The deposition from the Cross in the church of Saint-Germain-en-Laye (France): A masterpiece of Romanesque sculpture? Materials characterization to solve a 20th c. mystery

Journal of Cultural Heritage 40 (2019) 133–142

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Original article

The deposition from the Cross in the church of Saint-Germain-en-Laye (France): A masterpiece of Romanesque sculpture? Materials characterization to solve a 20th c. mystery夽 Alessia Coccato a,∗ , Luciana Mantovani b , Romano Ferrari a , Danilo Bersani c , Mario Tribaudino b , Pier Paolo Lottici c a

Association Patrimoine d’Italie, 3, rue des Chenets, 78100 Saint-Germain-en-Laye, France Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, Parma 43124, Italy c Department of Mathematical, Physical and Computer Sciences, University of Parma, Parco Area delle Scienze 157/a, Parma 43124, Italy b

a r t i c l e

i n f o

Article history: Received 14 January 2019 Accepted 23 May 2019 Available online 10 June 2019 Keywords: Raman spectroscopy X-ray powder diffraction Archaeometry Mastic incrustation sculpture Dating Synthetic pigments

a b s t r a c t Dating and authenticating stone-sculpted works of art is a challenging aspect of cultural heritage studies. In fact, it is often possible to provenance the rock, by comparison of petrological, mineralogical and geochemical data, but no dating of the sculpture can be obtained. Also, stylistic observations need to be considered with care. However, in the case of mastic incrustation sculptures, the applied polychromy can support dating studies, based on pigments and binders. In the church of Saint-Germain-en-Laye, a hautrelief representing the Deposition from the Cross is exposed. The calcareous slab is decorated with red and black mastics. It resembles closely the Deposition from the Cross in the transept of Parma Cathedral, dated 1178 and “signed” by Benedictus Antelami. However, the St-Germain Deposition appeared in 1994, when it was donated to the parish by the descendants of Julien Auguste Duperrier, marble worker and collector of Italian antiquities. His last trip to Italy took place in 1924. No information is available on his deal, neither on the transport means arranged, nor on the sculpture itself (author, contractor, date, etc.). Art historical and historical considerations propose either a 12th or 19th–20th c. context for the creation of the sculpture. Chemical analyses of the pigments and binders are therefore proposed to clarify the dating the work of art. Microscopic samples are characterized by a multi-analytical approach: vibrational spectroscopies and X-ray powder diffraction are used to characterize the rock and the polychrome mastic. The rock is identified as a micritic limestone, and shows sulphation issues. Through Raman scattering measurements, the pigments were identified: carbon in the black mastic, and a mixture of red lead and a modern synthetic pigment (PR49:1) in the red areas. This information sheds new light on the chronology and manufacture of the Deposition from the Cross of Saint-Germain-en-Laye. These results allow for a better definition of further lines of research, and to finally propose an authorship for the sculpture. © 2019 Elsevier Masson SAS. All rights reserved.

1. Introduction and research aims Dating and authenticating sculptures is a challenging subject [1–4]. In fact, the manufacturing of a sculpture cannot be dated just on the mineralogical-petrographical features of the rock. Stylistic considerations for authentication purposes can be misleading [5]. The identification of fakes, forgeries, copies, reproductions,

夽 This article is part of the special issue “Geosciences for Cultural Heritage”, composed of a selection of peer-reviewed papers presented at session S30 of Congress SGI-SIMP 2018. Guest editors: Fabrizio Antonelli (University IUAV of Venice), Alberto De Bonis (University of Naples “Federico II”), Domenico Miriello (University of Calabria), Simona Raneri (University of Pisa), and Alberta Silvestri (University of Padua). ∗ Corresponding author. E-mail address: [email protected] (A. Coccato). https://doi.org/10.1016/j.culher.2019.05.019 1296-2074/© 2019 Elsevier Masson SAS. All rights reserved.

imitations requires therefore the implementation of analytical techniques in a broader study on the object, including art historical expertise and documentary research [2–4,6–9]. The main objective of this study is to provide analytical data to support dating and authenticating of a mastic incrustation sculpture, which is exposed in the parish church of Saint-Germainen-Laye, France. The sculpture strongly resembles the “Deposition from the Cross” by Benedictus Antelami, which is visible in the Cathedral of Parma, Italy. However, it is not clear in which circumstances this second Deposition was created, by whom, and when and how it arrived in France. The sculpture was immediately recognized as a “double” of the analogous one in the Parma cathedral by Carol Heitz (1923–1995), and later by one of the authors, Romano Ferrari, who started the interdisciplinary research work on the two Depositions [10–12].

