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. Durana, , J.L. Perez-Rodriguezb, M.C. Jimenez de Harob, M.L. Franquelob, M.D.
Robadorc

a


Centre de Recherche et de Restauration des Musées de France, Palais du Louvre, 14
quai François Mitterrand, 75001 Paris, France
b
Materials Science Institute of Seville (CSIC-University of Seville), Avda Américo
Vespucio 49, 41092 Seville, Spain
c
Technical Architecture Faculty (University of Seville), Avda Reina Mercedes s/n, 41012
Seville, Spain
Abstract
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
1. Introduction
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.,
1
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.
2. Experimental
Wallpaintings were discovered in a large Roman building, located in the Republican city of
Hispalis and tentatively dated to the 1st century BC. The building was a great structure and
was built according to the raised skeleton technique, which is characterised by the parallel
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arrangement of at least three compartmentalised rooms and a corridor with different levels of
pavement. Some of the materials were located at a very low level, which could be indicative of
a partial basement (Fig. 1a and b) (Tabales, 2010). In the 11th century, after four centuries of
Arabic occupation, the Visigothic (post-Roman civilisation) religious complex (Basilica of St
Vicente) was destroyed, and a number of buildings and streets belonging to Islamic suburbs
were built in the vicinity of the actual catholic Cathedral (approximately 100 m away) (Fig. 1a
and c) (Tabales, 2010). The other wallpaintings were found in these Arabic buildings.
The sampling procedure was guided by the location of the paintings within the excavation site
and the colours observed on the surface of the paintings. Eight samples from the Roman epoch
(1st century BC) and two from the Arabic period (11th century AD) were investigated (Table 1).
Because the artefacts were buried, the samples were in excellent condition and were not
subjected to any previous restoration processes. The size of the samples was variable
(dimensions of 1.0 × 0.8 cm to 8.5 × 6.0 cm), and the thickness of the fragments ranged from
1.0 to 1.5 cm, including the mortar and pictorial layers. Visual examination of the samples
indicated that different colours were present in the fragments. Red, yellow, white, green and
black colourations were observed in Romanpaintings, and red and white colourations in
Arabicpaintings (Table 1). The samples were studied as received (fragments) and as crosssections.
The portable XRD-XRF apparatus used in the present study is based on a 4-mm beam from a
copper anode X-ray source (700 μA and 40 kV), which impinges on the coloured surface of the
mural painting fragments at an angle of 10°. Thus, the analysed area was approximately
4 mm × 3 mm (Pagès-Camagna et al., 2010). A 2-dimensional imaging plate detector was used
to collect the XRD signal. The diffraction pattern of polycrystalline samples typically consists of
concentric Debye-Scherrer rings, which result from the superposition of illuminated crystal
oriented in the Bragg condition. The Debye-Scherrer rings contain important information on
the micro-structure of the sample, including the grain size, preferential orientation,
crystallinity, mosaicity, stress, etc. Spotty rings are produced by coarse-grained mineral phases,
and continuous rings are produced by fine-grained mineral phases ( [Rodriguez-Navarro,
2006], [Rodriguez-Navarro et al., 2006] and [Eveno et al., 2010]). Because of the intensity of
reflections is more sensitive than the number of reflection spots, the intensity profile of the
Debye-Scherrer rings has been used to qualitatively estimate the size of mineral grains. In
general, the intensity of the reflections increases on average as with an increase in crystal size,
and the number of spots decreases ( [Rodriguez-Navarro, 2006] and [Rodriguez-Navarro et al.,
2006]). Other factors that affect the intensity profile of the rings include the structure factor,
the reflecting power of the compounds, and the proportion of the different crystalline phases
in the samples studied. Free software FIT2D (FIT2D software) was used to transform the 2dimensional images into standard 1-dimensional XRD diagrams. XRF elemental analysis was
performed with a Silicon Drift Detector, whose resolution is of 150 eV FWHM at 5.9 keV and
T = −10 °C. The distance from the sample to the detector was set to 2.5 cm, and light elements
were not detected due to the strong absorption of air between the specimen and the detector
( [De Viguerie et al., 2009], [Duran et al., 2009], [Duran et al., 2010a] and [Pagès-Camagna
et al., 2010]).
A dispersive integrated Horiba Jobin-Yvon LabRam HR800 system was used to perform Raman
experiments on the surface of the black fragment. Two external visible diode lasers (solid-state
source) are available as excitation lines, including a 532-nm (green) and 785-nm (red) laser;
however, the 785-nm laser was mainly used to minimise fluorescence. The apparatus was
equipped with a charge-coupled device (CCD) detector and a grating of 600 grooves/nm. An
optical microscope was coupled confocally to the Raman spectrometer, and the measured
3
area was approximately 25 μm2. The power of the laser ranged from 15 to 50 mW to avoid
damaging the painting.
Cross-sections of the samples were obtained from the wallpainting fragments. They were
prepared starting from a mould of methyl polymethacrylate where the samples were placed
horizontally and refilled up with epoxy resin of methylmethacrylate (Palpress several CE 0044).
The resulting material was cut with a fretsaw equipped with a Bahco 302-83S-blade, which was
polished with an automatic polishing machine and various grades of sandpaper (grain P-240, P500, P-800 and P-1200) and was finished with a cloth. The cutting and polishing process was
critical for almost all of the samples preparations ( [Duran et al., 2008] and [Duran et al.,
2010b]). The cross-sections were examined with optical and scanning electron microscopes.
