2009 International Nuclear Atlantic Conference - INAC 2009 Rio de Janeiro,RJ, Brazil, September27 to October 2, 2009 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-03-8

X-RAY FLUORESCENCE AND COMPUTED RADIOGRAPHY ANALYSIS OF A FAMOUS BRAZILIAN PAINTING FROM THE XIX

CENTURY

Cristiane Calza1, Davi F. Oliveira1, Henrique S. Rocha1, Andrea Pedreira2 and Ricardo Tadeu Lopes1

1 Laboratório de Instrumentação Nuclear – COPPE/UFRJ

Caixa Postal 68509 21941-972 Rio de Janeiro, RJ

ccalza@lin.ufrj.br

2 Museu Nacional de Belas Artes Rio de Janeiro, RJ

ABSTRACT This work used Energy Dispersive X-Ray Fluorescence (EDXRF) and Computed Radiography (CR) to evaluate the general conditions of the painting “Gioventú” (Eliseu Visconti, 1898), identifying possible problems, areas that revealed signs of previous retouchings and the pigments used by the artist. EDXRF measurements were carried out with a portable system consisting of an X-ray tube Oxford TF3005 with W anode, operating at 25 kV and 100 µA, and a Si-PIN XR-100CR detector from Amptek. Several spectra were obtained in each color, with an acquisition time of 300 s and a beam collimation of 2 mm. The spectra were analyzed using the software QXAS-AXIL (IAEA). The results revealed that the drawings were made over a preparatory layer of lead white. Some pigments identified were: yellow, red and brown ochre; umbra; vermilion; cobalt blue; etc. The experimental setup used in the CR analysis consisted of an Oxford X-ray source, operating at 50 kV and 200 µA, placed at 85 cm from the painting, a GE CR 50P Portable Computed Radiography Scanner and a Fuji Imaging Plate detector. The exposure time was 600 s. The radiographic images revealed that the painting was in a good state of conservation and also a complete composition hidden underneath the visible paint layer.

1. INTRODUCTION The scientific examination of artworks has gained increasing interest in the last years, allowing the characterization of materials and techniques employed by the artists. This analysis can be extremely valuable to conservation and restoration treatments. It can also supply important information that makes possible to identify an artist, to date a painting and to identify forgeries. However, the fact that every artwork is a unique piece emphasizes the necessity of working with non-destructive techniques [1-3]. This work used Energy Dispersive X-Ray Fluorescence (EDXRF) and Computed Radiography (CR) to analyze one of the most famous Brazilian paintings from the ending of the XIX century, belonging to the National Museum of Fine Arts Collection. “Gioventú” (oil on canvas, 65 x 49 cm) was executed by Eliseu Visconti in 1898. These techniques were used to evaluate the general conditions of the painting, identifying possible problems, areas that revealed signs of previous retouchings and the materials employed by the artist. In the figure 1 it is shown the analyzed painting.

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Eliseu d’Angelo Visconti (1866-1944) was born in Italy and, still in childhood, he moved to Brazil with his parents, where he was naturalized in 1890. In 1884, he was admitted at the Imperial Academy of Fine Arts, studying with the masters Victor Meireles, Henrique Bernardelli and Rodolfo Amoedo. In 1892, he won the Europe Travel Prize and traveled to Paris, attending at the École des Beaux-Arts, Académie Julian and École des Arts Décoratives, where he was pupil of Eugène Grasset. He won a silver medal in the Universal Exhibition of Paris, in 1900, with the paintings “Gioventú” and “Oreades”, and a gold medal in the International Exhibition of St. Louis (USA), in 1904, with the painting “The Recompense of Saint Sebastian”. Visconti is considered as the bridge between the XIX and the XX centuries, since he was, even in a late way, the pioneer of the Impressionism in Brazil, inspiring several pre-modernist painters, without cutting himself off the XIX century formal influences, as exemplified by the Realist element in his works [4]. Figure 1. “Gioventú”. Eliseu Visconti, 1898. Oil on canvas, 65 x 49 cm. National Museum of Fine Arts. Rio de Janeiro, Brazil.