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The present research addresses the problem of dating the deposition in Saint-Germain-en-Laye by an interdisciplinary approach, combining archival research, art historical observations and materials characterisation, involving specialists and connoisseurs in Italy and in France. 1.1. The Deposition of Saint-Germain-en-Laye: materials aspects, historical data and art historical considerations The “Deposition from the Cross” in Saint-Germain-en-Laye (Fig. 1) measures 1.10 × 2.30 m (as the one in Parma), and is broken at 2/3 of the length, the two pieces weighing approximately 800 and 400 kg, respectively. The inscription “ANNO MILLENO CENTENO SEPTVAGENO/OCTAVO SCVLTOR PATVIT MENSE SECVNDO/ANTELAMI DICTVS SCVLPTOR FVIT HIC BENEDICTVS” indicates the author and date of execution of the masterpiece: Benedictus Antelami, 1178 [13]. The polychromy in Parma is strongly altered from its original colours: just red and blackish hues remain from the original black, red, blue, green [14,15]. Also the sculpture in Saint-Germain-en-Laye shows polychromic decoration, with red and black, applied using the technique of mastic incrustation. This technique originated in the Byzantine Empire, and became widely diffused in the Mediterranean area between the 10th and 13th centuries [16–19]. It consists in carving the stone with a scalpel, and in filling the cavities with coloured mixtures of pigments and organic binders, i.e. the mastic, which is applied hot and then smoothed [16,20,21]. The binders encompass pine pitch, waxes, animal and vegetable fats, to guarantee the adhesion of the polychromatic decoration. For the colours, mainly black and red are found, obtained using the traditional pigments (haematite, carbon black) and other materials such as crushed glass and rocks [20–22]. The material history of the Deposition in Saint-Germain-en-Laye is mysterious: only one written document is available, which is a letter dated 1994, in which the heirs to a marble masonry business donated the sculpture to the local parish. The combination of archival research (Archives Départementales des Yvelines, Archives Départementales de la Creuse), and interviews allowed to reconstruct some additional dates concerning the family and business history. From the donation letter, we know that the sculpture, defined as “a copy in Carrara marble of the Deposition from the cross in Parma”, belonged to the family since “at least 80 years”, i.e. before the Great War (1914–1918). Arnaud Marie Duperrier (1864–1941), worked as a masonry entrepreneur in Saint-Germain-en-Laye since 1897. Oral traditions of the family report that Mr Duperrier had

regularly travelled to Italy to collect materials for his work as well as for his own pleasure, and that the last of these trips took place in 1924. It is from one of his travels that he brought this sculpture to France. His son, Julien Auguste Duperrier (1893–1980) worked with him. It is noteworthy to mention that Julien Auguste, installed the two parts of the sculpture, not fixed together, in the entrance corridor of the family house during the 1960s. In 1994 the heirs of Julien August Duperrier decided to donate the sculpture to the local parish for its devotional and artistic value [23]. According to the Loi de séparation des Églises et de l’État (9 December 1905), the sculpture belongs to the parish and is not listed as an historical monument. From the stylistic point of view, it appears that the Deposition in Saint-Germain is stiffer than that in Parma, and that the modelling of faces and tunics does not correspond precisely to other Antelami’s works. However, the precise reproduction of the details indicates a studied copy, either dating to the 19th–20th centuries, or to some medieval workshop linked to Antelami (Bruno Bern, Eliane Vergnole, Jean-René Gaborit, Cécile Garguelle, by F. Méténier [23]). Due to the poor constraints obtained from stylistic assessments, which suggest either a late 12th century or 19th–20th century date for the sculpture, the materiality of the sculpture was tested to obtain clues or circumstantial evidences to support the dating of the object. The two proposed periods appear to be sufficiently distant in time, and linked to completely different technological environments, so that the characterisation of the materials (rock, pigments, binders) could help distinguish between the two options. Even though the comparative investigation of the link between the two Depositions appears to be challenging and interesting, in this paper we will analyse the material components of the Saint-Germain sculpture only.

2. Materials and methods At first, observation under a 395 nm UV lamp was carried out, which showed no inhomogeneities on the sculpture. In this case, a minimally invasive approach on the sculpture (i.e. sampling) permitted a multi-analytical investigation of the rock and coloured mastic. A combination of Raman spectroscopy, infrared spectroscopy and X-ray powder diffraction on minute samples, as well as microscopic observations on thin sections is used to characterise the materials of a supposedly 12th century mastic incrustation sculpture.

