Technological Features of Roman Terra Sigillata from Gallic and Italian Centres of Production

Technological features of sherds of Roman terra sigillata were studied. The sherds analysed represented products of workshops which were most probably located in Gaul, central Italy, north-west Italy and the plain of the river Po. Equivalent firing temperatures were estimated by colour measurement, X-ray diffraction and thermal expansion measurement; in addition, the chemical and morphological features of the red sintered slips were investigated using scanning electron microscopy coupled with energy dispersive X-ray microanalysis. The combined results suggest that, relative to northern Italian products,terra sigillata from Gaul and central Italy was made by potters who were more successful in modifying slip composition and controlling firing temperature to obtain highly sintered slips. Northern Italian potters seem to have worked their clays less successfully and fired them at temperatures which were too low to overcome the limited presence of fluxes in the slip.     

Estimation of the Production Parameters of Very Large Medieval Bricks from St. Urban,Switzerland

The aim of the present study is to determine the production technology of a particular type of large medieval brick. The firing temperature and their soak times are estimated using a combination of colour and fabric, as well as mineralogical, microstructural and open porosity analysis. A replication experiment was carried out in order to validate the estimated predictions, and to give a realistic idea of the time needed to dry and fire each large brick. The experiment also suggests the temperature distribution and firing atmosphere in the kiln, as well as providing an estimate of fuel consumption. Analytical results and replication both provide information to assess the production technology, the time parameters and the firing temperatures involved in the production of the medieval bricks of St. Urban.     

Tracing firing technology through clay properties in Cuzco,Peru

The purpose of this study was to identify changes in firing practices that occurred during a timeframe that saw the introduction of European kiln technology to the Andes (AD 900–1800). Pottery from an excavated context at the archaeological site of Aqnapampa in the southern highlands of Peru was examined for changes in paste recipes that adapted local materials to increased firing temperatures indicative of evolving firing technologies. Sherds (60) and fragments refired to 890 °C from 12 stratigraphic levels were compared by style, surface treatment, paste color, and vitrification structures (ESEM). Four technological phases of the Cuzco pottery sequence emerged and were used to evaluate the trajectory of a single decorative style (Killke). Previously thought to have been produced in pre-Inca times and curated into later periods, the Killke sherds presented evidence that the style was produced using technologies introduced in the Inca and Spanish Colonial Period.     

THE DETERMINATION OF BRICK PROVENANCE AND TECHNOLOGY USING ANALYTICAL TECHNIQUES FROM THE PHYSICAL SCIENCES*†

This work applies established analytical techniques from the physical sciences to Irish brick, in order to gather evidence of ceramic technologies, provenance and sources of raw materials. Petrographic microscopy, X‐ray diffractometry and scanning electron microscopy with an energy‐dispersive X‐ray diffraction attachment were used to study the brick of Rathfarham Castle, Dublin, built c. 1618, where clay brick was introduced in 1771. Local clay was fired in the laboratory and analysed in a similar manner. The petrography of the pointing mortar was studied in order to gather evidence of ceramic provenance. This paper concludes that the brick was hand‐ moulded with a silica‐based, predominantly non‐calcareous clay of glacial origin, gathered locally, including fluxes and a high percentage of non‐plastic material. The mineralogy and petrography of the brick, together with the presence of pebbles and a coarse matrix, suggest that the raw clay was probably gathered from a glacial deposit. The presence of abundant pebbles and colour inhomogeneities suggests a lack of processing of the raw clay. The brick was probably fired in clamps at top firing temperatures ranging from 750°C to above 900°C. Transformation of limestone temper involving the breakdown of calcite and the generation of calcium silicates, and the new formation of plagioclase, high‐temperature quartz, hematite and spinel were revealed. The presence of spinel in ‘hot spots’ indicates that fuel was added to the raw clay in order to assist firing.     

