DISCOVERY AND CHARACTERIZATION OF AN UNKNOWN BLUE‐GREEN MAYA PIGMENT: VESZELYITE*

Blue‐green mosaic and polychrome masks and funerary offerings from the royal tombs of Calakmul, Mexico, were analysed by scanning electron microscope equipped with energy dispersive X‐ray spectroscopy (SEM‐EDS), X‐ray diffraction (XRD), and particle induced X‐ray emission (PIXE). This led to the first identification of the use of veszelyite, a rare hydrated copper‐zinc phosphate, as green pigment. Analyses of a geological sample of this mineral have been done to confirm the characterization of this Mayan pigment, which might help determine pre‐Columbian trade routes of precious and luxury objects in the ancient Maya Classic period (ad 250–800).     

THE CHEMICAL COMPOSITION OF BLUE PIGMENT ON CHINESE BLUE‐AND‐WHITE PORCELAIN OF THE YUAN AND MING DYNASTIES (ad 1271–1644)*

The chemical compositions of the glazes and pigments of 39 blue‐and‐white porcelains of Ming Dynasty date and three of Yuan date were examined by SR‐XRF. Both the analysis of the Fe/Mn ratio in the light blue areas of the glaze and a comparison of the Fe/Mn values between light blue, dark blue and clear glaze areas reveals that the samples can be divided into three groups. The results indicate that there are two significant changes of provenance of blue pigment during the Ming Dynasty and that some kinds of pigment were most probably imported from the Middle East. Considering literature records and other scholars’ studies, an outline picture of the pigment used on Chinese blue‐and‐white porcelain produced in Jingdezhen in the Yuan and Ming Dynasties is presented.     

A STUDY OF ANCIENT CHINESE PORCELAIN WARES OF THE SONG‐YUAN DYNASTIES FROM CIZHOU AND DING KILNS WITH ENERGY DISPERSIVE X‐RAY FLUORESCENCE*

Multi‐variable statistical analysis based on energy dispersive X‐ray fluorescence measurements on both porcelain body and glaze is employed to give clear and consistent classification of porcelain sherds from northern China of different styles from the Song‐Yuan dynasties (Ding and Cizhou styles), and also from the Sui‐Tang dynasties (Xing style). However, the observed separation is less clear for Cizhou style sherds produced at neighbouring kiln sites. Imitation Ding porcelain samples produced by ancient Cizhou potters are also analysed.     

A SCIENTIFIC INVESTIGATION ON THE PROVENANCE AND TECHNOLOGY OF A BLACK‐FIGURE AMPHORA ATTRIBUTED TO THE PRIAM GROUP*

The restoration of a Greek black‐figure amphora provided an opportunity to study the provenance and production technology of the vase. The composition of the ceramic body, determined by inductively coupled plasma optical emission spectroscopy (ICP–OES), matches that of Attic products. Investigation by X‐ray diffraction and reflectance spectroscopy suggests a maximum firing temperature around 900°C and a body re‐oxidation temperature around 800°C, respectively. The morphology and composition of black, red and dark red surface areas were studied by scanning electron microscopy and X‐ray energy‐dispersive analysis; the black areas show the features of a typical well‐vitrified black gloss, while the red areas were most probably obtained by simple burnishing of the body; the dark red additions, on the other hand, are the likely result of a partial re‐oxidation of a clay–ochre mixture.     

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.