Optical microscopy was performed with a Nikon OPTIPHOT microscope (×25, ×50, ×100
and ×200), and scanning electron microscopy was performed with a HITACHI S-4800
microscope equipped with an energy-dispersive X-ray analyser (EDX) Bruker XFlash 4010 at an
accelerating voltage of 20 kV. Samples were coated with gold film prior to the SEM-EDX
analyses, and powder samples collected on the surface of the fragments were also studied in
some cases. To confirm some of the results, conventional X-ray powder diffraction was
performed with a Panalytical diffractometer, model X’Pert Pro MPD (Cu Kα radiation, 40 kV,
40 mA).
3. Results and discussion
3.1. XRD/XRF portable system
3.1.1. Red and yellow pigments
The XRD/XRF portable system revealed that two types of red pigments, vermilion and red
ochre, were present in the Romanwallpaintings. In the Arabicpaintings, only haematite was
detected (Table 1).
Vermilion (HgS) was easily identified via XRF; mercury and sulphur were detected in Roman
samples 5 and 11 (Fig. 2a). Fig. 3a shows the XRD patterns recorded by the 2-dimensional
detector and, after conversion, the conventional 1-dimensional diagram of sample 11 (Fig. 3b)
(The XRD diagram of sample 5 is very similar to that of sample 11). In Fig. 3a, each ring
corresponds to diffracting crystallographic planes (incident beam at an angle θ from the
planes) for a set of grains under a suitable orientation. The continuous rings that appear in
Fig. 3a were formed by the superposition of reflections of cinnabar and calcite grains, and the
intensity profile along the diffraction rings is expressed by the changes of colouration
observed. As shown in Fig. 3a, the cinnabar rings have different colour (yellow-green) than
those of calcite (pink), showing the former higher intensity values. Thus, the results indicated
that the particle size of cinnabar was larger than that of calcite. Intensity values are also
function of other factors such as the proportion of phases in the sample; in this case, there
should be (in mass) more cinnabar than calcite in the paint. Also we should take into account
the high reflecting power and structure factor of the cinnabar, which provide values to be
added to those derived from particle sizes and phase proportion. Mercury sulphide has been
used by artists since antiquity (Gettens and Stout, 1966). Natural (from mining sources, also
called cinnabar) and synthetic vermilion have been used as pigments; however, XRD and XRF
cannot distinguish between natural and synthetic variants (Van der Snickt et al., 2008).
Vermilion was known to the Romans as minium and was one of their most valuable pigments
(Pliny the Elder, 1985). As Theophrastus asserted 200 years before Vitruvius, the cinnabar
mines used by the Romans were of Spanish origin and were located in Sisapo (Almaden at the
present time) ( [Mazzocchin et al., 2008] and [Duran et al., 2010b]).
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The identification of haematite (α-Fe2O3), red ochre (haematite, silica, clays) and yellow ochre
(goethite α-FeOOH, silica, clays) could not be achieved by XRF alone because iron is present in
everywhere. In the present study, relative high concentrations of iron were detected by XRF in
samples 1 (Arabic), 3 and 7 (both Romans) (Fig. 2b). The red pigment haematite was detected
by XRD in samples 1 and 3 (Fig. 4). Alternatively, goethite, a yellow pigment, was detected in
samples 3 and 7 (Fig. 4 and Fig. 5). Calcite (CaCO3) and quartz (SiO2) were also observed in all of
the samples. Moreover, the characteristic fingerprint peak of clays at 2θ ≈ 20° (Brindley and
Brown, 1980) was observed in Roman samples 3 and 7; however, peaks attributed to clays
were not observed in Arabic sample 1. These results suggest that two different types of
pigments were used, depending on the period in which the paintings were made. In particular,
red ochre and yellow ochre were observed in Romanpaintings, and haematite was detected in
Arabicpaintings. The ratio of calcite (2θ = 29.5°)/quartz (2θ = 27.6°) XRD peaks was higher in
the superficial layers of the Arabic fragments than in the Roman samples (Figs. 4a, c and 5a).
Continuous smooth diffraction rings corresponding to small haematite and goethite particles
sizes were collected in the imaging plates (Figs. 4b, d and 5b). Typically, natural iron
oxyhydroxides and iron oxides were mixed with clay minerals (kaolinites, illites, smectites, etc)
and used as pigments (Hradil et al., 2003). Red ochre was one of the first pigments used in
ancient paintings ( [Menu, 2009] and [Pallecchi et al., 2009]), and Roman artists ( [Mazzocchin
et al., 2004], [Weber et al., 2009] and [Aliatis et al., 2010]) used both natural and artificial
ochres, which were obtained by the calcination of yellow ochres (Pliny the Elder, 1985).
Hispano-arabicpainting is often dichromatic, and the design is made in red on the white
mortar. The symbolic aspects of red colours in the Middle Ages are well-documented;
however, in the studied artwork, we believe that haematite was used as a pigment due to its
ease of preparation, location and cost. Moreover, the colour of haematite provides a stark
contrast against a white background and promotes a strong visual effect (Rallo Gruss, 2003).
