Clays from the Bay of Naples (Italy): New insight on ancient and traditional ceramics (original) (raw)
Related papers
Applied Clay Science, 2009
The Gran Potenza clay and the Pomici di Avellino pyroclastics, respectively the clay sediments and temper of the typical ceramic manufacture in Benevento area (Italy), were mixed in different proportion and fired at 850°, 900° and 950 °C. These experimental replicas were compared with historical ceramic products of Benevento. The similarities and/or differences between archaeological materials and replicas (in terms of amount of temper, firing temperature, pore system, etc.) have been discussed. The whole data confirm the wide utilization of the local available clayey raw material and the Pomici di Avellino, and give a new contribution on the petrophysical modifications of volcanic-rich ceramic pastes that occur in the firing temperature range comprised between 850° and 950 °C. Some peculiar features in the historical manufacturing are also reported.
Archaeological and Anthropological Sciences, 2018
The unusual discovery of a potter's workshop suddenly destroyed by a firing-cum-collapse event at Montebello Vicentino (northeastern Italy), dated to the Late Iron Age (ca. late fifth-fourth centuries BC), offers the unique possibility of studying two parallel operational sequences or chaines opératoires of ceramic manufacturing in this period, by direct analysis of the various base materials and products lost during destruction. Raw materials (prepared clay batch, sand, and other temper inclusions), unfired vessels knocked to the ground by the collapse, and samples of fired pottery were comprehensively characterized by petrographic and mineralogical analysis. Comparisons with similar ceramic products found at nearby settlements of Montebello can also better define the differences between production which was actually taking place at the workshop at the moment of destruction and previous work, as documented by sherds found at the same site.
Clay source and firing temperatures of Roman ceramics: A case study from Plovdiv, Bulgaria
Geoarchaeology, 2019
During urgent archaeological excavations in the city of Plovdiv (South Bulgaria), a Roman pottery workshop was found, including several dome kilns, ceramic sherds, and a large clay deposit incorporating yellow and gray clay layers. A set of the ceramic specimens (kitchenwares and tablewares) and raw clay samples were investigated using a portable device for X-ray fluorescence and laboratory equipment for magnetic measurements, aiming to provide specific information about the origin and firing technology of the pottery. Despite significant difference in calcium content between local raw clay and pottery samples, we conclude that local natural clay sources were used and the initial stages of production involved clay purification, although we cannot rule out the procurement of more distant clay sources. Magnetic susceptibility testing allowed for determination of the maximum firing temperatures, showing that the pottery were fired predominantly at 780°C, with some samples being fired at temperatures up to 860°C. Magnetic analyses show that kitchenwares were fired under more uniform conditions than the tablewares, which undoubtedly reflected in the quality of the vessels produced.
Thermal and mineralogical contribution to the ancient ceramics and natural clays characterization
Journal of Thermal Analysis and Calorimetry, 2006
In the present work 39 ancient ceramic sherds from the archaeological excavation of Abdera, North-Eastern Greece, dating to 7 th century B.C., and 11 local raw clay bricks, fired at temperatures ranging from 500 to 1000°C, were characterized by ICP-AES, powder X-ray diffraction (PXRD) and thermal analysis (TG-DTA) techniques. It has been found that the mineralogical composition of the most studied sherds is quartz, feldspars and micas, which is in agreement with the composition of the local bricks. Chlorite is also present in a few samples, while there is one completely different sherd, which belongs to the Ca-rich clays. From the simultaneous TG/DTG and DTA data, under nitrogen atmosphere in the temperature ranges ambient to 1000°C, we comment on the possible firing temperature and distinguish between samples of different origin. The existence of muscovite or illite in most of the samples denotes that the firing temperature was lower than 950°C, while the existence of chlorite means that the firing process in these samples stopped before 700°C. A very different thermogram gave the Ca-rich ceramic sherd, due to the existence of calcite, denoting that the firing temperature was about 700°C.
Thermal behaviour of ceramics obtained from the kaolinitic clays of Terra Alta, Catalonia, Spain
Journal of Thermal Analysis and Calorimetry, 2021
The thermal properties and evolution of mineralogy and colour of kaolinitic clay from the Terra Alta region were studied. The mineralogy of these materials consists mainly of kaolinite (13-27 mass%) and quartz (48-86 mass%). Minor illite, hematite, K-feldspar and calcite also occur. The linear expansion and absorption curves were used to predict the optimal firing temperature of the raw clays. During firing, from 1100 °C the water absorption decreases steeply, due to an increase in liquid phase, which penetrates into the pores and close the porosity. At this temperature, the firing shrinkage increases progressively. The fired clays are mainly composed of quartz, cristobalite and mullite, with minor hematite and rutile. Mullite starts to appear at 1050-1100 °C. SEM observations show that porosity decreases with the firing temperature. The colour properties were measured in the raw clays and in the fired bricks at different temperatures. The lightness, L*, is lower in the fired test pieces respect to the natural clays. This colour varies according to the hematite content, being from white to reddish in the fired samples.
