOLOGICAL CONTEXTS*

Palygorskite is a rare clay mineral used by the ancient Mayas for fabricating the Maya blue pigment and for other purposes. It seems to have been obtained from a restricted area in the Yucatán peninsula where important archaeological sites are found. Geological samples from different localities in this area show a high content in palygorskite, indicating that this clay is widespread in Yucatán. Combining structural, morphological, compositional and geochemical methods, we analysed the common characteristics of Yucatecan palygorskites, and compared them with palygorskites from other origins around the world. These results can be used for defining a fingerprint of Yucatecan palygorskite to be used in provenance studies of archaeological artefacts, in particular the Maya blue pigment.     

INVESTIGATION ON ROMAN LEAD GLAZE FROM CANOSA: RESULTS OF CHEMICAL ANALYSES*

Five sherds of green glazed pottery excavated at Canosa (Apulia) in Italy have been analysed by scanning electron microscopy. The aim of the investigation was to determine the chemical composition of the glazes and thus obtain information on the methods used in their production. The glazes were all of the high‐lead type, coloured green by the addition of copper. Intermediate layers, observed at the interface between the glaze and body and giving the appearance of an applied white slip, were the result of the crystallization of lead feldspar from the molten glaze. Non‐calcareous clays were used in the production of the pottery bodies. Concentration profiles from the glaze exterior to the body suggested that the glazes were produced by applying a suspension consisting of lead oxide plus silica to the bodies. On the basis of the glaze and body compositions, it is suggested that the Canosa glazed pottery was produced locally.