3.1.2. Green pigments
Celadonite (K(Mg, Fe, Al)2(Si, Al)4O10(OH)2) was detected by XRD and attributed to the green
coloured pigment in Roman sample 12 (Fig. 6). The quartz grains and celadonite particles in
sample 12 were large and relatively intense rings were observed. In addition, the diffraction
rings were dotted, indicating a non-homogeneous distribution or isolated particles (Fig. 6b) (
[Rodriguez-Navarro, 2006] and [Rodriguez-Navarro et al., 2006]). One of the mean XRD peaks
of mica compounds is observed at 2θ = 9°. However, in experiments performed in reflection
mode, low angles (2θ < 16–17°) are lost due to the experimental restrictions of the portable
XRD/XRF system. Thus, to confirm the presence of celadonite, conventional X-ray powder
diffraction experiments were performed on sample 12, and diffraction peaks corresponding to
the aforementioned phase (2θ ≈ 8.8°, 24.5°, 33.3° and 34.8°) were observed; these results are
similar to those obtained by using the XRD portable system. “Green earths” used as pigments
since antiquity are still in use in the creation of artwork: they are mainly constituted of micas
celadonite and/or glauconite (phyllosilicates), both minerals are formed under different
geological conditions (Ospitali et al., 2008). In these paintings, only celadonite has been
detected. Both minerals are iron-rich dioctahedral micas that are deficient in potassium and
have small tetrahedral substitution (Brindley and Brown, 1980). Celadonites and also
glauconites have been studied by numerous methods (Drits et al., 1997) and are typically
present as dull grey–green to bluish green masses. In the present study, iron and potassium
were detected by XRF, along with copper (Fig. 2c), which was not justified with the detection
of any compound by XRD. A copper source is not typically used for micro-XRF portable systems
5
because copper fluorescence lines are always present in the spectra; thus, the detection of
copper is often difficult ( [Gianoncelli et al., 2008] and [Duran et al., 2009]). However, in the
XRF spectrum of sample 12, a Cu Kβ peak was clearly visible (Fig. 2c magnification), indicating
that the Cu was present in the sample (Duran et al., 2011).
3.1.3. White and black pigments
The detection of calcite by XRD as the main component was certain in all the surfaces of the
fragments studied (Table 1). In the fresco wallpainting technique, pigments are mixed with
water to make a suspension (paint) and applied to the wet plaster, which is made of hydrated
lime and aggregates. Dissolved lime diffuses from the plaster into the paint layer and then
carbonates, forming calcite and acting as a binder for the pigment. As shown in Fig. 2,
significant amounts of calcium were also detected in the XRF spectra. Furthermore, in samples
1 (Arabic), and 3, 5, 7, 11 and 12 (Roman), calcite was detected by XRD (Fig. 3, Fig. 4,
Fig. 5 and Fig. 6) together with coloured compounds (cinnabar, haematite, goethite and
celadonite) and quartz. Alternatively, in white-coloured fragments, only calcite and quartz
were detected, as shown in the XRD spectra of Arabic sample 2 and Roman fragments 4 and
13.
In sample 14 (the black Roman fragment), only calcite and quartz were detected by XRD. No
characteristic chemical elements responsible for the black colour were observed by XRF. Light
elements such as carbon or phosphorus, which are normally responsible for the black colour,
are not usually detected by XRD/XRF due to the strong absorption of X-rays due to the air
(2.5 cm) between the sample and the XRF detector. For instance, at the energy of Si–K
(1.74 keV), X-ray transmission in 1 and 3 cm of air is approximately 40% and 5%, respectively (
[Gianoncelli et al., 2008] and [De Viguerie et al., 2009]). Thus, other techniques were used to
characterise black pigments.
3.2. Optical and scanning electron microscopy and EDX analyses
To conduct EDX and SEM analyses, samples of the wallpainting fragments were collected and
cross-sections of the material were done in some cases. The information provided by these
techniques allowed us to study the paintings in more detail. In particular, the distribution of
the layers was evaluated, and the minority components and the morphology of the particles
were analysed.
3.2.1. Red and yellow pigments
The EDX spectra of the red layer of the Arabic sample 1 indicated that the material consisted
primarily of Fe, Ca, Si and Al. However, in punctual analyses, the presence of almost only iron
(Fig. 7a) was detected, likely due to the presence of haematite, as previously observed by XRD.
The cross-section of the Roman sample 3 showed the presence of two differentiated colour
layers by optical microscopy (Fig. 8a): an external red and an internal yellow one, with similar
elemental composition: Si, Ca, Fe, Al, Mg and K (by EDX analyses).
The EDX analyses of the red and yellow layers of the cross-sections of Roman (samples 3 –red
and yellow– and 7 –yellow) and Arabic (sample 1 –red) fragments (Fig. 7b and c) were
compared. The ratios silicon/calcium and aluminium/calcium peak intensities are higher for
Roman samples than for the Arabic one. The ratio silicon/iron is lower for the Arabic sample,
showing that higher amounts of silicon and aluminium appeared in the Roman fragments and
6
of iron in the Arabic one. In addition, punctual analyses and elemental mappings of the Roman
samples seemed to indicate that the presence of iron was associated with aluminium and
potassium (forming clays), as shown in Fig. 9a. Iron was also observed in the Arabic sample
(Fig. 9b); however, iron in the Arabic fragment was associated with calcium and was not
correlated with aluminium and potassium. In fact, silicon appeared in the zones in which iron
was absent. These results suggest that Arabs employed haematite as a pigment and Romans
used red ochre and yellow ochre for colouration. Although the XRD results support this
assertion (Fig. 4 and Fig. 5), it is unclear whether the clay content of the ochre pigments was
naturally high, or if clay and sand were combined with the pigment and hydrated lime in the
mortar-forming process, as suggested by other authors (Weber et al., 2009).