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X-Ray Fluorescence analysis is a widely used spectroscopic technique in archaeometry to investigate the composition of pigments (in manuscripts, paintings, ceramics and other artifacts), metal alloys, coins and statuary. It is a non-destructive technique to make possible qualitative and quantitative multielemental analysis with good precision and accuracy [1,5]. The most recent developments in X-ray tubes and detectors have led to the introduction of small and portable instruments, which can be used for the in situ analysis of cultural objects in museums and galleries [6]. The analysis of the pigments used in a painting is important for many reasons. The first is the possibility of evaluate the artist working method: which pigments were used, in such way these pigments were mixed to create a specific coloring, and also, which pigments were used in the preparatory layer. This analysis is also extremely important for restoration procedures, since it can helps to distinguish the original regions from retouchings or later added ones. Thus, pigment characterization may be crucial to important decisions such as those regarding the removal of spurious layers or the choice of the most suitable pigment for retouchings. A third purpose is related to conservation: because some pigments may be affected by environmental conditions, a painting may require specific practices for storage and/or exhibition. In addition, the pigments identification can be necessary before applying chemical treatments to reverse or to stop deterioration processes. Finally, since the chronology of pigments use is well-known, is possible to establish the provenance, historical period and, consequently, the authenticity of a painting [7-9]. Radiographic techniques have been used in museums to study archaeological artifacts, in order to reveal internal details that would otherwise be invisible. In paintings, radiography can reveal the extent of old damages concealed by restoration procedures; the successive phases of the artist’s creation (preparatory drawing, underpainting and changes of design); the nature of the support; the canvas weave; presence of lead pigments, nails and changes in the original surface topography (caused by drying of the ink, like cracking and detachment, and changes in the fabric). X-rays are attenuated differently by the various areas of the painting depending on several factors including the energy of the radiation; density, thickness and composition of the paint layer; and the elemental composition of the support elements (ground, canvas, stretchers, etc.). High Z elements absorb X-rays more efficiently than low Z elements, consequently, pigments that contain elements like Pb, such as lead white or lead-tin yellow, absorb more radiation and appear as light areas on the images. Other pigments, like ochre, for example (that contains Fe), and crackings, do not absorb as many X-rays and appear as dark areas [10-12].

2. EXPERIMENTAL The experimental setup used in the Computed Radiography of the painting “Gioventú” consisted of an Oxford X-ray source, operating at 50 kV and 200 µA, placed at 85 cm from the painting, a GE CR 50P Portable Computed Radiography Scanner and a Fuji Imaging Plate detector. The IP detector (35 x 43 cm) was fixed behind the canvas to perform each radiograph, using an exposure time of 600 s. The images were revealed by introducing the exposed IP in the scanner, which also erased the film after the image processing. Finally, the four radiographs obtained to the canvas were connected, by means of appropriate software, to compose the radiograph of the whole painting, which can be observed in the figure 4.

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The EDXRF analysis was carried out with a portable system developed in the Nuclear Instrumentation Laboratory, consisting of an Oxford TF3005 X-ray tube and a Si-PIN XR-100CR detector from Amptek (with 6 mm2 active area and a 25 µm Be window). The X-ray tube presents a tungsten (W) anode, a 127 µm Be window and maximum operating current and voltage of 0.5 mA and 30 kV, respectively. The angle between the X-ray tube and the detector window is 60°, the source-sample and the detector-sample distances are 4 cm. The system is adapted to a tripod, which makes possible to reach higher regions during the analysis of paintings and statues. In each color and different hue in the painting were obtained several spectra, working at 25 kV and 100 µA, with an acquisition time of 300 seconds and a beam collimation of 2 mm. The spectra were analyzed using the software QXAS-AXIL, from IAEA.

3. RESULTS AND DISCUSSION

3.1. Computed Radiography analysis The radiographic images revealed that the painting was in a good state of conservation. Only small regions of loss of paint support could be observed: the more significant, over the left shoulder of the portrayed girl and the others at the right and left sides of the canvas, near to the frame. These regions appear as black areas in the canvas, since they allow X-rays to pass through them, darkening the Imaging Plate fixed behind the canvas. The figures 2 and 3 show details of two regions of loss of support.

