TECHNOLOGY AND COLOUR DEVELOPMENT OF HISPANO-MORESQUE LEAD-GLAZED POTTERY

Lead-glazed pottery from the medieval workshop of Les Olleries Majors (Paterna, Spain) has been studied by Mössbauer spectroscopy, X-ray diffraction, X-ray fluorescence and optical spectroscopy. Yellow, brown and honey-coloured glazes occur on pots glazed on only one surface. They have virtually identical compositions and transmittance spectra, their apparent differences in colour are due to the colours of the underlying pastes. Yellow glazes occur on cream-coloured calcareous bodies, honey-coloured glazes occur on less calcareous bodies with some development of hematite, while brown glazes occur on red siliceous cooking-pots. Green glazes are found on pots glazed on both surfaces; the glazes trapped CO₂ evolved by decomposing carbonates, resulting in an internal reducing environment. This caused the reduction of iron to the ferrous state which coloured the glaze green by diffusion.     

THE JUDICIOUS SELECTION AND PRESERVATION OF TUFF AND TRAVERTINE BUILDING STONE IN ANCIENT ROME*

The Republican and early Imperial monuments of Rome are, for the most part, built of tuffs quarried from at least seven pyroclastic deposits erupted from nearby Monti Sabatini and Alban Hills volcanoes. Remarks by Vitruvius (2.7.1–5), field observations of the monuments, and petrographic and rock testing studies of samples from Roman quarries demonstrate that Roman builders developed a good knowledge of the diverse material properties of the tuffs over centuries of use and exposure. Measurements of compressive strength, specific gravity, water absorption and adsorption of water vapour confirm that the petrographic characteristics of each tuff lithology strongly influence its strength and durability. Early construction utilized weakly durable, soft or vitric tuffs such as Tufo del Palatino or Tufo Giallo della Via Tiberina that are susceptible to decay, as at Temple C (290 bc ) of the Largo Argentina Sacred Area. Late Republican structures, such as the Temple of Portunus (80–90 bc ), employed somewhat durable, vitric–lithic Tufo Lionato reinforced with travertine, a durable limestone quarried near Tivoli. Roman builders selected the material properties of the tuffs to advantage for specific structural elements within large public monuments of the first century bc and the first century ad , as at the tabernae of the Forum of Caesar (46 bc ), where an upper storey of lightweight Tufo Lionato is supported by robust, lithic–crystal Lapis Gabinus pillars and flat arches reinforced with travertine. The tuffs are not very durable building stones; Romans preserved them with protective stucco, and travertine and marble cladding. Their high water intake, coupled with direct exposure to rain, daily fluctuations in relative humidity and urban weathering at present makes them especially vulnerable to decay.     

THE EFFECT OF SALTS ON THERMAL AND HYDRIC DILATATION OF POROUS BUILDING STONE*

Fifteen desalinated sandstone drill core samples from Umm Ishrin Sandstone Formation in Petra (Cambrian age) were used for this study. The samples were mineralogically analysed using X‐ray diffraction and their physical properties were also determined. Samples with similar physical properties and mineralogical composition were taken for further experimental work. After desalination, thermal and hydric dilatation coefficients were measured, then three types of salts (NaCl, KCl and Na₂SO₄·10H₂O), which have high solubility and consequently are the most dangerous to building stone (and are also detected in the sandstone monuments in Petra), were introduced into the samples and their contents were calculated. The results show that salt crystallization in the pores of building stones can increase their thermal dilatation and decrease their hydric dilatation to varying extents, depending on the nature of the salt. The average increase in the thermal dilatation coefficient per unit mass of salt is the lowest for the Na₂SO₄·10H₂O‐salted samples with a value of 5.3%, while the NaCl‐salted samples have the highest value with 7.8% per salt mass. The average percentage of the decrease of the hydric dilatation coefficient is 1061% for Na₂SO₄·10H₂O‐salted samples per mass of salt content; the NaCl‐salted samples have a value of 1510% per mass of salt content, and the KCl‐salted samples almost the same value. For the salt‐free samples, it was found that in climatic conditions with a high temperature range, the deterioration of sandstone due to temperature fluctuation is more effective than that caused by change in the moisture content, while samples with high salt content suffer more from hydric dilatation.     

GEOCHEMICAL AND ENGINEERING GEOLOGICAL PROPERTIES OF THE VOLCANIC TUFFS USED IN THE ETRUSCAN TOMBS OF NORCHIA (NORTHERN LATIUM,ITALY) AND A STUDY OF THE FACTORS RESPONSIBLE FOR THEIR RAPID SURFACE AND STRUCTURAL DECAY

The geochemical and engineering geological properties of the tuffs used in the rock‐cut cliff tombs of the Etruscan necropolis of Norchia were investigated to evaluate their susceptibility to different weathering agents and confirm their origin. For the first time, materials were characterized by X‐ray powder diffraction (XRD), Fourier‐transform infrared spectroscopy (FT–IR), thermogravimetric analyses (TGA, DGA and DTG), scanning electron microscopy (SEM–EDS) and energy‐dispersive X‐ray fluorescence (ED–XRF), and their different origins confirmed. Tests of material properties indicate that both tuffs are poorly durable, but one of them is less susceptible to weathering. Although tombs made with the more resistant material show limited surface weathering, they undergo severe structural damage because of stress release and plant root infiltration. This, combined with the microclimatic conditions established inside river canyons, can trigger rock falls, leading ultimately to the complete destruction of these tombs.     