The morphology of the particles was studied by directly visualising the fragments via SEM or by
collecting powders from the surface of the fragments. As shown in Fig. 10a, calcite particles
(approximately 1–3 μm) and granular haematite particles with a size less than 0.5 μm were
observed in the Arabic sample. Alternatively, in the Roman sample, granular goethite particles
with a diameter less than 0.5 μm were detected. As shown in Fig. 10b, the goethite present in
the Roman samples was associated with relatively large, laminar particles of clays. Moreover,
in Roman samples, characteristic laminar clay particles (size around 10 μm) were observed in
red and yellow pigments (Fig. 10c). The morphology results obtained in the present study are
similar to those commonly described in the literature ( [Gettens and Stout, 1966] and [Henning
and Störr, 1986]) and are in agreement with the qualitative results derived from the XRD 2dimensional images.
Using SEM-EDX, two different compositions were observed in the upper zone of the crosssection of Roman sample 11 (Fig. 8b). Moreover, Hg and Fe mappings indicated that two
different red layers were present in the material. In particular, the upper layer corresponded
to an Hg-based compound, and the inner layer was attributed to a Fe-based mineral (Fig. 9c).
According to the XRD results, only cinnabar, calcite and quartz were present in the fragments
(Fig. 3). Thus, the penetrability of X-rays played an important role in the analysis of sample 11.
The X-rays attenuation length is defined as the depth into the material measured along the
surface normal where the intensity falls to 1/e of its value at the surface (Henke et al., 1993).
To calculate X-ray penetration, the composition and density of the material (cinnabar), the
photon energy (Cu Kα radiation) and the incidence angle (around 10°) were considered. The
theoretical attenuation length of cinnabar was 1.105 μm, and cinnabar grains with a diameter
of approximately 2–6 μm were observed by SEM. Thus, due to the fairly homogeneous
distribution of large cinnabar grains (previously observed in the 2-dimensional XRD images
shown in Fig. 3) in the surface layer, X-rays from the XRD/XRF portable system could not
penetrate into the inner layers. As a result, iron-based compounds (possibly red ochre) were
not detected. Coarse cinnabar grains with various sizes were observed in the images (Fig. 10d).
The grains appear to be broken fragments rather than single rounded homogeneous crystals;
thus, the cinnabar used in the pigment is likely a natural variety.
3.2.2. Green pigments
The EDX spectra of sample 12 revealed that Si, Ca, Fe, and also K, Al and Mg were present in
the green-coloured fragment (Fig. 7d). The association of the colour with this kind of
composition leads us to the conclusion that the colour can be attributed to green earth, also
according to the presence of quartz and celadonite (detected by XRD) (Fig. 6). Microscopically,
7
platy crystals, characteristics of celadonite, were observed (Fig. 10e). In addition to green
earth, another compound based on calcium, copper and silicon was detected in some punctual
EDX analyses; similar results were previously observed by the XRF analyses (Fig. 2c
magnification). Hexagonal crystals of about 20 μm were likely applied, possibly to retain the
colour (Fig. 10f). These results seemed to indicate the presence of Egyptian blue, a pigment
which is very often added to green earth pigments in Romanwallpaintings.
3.2.3. Black and white pigments
Phosphorus and calcium were detected in sample 14 by SEM-EDX (punctual analyses) (Fig. 7e),
which was associated to the presence of ivory black. In addition, carbon-based black pigments
were suspected by micro-Raman spectroscopy due to the appearance of broad Raman bands
centred near 1330 and 1590 cm−1 (Figure not shown) (Duran et al., 2011). Based on these
results, we concluded that two types of pigments were very possibly responsible for black
coloured fragments (phosphor and carbon-based compounds).
High amounts of calcium were detected in white fragments and in white areas of other
fragments. Fig. 10g and h shows the morphology of calcite and quartz in the superficial zones
of the mortars. Granular calcite displayed particle sizes of 1–3 μm, and continuous rings with
low intensities were observed in the XRD 2-dimensional images, indicating that a large number
of small calcite grains were homogeneously distributed throughout the superficial layer of the
samples.
4. Conclusions
During the archaeological excavations in the PatiodeBanderas of RealesAlcazares’ Palace,
fragments of Roman and Arabicwallpaintings were discovered. Red, yellow, white, green and
black coloured fragments were collected from the Romanwallpaintings, and red and whitecoloured fragments were obtained from the Arabicpaintings (Table 1).
To produce the red colour, different pigments were used, depending on the origin of the
painting. Namely, in the Romanpaintings, red ochre and vermilion were employed.
Alternatively, in the Arabicpaintings, haematite was used. The distinction between red ochre
and haematite was possible thanks to the use of XRD and SEM-EDX. For instance, haematite
and clays (forming red ochre) were detected by XRD in some of the red samples of Roman
origin. Punctual chemical analyses and elemental mappings revealed that iron was associated
with aluminium and potassium in these samples. Similar to red paints, Roman artists used
yellow ochre to obtain yellow decorations. Alternatively, haematite was detected in the
Arabicpaintings; in particular, the results indicated that iron and calcium were associated. It is
known the admiration, emulation, assimilation and continuity of Islamic art from the ancient
Roman world. Hispano-arabic art is a fusion of visigothic and Roman Iberian art and has a
strong base in local tradition ( [Maravall, 1992] and [Rallo Gruss, 2003]).