MINERALOGICAL INVESTIGATIONS OF MEDIEVAL BRICK SAMPLES FROM BÉKÉS COUNTY (SE HUNGARY)

Brick samples from nine archaeological sites representing seven contemporary medieval settlements in Békés County (SE Hungary) were analysed by quantitative X‐ray powder diffraction, optical microscopic, scanning electron microscopic and coupled thermal analytical – evolved gas analytical methods. The aims of this study were to give a mineralogical–petrographical characterization of the brick samples, to gain possible information on the raw clay and the admixed materials, and to determine the firing techniques applied in medieval southeastern Hungary. The mineralogical composition of the samples suggests that the locally extracted clay was mixed with fluvial sand and wheat (Triticum monococcum L.) chaff. The moulded bricks were fired in clamps. The different degrees of calcite consumption suggest that the firing temperature ranged from ～750°C to ～950°C. Moreover, the well‐developed reaction coronas on calcite grains indicate long firing times, lasting perhaps several days.     

Assessing the Accidental Versus Deliberate Colour Modification of Shell Beads: a Case Study on Perforated Nassarius kraussianus from Blombos Cave Middle Stone Age levels

Colour plays an eminent role in beadwork. Colour modifications are reported on early shell beads from Middle Stone Age sites. However, identifying the colouring agent and demonstrating the intentional nature of the colouring process is not straightforward. Here, we provide analytical data on colour and structural modifications observed on Nassarius kraussianus (Nk) collected in modern thanatocoenoses and on shells of the same species experimentally heated in oxidizing and reductive atmospheres. Comparison with Nk shell beads from the 72 ka old Middle Stone Age levels of Blombos Cave, South Africa, and contextual analysis of other malacological remains from the same levels that were not used as ornaments identify the mechanisms responsible for the change of colour in modern Nk thanatocoenoses and heated shells, and show that although some Nk shell beads were heated, intentional heat treatment of shell beads is not demonstrated.     

Studying the process of enamel powder preparation for émail champlevé by colour measurements and μ‐X‐ray mappings

Colour measurements and non‐destructive μ‐X‐ray mappings have been used for the first time in a comprehensive study of medieval émail champlevé works from different production areas in France and Germany. This approach has given a new insight into the enamel powder preparation process of the glass material used for enamelling. Colour measurements demonstrated that all production centres used glass of very similar hues, but with large differences in colour saturation. The μ‐X‐ray mapping results of blue enamels are described by a semi‐qualitative approach. Significant variations in oxide contents of lead, cobalt, manganese and antimony oxides were found. The variations suggest that more than one glass material was used to prepare the powder for enamelling. The variations in antimony and cobalt show that glass had different degrees of opacity and colour depth. The manganese and lead contents, which do not correlate with the cobalt or antimony contents, indicate that probably glass of different base compositions was used to prepare the enamel powder for one champlevé field.     

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.     

Inheritance relationship between Zhanggongxiang kiln celadon and Ru Guan celadon: Comments on the rationality of Raman Ip value evaluating firing temperature

The development of Chinese ceramics culminated during the Song dynasty. At this time, exquisite celadon works emerged, such as Ru Guan celadon and Southern Song dynasty official kiln celadon, which exhibited the glory of their era. Since the excavation of Zhanggongxiang kiln celadon in Ruzhou city, Henan province, China, it has been attracting widespread scholarly attention at home and abroad. Most scholars have suggested that Zhanggongxiang is the official kiln of the Northern Song dynasty. In this paper, taking the celadon unearthed from the Zhanggongxiang kiln as a sample, the combination of laser Raman spectrum and thermal expansion methods is used to study the inheritance relationship between Zhanggongxiang celadon and Ru Guan celadon in the firing process. Meanwhile, the rationality of using Raman I_p value to evaluate the firing temperature of ceramics is reviewed. The main conclusions are as follows. First, the firing temperature of Zhanggongxiang celadon with various glaze colours is quite different, whereas the firing temperature of the same glaze colour is similar, thereby inheriting the firing technology of Ru Guan porcelain. Second, the I_p value of glaze cannot evaluate the firing temperature of porcelain with similar firing temperature. The I_p value corresponds to a range, within which it does not fully conform to the rule that the larger the I_p value, the higher the firing temperature. The I_p value is also associated with the formulation in addition to firing temperature. It is applicable to evaluating porcelains with a similar formulation but a large temperature difference.     