MECHANICAL PERFORMANCE OF QUARTZ-TEMPERED CERAMICS: PART I,STRENGTH AND TOUGHNESS*

The effect of quartz temper on the physical and mechanical properties of clay ceramics and the elucidation of the underlying mechanisms that are responsible for these effects are presented here. Characteristics studied included bulk density, open and closed porosity, density of impervious portion and fracture morphology. Mechanical behaviour was studied by measuring energy dissipation during fracture, Young's modulus, initial fracture toughness and strength in flexure. The significant increase in toughness with quartz volume fraction is explained by the development of a model that accounts for the crack distribution around the grains. The archaeological implications of the work are discussed on the basis of all the parameters that might affect the potter's choices of raw materials.     

MECHANICAL PROPERTIES OF STONE ARTEFACT MATERIALS AND THE EFFECT OF HEAT TREATMENT*

Mechanical testing of lithologies used for stone tool manufacture has shown that fracture toughness is the most objective measure of the quality of raw materials shaped by either flaking or pecking/grinding. Materials amenable to pressure flaking and blade manufacture have low values of fracture toughness, whereas those shaped by pecking/grinding have high values. The fracture toughness test is also the most definitive for quantifying the improvement in flaking properties of materials subjected to intentional heat treatment. Cryptocrystalline and macrocrystalline siliceous lithologies demonstrate a well-defined, gradual reduction in fracture toughness with increased temperature. When heated to optimum temperatures, their fracture toughness approaches that of obsidian, the lithology generally regarded as having the best flaking properties.     

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.     

THE RELATIONSHIP BETWEEN LITHOLOGY,FLAKING PROPERTIES AND ARTEFACT MANUFACTURE FOR AUSTRALIAN SILCRETES*

Mechanical properties of Australian silcrete strongly influenced raw material selection and artefact manufacture. Microcrystalline silcrete, with high compressive and tensile strength, is suitable for blade tools requiring fine retouch. Fine‐grained silcrete (high compressive strength but lower tensile strength) was often used for blade‐based implements, but is more susceptible to edge fracturing. Medium‐grained silcrete has poor flaking properties (low compressive and tensile strength) and was often used for flake manufacture. Thus material determinism can explain much of the variability in silcrete artefact morphology and assemblage composition. Silcrete compressive strength is positively correlated with percentage of microcrystalline matrix and negatively correlated with average grain size, so hand lens examination of a silcrete sample can give a good indication of its likely flaking quality.     

MECHANICAL PERFORMANCE OF QUARTZ-TEMPERED CERAMICS: PART II,HERTZIAN STRENGTH,WEAR RESISTANCE AND APPLICATIONS TO ANCIENT CERAMICS*

Mechanical performance of ceramics can be measured by various techniques. Conventional testing usually requires multiple samples of large size and specific geometries and for this reason cannot be usually applied directly to ancient pottery. However, Hertzian strength and wear resistance can be measured on the same specimen, of small size, and it is shown that these tests can describe, to a good approximation, the basic ceramic mechanical propertics (strength and toughness). Therefore, these tests are proposed for use on archaeological specimens. An application on Punic amphorae found in Corinth is presented.     

The Protection of Archaeological Sites in Taiwan

Abstract

There are roughly 2300 recognized archaeological sites in Taiwan. Under the Cultural Properties Preservation Law (CPPL) of 1982, archaeological heritage falls under the category of 'historic relics'. However, archaeological sites are not designated as such until they have been excavated and studied to prove their cultural value. Protection of the archaeological heritage has been reinforced through the Environmental Impact Assessment Act (EIAA), which regulates all environmental management plans. These study and determine the degree and scope of the potential impact of development on the cultural environment.

The CPPL was extensively amended and promulgated in 2005, and in this recent document discussed archaeological heritage in a distinct chapter (Chapter 3 with 16 acts). Furthermore, three regulations have been issued concerning the examination of designations of archaeological sites, qualification standards for excavation, as well as the administration and protection of archaeological sites. The newly enacted Cultural Law and Regulations confer competent authorities at all levels with all powers to supervise, administer, and then protect valuable buried cultural property. Although the protection of archaeological heritage has been better enforced since 2005, archaeological remains in Taiwan are still under various threats. Preservation of the cultural heritage is threatened by development, in many cases resulting in impasse. This paper discusses several recent examples of such dilemmas and presents a personal opinion on a better way to settle the controversy.