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.     

Lipid Residues from Low‐Fired Pottery

This paper assesses the fate of lipids associated with low‐temperature and pit‐fired pottery to determine to what degree organic compounds persist or are removed during short‐firing episodes below 800 °C. Three different types of clay were fired using contrasting techniques including at 400 °C for 4 h in a muffle furnace, and pit‐firing in which pottery was fired to higher temperatures but for shorter periods of time. Total lipid extracts obtained by solvent extraction of test sherds were screened using gas chromatography‐flame ionization detection (GC‐FID) to determine the lipid concentrations and gas chromatography–mass spectrometry (GC–MS) to identify the organic compounds present. The results showed that firing of clay removes all naturally occurring alkyl lipids; however, during pit‐firing, diterpenoid lipids were introduced into the clay as a condensate from pine ( Pinus spp.) wood used as fuel. These results confirm that alkyl lipids, e.g., fatty acids, can be reliably associated with the use of vessels, although caution is required when interpreting the origins of lipids that might derive from fuel used in firing.     

Firing Techniques of the Impasti from the Protohistoric Site of Concordia Sagittaria (Venice)

⁵⁷Fe Mössbauer spectroscopy provided relevant information on the firing techniques employed in manufacturing concotto and coarse pottery, two types of fired clay mixtures (impasti) of the protohistoric settlement site of Concordia Sagittaria. The firing techniques of Concordia were reconstructed by comparing the Mössbauer patterns of the artefacts with those of the local raw clays fired in the laboratory. The concotto was produced in kilns by firing clay mixtures under oxidizing conditions at 700–1000°C, or at lower temperatures in the open air. The firing of these clay mixtures containing mainly ground pieces of waste pottery, resulted in hard and variously coloured construction materials, particularly suitable for humid environments. In turn, the coarse pottery was produced by firing clay mixtures more homogeneous than those used for the artefacts of concotto. The firing of coarse pottery was performed under reducing conditions at about 900°C with a final exposure to air by opening the hot kiln. Light and agreeable coarse pottery, with a red surface on the grey-black core, was obtained when the effective temperature of air was higher than 500°C.     

Unglazed pottery from the masjed-i jom’e of Isfahan (Iran): technology and provenance

The masjed-i jom’e of Isfahan is one of the earliest mosques of Iran. Since 1970, Italian researchers performed an extensive archaeological investigation uncovering huge amounts of finds. This study aims at investigating the technological features and provenance of the unglazed pottery finds by using a minero-petrographic approach. Twenty-three samples of storage, table and cooking wares were selected based on the recurrence of typologically identifiable fragments and fabrics. Two bricks, seven production indicators (spacers, kiln furniture, slags) and a local clay were analysed for comparison. The production indicators and most of the pottery show high-CaO concentration. Thick-walled wares contain coarse sedimentary/metamorphic inclusions. Samples with thinner walls contain similar but fine/well-sorted inclusions. The mineralogy and microstructure indicate firing temperatures mainly ranging from 850 to 1000 °C. Low-CaO samples contain coarse sedimentary inclusions; in one sample, volcanic lithics are present. Firing temperatures range from about 800 to 950 °C, and the low-CaO character can be related to their specific function for cooking foods. One sample, found in older stratigraphic levels, differs for its peculiar calcitic temper and lower firing temperature. Local production of most samples was constrained by the composition of the inclusions compatible with the sediments of the Isfahan area. High-CaO pottery shows compositional affinity with production indicators, local clay and tiles produced in Isfahan during the Safavid period. Cooking ware usually contains local temper, with the exception of a sample with volcanic inclusions, for which a non-local provenance is supposed. No appropriate information is, however, available regarding the low-CaO clays used in the area.     

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.     

ON THE USE OF COLOUR COORDINATES TO EVALUATE FIRING TEMPERATURES OF ANCIENT POTTERY*

Colour measurement was investigated as a means to evaluate equivalent firing temperatures of ancient pottery. Colour coordinates were determined on samples of six clays previously fired, and then refired, in the temperature range 600–1100°C. Under the adopted conditions, significant variations of colour hue and saturation were normally observed on refired samples only after the original firing temperature had been exceeded; less reliable information was provided by luminosity. Original firing temperatures of clay samples were correctly recognized in most cases by projecting the points representing samples’ colour on to the a*b* plane of the ClEL*a*b* colour space.     

Archaeometric study of medieval pottery excavated at Stari (Old) Ras,Serbia

A combined study of a series of polychromatic and monochromatic glazed medieval pottery shards excavated from the archaeological area of Stari (Old) Ras in southern Serbia, including petrographic and chemical analysis, powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy, allowed us to clearly distinguish between two groups of ceramics. Ras pottery, made of fine-grained well-cleaned clay and characterised by a rich mineral assemblage, was produced by firing in a temperature range between 800 and 900 °C. Reljina Gradina ceramics were produced at similar temperatures from materials which, with regard to mineralogical and chemical composition, show clear similarity with local clay, suggesting that these samples are of local origin and production. This work is the first systematic archaeometric study of medieval pottery excavated on the territory of Serbia.     