The XRD results indicated that quartz and celadonite were present in the green coloured
fragments, and the EDX results showed the presence of Si, Ca, Fe, K, Al and Mg; thus, we
concluded that the green colour of Roman samples was achieved with green earth. Moreover,
Egyptian blue was also detected by SEM-EDX and XRF. The composition of the black fragment
was based on phosphor (ivory black) and carbon-based pigments.
The pigments detected in the Romanwallpaintings studied in this paper are seen to be those
that are quite normally encountered in Roman villas; namely, red and yellow ochres, vermilion,
8
green earth, Egyptian blue and carbon and phosphor-based black pigments (carbon black and
ivory black) were detected ( [Edreira et al., 2001], [Mazzocchin et al., 2004], [Edwards et al.,
2009], [Weber et al., 2009], [Aliatis et al., 2010] and [Duran et al., 2010b]).
In addition, a first qualitative approach about the size and shape of the particles in the
pigments was determined by acquiring XRD images with a 2-dimensional detector (imaging
plate) and tested by scanning electron microscopy. The results obtained from both techniques
were in agreement. In particular, the results revealed that haematite and goethite displayed
small particle sizes (<0.5 μm), and celadonite and calcite possessed similar particle sizes (1–
3 μm). Moreover, celadonite and calcite particles were smaller than those of cinnabar (2–
6 μm) and other laminar clays detected in ochre (10 μm). In addition, Egyptian blue particles
were approximately 20 μm in diameter. The data obtained in the present study coincide with
those described in the literature.
From a technical point of view, the portable XRD/XRF system developed by the C2RMF
laboratory was used to successfully characterise the paintings. With this equipment,
elemental, chemical and structural analyses were combined, and non-destructive analyses
were achieved. In addition, the micro-structures of the samples and the grain size of the
particles were determined. It is important to point the high quality of the results obtained
from the new portable XRD/XRF system. However, SEM-EDX allowed a more thorough
identification of the components of pigments. As a result, the sequence of the layers and the
morphology of the particles were described in detail.
Acknowledgements
This work was supported by project BIA 2009-12618, EU-ARTECH (contract number RII3-CT2004-506171), MEC/FULLBRIGHT 2007 and JAE Doc 088. The authors gratefully acknowledge
C2RMF staff (especially Dr. Jacques Castaing), Miguel Angel Tabales from the RealesAlcazares
of Seville, Cristina Gallardo from the Materials Science Institute of Seville, Almudena Muñoz
(architect) for their assistance and the useful comments from the reviewers. Samples were
provided by Miguel Angel Tabales.
References
Abe et al., 2009
Y. Abe, I. Nakai, K. Takahashi, N. Kawai, S. Yoshimura
On-site analysis of archaeological artifacts excavated from the site on the outcrop at
Northwest Saqqara, Egypt, by using a newly developed portable fluorescence spectrometer
and diffractometer
Anal. Bioanal. Chem., 395 (7) (2009), pp. 1987–1996
Aliatis et al., 2010
I. Aliatis, D. Bersani, E. Campani, A. Casoli, P.P. Lottici, S. Montovan, I.G. Marino
Pigments used in Romanwallpaintings in the Vesuvian area
J. Raman Spectrosc., 41 (2010), pp. 1537–1542
9
Bearat, 1997
H. Bearat
Quelle est la gamme exacte des pigments romains? Confrontation des résultats d’analyse et
des texts de Vitruve et de Pline
H. Bearat, M. Fuchs, M. Maggetti, D. Paunier (Eds.), RomanWallPaintings: Materials,
Techniques, Analysis and Conservation, Proceedings of the International Workshop, Institute
of Mineralogy and Petrology of Fribourg, Fribourg (1997), pp. 11–34
Blanco Freijeiro, 1984
A. Blanco Freijeiro
La ciudad antigua In Historia de Sevilla
Seville University (ed) (1984) 108
Brindley and Brown, 1980
G.W. Brindley, G. Brown
Crystal Structures of Clay Minerals and Their X-ray Identification
Mineralogical Society London (ed) (1980)
Cardell et al., 2009
C. Cardell, L. Rodriguez-Simon, I. Guerra, A. Sanchez-Navas
Analysis of Nasrid polychrome carpentry at the hall of the Mexuar Palace, Alhambra complex
