Multi-methodological study of Early Modern Age archaeological glazed ceramics from Prague (original) (raw)
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Various medieval unglazed and glazed ceramic artifacts discovered during archaeological excavations at the monastery of Karaachteke near Varna (Bulgaria) are for the first time chemically and structurally characterized by ICP-OES, XRD, SEM-EDS and the Archimedes method aiming to understand the technology of medieval ceramics production. The unglazed artifacts water absorption ranges from 10 mass % to 15 mass %, which indicates that the ceramics are well sintered and most probably fired at a high temperature, ca 950 o C - 1050 o C. The artifacts contain a certain amount of coloring oxides (Fe 2 O 3 + TiO 2 ), which determine their slightly red color. The phase composition indicates the presence of crystalline phases of quartz and plagioclase, the amount of which differs in the different samples. SEM proves the presence in the sintered ceramic body of coarse quartz grains having a size of 0.05 mm to 0.3 mm. This leads to the conclusion that highly sandy clay or ceramic body containing...
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This paper presents recent research results on glazes and ceramic bodies in glazed ceramic lunette reliefs from the second half of the 16 th century. The main objective was to identify dyes in the coloured coatings and defects in the glazes using multiple instrumental techniques (X-ray fluorescence, portable X-ray fluorescence, X-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy and elemental SEM-EDS analysis, dilatometry and thermomechanical analysis). The research confirmed the presence of ionic dyes (Cu, Fe, Co, Sb, Mn ions) in medium lead glazes (approx. 28-63 wt. %), but also various types of yellow pigments in the Pb-Sb, Pb-Sn and the Pb-Sb-Sn systems were identified. Various defects were observed on the surface of glazes. In the case of the yellow glaze, the examination showed a lower lead content in the top layer. The defects-corrosion holes-were caused by selective corrosion in the environment of the waste pit. The green glazes in the lunette reliefs were damaged due to ageing of ceramics fired at low temperatures or due to irreversible moisture expansion of ceramic bodies.
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Degradation Processes of Medieval and Renaissance Glazed Ceramics
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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 occur...
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Journal Raman Spectroscopy, 2022
Sixteen glazes on medieval (14th–16th century AD) pottery fragments from Vega pottery workshop (Burgos, Spain) were characterized to investigate the production technology. To this end, Raman spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) were used. The studied glaze samples correspond to fragments of high-quality glazed ware used by the wealthiest society in the city of Burgos. The most representative types of glazes, corresponding to honey-marble, honey-yellow, bright light green, and dark green types, were analysed. Raman spectroscopy shows lead was used as a fluxing agent in glaze production. SEMEDX analysis confirms the use of lead oxide and evidences that most of the samples underwent at least two firing processes. No Raman signals of crystalline phases were detected on either glaze surfaces or glaze thin-sections. The exception is the single firing of dark green glazes, which show pseudobrookite and rutile at the clay body/glaze interface measured in thin section. No colouring crystalline phases were identified by Raman spectroscopy either. However, SEM-EDX shows iron was the most-used colouring agent whereas copper was used for bright light green glazes. The polymerization index (Ip) values were used to estimate the firing temperatures. The polymerization index values are typically low for lead glazes and indicate firing temperatures below 700C.