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|Analytical study of Roman and Arabic wall paintings in the Patio De Banderas of Reales Alcazares’ Palace using non-destructive XRD/XRF and complementary techniques|
A portable XRD/XRF system and complementary laboratory techniques were employed to improve the knowledge of the procedures used to create Roman and Arabicwallpaintings. Integrated physico-chemical investigations were conducted on fragments of artworks collected from the archaeological excavation of the PatiodeBanderas in the RealesAlcazares’ Palace of Seville (Spain), and a comparative study on the pigments from both historical periods was performed. As a result, pigments such as vermilion, red ochre, yellow ochre, green earth, Egyptian blue, carbon and phosphor-based black pigments were detected in Roman samples; however, in the Arabic fragments, only haematite was observed. In addition, the size and shape of the particles of the wallpaintings were studied with an XRD 2-dimensional detector and SEM-EDX.
Keywords XRD/XRF portable system; Roman and Arabicwallpaintings; 1st century BC; 11th century AD; RealesAlcazares’ Palace; SEM-EDX
RealesAlcazares Palace was built by Abd Al-Rahman III, the first caliph of Andalusia, in 913 after a revolt against the government of Cordoba. The palace was built over an ancient Roman settlement outside the city walls of Seville, where the Basilica of St Vicente was located and St Isidoro was buried (Durán-Benito et al., 2007). From 2008 to 2010, an archaeological investigation in the PatiodeBanderas of the RealesAlcazares’ Palace (Fig. 1a) was conducted (Tabales, 2010), and remains of Roman decorated buildings with wallpaintings from the 1st century BC were found. Hispalis (Roman ancient name of Seville) was considered the most important commercial and industrial Hispano-Roman city in the Betic region (Blanco Freijeiro, 1984). The nearby Roman city of Italica, a residential city, is well preserved and provides an impression of the appearance of Hispalis in the later Roman period. During the stratigraphic archaeological investigations carried out in the site, the archaeologists also salvaged Arabic architectural elements and painted decorations from the 11th to the early 13th century. Remains of construction from the 2nd century BC, and the 1st, 3rd, 4th and 5th centuries AD were also discovered; however, wallpaintings were not found (Fig. 1a).
The technique and pigments used by ancient Romans to render and paint walls are of great interest to many researchers. In recent years, numerous studies have been carried out on Romanwallpaintings in Italy, France, England and Spain ( [Delamare, 1983], [Bearat, 1997], [Edreira et al., 2001], [Mazzocchin et al., 2004], [Mazzocchin et al., 2008], [Edwards et al., 2009], [Weber et al., 2009], [Aliatis et al., 2010], [Duran et al., 2010a] and [Duran et al., 2010b]). Contemporary written sources ( [Pliny the Elder, 1985] and [Vitruvius, 2005]) provide valuable information on the preparation and application of lime, mortars and pigments, and the fresco paint technique. Coloured pigments were applied when the walls were still damp. In Hispanic monuments with Islamic iconography, evidence of painted fresco decorations has been found (Rallo Gruss, 2003); however, this type of artwork has not been widely studied from a scientific point of view (Cardell et al., 2009). The palette of ornamentation of Islamic buildings is dichromatic (usually red and white), and its design is geometric and repetitive. As a result, this type of ornamentation is a rapid method of decoration (Rallo Gruss, 2003).
In the field of cultural heritage, the objects under study are often precious and unique works of art. Thus, to maintain the artistic value of the work, destructive sampling is minimised ( [Herrera et al., 2009] and [Deneckere et al., 2010]), and non-invasive techniques such as X-rays fluorescence (XRF), μ-Raman or μ-FTIR are often performed ( [De Viguerie et al., 2009], [Kato et al., 2009], [Miliani et al., 2009], [Pinna et al., 2009], [Ricciardi et al., 2009], [Deneckere et al., 2010] and [Nazaroff et al., 2010]). Recently, novel equipment for the in situ analysis of artwork has been developed. In particular, devices that combine two different techniques in the same system have been produced. However, only a few portable X-ray diffraction (XRD) systems for phase identification are currently available ( [Uda et al., 2005], [Chiari, 2008] and [Abe et al., 2009]). XRD requires careful alignment and reproducible incident angles, reflection angles and source-sample-detector distances, etc. Moreover, XRD analyses usually require long acquisition times due to the low intensity of the diffracted beam. Recently, a portable XRD/XRF laboratory equipment has been designed and constructed in the C2RMF (Centre de Recherche et de Restauration des Musées de France) laboratory ( [Gianoncelli et al., 2008], [De Viguerie et al., 2009], [Duran et al., 2010a], [Eveno et al., 2010] and [Pagès-Camagna et al., 2010]). Although the aforementioned device can analyse artefacts in situ, if this cannot be achieved, the object must be transported to the laboratory. Amorphous phases or phases present in very low concentrations are difficult to characterise with the aforementioned techniques. In this case, the combination of energy-dispersive X-rays and scanning electron microscopy provides useful information; however, to apply these techniques, the artefact must be sampled.
The identification and study of pigments used in the Roman and Arabicwallpaintings discovered in the excavations of the RealesAlcazares’ Palace can provide art historians precise information on the techniques used in the creation of the work itself and can provide conservators and restorers with guidelines on the materials necessary for conservation. Integrated physico-chemical investigations were carried out on artwork fragments of the PatiodeBanderas to obtain useful information on the techniques and materials used by the Romans and Arabs. In addition, a comparative study on the pigments from both historical periods was performed. The present paper is one of the first articles devoted to the study of both Roman and Arabicwallpaintings discovered in Seville, and the results of the current investigation were compared to those of similar artworks from the same period found in other locations. To analyse the paintings, a novel XRD/XRF portable system and complementary techniques such as micro-Raman, SEM-EDX and optical microscopy were employed at the Materials Science Institute of Seville and the Centre de Recherche et de Restauration des Musées de France at the Louvre Museum.