(Granada, Spain), combining microscopic, chromatographic and spectroscopic methods
Archaeometry, 51 (4) (2009), pp. 637–657
Chiari, 2008
G. Chiari
Saving art in situ
Nature, 453 (2008), p. 159
De Viguerie et al., 2009
L. De Viguerie, A. Duran, A. Bouquillon, V.A. Solé, J. Castaing, P. Walter
Quantitative X-ray fluorescence analyses of an Egyptian faience pendant and comparison with
PIXE
Anal. Bioanal. Chem., 395 (7) (2009), pp. 2219–2225
10
Delamare, 1983
F. Delamare
Les peintures murales romaines de l’Acropole de Léro
Revue d’Archéometrie, 7 (1983), pp. 85–98
Deneckere et al., 2010
A. Deneckere, W. Schudel, M. Van Bos, H. Wouters, A. Bergmans, P. Vandenabeele, L. Moens
In situ investigations of vault paintings in the Antwerp cathedral
Spectrochim Acta A, 75 (2010), pp. 511–519
Drits et al., 1997
V.A. Drits, L.G. Dainyak, F. Muller
Isomorphus cation distribution in celadonites, glauconites and Fe-illites determined by
infrared, Mössbauer and EXAFS spectroscopies
Clay Miner, 32 (1997), pp. 153–179
Duran et al., 2008
A. Duran, J.L. Perez-Rodriguez, M.C. Jimenez de Haro, L.K. Herrera, A. Justo
Degradation of gold and false golds used as gildings in the cultural heritage of Andalusia, Spain
J. Cult. Herit, 9 (2) (2008), pp. 184–188
Duran et al., 2009
A. Duran, J.L. Perez-Rodriguez, T. Espejo, M.L. Franquelo, J. Castaing, P. Walter
Characterisation of illuminated manuscripts by laboratory-made portable XRD and micro-XRD
Systems
Anal. Bioanal. Chem., 395 (7) (2009), pp. 1997–2004
Duran et al., 2010a
A. Duran, J. Castaing, P. Walter
X-ray diffraction studies of Pompeian wallpaintings using synchrotron radiation and dedicated
laboratory made systems
Appl. Phys. A, 99 (2010), pp. 333–340
Duran et al., 2010b
A. Duran, M.C. Jimenez de Haro, J.L. Perez-Rodriguez, M.L. Franquelo, L.K. Herrera, A. Justo
11
Determination of pigments and binders in Pompeian wallpaintings using synchrotron radiation
– high resolution X-ray powder diffraction and conventional spectroscopy-chromatography
Archaeometry, 52 (2) (2010), pp. 286–307
Duran et al., 2011
A. Duran, M.L. Franquelo, M.A. Centeno, T. Espejo, J.L. Perez-Rodriguez
Forgery detection on an Arabic illuminated manuscript by micro-Raman and X-ray fluorescence
spectroscopy
J. Raman Spectrosc., 42 (2011), pp. 48–55
Durán-Benito et al., 2007
A. Durán-Benito, L.K. Herrera-Quintero, M.D. Robador-González, J.L. Pérez-Rodríguez
Color study of Mudejar paintings on the pond found in the palace of “RealesAlcazares” in
Sevilla
Color Res. Appl., 32 (6) (2007), pp. 489–495
Edreira et al., 2001
M.C. Edreira, M.J. Feliú, C. Fernandez-Lorenzo, J. Martin
Romanwallpaintings characterization from Cripta del Museo and Alcazaba in Merida (Spain):
chromatic, energy dispersive X-ray fluorescence spectroscopic, X-ray diffraction and Fourier
Transform Infrared spectroscopic analysis
Anal. Chim. Acta, 434 (2001), pp. 331–345
Edwards et al., 2009
H.G.M. Edwards, P.S. Middleton, M.D. Hargreaves
Romano-British wallpaintings: Raman spectroscopic analysis of fragments from two urban sites
of early military colonisation
Spectrochim Acta A, 73 (2009), pp. 553–560
Eveno et al., 2010
M. Eveno, A. Duran, J. Castaing
A portable X-ray diffraction apparatus for in situ analyses of masters’ paintings
Appl. Phys. A, 100 (2010), pp. 577–584
Gettens and Stout, 1966
R.J. Gettens, G.L. Stout
12
Painting Materials: A Short Encyclopaedia
Dover Publications, Inc, New York (1966)
Gianoncelli et al., 2008
A. Gianoncelli, J. Castaing, L. Ortega, E. Doorhyée, J. Salomon, P. Walter, J.L. Hodeau, P. Bordet
A portable instrument for in situ determination of the chemical and phase compositions of
cultural heritage objects
X-Ray Spectrom., 37 (2008), pp. 418–423
Henke et al., 1993
B.L. Henke, E.M. Gullikson, J.C. Davis
X-Ray Interactions: photoabsorption, scattering, transmission and reflection at E = 50–
30000 eV, Z = 1–92
At. Data Nucl. Data Tables, 54 (2) (1993), pp. 181–342
Henning and Störr, 1986
K.H. Henning, M. Störr
Electron Micrographs (TEM, SEM) of Clays and Clay Minerals
Akademie-Verlag Berlin, Berlin (1986)
Herrera et al., 2009
L.K. Herrera, S. Montalbani, G. Chiavari, M. Cotte, V.A. Solé, J. Bueno, A. Duran, A. Justo, J.L.
