THE BEGINNINGS OF TIN-OPACIFICATION OF POTTERY GLAZES

A multidisciplinary programme of research on the glazed ceramics of the Islamic world has been focused on questions of their dating, provenance and technology. One particular question has been the development of tin-opacified glazes, and the nature of glaze opacification generally in the Islamic world. The findings of the various studies combine to indicate that tin was first used experimentally in Basra, Iraq, in the first half of the eighth century AD, apparently within the context of pre-Islamic opaque-glaze technology. Over the course of the next century, an opaque-glaze technology entirely reliant on tin oxide inclusions was developed in Iraq and Egypt and, subsequently, this technology spread to the rest of the Islamic world and also to Europe.     

AMALGAM TINNING OF CHINESE BRONZE ANTIQUITIES*

This paper investigates the question whether or not amalgam tinning was used for the plating of bronze objects in pre‐Han and Han dynasty China. The relevant literary sources are reviewed and amalgam tinning is characterized experimentally with regard to its micro‐structure and residual mercury content using metallography and electron microprobe analysis. Examination of a tinning sample from a Warring States dagger previously assumed to be amalgam tinned demonstrates that this was probably not the case, but that a trace of mercury found in the plating is likely to be the result of contamination.     

FINGERPRINTING ANCIENT EGYPTIAN QUARRIES: PRELIMINARY RESULTS USING LASER ABLATION MICROPROBE-INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY*

Microchemical analysis of minerals present in pottery and stone artefacts may help determine their provenance. Electron microprobe major element analyses of augite suggest that minor elements (Ti0₂,MnO, Aa₂O) are important in fingerprinting basalts. This points to the potential usefulness of trace elements. Augite present in six basalt samples (representing all known/suspected Pharaonic basalt quarries in northern and middle Egypt) and basaltic temper fragments in two New Kingdom pottery sherds was analysed for 28 trace elements (Sr, Ba, Th, U, Zr, Hf, Nb, Ta, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Sc, V, Cr, Ni, Ga) by laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS, laserprobe). Cluster and discriminant analysis indicate that (1) laserprobe trace element data are more effective at fingerprinting basalts than conventional electron-microprobe data and (2) basaltic temper in the two sherds does not match any of the quarries. Microbeam techniques providing trace element data may represent the future for mineral-based provenance studies.     

The Application of Scanning X‐ray Fluorescence Microanalysis in the Examination of Cultural Materials

The use of a new analytical technique for the elemental characterization of artefacts is described. The new equipment is capable of X‐ray fluorescence analysis in conventional mode as well as for elemental scanning of small objects, fragments or microsamples. The Omicron, manufactured by Kevex Instruments Inc., is equipped with a microfocused X‐ray tube, which can be collimated to a 50 μ beam and used to scan objects over a maximum range of 256 × 256 pixels. False‐colour elemental distribution maps allow the user to image small features, differently pigmented areas, or whole objects in the machine completely non‐destructively. Analyses can be carried out in air, under helium or in vacuum. Two examples of the application of the new technique are described: first, to the surface decoration on a Greek Attic white ground lekythos; and, second, to the pigments used on a small painting, a ‘Pittura’, on copper by the Dutch artist, Frans van Mieris (1635–81) in the collections of the J. Paul Getty Museum.     

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.     

ROMAN GLASS‐MAKING AT COPPERGATE,YORK? ANALYTICAL EVIDENCE FOR THE NATURE OF PRODUCTION*

Ceramic vessels and associated vitreous debris, excavated at Coppergate, York, UK, have been interpreted as the remains of Roman glass‐making from the raw materials. This paper reports the results of analysis of this assemblage by XRF, ICPS, XRD, SEM– EDAX and thin‐section petrography. These findings suggest that some ceramic vessels, used as crucibles, have been subjected to temperatures up to 1200°C, well above the firing temperatures of the local domestic assemblage from which they were selected. Analysis of quartz‐rich debris, intimately mixed with glass in some samples and in others interleaved with glassy phases, indicates partially reacted glass‐making raw materials, with α‐quartz, tridymite and cristoballite phases represented. This could represent evidence either of a failed attempt to frit the raw materials, or a batch that had not fully fused. Variability in the composition of glass at the site is viewed in the light of glass‐making technology, and possible interpretations concerning this episode are discussed in the light of the archaeological evidence.     

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.     

PROVENANCE OF THE LIMESTONE USED IN TEOTIHUACAN (MEXICO): A METHODOLOGICAL APPROACH*

This work shows the preliminary results of an international project for the interdisciplinary study of the limestone used in the plasters of the ancient city of Teotihuacan. The limestone provenance was studied using a new approach based on the chemical analysis of the lime lumps that were selected because they represent the composition of the original limestone rock. The results show that the applied methodology was successful and that the limestone used to produce the lime employed to make the floor of the main courtyard at Teopancazco (Teotihuacan), comes from the region near Tula (Hidalgo).     

安岳石窟经目塔5.12汶川大地震后抢救性修缮——兼论三维激光扫描、计算机模拟技术在文物保护中的运用

"5.12汶川特大地震"对安岳石窟所属的孔雀洞经目塔产生了较大的影响和破坏。本次勘察修缮设计目标是修复经目塔震后的直接残损,对其结构进行必要的加固,减缓风化对塔体的影响,由于破坏的突然性及抢救工作的迫切性要求,从勘察到设计仅仅1个多月时间,勘察设计方在工作之初便决定引入三维激光扫描技术,并在评估及设计过程使用计算机模拟复原技术,力求准确翔实的得出经目塔震后的评估结论,及为震落构件找到准确的原有位置。作为最终修缮设计的依据。并通过结构计算,最终确定经目塔的修缮方案。本次勘察设计过程中引入的三维激光扫描技术及计算机模拟技术在石质文物勘察设计中均具有突破性进展,为今后石质文物的科技保护进行了切实有效的探索。