Fig. 1. The deposition from the Cross in the parish Church of Saint-Germain-en-Laye. Photo by Xavier Guenez.

A. Coccato et al. / Journal of Cultural Heritage 40 (2019) 133–142

For the rock (P, pierre), four samples were collected, from the sides (SG-P1 with chisel and hammer, SG-P2 with an electric drill) and also from the front surface (chisel and hammer, SG-P-t1 with the polished surface and SG-P-t2 beneath it), taking advantage of the pre-existing fracture, and sampling in a nonfigurative area. This latter sampling aims to investigate the application of a surface treatment. After non-destructive analyses, thin sections were prepared from samples SG-P1 and SG-p-t1 for a detailed characterisation of the stone. For the coloured mastic, which is red (R, rouge) and black (N, noir) in the letters, black in the decorated frame (M, mastic), three samples each were collected with a scalpel in areas already damaged, throughout the surface of the relief. In total, thirteen samples were collected (Table 1). Optical microscopy on thin sections was carried out using a Leica MZ 125 stereo optical microscope apparatus. X-ray powder diffraction analyses (XRD) were performed by means of a Bruker D2 Phaser powder diffractometer, with Cu-K␣ radiation, Ni filtered, operating at 30 kV and 10 mA, in a 2␪ range between 5◦ and 60◦ , with steps of 0.02◦ and a sampling time of 1 second. The samples were powdered in an agate mortar and a few milligrams transferred to a zero background sample holder for the analysis. Diffraction patterns were interpreted using the Bruker software EVA. Raman spectra were collected using an Olympus BX40 microscope (50×) attached to a Jobin-Yvon Horiba LabRam confocal Raman spectrometer, equipped with a charge-coupled detector (CCD). The samples were excited with the 632.8 nm line of a He:Ne laser (0.6 or no filter). The spectra were collected in backscattered geometry, in two spectral ranges 120–1150 cm−1 and 1050–1850 cm−1 , with 5–60 seconds counting time and 10–60 accumulations. Fourier-transform infrared absorption (FT-IR) spectra have been obtained using a Jasco 6100 spectrometer, in attenuated total reflection (ATR) mode, using a single-reflection diamond/KRS5 ATR equipment model “Miracle” by Pike, with a DLaTGS detector. The diamond diameter (spot size on the sample) was 1 mm. Spectra have been acquired with a resolution of 4 cm−1 , in the range 650–4000 cm−1 , using a repetition of 100 scans. Both XRD and vibrational spectroscopies find a wide application in the field of archaeometry and conservation science, proving effective and complementary in the obtained information: organic and inorganic materials, ordered and disordered ones can be successfully characterised by a combination of the two techniques [24–26]. In this case, X-ray powder diffraction was performed first, on one (or on part of one) sample per type. As a second step, Raman spectroscopy allowed to confirm and to extend the range of iden-

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tified materials, especially as it concerns materials not present in the XRD database, and disordered ones. Finally, FT-IR ATR analyses were performed on selected samples to evaluate the organic compounds present. For the stone, thin section observations supported the identification of the lithofacies. 3. Results and discussion It is well known that the identification of applied materials, such as pigments, can highlight discrepancies between the historical and geographical use of materials and the proposed manufacture period and area [6,7]. Moreover, for some synthetic materials, production/discontinuation dates are well known, even though many pigments were continuously used since prehistory, and cannot be used for dating/authenticating purposes. Finally, an antique object could contain modern pigments as a result of restoration treatments and later interventions, so care needs to be taken in the case of polychrome sculptures [27]. 3.1. Rock The identification of the sculpture as Carrara marble, as stated in the donation letter, has been discarded, thanks to the observation of the macroscopic features of the stone, which is a micritic limestone. The diffraction and Raman results show a rather simple mineralogical composition. XRD on the sample SG-P2, collected from the side of the sculpture, and on SG-P-t2 from the front, all show clearly the characteristic reflections of calcite (CaCO3 ) and quartz (SiO2 ) (Fig. 2). Raman spectroscopy and FT-IR confirm the presence of calcite both in sample SG-P1 and SG-P-t1 [Raman [28,29]: 1087, 712, 281, 147–153 cm−1 (Fig. 3), IR [30]: 1412, 874, 712 cm−1 (Fig. 4)]. On sample SG-P-t1, which represents the polished surface of the sculpture, gypsum (CaSO4 ·2H2 O) is identified (Raman [31]: 1008 cm−1 (Fig. 3), FT-IR [30]: 1116, 667 cm−1 ), as well as haematite (␣-Fe2 O3 ) in a reddish vein (Raman [28,29] (Fig. 3): 661, 607, 410, 295, 247, 225 cm−1 ). The IR bands at 2955, 2922, 2853 and 1746 cm−1 indicate a lipidic compound (i.e. an oil [30]) applied to the surface, likely as a finishing treatment (Fig. 4, Table 3). Even if the mineralogical composition of Carrara marble and of limestones can be considered identical [32], one is a metamorphic rock while the others are sedimentary [33,34]. Carrara marble is reported to have an average grain size ranging from 0.01 to 0.5 mm [33,35–37], and maximum grain size (MGS) of 0.25 to 1.5 mm [36,38–41]: it is anyway considered a fine-grained marble, as its MGS is less than 2 mm [32,39]. The bigger grain size in marble