Perez-Rodriguez
Advanced combined application of μ-X-ray diffraction/μ-X-ray fluorescence with conventional
techniques for the identification of pictorial materials from Baroque Andalusia paintings
Talanta, 80 (1) (2009), pp. 71–83
Hradil et al., 2003
D. Hradil, T. Grygar, J. Hradilova, P. Bezdicka
Clay and iron oxide pigments in the history of painting
Appl. Clay Sci., 22 (5) (2003), pp. 223–236
Kato et al., 2009
N. Kato, I. Nakai, Y. Shindo
13
Change in chemical composition of early Islamic glass excavated in Raya, Sinai Peninsula,
Egypt: on-site analyses using a portable X-ray fluorescence spectrometer
J. Archaeol. Sci., 36 (8) (2009), pp. 1698–1707
Maravall, 1992
J.A. Maravall
El concepto de España en la Edad Media
Centro de Estudios Constitucionales, Madrid (1992) p. 54
Mazzocchin et al., 2004
G.A. Mazzocchin, F. Agnoli, M. Salvadori
Analysis of Roman age wallpaintings found in Pordenone, Trieste and Montegrotto
Talanta, 64 (3) (2004), pp. 732–741
Mazzocchin et al., 2008
G.A. Mazzocchin, P. Baraldi, C. Barbante
Isotopic analysis of lead present in the cinnabar of Romanwallpaintings from the Xth Regio
(Venetia et Histria) by ICP-MS
Talanta, 74 (2008), pp. 690–693
Menu, 2009
M. Menu
The analysis of prehistoric art
Anthropologie, 113 (3–4) (2009), pp. 547–558
Miliani et al., 2009
C. Miliani, B. Doherty, A. Davery, A. Loesch, H. Ulbricht, B.G. Brunetti, A. Sgamellotti
In situ non-invasive investigation on the painting techniques of early meissen stoneware
Spectrochim Acta A, 73 (4) (2009), pp. 587–592
Nazaroff et al., 2010
A.J. Nazaroff, K.M. Prufer, B.L. Drake
Assessing the applicability of portable X-ray fluorescence spectrometry for obsidian
provenance research in the Maya iowlands
J. Archaeol. Sci., 37 (4) (2010), pp. 885–895
14
Ospitali et al., 2008
F. Ospitali, D. Bersani, G. Di Lonardo, P.P. Lottic
‘Green earths’: vibrational and elemental characterization of glauconites, celadonites and
historical pigments
J. Raman Spectrosc., 39 (2008), pp. 1066–1073
Pagès-Camagna et al., 2010
S. Pagès-Camagna, E. Laval, D. Vigears, A. Duran
Non-destructive and in situ analysis of Egyptian wallpaintings by X-ray diffraction and X-ray
fluorescence portable systems
Appl. Phys. A, 100 (2010), pp. 671–681
Pallecchi et al., 2009
P. Pallecchi, G. Giachi, M.P. Colombini, F. Modugno, E. Ribechini
The painting of the Etruscan “Tomba della Quadriga Infernale” (4th century BC) in Sarteano
(Siena, Italy): technical features
J. Archaeol. Sci., 36 (2009), pp. 2635–2642
Pinna et al., 2009
D. Pinna, M. Galeotti, R. Mazzeo (Eds.), Scientific Examination for the Investigation of
Paintings: A Handbook for Conservators-restorers, Centro Di della Edifimi srl, Firenze (2009)
Pliny the Elder, 1985
Pliny the Elder
Natural History
Les belles lettres, Paris (1985)
Rallo Gruss, 2003
C. Rallo Gruss
Hispano-Islamic mural painting: tradition or innovation?
Al-Qantara, 24 (1) (2003), pp. 109–137
Ricciardi et al., 2009
P. Ricciardi, P. Colomban, A. Tournie, M. Macchiarola, N. Ayed
A non-invasive study of Roman age mosaic glass tesserae by means of Raman spectroscopy
15
J. Archaeol. Sci., 36 (11) (2009), pp. 2551–2559
Rodriguez-Navarro, 2006
A.B. Rodriguez-Navarro
XRD2DScan: new software for polycrystalline materials characterization using two dimensional
X-ray diffraction
J. Appl. Cryst, 39 (2006), pp. 905–909
Rodriguez-Navarro et al., 2006
A.B. Rodriguez-Navarro, P. Alvarez-Lloret, M. Ortega-Huertas, M. Rodriguez-Gallego
Automatic crystal size determination in the micrometer range from spotty X-ray diffraction
rings of powder sample
J. Am. Ceram Soc., 89 (2006), pp. 2232–2238
Tabales, 2010
M.A. Tabales
Internal Report “Resumen de los trabajos arqueológicos realizados en 2009 en
PatiodeBanderas”
(2010) p. 14
Uda et al., 2005
M. Uda, A. Ishizaki, R. Satoh, K. Okada, Y. Nakajima, D. Yamashita, K. Ohashi, Y. Sakuroba, A.
Shimono, D. Kojima
Portable X-ray diffractometer equipped with XRF for archaeometry
Nucl. Instrum Methods Phys. Res. B., 239 (2005), pp. 77–81
Van der Snickt et al., 2008
G. Van der Snickt, W. De Nolf, B. Vekemans, K. Janssens
μ-XRF/ μ-RS vs. SR μ-XRD for pigment identification in illuminated manuscripts
Appl. Phys. A, 92 (2008), pp. 59–68
Vitruvius, 2005
Vitruvius M.H. Morgan (Ed.), De architectura libri decem: II (Materials) and VII (Finishes and
Colours), Kessinger Publishing, Whitefish (2005)
16
Weber et al., 2009
J. Weber, W. Prochaska, N. Zimmermann
Microscopic techniques to studyRoman renders and mural paintings from various sites
Mater. Character, 60 (2009), pp. 586–593
17
Table 1. Description of the samples collected from the wallpaintings: period, notation
(sample number), micrograph, fragment dimensions, composition and analytical
techniques employed for characterization.
Period
Sample Photograph
number fragment
of
the Fragment
dimensions
Composition
Techniques
employed
3
Red ochre,
yellow
3.5 × 1.5 × 1.5 cm ochre.
calcite,
quartz
4
6.5 × 4.0 × 1.5 cm
Calcite,
quartz
XRD-XRF
portable,
O.M.
2.5 × 2.5 × 1.5 cm
Vermilion,
calcite
XRD-XRF
portable,
O.M.