IBERIAN CERAMIC PRODUCTION FROM BASTI (BAZA,SPAIN): FIRST GEOCHEMICAL,MINERALOGICAL AND TEXTURAL CHARACTERIZATION

Ceramic fragments from the archaeological excavation of the Iberian–Roman city of Basti (Spain) were studied from a geochemical point of view and by applying a statistical tool to X‐ray fluorescence data to discover similarities between ceramic materials. The analysis of these samples was completed by performing a mineralogical analysis, textural observation, and by characterizing the porous system and the colour of the pieces. Our results enabled us to identify the source area of the clayey raw material in the surroundings of Basti and to estimate the firing temperature of the ceramics. Differences in the chemistry were confirmed by characteristics of the pastes and the mineralogical composition of the pieces. Some samples show black cores, which would suggest the presence of organic matter in the raw material and fast firing of the ceramics. The main types of temper were quartz grains and gneiss fragments, although carbonate grains were also identified. Our evidence suggests that most of the samples were well fired. New silicate phases were found to be present in several samples. The mercury intrusion porosimetry verified and confirmed the firing temperature of non‐carbonated samples. Colorimetry showed that the colour of the ceramics varied according to the amount of CaO that they contained.     

Mössbauer Spectroscopic and Chromaticity Analysis on the Colourative Mechanism of Ancient Goryeo Celadon from GangJin and Buan

In ancient Goryeo celadon excavated from the kiln sites in the GangJin and Buan areas, the effect of the chemical composition and ionic state of Fe on the colour was evaluated by Mössbauer spectroscopy and chromaticity analysis. According to chromaticity analysis, the L* value (brightness) of the glaze was shown to be affected more by TiO₂ and MnO than by Fe₂O₃, and the body was affected more by Fe₂O₃ than by TiO₂. The a* value was found to be affected by Fe₂O₃ and TiO₂ in the glaze, whereas there was hardly any change in the body according to the composition. As for the b* value, changes due to the composition were shown to be smaller than those for the L* and a* values. According to the Mössbauer spectroscopy results, as the quantities of TiO₂ and Fe₂O₃ are increased, Fe²⁺/Fe³⁺ decreases; while the changes in Fe²⁺/Fe³⁺ with MnO and P₂O₅ are negligible. As the quantity of Fe²⁺/Fe³⁺ increases, the a* and b* values decrease, which results in the change of colour from red–yellow to blue–green. The characteristic green colour can be attributed to increased L* (brightness) and decreased a* and b* values (blue–green shift) due to the reduced Fe ion, which is mainly determined by the TiO₂ and Fe₂O₃ contents.     

Pottery firing temperatures: a new method for determining the firing temperature of ceramics and burnt clay

A new method for determining the maximum firing temperature of ceramics and burnt clay is presented. The technique relies on measuring the magnetic susceptibility on a step-wise re-fired sample. The validity of the method has been tested by determining firing temperatures of two sets of clay samples fired at temperatures ranging from 400 to 1000 °C. Aliquots of the same samples have been studied petrographically by optical microscopy on thin sections and analyzed by powder X-ray diffraction in order to monitor structural and mineralogical changes as a function of temperature. The method is demonstrated on samples from four geographically widely different sites and it is applied to a larger set of ceramics of Late (ca. AD 900–AD 1450) and Inca (ca. AD 1480–AD 1532) periods from the Northwestern Argentine region, dating to a limited period of time prior to the fall of the Inca Empire. The method is shown to be a powerful tool in revealing archaeological information about the change in firing technologies in the pre-Hispanic societies in the Andean area through time.     