Table 1 Overview of collected samples and performed analyses.

Rock SG-P1: back of the slab (fragment) SG-P2: back of the slab (powder) SG-p-t1: front of the slab, right of the fracture, worked surface SG-p-t2: front of the slab, right of the fracture Black mastic (border) SG-M1: decorative border, bottom right SG-M2: decorative border, left, third medallion from the bottom SG-M3: decorative border, right, second medallion from the bottom Black mastic (letters) SG-N1: flag on the right side SG-N2: flag on the left side SG-N3: black line, close to SG-R2 Red mastic (letters) SG-R1: letter N “de/po/ni/tur” SG-R2: letter H “Mathias” SG-R3: letter S “Benedictus”

XRD

Raman spectroscopy

X

X X X X

X

X

X

X

X X X

FT-IR spectroscopy

X X

X

X X X

X

X X X

X

XRD: X-ray powder diffraction analyses; Fourier-transform infrared absorption (FT-IR): Fourier-transform infrared absorption.

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Fig. 2. X-ray powder diffraction of the rock samples SG-P2 and SG-p-t2.

Fig. 3. Raman spectra of the rock samples. Top spectrum: worked surface of the sample SG-p-t1 (60 seconds, 5 accumulations), bottom spectrum: reddish vein visible in SG-P1 (cross section: 30 seconds, 10 accumulations) Ca: calcite, Ha: haematite, CS: calcium sulphates.

Fig. 4. Fourier-transform infrared absorption (FT-IR) attenuated total reflection (ATR) of the rock SG-p-t2.

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Table 2 Occurrences of lithol red pigments. Year

Type of artwork

Author and title

Pigment

Reference

1907 1908 26/10/1926–20/02/1928 1929 1942–1944 1952 1958–1960 1958–59 1962 1949–1968

Print on paper Print on paper Print on paper Print on paper Mixed media on canvas Paint on canvas Paint on canvas Paint on canvas Paint on canvas Paint on canvas

“Nevertheless” (The Metropolitan Museum of Art, New York, US) “Drink Coca Cola” (The Metropolitan Museum of Art, New York, US) Italian postage stamp (60 c. + 30 c.) Leonetto Cappiello “Nitrolian” (National Gallery of Australia, Canberra, AUS) Piet Mondrian “Victory Boogie Woogie” (Gemeentemuseum, The Hague, NL) Sam Francis “Blue” (Sam Francis Foundation, Glendale, US) Sam Francis “Round the world” (Sam Francis Foundation, Glendale, US) Mark Rothko “Seagram Murals” (Tate Modern, London, UK) Mark Rothko “Harvard Murals” (Harvard University, Cambridge, US) Lucio Fontana “concetto spaziale 56 P 7” (Galleria Tornabuoni, Florence, IT)

PR49:1 PR49:1 PR49:1 PR49 Lithol red PR49:1 PR49:1 PR49 PR49 PR49:2

[62]

