Advances in Polychrome Ceramics in the Islamic World of the 12th Century AD

As part of a multidisciplinary programme of research on Islamic glazed pottery, the development of polychrome decoration during the 12th century AD has been investigated by examining polished sections through glazed pottery in an analytical scanning electron microscope. The two main decorative techniques used were underglaze and overglaze painting. The results suggest that true underglaze decoration, involving the application of pigment without any associated slip, was first developed in Syria, from where it spread to Iran, on to China and ultimately across wide areas of the world. In contrast, the overglaze technique used on mina'i ware was both very short‐lived and confined to Iran. The analytical results suggest that the probable explanation for this was the technical problems associated with maturing the overglaze paint and the consequent risk of unsatisfactory products.     

A PRELIMINARY PETROGRAPHIC ANALYSIS OF CYPRIOT WHITE SLIP II WARE*

Samples of Late Bronze Age White Slip II ware from Cyprus were analysed using optical and scanning electron microscopy in conjunction with energy and wavelength dispersive analyse The slip has a novel granular nature and the coarser aggregates are impressed into the outer surface of the body, indicating that it was applied to a moist surface before the vessels were fired. It has a consistent mineral assemblage (Mg‐chlorite + illite‐smectite + sphene + anatase/rutile ± albite) which is very similar to that of hydrothermally altered zones associated with copper orebodies in the Troodos Massif which were mined in antiquity Our analysis suggests that the raw material for the slip was not found at the ground surface, because the alteration assemblage is unaffected by oxidation and copper carbonate or iron staining. It may, therefore, be a by‐product of sub‐surface ore extraction     

COLOURED OPAQUE GLASS BEADS OF THE MEROVINGIANS*

Monochrome coloured opaque glass beads of the Merovingians have been examined by different analytical methods. A large number of mostly unprepared beads have been measured by X‐ray fluorescence analysis. X‐ray diffraction was used for the identification of the crystalline colouring and opacifying pigments, and electron probe micro‐analysis as well as scanning electron microscopy were applied to study the composition and the microstructure of a white, brown, green, orange and yellow glass bead. After subtracting the content of colouring oxides of the glass beads and normalizing the residual values to 100% an identical soda‐lime‐glass matrix was obtained. The origin of the colouring metal oxides is discussed.     

AN ANALYSIS OF THE GEM‐BLUE GLAZE OF YE WANG'S KOJI POTTERY*

Koji pottery is a glazed ceramic art used widely for figurines. In early Taiwan, it was employed in temple construction for decorative purposes. Ye Wang (1826–87) is the first historically documented Koji artist of Taiwan and also the most prominent Koji pottery artist, noted for his modelling and glazing skills. Unfortunately, his unique technique was lost following his death in 1887. In order to provide vital information for ongoing conservation work on Koji pottery, this study analysed the physical and chemical characteristics of Ye Wang's gem‐blue glaze, to discover the glaze formula. DSC combined with the two‐thirds rule revealed that the firing temperature of Ye Wang's works of art was most probably around 878–923°C. EPMA revealed that the gem‐blue glaze has high alkali levels, and belongs to the PbO–K₂O–B₂O₃–Na₂O–SiO₂ system, deriving its unique colour from copper, iron, manganese and cobalt. This study found high potassium levels in the gem‐blue glaze, which are generally a characteristic of traditional Chinese glazes. In addition, a unique discovery of boron, commonly used in famille rose, was also identified in the glaze. By comparing spectra of historical and reconstructed glazes and adjusting the proportion of chromophoric elements, this study found a glazing formula with colours close to those of Ye Wang's gem‐blue glaze.     

FRESCO AND LIME‐PAINT: AN EXPERIMENTAL STUDY AND OBJECTIVE CRITERIA FOR DISTINGUISHING BETWEEN THESE PAINTING TECHNIQUES

Identification of the painting technique adopted by an artist is often debated in studies on the characterization, restoration and conservation of mural paintings. However, objective criteria to identify the two main lime‐based painting techniques, fresco and lime‐paint, have not yet been systematically verified on replicas. Replicas were painted following both fresco and lime‐painting techniques. A comparison of microstratigraphic sequences and distribution of chemical elements reveals systematic differences between the two techniques, providing objective distinguishing criteria. Samples from the Abbey of Chiaravalle (Milan, Italy) and Pompeii were also analysed, and the results were compared with experimental data to validate the recommended criteria.     