TIME‐OF‐FLIGHT NEUTRON DIFFRACTION CHARACTERIZATION OF CERAMIC FINDINGS FROM SOUTHERN AND WESTERN SICILY*

We present the results of a study that is part of a wider research programme regarding knowledge of the initial living phases of Sicilian agricultural and pastoral society. Three sets of ceramic samples were analysed through time‐of‐flight neutron diffraction (TOF‐ND) to derive information about the composition of the clay and the manufacturing techniques. The first two sets of sherds came from an excavation in Licata, close to Agrigento, and are composed of findings dated around the third century bc , while the third set was of samples from prehistoric sites located in the northwestern part of Sicily. Measurements were performed to obtain a quantitative identification of the mineralogical composition of the samples in a totally non‐destructive way. Hints about manufacturing techniques and firing temperatures are derived to provide information on provenance and production processes of the objects.     

ARCHAEOMETRIC ANALYSES ON ‘CORINTHIAN B’ TRANSPORT AMPHORAE FOUND AT GELA (SICILY,ITALY)*

The aim of this work is to throw light on the archaic production of ‘Corinthian B’ amphorae, which are widely diffused in the Western Mediterranean basin and are also present in Greece, but whose geographical provenance is still under discussion. We analysed a group of 37 samples belonging to different ceramic classes dated to the sixth and fifth centuries bc . In particular, there were 19 sherds of trade amphorae of the so‐called archaic ‘Corinthian B’ type, from archaeological excavations in Gela (Sicily, Italy). As a comparison, we also investigated 18 samples of tiles and local coarse pottery from Sibari (Calabria, Italy). The samples were analysed using different techniques, such as optical analysis with a polarized‐light microscope (OM), X‐ray diffraction (XRD), Fourier transform–infrared absorption (FT–IR) and inductively coupled plasma–optical emission spectroscopy (ICP–OES). The combination of these complementary analytical methods allowed us to characterize the samples, determine their firing temperatures and identify the probable provenance. The study of thin sections of sherds by OM allowed us to divide the investigated amphorae into two main groups: the first was characterized by a composition that suggested a Western provenance, in particular from the Calabrian–Peloritan region; the second one was very similar to the ‘Corinthian B’ amphorae that come from Corinth and have been classified as ‘fabric class 1’ by Whitbread (1995 ). The XRD and FT–IR results permitted us to determine the mineral composition of the findings and to estimate their firing temperature. The ICP–OES technique was particularly useful in identifying the production centres. In fact, in the studied pottery, this analysis revealed Ni and Cr values that were noticeably different between Greek and southern Italian production.     

FIRING ANALYSIS OF SOUTH-EASTERN MISSOURI INDIAN POTTERY USING IRON MÖSSBAUER SPECTROSCOPY*

The Mössbauer spectra of prehistoric pottery and clay from the Malden Plain of south-eastern Missouri, USA, were examined. The pottery dates from AD 500 to 1400. The earlier sherds were tempered with sand and the later ones with shell. The sherds and clay contain a mixture of illite, smectite, and kaolinite. Most samples of clay and sherds contained both ferric and ferrous species. The spectral parameters for the ferric species were %DLE_Q～0. 7—1.1 mms^-1 and δ～0.0–0.3 mms^-1 for the ferrous species, ΔE_Q～2.1–2.7mms^-1 and δ～0.7–1.0mms^-1. The ferric to ferrous ratio is more accurately determined from the spectra than from consideration of the colour or the firing core of the sherds, which are not always related to the iron species ratio. Differences among sherds in the ferrous ΔE_Q can be related to original temperature of heating but with low precision.     