accounts for its translucency, while limestone, even when polished, is opaque. Thin section analysis (Fig. 5) allowed to investigate the petrography of the stone, which confirmed its sedimentary origin, highlighting the presence of microcrystalline calcite (2–3 ␮m calcite crystals and grey calcitic veins), and of abundant cretaceous foraminifera (100–300 ␮m). This could correspond to Pietra d’Istria [33,34,42,43], or to other similar limestones, such as Asiago (Maiolica formation [44,45]) or Prun (Scaglia Rossa formation) stones [34]. Pietra d’Istria (Kirmenjak) is a white-greyish micritic limestone [46] or a mudstone [47], showing conchoidal fracture. The sedimentary joints (stylolites) are marked by yellow ochre, quartz, calcite, plagioclase, and clays (sericite, chlorite, smectite, vermiculite, kaolinite, illite, illite-smectite, muscovite) [34,42,48]. In Porezzo, Rovigno and Orsera (Poreˇc, Rovinij, Vrsar), Jurassic levels are to be found, while lower cretaceous levels appear in Porezzo and Orsera [34]. The Istrian stone variety liburnica, moreover, shows foraminifera fossils [34]. Asiago stone (biancone) is a lower cretaceous whitish micritic limestone in the formation of the Majolica Veneta. It contains fossils and silica-rich stylolitic layers, and it shows conchoidal fracture [33,44,45]. Prun stone is a rosy-whitish micritic mudstone with foraminifers shells, conchoidal fracture and stylolitic joints, formed in the upper Cretaceous (Scaglia Rossa formation) [34]. 3.2. Black mastic (border) Three samples of black mastic of the border were collected. They were brittle and electrostatically charged, showing whitish specks under the microscope.

[65] [67] [80] [81] [71,82] [83]

One of the samples (SG-M2) was analysed by XRD. The identified crystalline phases are calcite and hydrocerussite [Pb3 (CO3 )2 (OH)2 ], which are both white coloured. No information on the black phases was obtained by XRD (Fig. 6). The low range Raman spectra show the presence of Ca-based carbonates and sulphates: calcite (1086, 713, 282 cm−1 [28,29]) and calcium sulphates in the system CaSO4 –H2 O (1027, 1010, 627 cm−1 [31]). The Raman bands at 276 and 138 cm−1 in samples SG-M1 and SG-M2 (Fig. 7) are very close to those of massicot (orthorhombic PbO), as their position seems to depend on the laser power [49,50]. This lead-based compound could have been added as a pigment, or it could be a degradation product of hydrocerussite [51]. Barium sulphate BaSO4 (987, 456 cm−1 ) is also identified clearly in sample SG-M3 (Fig. 7), while in other spectra only the band at 987 cm−1 is visible [52]. The hypothesis of a carbon-based black pigment is confirmed by the detection of two broad bands at about 1590 and 1330 cm−1 (Fig. 8) [28,53]. FT-IR spectroscopy confirms the presence of calcium carbonate (broad band at ca. 1400 cm−1 ), as well as of gypsum and barium sulphate (1111 and 671 cm−1 ); moreover, the IR bands at 2954, 2918, 2849 cm−1 are compatible with an oleic binder [30]. These results show that the black mastic of the border is composed of a carbon-based black pigment, mixed with inorganic extenders (Pb-containing pigments, barium sulphate and calcium compounds, Table 3), and an organic binder. For reference, 11th–12th century Southern Italian black mastics showed a mixture of carbon black, alkali feldspars and calcite, [21]. The presence of barium sulphate has been associated with forgeries [54], modern productions [52,55–57], or modern restorations on genuine artefacts [27].

Fig. 5. Photomicrograph of the thin section prepared from SG-p-t1, showing cretaceous foraminifera.

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Fig. 6. X-ray powder diffraction of the coloured mastics.

Fig. 7. Raman of the black mastics (top to bottom: SG-N2: 20 seconds, 20 accumulations, SG-M2: 20 seconds, 20 accumulations, SG-M3: 60 seconds, 20 accumulations). Ma: massicot; Ba: barium sulphate; CS: calcium sulphate.

3.3. Black mastic (letters) As for the black mastic of the border, the three collected samples are brittle and electrostatically charged. SG-N1 was selected for XRD. The diffractogram is similar to the one of SG-M2: calcite and hydrocerussite are identified. Some of the unidentified peaks of SG-M2 are present here as well, indicating that the two mixtures are similar, but not identical (Fig. 6). The vibrational spectroscopic analyses show calcite (Raman [28,29]: 1086, 711 cm−1 (Fig. 7), IR [30]: 1391, 871 and 711 cm−1 ), barium sulphate (Raman [28,29]: 988 cm−1 (Fig. 7), IR [30]: 1108, 1005, 983 cm−1 ), calcium sulphates (Raman [31]: 1007, 1016 and 1026 cm−1 (Fig. 7), IR [30]: 728, 679 cm−1 ), cerussite PbCO3 and