Roman
5
(1st
century
BC)
XRD-XRF
portable,
O.M., SEMEDX
7
Yellow
ochre,
1.0 × 0.8 × 1.0 cm
calcite,
quartz
XRD-XRF
portable,
O.M., SEMEDX
11
Vermilion,
red ochre,
2.3 × 1.5 × 0.8 cm
calcite,
quartz
XRD-XRF
portable,
O.M., SEMEDX
12
Green earth,
Egyptian
5.5 × 3.0 × 1.5 cm
blue, calcite,
quartz
XRD-XRF
portable,
O.M., SEMEDX
18
Period
Sample Photograph
number fragment
of
the Fragment
dimensions
Composition
Techniques
employed
Calcite,
quartz
XRD-XRF
portable
13
1.5 × 1.5 × 0.9 cm
14
Carbon
based black,
8.5 × 6.0 × 1.7 cm ivory black,
calcite,
quartz
XRD-XRF
portable,
microRaman,
O.M., SEMEDX
Haematite,
4.5 × 4.5 × 1.5 cm calcite,
quartz
XRD-XRF
portable,
O.M., SEMEDX
Arabic
(11th
1
century
AD)
2
1.3 × 1.0 × 1.0 cm
Calcite,
quartz
XRD-XRF
portable,
O.M.
19
Figure captions
Figure 1. (a) Plan of the archaeological site of the PatiodeBanderas of RealesAlcazares’ Palace,
including the different remains of construction from the 2nd century BC to the 11–13th
century AD (b) and (c) show the plans of the PatiodeBanderas and the location of Roman
building rests (from 1st century BC) and Arabic buildings and streets (from 11th to 13th
century AD) from which Roman and Arabicwallpaintings were discovered (sampling zones are
marked with green and blue squares) (plans were provided by M.A. Tabales). (For
interpretation of the references to colour in this figure legend, the reader is referred to the
web version of this article.)
Figure 2. XRF spectra collected from the superficial layers of the wallpaintings fragments: (a)
Roman red sample 5; (b) Arabic red sample 1; (c) Roman green sample 12 (and magnification).
(For interpretation of the references to colour in this figure legend, the reader is referred to
the web version of this article.)
Figure 3. (a) XRD pattern of the Roman sample 11 as recorded in reflection mode on the 2dimensional detector (coloured surface in fragment); (b) Conventional XRD diagram (Roman
sample 11) [Cin = cinnabar; C = calcite; Q = quartz]. (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
Figure 4. XRD diagrams and XRD patterns obtained from the 2-dimensional detector: (a,b)
Arabic sample 1 (coloured surface in fragment) (black diagram), and (c,d) Roman sample 3
(coloured surface in fragment) (red diagram) [H = haematite; G = goethite; C = calcite;
Q = quartz; Cl = clays]. (For interpretation of the references to colour in this figure legend, the
reader is referred to the web version of this article.)
Figure 5. XRD diagram (a) and XRD pattern (b) of Roman sample 7 (coloured surface in
fragment) [G = goethite; C = calcite; Q = quartz; Cl = clays]. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this
article.)
Figure 6. Conventional XRD diagram (a) and XRD patterns (b) of Roman sample 12 (coloured
surface in fragment) [Cd = celadonite; Q = quartz; C = calcite; Cl = clays]. (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version of this
article.)
Figure 7. EDX spectra corresponding to: (a) the punctual analysis on the red layer of the crosssection of Arabic fragment 1; (b) the general analysis on the red layer of the cross-section of
Roman fragment 3; (c) the general analysis on the red layer of the cross-section of Arabic
fragment 1; (d) the general analysis on the green layer of the cross-section of Roman fragment
12; (e) the punctual analysis on the cross-section of Roman fragment 14. (For interpretation of
the references to colour in this figure legend, the reader is referred to the web version of this
article.)
Figure 8. Cross-sections micrographs of: (a) Roman sample 3 (red and yellow), (b) Roman
sample 11 (two red layers). (For interpretation of the references to colour in this figure legend,
the reader is referred to the web version of this article.)
20
Figure 9. Elemental mappings performed on: - (a) the yellow and red layers of the cross
section of sample 3 (Roman): (a-1) secondary electron images, (a-2) Fe mapping, (a-3) Al
mapping, (a-4) K mapping; - (b) the red layer of the cross section of sample 1 (Arabic): (b-1)
secondary electron images, (b-2) Fe mapping, (b-3) Ca mapping, (b-4) Si mapping; - (c) the red
layers of the cross section of sample 11 (Roman): (c-1) secondary electron images, (c-2) Fe
mapping, (c-3) Hg mapping. (For interpretation of the references to colour in this figure
legend, the reader is referred to the web version of this article.)
Figure 10. SEM images showing the morphology of: (a) haematite particles and calcite grains in
Arabic sample 1; (b) goethite and clays particles in Roman sample 3; (c) clays associated with
haematite and goethite particles in Roman sample 3; (d) cinnabar grains in the cross-section of
Roman sample 11; (e) green earth (mainly celadonite) in Roman sample 12; (f) Egyptian blue
grains in sample 12; (g) calcite grains (Arabic sample 1); (h) quartz grains (Roman sample 3).
21
Figure 1
22
Figure 2
23
Figure 3
24
Figure 4
25
Figure 5
26
Figure 6
27
Figure 7
28
Figure 8
29
Figure 9
30
Figure 10
31