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.
Lead isotope analyses have been undertaken on a group of Islamic lead-glazed pottery artefacts from Fustat, Egypt, spanning the period from the eighth to the 14th century ad , that had previously been the subject of a comprehensive typological, chronological, petrographic and technological study. Comparison of the lead isotope ratios for the glazes with those for lead ores from Egypt, Iran, Tunisia, Anatolia, Greece, Sardinia and Spain provided information on the possible sources of the lead used in the production of the glazes. The results show that the lead used in glaze production by the Islamic potters at Fustat was most probably obtained from distant ore sources in Iran or Tunisia, Sardinia, Spain and the Taurus Mountains. Different ore sources were favoured in different periods and, to a limited extent, for different types of pottery, but at no time did the Fustat potters use the potentially more accessible Egyptian ore sources.
Previous research has established that Iznik pottery differs from other Islamic stonepaste pottery in that its stonepaste bodies contain lead oxide as well as soda and lime, and that a significant proportion of the tin oxide in its glaze is present in solution rather than as tin oxide particles. In order to better understand these distinguishing features, the chemical compositions and microstructures of Iznik pottery and tile samples, together with those of lumps of glass found in association, were investigated using both scanning electron and optical microscopy. These data have been supplemented by the study of replicate lead-alkali glazes produced in the laboratory with a range of different compositions. The results demonstrate that separate soda-lime and high-lead glasses were used in the production of Iznik stonepaste bodies, and that the total glass contents of the bodies were significantly higher than those quoted by Ab ¨ 'l-Q å sim, who was writing in about AD 1300. The very high purity of the lead-soda Iznik glazes indicated that the alkali flux used was either a purified plant ash or an as yet unidentified mineral source of soda. Replication experiments established that the high solubility of tin oxide in the glaze was due to the high purity of the glaze constituents. Furthermore, it is suggested that tin oxide was added to the glaze in order to give it a very slight opacity and thus obscure any blemishes in the underlying body.
Archaeological excavations between 1984 and 2001 at the early Christian cemetery church in Sion, Sous‐le‐Scex (Rhône Valley, Switzerland), brought to light more than 400 pieces of coloured window glass dating from the fifth or sixth centuries ad. The aims of this paper are threefold: first, to characterize the shape, colour and chemical composition of the glass; secondly, to understand whether the production of the coloured window panes followed traditional Roman glazing techniques or was of a more innovative nature; and, thirdly, to provide some indications as to the overall design of these early ornamental glass windows. Forty samples of coloured glass have been analysed by wavelength‐dispersive X‐ray fluorescence. The results of the chemical and the technological studies showed that most of the glass was produced using recycled glass, particularly as a colouring agent. Some of the glass was made of essentially unmodified glass of the Levantine I type. The results taken together seem to confirm that raw glass from this region was widely traded and used between the fourth and seventh centuries ad. The artisans at Sion were apparently still making use of the highly developed techniques of Roman glass production. The colour spectrum, manufacture and design of the windows, however, suggest that they represent early examples of ornamental coloured glass windows.
The isotope fractionation of all ozone isotopologs of mass 48-54 u has been measured with high accuracy. The data represent a standard for the magnitude of the ozone isotope effect since pressure, temperature, and composition of the gas in which ozone is produced are well known. While 17 O 17 O 17 O and 18 O 18 O 18 O are depleted by Ϫ1.5% and Ϫ3.9%, respectively, all others are enriched with 16 O 17 O 18 O showing the highest value of 19.8%. Enrichments or depletions are independent of the isotope composition of the oxygen gas.
Abstract:The history and iconography of Swiss stained glass dating between the 16th and 18th centuries are well studied. However, the chemical and morphological characteristics of the glass and glass paints, particularly the nature of the raw materials, the provenance of the glass, and the technology used to produce it are less well understood. In this paper, we studied two sets of samples from stained-glass panels attributed to Switzerland, which date from the 16th to 17th centuries: the first set comes from Pena National Palace collection, the second from Vitrocentre Romont. The aims were to identify the materials used in the production of the glass, to find out more about their production origin and to characterize the glass paints. Both glass and the glass paints were analysed by particle-induced X-ray emission; the paints were additionally analysed by scanning electron microscopy-electron-dispersive X-ray spectroscopy (SEM-EDS). The results show that the glass from both sets was probably produced in the same region and that wood ash was used as a fluxing agent. Different recipes have been used to make the blue enamels. However, the cobalt ore used as a coloring agent in all of the blue enamels came from the mining district in Schneeberg, Germany.
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