X-RAY DIFFRACTION OF EARLY IRON AGE POTTERY FROM WESTERN NORWAY

X-ray diffraction has been used to analyse the surfaces and cores of sherds from pottery from Voss and Etne. two late Roman-early Migration Period sites in western Norway. Results show: (1) the presence of illite and illite/smectite in black-burnished ware from inhumation graves which suggests that this ware was never subjected to temperatures as high as 375°C, (2) the absence of these heat-sensitive clay minerals in red ware from cremation graves at these sites which suggests a secondary firing at 700–800°C, (3) the clay minerals are similar in the cores and surfaces of the black pottery which suggests that the colour differences are due to firing procedures rather than the application of a slip, and (4) chlorite is present in all of the samples which is an indication that the ware originated in a Voss workshop where chlorite is present in other pottery found there and in the local geologic deposits.     

Technological aspects of Mesopotamian Uruk pottery: estimating firing temperatures using mineralogical methods,thermal analysis and luminescence techniques

The Middle Uruk phase in Mesopotamia (3600–3500 bc) has been characterised by the massive production of “bevelled rim bowls” (BRBs). They are characterised by their similar shape and volume in Mesopotamia and surroundings. However, their production method has not been studied in detail, including the firing temperature. The determination of the firing temperature of ancient pottery has been attempted by studying mineral phase transformation sequences; although, very little knowledge exists about such transformations in mixtures or thermal analyses. These methods usually provide imprecise firing temperatures between 500 and 800 °C, as other factors such as the raw materials or firing time and conditions must be considered. As an alternative, luminescence techniques have been tested with promising results, as they have provided reliable maximum firing temperatures for ancient pottery at mild conditions (below 600 °C) with high precision. In this work, the firing temperatures of BRB samples from two archaeological sites located in the Middle Euphrates Valley (Syria) have been studied using mineralogical, chemical and thermal analysis. Both mineral characterization techniques and thermal analyses show agreement and firing probably below 600–700 °C. Luminescence yields ambiguous results but circumstantial evidence on the firing temperature between 400 and 550 °C.     

苏家村遗址烧土样品的过火温度研究

烧土制品作为最早的人工建筑材料,使人类的居住环境得到了根本性的改善。然而,学界关于烧土建筑的成因存在人为烘烤处理、缘自火焚、废弃习俗等多种观点。通过科技手段研究烧土制品的过火温度,有助于科学分析烧土建筑的成因,探讨与之相关的建筑工艺,丰富史前建筑史研究。磁学研究表明,考古遗址中的土壤及其他沉积物在受热后新生成了磁铁矿、磁赤铁矿等强磁性矿物导致磁性显著增强,且矿物成分和磁性几乎不会再发生变化;但当重烧的温度接近或大于原始烧成温度时,样品中原始矿物的破坏或新矿物的生成,会引起矿物磁性的改变。基于这一原理,实验室内分析受热黏土的磁化率随再加热温度的变化特征,可反映烧土制品的过火温度。苏家村遗址是大汶口文化晚期至龙山文化中期早段一处重要的聚落遗址,遗址中第5层为厚约20～40 cm的红烧土层且覆盖整个遗址,推测为房屋倒塌造成的建筑垃圾堆积层或人为堆积层,出土大量烧土块。本研究利用X射线衍射分析法、X射线荧光光谱分析法和磁化率法等对苏家村遗址出土的烧土样品开展了组成及构造特征和样品的过火温度的综合分析。结果表明,苏家村遗址烧土样品中的白灰层中人为地添加了白色陶土原料,土层中有意地添加了植物残骸作...     

Spectrochemical Characterization of Red Pigments Used in Classic Period Maya Funerary Practices

We studied the composition, colour chromaticity and form of application of red pigments in human bone samples from seven Classic period Lowland Maya sites. The samples were analysed by X‐ray diffraction, scanning electron microscopy (SEM) and X‐ray energy‐dispersive spectroscopy (EDS). Colour was measured using conventional colour identification standards (Munsell) and reflectance spectroscopy. Cinnabar and hematite were identified as the pigments used. We conclude that the reflectance method has advantages over conventional visual results, as it provides precise, objective and quantifiable optical data to distinguish the chromaticity, colour saturation and brightness of the pigments.