Technological examination of Neolithic-Bronze Age pottery from central and southeast Europe and from the Near East

Scanning electron microscopy is used to examine sequences of pottery sherds from central and southeast Europe, Greece and the Near East spanning the period from the Neolithic to the Bronze Age, in order to obtain information on the ceramic technologies employed in antiquity. On the basis of the vitrification observed and the chemical composition, the types of clay and firing procedures (temperature and atmosphere) employed in the manufacture of the pottery are defined. Two under-lying trends in the associated ceramic technologies are thus identified. The first is based on the use of non-calcareous or “unstable” calcareous clays fired in a reducing atmosphere at temperatures below 800 °C and the second on the use of “stable” calcareous clays fired in an oxidizing atmosphere at temperatures in excess of 800 °C.     

CHEMICAL–MINERALOGICAL ANALYSES AND MICROSTRUCTURAL STUDIES OF PREHISTORIC POTTERY FROM RAHMATABAD,SOUTH‐WEST IRAN*

A series of prehistoric pottery samples excavated from Rahmatabad, south‐west Iran, were investigated using XRF and XRD analyses to determine their chemical and mineralogical compositions. The sample microstructures were also studied by SEM/EDX. The relative similarity of compositions, the fine, dense and homogeneous microstructures and the presence of high‐temperature phases such as diopside and mullite showed the use of high firing temperatures, in the range 950–1050°C. This, along with the homogeneity in shape, decoration and size ranges of the ware, all indicate the adoption of specialized pottery‐making techniques by the potters of Rahmatabad in the fifth to fourth millennia bc .     

Archaeometric Investigation of Medieval Pottery from Excavations at Novo Brdo,Serbia

Medieval pottery from excavations at Novo Brdo, Serbia, an important mining and trading centre during the 14th and 15th centuries, was investigated by a combination of optical microscopy, inductively coupled plasma – optical emission spectrometry, Fourier transform infrared, micro‐Raman and energy‐dispersive X‐ray fluorescence spectroscopy and X‐ray powder diffraction methods in order to determine its composition and firing temperature. The samples investigated were made of medium‐ to coarse‐grained, non‐calcareous clay, by a relatively well‐controlled firing procedure in an oxidizing atmosphere. The firing temperature was estimated to be 850–950°C. The similarity between the chemical composition of the investigated pottery and the local raw clay, combined with the outward appearance and the archaeological findings, indicate domestic production. The pottery is covered with the transparent lead‐rich glaze. Iron and copper were used as colourants.     

Technological Characterization of Campanian Pottery of Type A,B and C and of Regional Products from Ancient Calabria (Southern Italy)

Sherds of Campanian pottery were studied by SEM‐EDX. SEM images show that slips of Campana C are scarcely sintered and are thicker than the well vitrified coatings of Campana A and B and imitations of Campana B. Slips of products with a grey slip on a grey body are very thin and well vitrified. EDX analyses indicate that slips are richer in aluminium and iron, and poorer in silicon and calcium, with respect to the bodies. Higher potassium is also found in all of the coatings except those of Campana A. Here relatively high sodium makes the total alkalis comparable with those of the other products, except Campana C, where it is somewhat lower. Measurement of thermal expansion and X‐ray powder diffractograms suggest that firing temperatures were mostly in excess of 900°C, but some samples of Campana C seem to have been fired below 800°C.     

The Firing Temperature of Pottery from Ancient Mesopotamia,Turkey, Using Luminescence Methods: A Case Study for Different Grain‐Size Fractions

The assessment of the firing temperature of a prehistoric pottery sample collected from ancient Mesopotamia, Turkey was studied using luminescence techniques. The methods for this estimation involved the observation of the thermal and pre‐dose sensitization with various re‐firing temperatures for both TL and the OSL signals. In the former case, the 110°C TL peak and the rest of the glow curve were used as proxies in this study. In the framework of a first attempt to investigate the impact of grain‐size dependence on the sensitization of the luminescence signals, the aforementioned study was performed with four different pottery grain‐size fractions: (i) less than 60 μm, (ii) 60–90 μm, (iii) 90–180 μm and (iv) 180–250 μm. The results clearly demonstrated the firing temperature mark of ～500°C in for the grain size of 90–180 μm, while—as in the case of the lower grain‐size fraction—a third proxy, the ratio of the pre‐dosed to the thermal sensitization, was seen to indicate the firing temperature. The remaining two grain‐size fractions failed to provide any meaningful results with regard to the firing temperature estimation. The dependence of the TL characteristics on the grain size was explained in the framework of the mixed mineralogy.     

