Ruiz-Ardanaz, I. (Iván)

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    Revealing the manufacturing technology to produce the unique carreaux de pavement found in the Iberian Peninsula
    (2023) Duran-Benito, A. (Adrian); Lasheras, E. (Esther); Gil-Fernández, M. (Marta); Ruiz-Ardanaz, I. (Iván)
    Carreaux de pavement is a type of mediaeval tile common in northwestern Europe, whose method of producing has been unknown until now. In this article, the kiln firing conditions of the unique carreaux de pavement found in the Iberian Peninsula were determined by comparing the physicochemical and mineralogical properties of the archaeological tiles with those of some reproductions of the tile's body manufactured in the laboratory (replica) made by varying the firing temperature and time, as well as the sample size and thickness. The resistance to acid digestion exhibited by the fired samples was especially revealed. According to the results and the modelling performance with the collected data, it was established that the maximum firing temperature was between 900 and 975 °C, and the time was longer than 24 h. These results show the technology used by mediaeval French potters and are a basis for future studies.
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    Mineralogical characterization of carreaux de pavement from Northern Spain (Tiebas, Navarre)
    (2021) Duran-Benito, A. (Adrian); Lasheras, E. (Esther); Ruiz-Ardanaz, I. (Iván)
    Several medieval tiles from Tiebas Castle in Navarre, classified as carreaux de pavement, were mineralogically analyzed. The aim was to add information to the very scarce analytical data available for carreaux de pavement in order to provide a quality primary work, mainly descriptive, in this topic. The characterization techniques applied were: optical microscopy (OM), colorimetry, Fourier transform infrared (FT-IR) spectroscopy, differential thermal analysis and thermogravimetry (DTA-TG), X-ray fluorescence (XRF) spectroscopy, petrographic microscopy (PM), X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS). The tiles comprised three layers: a top glaze with mainly silicon and lead-based compounds; a thin layer of silicoaluminate (very possibly kaolinite) called engobe under it; and the pastes, composed of quartz, hematite, potassium feldspars and calcite. Honey glazes were richer in iron, being copper-based compounds responsible for dark green glazes. The orangish-reddish color of the pastes was provided by hematite. Although the tiles were found in three different locations within the castle, no significant differences were detected among them. The carreaux de pavement from Tiebas had similarities with that from the Bordeaux region. According to the composition data and thickness of tiles from other French carreaux de pavement, the Tiebas artifacts were dated to the 13th century.
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    Tiebas Castle’ tuiles vernissées: Characterization, raw clay provenance, and manufacturing technology
    (Elsevier B.V., 2024) Durán, A. (Adrián); Lasheras, E. (Esther); Ruiz-Ardanaz, I. (Iván); Úriz-Asiain, O. (Orreaga)
    Tiebas Castle was built between 1254 and 1264 as a royal residence of the kings of Navarre. The Castle was decorated with architectural luxuries imported from the French court. Some decorative elements of this French style are the polychrome roof tiles, called tuiles verniss ́ees; and the glazed floor tiles, called carreaux de pavement. Both are the unique that have been found in the Iberian Peninsula. Elemental and mineralogical analysis allowed us to distinguish two different types of pastes that were used for both tuiles verniss ́ees and carreaux de pavement: yellowish and reddish. The reddish paste was composed mainly of quartz, and to a lesser extent of haematite and illite. The yellow pastes were very rich in calcite and other calcium-bearing minerals (gehlenite, anorthite, diopside or wollastonite) and poorer in quartz and haematite. The different colour tones of the yellow paste samples allowed them to be classified into five subgroups (YP-1, YP-2, YP-3, YP-4, and YP-5). This classification turned out to coincide with a somewhat different mineral composition. The study of the mineral phases newly formed (gehlenite, anorthite, diopside and wollastonite) or destroyed (illite) during firing allowed us to estimate the maximum firing temperature of each of the subgroups. The temperature ranges for each subgroup were as follows: 750–800 ◦C (YP-5), 850–900 ◦C (YP-4), 900–925 ◦C (YP-3), 925–950 ◦C (YP-2), and 950–1000 ◦C (YP- 1). The study of its possible raw materials allowed us to identify that the yellow pastes from tuiles vernissées and carreaux de pavement were prepared from a mixture of two clays. One of them was the decalcification clay (A15 clay) with which they also made the reddish pastes. The other component of the mixture was the marl from Castle hill. The proportion that the artisans used of both raw materials was 1:2 (twice as much marl as decalcification clay).