CHARACTERIZATION OF ARCHAEOLOGICAL AND IN SITU SCOTTISH WINDOW GLASS

Scottish window glass from both archaeological sites and historic buildings was examined using portable X‐ray fluorescence (pXRF) and scanning electron microscopy – energy‐dispersive X‐ray micro‐analysis (SEM–EDX). The elemental composition of the glass provides information regarding the materials used and, subsequently, an approximate range of dates of manufacture. pXRF is shown to be more vulnerable than SEM–EDX to the effects of surface corrosion and matrix effects in archaeological samples. The study showed that the production of window glass in Scotland from the 17th century onwards appears to closely parallel that in England. It also demonstrated the potential of pXRF for in situ studies of window glass in historic buildings. pXRF was used to assess two Scottish buildings; one in state care and one in private ownership. The building in state care, the Abbot's House at Arbroath Abbey, showed a uniform glass type, suggesting that the building was re‐glazed completely at some point during the late 19th or early 20th century. The building in private ownership, Traquair House, had a range of glass types and ages, demonstrating a different maintenance and repair regime. This type of data can be useful in understanding historic buildings in the future, particularly if re‐glazing is being considered.     

Enamel Ultrastructure of Cattle from the Quaternary Period in India

Abstract

The present paper examines tooth enamel of three species of cattle, Bos acutifrons, Bos namadicus and Bos indicus, which are supposed to have been phylogenetically related and belong to the Quaternary period. It aims to show whether in a short geological time span of 2myrs, the changing environs that cattle were exposed to during the Early Holocene have caused any microstructural changes in their tooth enamel.

Mammalian teeth exhibit a very complex arrangement of prisms in the enamel. The prisms are bundles of hydroxyapatite crystallites, arrangement of which is genetically determined and subject to evolutionary change. Hypsodonty or high crowned molars are such examples where concomitant masticatory stress factors near the enamel-dentin junction (EDJ) are known to have affected and altered the enamel microstructure in several large mammalian genera. Modified radial enamel in the deep enamel layer in some ungulates, including cattle, is an adaptive response to these stress factors which appeared much earlier (Tertiary) in the evolutionary history of these large mammals.

The cattle enamel analysed here revealed several levels of structural complexity indicating its functional designations. The schmelzmuster in cattle are formed of three enamel types: radial enamel (outer enamel), Hunter-Schreger Bands (mid enamel), and modified radial enamel (inner enamel). There is an increase through time in the percentage of Hunter-Schreger Bands (HSB), which cover up to about 68% of the entire enamel surface among recent cattle. The modified radial enamel and radial enamel do have a receding trend in the Holocene, compared to their Pleistocene ancestors.     

A NOVEL APPROACH TO STUDIES OF PREHISTORIC EXPLOITATION OF STONE TOOL MATERIALS USING MATERIAL COMPOSITION,SURFACE MORPHOLOGY,MICROSTRUCTURE AND MECHANICAL PROPERTIES*

For a comprehensive understanding of material exploitation in prehistory, we applied advanced analytical methods to Japanese prehistoric stone tool materials. Compositions, surface morphologies, microstructures and mechanical properties of the primary lithic materials were analysed. As a result of the tests on actual Palaeolithic artefacts, preferential material selection was observed based on composition, structure and other physical properties of the materials. Homogeneous materials composed of a single type of mineral—α‐quartz—were intentionally selected for Palaeolithic tools regardless of the type of rock. These materials unexceptionally present higher hardness and strength. Moreover, materials composed of extremely fine crystal grains of ~0.1 µm in size with highest hardness and strength were selectively used for sharp‐edged blades. These results lead us to the conclusion that quantitative and objective analyses will give us precise information on prehistoric materials, which will enable us to make an analytical approach to the comprehension of prehistoric exploitation of stone materials. This could eventually complement the traditional interpretation of material exploitation based on conventional petrological classifications.     

EVALUATION OF THE ANALYTICAL POTENTIAL OF LASER‐INDUCED BREAKDOWN SPECTROMETRY (LIBS) FOR THE ANALYSIS OF HISTORICAL GLASSES*

The novel and—for archaeometrical applications—still rarely used Laser‐Induced Breakdown Spectrometry (LIBS) was tested on various standard glasses for its spectrometric performance. LIBS is an almost non‐destructive method based on the time‐resolved detection of optical emission following direct laser ablation. A frequency‐quadrupoled Nd:YAG laser at 266 nm was found to cause a hardly visible crater of c. 200 µm in diameter. The application of an innovative high‐resolution Echelle spectrograph allows the fast and simultaneous determination of up to 90 elements in the spectral range from 200 to 780 nm, with a resolution of 10–30 pm under ambient conditions. In principle, LIBS has a high analytical potential for archaeometry; in particular, for the determination of light elements (Li, Be, B and others). Because the measurement parameters (laser energy, delay time and number of pulses) do not independently influence the emission signal, their optimization proved to be complex and is rather a compromise for the range of elements. The effects of sample distance, surface roughness and the accumulation of depth profiles were studied. Problems arose for the determination of sodium and potassium in higher contents due to self‐absorption effects. Quantification tests using a silicon line as internal standard yielded a precision range between 3% and 20% relative, but in general no satisfying accuracy for a number of elements. However, these problems might be overcome in the near future by improved spectrometer set‐ups and matrix correction approaches.