Figure 2. Detail of the radiograph: region of loss of support (dark area) located in the left shoulder of the girl. The canvas weave can be also observed.

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Figure 3. Detail of the radiograph: regions of loss of support (dark areas) located in the right side of the painting, near to the frame. The canvas weave can be also observed. The radiographs also revealed some details such as the canvas weave and the stretching marks, originated when the fabric was fixed on the wooden support. The use of lead white, that appears as light areas, in the body of the girl and in the wings of the angel (in the underpainting) can be clearly observed. Since lead presents high atomic number (Z = 82), these regions absorb the X-rays more efficiently, preventing the darkening of the IP. The use of ochre, that appears as dark areas, especially in the stem of the tree and in the body of Saint Sebastian (underpainting), follows the same principle. The ochre pigments contain iron (Z = 26) and allow the X-rays to pass through these regions, darkening the IP. However, the most important result of the CR analysis was the discovery of a complete composition hidden underneath the visible paint layer, as seen in the radiograph of the whole painting (figure 4). This previous composition is very similar to the painting “The Recompense of Saint Sebastian” (1897), distinguished with a gold medal in the International Exhibition of St. Louis (USA) in 1904. The figure of Saint Sebastian - tied to a tree by his ankles, wounded by arrows, with arms crossed over his chest - can be clearly observed at the left side of the canvas. An angel, with opened wings, places a wreath of laurel (or flowers) upon his head as a divine recompense for his sufferings. On the right side, near to the loss of support (darker area), are seen two small figures portraying merciful ladies. It seems that the artist performed a study for the “Recompense of Saint Sebastian”, which was later abandoned, and the canvas was reused to execute the painting analyzed in this work. In the figure 5 it is shown the painting “Recompense of Saint Sebastian”.

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Figure 4. Computed radiograph of the painting “Gioventú”, showing a complete composition underneath the original painting. This composition seems to be an a study for the painting “Recompense of Saint Sebastian” (figure 5).

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Figure 5. “Recompense of Saint Sebastian”. Eliseu Visconti, 1897. Oil on canvas, 218 x 133 cm. National Museum of Fine Arts. Rio de Janeiro, Brazil. In the figure 6 it is shown a detail of the face of Saint Sebastian. In the later painting focusing this theme the angel places an aureole upon the head of the saint; however, in the study shown in the radiograph can be seen a laurel wreath. In the radiograph, the underlying painting appears more visible than the “original” painting (“Gioventú”). The contours of the girl’s body are tenuously distinguished: her left shoulder and the arm that seemed to be in a distinct position, the diaphanous veil and her face fused with the angel wings.

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Figure 6. Detail of the radiograph: an angel places a laurel wreath upon the head of Saint Sebastian (in the later painting, figure 5, can be seen a saint’s aureole).

3.2. EDXRF analysis The element tungsten found in all spectra is due to the X-ray tube anode. The results revealed that the drawings were made over a preparatory layer containing lead white (2PbCO3.Pb(OH)2) pigment. This pigment was also used as whitener, mixed to the other colored pigments, in order to obtain lighter hues. Lead white is one of the oldest manufactured pigments, which use dates back to antiquity, remaining the most used white pigment until the XIX century. Like cinnabar, it was used as cosmetic (face powder) from the Antiquity to the Middle Ages. The pigment was made by stacking lead strips in porous jars with vinegar and burying in animal manure, which generated the heat necessary to speed up the reaction [13,14]. In the skin tones of the portrayed girl the presence of Fe and Pb in the spectra indicates the use of a mixture of ochre (Fe2O3.H2O) and lead white pigments. Ochre pigments are obtained from naturally tinted clay since prehistoric times. The word “ochre” comes from the Greek ochros (yellow) and the chemical responsible for this color is ferric oxide monohydrate. The