Minero-petrographic characterization of fine ware from Cales (South Italy)

79 samples of black glazed pottery, Terra sigillata, fine common ware, and production indicators were recovered in the archaeological site of Cales and investigated via a multi-analytical program (polarized light microscopy, thermal analyses, XRPD, XRF, FESEM, FESEM-EDS). Among the materials, finds of important production indicators, represented by welded pieces of black glazed pottery and spacers, attest a local production. Polarized light microscopy shows that the inclusions consist of feldspar, quartz, mica, calcite, and lithic fragments of both volcanic and sedimentary nature. Additional information about the mineralogical assemblage comes from the XRPD that revealed the presence of neoformed Ca-silicates, indicating equivalent firing temperatures ranging from 750 to 1050°C. All the samples show a Ca-rich character and an extreme compositional homogeneity, including the production indicators. The comparison with some Ca-rich Campanian clay raw materials shows a greater affinity with the Mio-Pliocene marine clay sediments of the Apennine sector, which include local clays. This allowed us to formulate the first hypotheses about clay sources used to produce fine pottery during the third century BCE to the early imperial period in Cales.     

MOESSBAUER SPECTROSCOPIC,CHEMICAL AND MINERALOGICAL CHARACTERIZATION OF IBERIAN POTTERY

Three types of Iberian pottery from the same excavation and archaeological level have been studied by Moessbauer spectroscopy, atomic absorption spectroscopy, X-ray diffraction, and transmitted-light polarizing microscopy. The results are compatible with a common origin, a firing temperature below 850 °C, and a different fabrication technique for each pottery type.     

Ancient Egyptian Pottery from the Subsurface Floodplain of the Saqqara–Memphis Area: Its Mineralogical and Geochemical Implications*

Potsherds recovered from the Saqqara–Memphis floodplain in Egypt, dated according to their typology and radiocarbon dating of the included sediments, are analysed geochemically and mineralogically to identify source materials and fabrication characteristics. Pottery layers were identified and potsherds were recovered from several settlement levels. Sherd typology was used to identify sherds from four periods (the Old and New Kingdoms, and from the Late Period to the Ptolemaic). The Pharaonic pieces were found at depths of between 8 and 12 m and the later material was between 6 and 3 m. Chemical analyses of the potsherds revealed three main source materials: local Nile silt, marl clay and mixed Nile silt–marl. Two marl clay types were recognized: marl clay from Upper Cretaceous marine sediment and another one from Late Pliocene deltaic sediments. The mineralogical composition of the pottery samples shows that the estimated firing temperature was about 850–900°C. No consistent differences in sherd mineralogy and geochemistry were found according to pottery types, so that the ancient Egyptian potters used essentially the same materials throughout the Pharaonic period. However, this initial study has revealed the existence of extensive pottery‐rich occupation sites buried within the Nile floodplain deposits between Memphis and Saqqara.     

Firing temperature of a clay core sample in a bronze tripod from Daxinzhuang Site in China using TL techniques

In this paper, we studied the thermal history of a clay core sample from one leg of a bronze tripod unearthed at Daxinzhuang Site, Shandong, China. The properties of the luminescence signals of quartz depend on the maximum temperature at which the quartz was annealed in the past. We examined the feasibility of measuring the thermoluminescence (TL) sensitivity change of quartz for exploring the firing temperature of archaeological materials. The sensitization factor of the 110°C TL peak (S₂/S₁) and the ratio of the 210°C TL peak to the 110°C TL peak at different annealing temperatures were utilized to unveil the firing temperature in the clay core sample. The firing temperature of the clay core sample was approximately 700°C–800°C, proving the clay core has been fired. This result proved that the clay core has been fired by human agencies and indicated on the temperature of the clay core in drying and firing given by the foundry workers before the actual casting step.     

山东青州和沂源地区出土彩绘陶器的测试分析

彩绘陶器以其绚丽多彩的彩色装饰为主要特征,对它们的相关研究将不断丰富古代制陶工艺及颜料加工技术的认识。为此,本研究利用EDXRF、XRD、SEM、热膨胀分析等技术手段对山东青州香山汉墓和沂源战国墓葬出土彩绘陶器的组成结构及烧制温度进行了深入分析,首次发现了先以滑石粉打底其上再绘朱砂的彩绘陶品种。沂源战国墓葬中出土了表面用锡层作装饰的陶器,这是在我国北方地区的墓葬中首次发现这种"锡涂陶"。青州香山汉墓出土的陶俑和器物的胎料组成相近,而烧成温度存在明显差异,陶俑的烧成温度要高于器物。这些结果可为研究彩绘陶器的工艺发展提供新资料。     

Determining the Firing Temperature of Low‐Fired Ancient Pottery: An Example from the Donghulin Site,Beijing, China

The traditional thermal expansion method using a dilatometer fails to accurately determine the original firing temperatures of low‐fired ancient pottery. For this reason, we have developed an improved method of determining firing temperatures for low‐fired pottery. This paper explains the theory of the improved method and presents the reasonably satisfactory results obtained on ancient pottery from the Donghulin site (c. 10 000 bp ). The method and the results are very important for the study of ancient pottery culture and clay moulds used for bronze casting.     

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.