Heritage
The earliest foundry site of Pre-Roman Padua, in the Veneto region (north-eastern Italy), provided evidence of craft activities and residential areas dated between the end of the 9th and 1st centuries BCE. Common and fine wares were found, most of them belonging to two main ceramic classes: (i) highly dark-colored bodies with silicate inclusions; (ii) carbonate-tempered pots. Macroscopic and petrographic (POM) descriptions and spectroscopy—mineralogical (XRPD) and geochemical (XRF)—analyses were carried out to define the provenance and technological choices (production recipes and firing conditions). The first ceramic class comprised diverse local/regional productions made with a common geo-resource, consisting in quartz-rich illitic clays, for which pit firing conditions generally under 850–900 °C were adopted. The purification of the starting base clays, the tempering of the clayey pastes with silica-rich grains and/or the polishing of surfaces were accomplished for fine wares. Th...
Applied Clay Science, 2006
The effect on ceramic products of firing conditions in the presence of abundant organic matter is assessed here experimentally by reproducing two ancient firing techniques: pit firing, characterised by a high heating rate and short residence time in a reducing atmosphere; kiln firing, with a low heating rate and long residence time in an oxidising atmosphere. As expected, pit firing conditions produced uniformly reduced ceramics, and gehlenite, diopside and spinel occurred at suitable temperatures (above 900°C
2004
This study describes the results of petrographical, mineralogical and chemical analyses carried out on coarse tempered cooking pottery, sampled in the archaeological sites of Herdonia, Posta Crusta (Ordona, FG) and San Giusto (Lucera, FG). From the latter site, two fragments of a pottery kiln, coeval with sherds (IV and V centuries AD), were also investigated. Two groups of clayey sediments of different nature (alluvial and marine) sampled in the neighbouring of the archaeological sites were also analysed. By means of the petrographical analyses, all cooking pottery and the two kiln fragments were grouped in the same coarse tempered group, characterised by the scarce presence of trachytic and glassy fragments, anhedral and zoned augitic pyroxenes and feldspars. PXRD analyses show an abundant presence of quartz and feldspars, followed by pyroxenes and variable quantities of calcite and hematite. Among clay minerals, illite plus muscovite are more abundant than smectite. XRF analyses data display SiO 2 , Al 2 O 3 , Fe 2 O 3 and K 2 O as main oxides, with variable quantities of CaO. In the case of the clayey samples, petrographical investigations on thin-section of psammitic fractions outlined the differences between Argille subappennine (Marine group-Pleistocene) and the alluvial deposits of Celone River (Alluvial group-Holocene). The occurrence of volcanic products, chert, garnet, quartzarenites and limestones in the archaeological materials and in the alluvial samples, let us suppose that cooking pottery was made with alluvial clayey silt. The apparent chemical discordance between pottery and alluvial samples bulk compositions can be due to textural and compositional variability of the alluvial deposits. All ceramics were fired in oxidising conditions, although in many cases a "dark core" was still present. Textural features, observed through petrographical microscope, and PXRD analyses suggested a firing temperature between 600 and 800°C.
Archaeological and Anthropological Sciences, 2016
The westernmost of the Greek-Sicilian towns, Selinunte, founded in western Sicily during the second half of the seventh century BCE, gives amazing evidences of a historic activity of ceramic production (seventh to third century BCE). The present study aims to identify the raw materials available in the vicinity of the archaeological site of Selinunte, which were possibly used by the ancient potters, and to characterise them by means of petrographic and chemical techniques. A sampling campaign of clays and sands for tempering was undertaken in the archaeological site and the adjacent area. Moreover, locally produced archaeological bricks and tiles were considered helpful for comparison regarding the definition of local ceramic macro-and micro-fabrics and were analysed as well. The comparison between textural, mineralogical and chemical data allowed us to highlight a good similarity between the clayey materials available in the area and the local ancient bricks and tiles. Their compositional resemblance suggests the hypothesis of a systematic use of the studied clays for ceramic productions from the Archaic to the Hellenistic period. The preliminary archaeometric results obtained so far could enhance the distinction between local manufactures and imports and may well lead to the identification of ceramic artefacts produced by the Archaic-Hellenistic workshops of Selinunte at various consumption sites.
Clays and Clay Minerals, 2010
In cases where the provenance of raw materials used in the manufacture of local archeological ceramics is of interest, a detailed study of thermal transformations of minerals may be useful. The purpose of this study was to measure mineralogical transformations of different types of clays obtained during experimental firing runs, carried out at different temperatures, with the main goal of establishing Algarve reference groups based on the composition of raw material and high-temperature mineralogy, which may be compared with ceramics in studies of provenance. Eleven samples of clay-rich raw materials from the Algarve Basin (southern Portugal) were fired to temperatures ranging from 300 to 1100ºC in increments of 100ºC under oxidizing conditions. These were chosen to have variable chemical and mineralogical compositions, representing the main compositional range of the clay deposits from the region. Mineralogical and geochemical characterizations of the original clays were carried out by X-ray diffraction (XRD) and X-ray fluorescence (XRF), respectively. Mineral transformations on the fired products were also studied by XRD.