Search Results (6)

Recent archaeological sites dating to the late 19th and early 20th centuries have rarely been studied to date. Among the 500 “glassy” beads excavated from Dohouan (Côte d’Ivoire), elemental analyses reveal that fewer than half contain abnormally high alumina contents, associated with a soda–potash–lime flux (three compositional groups). The remaining beads are typical lead-based glass. The Raman spectra of the alumina-rich beads are quite complex due to their glass–ceramic nature, combining features similar to the vitreous phase of porcelain glaze with the presence of various crystalline phases (quartz, wollastonite, calcium phosphate, calcite). Organic residues are also observed. Colors are primarily produced by transition metal ions, although some specific pigments have also been identified. These characteristics suggest that the alumina-rich beads were manufactured by pressing followed by sintering, as described in patents by Richard Prosser (1840, UK) and Jean Félix Bapterosse (1844, France). A comparison is made with beads from scrap piles at the site of the former Bapterosse factory in Briare, France. This process represents one of the earliest examples of replacing traditional glassmaking with a ceramic process to enhance productivity and reduce costs. Full article

The excavation of the Lieshan Kiln site represents a significant advance in the field of ceramic archaeology. Previous scholars fixated on the white porcelain unearthed from this kiln, yet this study zeroed in on celadon from the Northern Song and Jin Dynasties. Celadon samples were analyzed using colorimetry, energy-dispersive X-ray fluorescence spectroscopy (ED-XRF), scanning electron microscopy (SEM), polarizing microscopy, X-ray photoelectron spectroscopy (XPS), and thermal expansion analysis. Results revealed that material and technological advancements in the production of the Lieshan Kiln and reveal the special phase-separated structure in the glaze of the transparent celadon, with a weakly reduced firing atmosphere. Celadon bodies from both periods were crafted from local sedimentary clays in a single-ingredient formula, with the Jin Dynasty refining the preparation, leading to enhanced density and higher firing temperatures compared to the Northern Song Dynasty. The celadon glaze, a high-calcium type made up of glaze ash and specific clays, differed from the body materials. The high SiO₂/Al₂O₃ molar ratio, along with Fe₂O₃ and trace P₂O₅, promoted phase separation. Glaze coloration was modulated by the interaction of Fe³⁺ and Fe²⁺ ions, and chemical coloration by Fe ions prevailed when phase-separated particles were minute enough to avoid Rayleigh or Mie scattering. In conclusion, the study deepens the understanding of ancient ceramic production by exploring the phase separation structure and coloring mechanism of the celadon. Full article

Ceramic sherds from approximately 20 samples of lead-glazed tableware, recovered from diverse archaeological sites, including three repurposed storage pits transformed into dumpsters within the medieval city of Santarém (13th–14th century), underwent a meticulous examination. This investigation utilised techniques such as micro-Raman, ground-state diffuse reflectance absorption, and X-ray fluorescence spectroscopies, in addition to X-ray diffraction and stereomicroscopy. A parallel study was conducted on contemporaneous European ceramics (glazed sherds) sourced from archaeological sites dating back to the 13th–15th centuries in Saintonge (France), Ardenne, Zomergem, and Bruges (Belgium), as well as Surrey–Hampshire, Kingston, and Cheam (England). The first premise for comparing the Santarem samples with European production locations was their frequent commercial relations with Portugal and the frequency of these productions being found in Portugal. The colour of the ceramic bodies is predominantly white or whitish, with a few exhibiting a vivid red hue. Analyses of the fabric, mineralogical, and elemental composition of the sherds suggest that the majority of Santarém’s glazed ceramics were locally or regionally produced, potentially derived from a Pliocene kaolin-rich sand formation. However, this conclusion is not supported by the absence of discovered lead glaze kilns or workshops in Santarém for the late Middle Ages. Full article

Fábrica de Loiça de Sacavém (ca. 1858–1994) was among the first to produce white earthenware in Portugal, becoming one of the country’s leading ceramic manufacturers during the late 19th to early 20th centuries. Research on white earthenware has accompanied the growing interest in post-industrial archaeology but is still poorly explored compared to more ancient ceramic productions. This study focused on the ceramic body, glazes, and colourants of tableware produced by Fábrica de Loiça de Sacavém during the first 50 years of its activity (1859–1910). A multi-analytical approach was selected to investigate the chemical and mineralogical composition of the ceramic body, glaze, and pigments using optical microscopy, variable-pressure scanning electron microscope energy-dispersive X-ray spectroscopy (VP-SEM-EDS), μ-Raman spectroscopy, μ-X-ray Diffraction (μ-XRD), and reflectance spectroscopy (hyperspectral image analysis). The studied tableware was produced with a Ca-poor siliceous–aluminous white earthenware ceramic body covered with transparent alkali lead or lead borosilicate glaze, and most colourants were complex Cr-based pigments. These results are in agreement with the little documental evidence from this period found in the manufacturer’s archives. Full article

Dalian Island is located in the sea area near Pingtan County, Fujian, Southeast China. The sea area used to be the junction of the eastern and western ship routes on the Maritime Silk Road, and is also an important region for underwater archaeology in China. This study focused on a sauce-glazed ware of the Song Dynasty, with serious degradation, which was salvaged out of the water at the Dalian Island Wharf. Optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and micro-Raman spectroscopy were used to comprehensively analyze the composition, phase attributes and microstructure of the ware and the surface-attached coagula. The findings revealed that the sea wave-borne debris scoured the surface of the ware, causing mechanical damage to varying degrees and a significant decrease in its degradation resistance. This was the primary factor accounting for the poor preservation state of the salvaged ceramic ware, and the precondition for the subsequent attachment of marine organisms and the deposition of inorganic pollutants. The calcareous skeletons formed on the surface induced by the bio-mineralization of coralline algae (a type of marine plant) could resist the mechanical action caused by the motion of sea waves, thereby slowing down the ware’s degradation process. In other words, the calcareous skeletons played a ‘bio-protective’ role to a certain degree. In addition, inorganic pollutants represented by iron rusts also participated in the corrosion of the glaze. Some pollutants were directly deposited on the pits and cracks on the surface of the ware, which brought stress to the glaze and glaze/body interface, causing the glaze to further crack and spall. Moreover, iron rusts reacted with the glaze, leading to chemical alteration, accompanied by the formation of iron silicate as the alteration product. Anorthite crystals in the interlayer did not participate in the reaction but remained at the original position. The alteration product gradually replaced the original glass phase of the glaze and entered into the body via pores and cracks. In conclusion, the complex degradation morphology of the salvaged sauce-glazed ware could be attributed to the combined action of mechanical damage, marine bio-fouling, and chemical alteration. Full article

Corrosion effects in deposit environments (soil, waste pit, etc.), together with the glaze adherence and fit, could cause severe deterioration accompanied by different types of defects or growth of corrosion products. The aim of this work was to identify the source of surface degradation of the lead-glazed ceramics sets from the Prague area from the Romanesque to the Renaissance period. A combination of X-ray fluorescence (XRF), X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and simultaneous thermal analysis (STA) techniques along with stress state calculations was used to study the defects. Based on the interpretation of the possible sources of the observed defects, four types of degradation effects were schematically expressed for the archaeological samples. It was shown that the glazes were already appropriately chosen during the production of the Romanesque tiles and that their degradation occurred only due to long-term exposure to unsuitable environmental conditions. Full article