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colored clay is ground and washed to obtain the yellow ochre pigment and, to produce the red one, is necessary to heat until remove the water. Controlling the heating it is possible to produce a range of warm yellows to bright red. Red ochre occurs naturally in volcanic regions, where thermal activity has caused the dehydration. The excellent permanence of the color and the abundance of raw material allowed these pigments to remain among the cheapest artists colors available [13]. In the hair of the girl were identified: Mn and Fe – this result indicates the use of a mixture of ochre and umber (Fe2O3.Mn2O) pigments. The umber pigments first appeared in the late XV century, when were described as being new, and comprises hydrated iron and manganese oxides. In its natural state it is known as raw umber and when heated it becomes a richer brown, known as burnt umber. Its original source was Umbria (Italy), although it is also mined in Devon and Cornwall. The word “umbra” comes from Latin and means “shadow” [13,15]. In the figure 7 it is shown a characteristic XRF spectrum of the hair of the girl. In the red areas like the girl lips, the little fruits in the bushes and the flowers in the trees, the elements identified were: S, Fe and Hg, characterizing the use of a mixture of red ochre and vermilion (HgS). Vermilion was developed by the Chinese around 2000 years before the Romans used it. This red pigment is made by crushing, washing and heating the mineral cinnabar to give a strong red pigment. Alternatively, it was made by mixing mercury and molten sulphur with heating. In the Roman age, cinnabar was mined at Almaden, Spain. It was extensively used in wall decorations, statues and also by gladiators (as body paint) and Roman ladies (as lipstick) [13]. In the figure 8 it is shown a characteristic XRF spectrum of the lips of the girl.

Figure 7. A characteristic XRF spectrum of the hair of the portrayed girl.

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Mn

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WW Pb

Pb

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nts

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INAC 2009, Rio de Janeiro, RJ, Brazil.

Figure 8. A characteristic XRF spectrum of the lips of the portrayed girl.

In the vegetation (trees, grass and foliage), which exhibits a great diversity of hues, from light to dark green, passing by the green-bluish and the green-yellowish ones, were identified the use of viridian (Cr2O3.2H2O) or chromium oxide (Cr2O3), yellow ochre and cobalt blue (CoO.Al2O3). These pigments were mixed, in different proportions, with lead white, to create distinct colorations. In the light and dark green areas, like the grass and the bushes behind the girl, respectively, can be used viridian or chromium oxide. Because XRF is an elemental analytical technique, it cannot differentiate between viridian and chromium oxide pigments (the only difference between them is the molecule of water). In the green-bluish vegetation, over the left shoulder of the girl, the artist used a mixture of viridian (or chromium oxide) and cobalt blue to create this particular coloration. In the green-yellowish grass were used the chromium based pigments mixed with yellow ochre. Chromium oxide green was first produced in 1809 and was used on a limited basis until 1820, when a substantial source of chromium ore was found in North America and a large scale production began. Viridian green was discovered as a pigment in 1838 and the process of its manufacturing was patented by Guignet in 1859. The name viridian comes from Latin viridis (green). Although cobalt was isolated only in 1735, by the Swedish chemist George Brandt, cobalt minerals have been used to produce blue pigments since the Antiquity, particularly to color glass. Cobalt blue was developed in 1802 by Thenard, partly as a result of studying the production of Sévres porcelain, and replaced smalt pigment [13,16,17]. In the yellow veil that covers the girl, from the waistline, were identified Fe and Pb, indicating the use of yellow ochre mixed with lead white. Finally, in the stems of the trees, the presence of Fe characterizes the use of brown ochre.

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HgHgFe

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4. CONCLUSIONS The present study reported the use of an EDXRF portable system and Computed Radiography to evaluate a famous Brazilian painting from the XIX century: “Gioventú” (Eliseu Visconti). The XRF results characterized the original pigments used by the artist and the preparatory layer. Computed Radiography analysis complemented the characterization of the painting, revealing the canvas weave, small regions of losses, the use of lead white and the existence of a hidden composition under the painting. The information obtained with the EDXRF and CR analyses will be used to create a database about the XIX century Brazilian Collection of the National Museum of Fine Arts, in order to assist restorers, conservators, art students and researchers in the field of archaeometry.

ACKNOWLEDGMENTS The authors would like to thank the staff of The Paintings Restoration Laboratory, from the National Museum of Fine Arts, for their valuable support, and also FAPERJ and CNPq.

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