hydrocerussite (Raman [28,29]: doublet at 1048–1054 cm−1 , IR [30]: 1044, 848, 679 cm−1 ). Massicot is identified as well by the Raman bands at 140 and 276 cm−1 (Fig. 7) [49,50]. This lead (II) oxide could be, again, a pigment or a degradation product of the cerussite and hydrocerussite [51]. Moreover, the typical broad bands of carbon at ca. 1340 and 1580 cm−1 are identified in the high-range of the spectrum (Fig. 8) [28,53]. Again, the IR bands at 2954, 2916, 2847 cm−1 are compatible with an oleic binder [30]. As a result, in the black mastic of the letters, black pigments (carbon black) are mixed with inorganic additives and pigments, such as lead white, calcite, barium sulphate (Table 3). The latter possibly indicates a modern manufacture. Calcium sulphates are interpreted as degradation products.

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Fig. 8. High-range Raman spectra of the black mastics (top: SG-M1 and bottom: SG-N2: 60 seconds, 20 accumulations). Ca: calcite; C: amorphous carbon.

Table 3 Summary of the identified compounds in all the samples.

Stone Black mastic (border) Black mastic (letters) Red mastic (letters)

CaCO3

SiO2

␣-Fe2 O3

CaSO4 -H2 O

Pb3 (CO3 )2 (OH)2

X X X X

X

X

X X X X

X X X

3.4. Red mastic (letters) The red mastic appears brittle, and the freshly exposed surface (after the sampling) shows a slightly lighter red hue, as well as a bright red luminescence upon UV illumination (395 nm). Traditional pigments such as vermillion and minium can darken upon exposure to humidity, light, chloride species, oxidising or alkaline substances [51]. Moreover, many red pigments, both traditional and modern, fluoresce in various shades of red [58], so that these observations are not diagnostic. Sample SG-R3 was chosen for XRD analyses. The powdering was hampered by the texture of the material, which indicates the presence of organic binders. The diffractogram (Fig. 6) allowed to identify calcite, minium (Pb3 O4 ), barium sulphate and hydrocerussite. Of these materials, one imparts the red colour, with lead white adjusting its shade, while the others are likely to be present as mineral charges (barium sulphate and calcite). The observation under the Raman microscope allowed to identify some white and black specks. Raman spectra were collected on the three samples, on both sides (i.e. the side in contact with the rock and the flat side corresponding to the sculpted surface). Vibrational spectra confirmed the XRD results (a representative extended Raman spectrum is reported in Fig. 9): calcite (Raman [28,29]: 1087, 713, 281 cm−1 , IR [30]: 873 cm−1 ), gypsum (IR [30]: 1117, 669 cm−1 ), cerussite (Raman [28,29]: 1054 cm−1 , IR [30]: 679 cm−1 ), minium (Raman [28,29]: 549, 122 cm−1 , IR [30]: 679 cm−1 ). Raman spectroscopy indicates an additional leadcontaining compound, that is massicot, as indicated by the bands at 275 and 137 cm−1 [28,49,50]. This compound is naturally associated with minium and it was used as a pigment on its own, but it could also be a degradation product of lead-containing pigments [51,59]. As no black material could be identified in the low range spectra, high-range Raman spectra confirmed the presence of carbon black (1590 and 1310 cm−1 ) [28,53]. Moreover, a series of features pointing to a synthetic pigment appeared (for the relative

PbCO3

Orthorhombic PbO

X X

X X X

Pb3 O4

Disordered C

BaSO4

X

X X X

X X X

PR49:1

Organic matter

X

X X X X

intensities symbology refer to [60]): 1614m, 1599m, 1556m-w, 1480s, 1463m, 1447m-w, 1421m-s, 1411m-s, 1347m, 1255m-w, 1230m, 1212 s, 1203vs, 1135w, 1096m-w, 1047w, cm−1 [61–65]. The best correspondence is with PR49:1, which also explains all the bands in the low range: 988s (with contribution from the barium sulphate [52]), 720vs, 645m-w, 602m, 542m, 528m-s, 410m-s, 302m-w cm−1 [64,66]. Finally, also here the IR bands at 2916, 2849 cm−1 , compatibles with an oleic binder, are present [30]. The red colour is obtained by a combination of a traditional pigment, minium, with a synthetic one, PR49:1, mixed with some extenders (calcite, barium sulphate) and other pigments (lead white, massicot) (Table 3). The successful identification of the red pigments was achieved thanks to Raman spectroscopy [61–64,67], while none of the diffraction peaks of PR49:1 indicated in literature could be seen in the diffractogram [68,69], nor in the FT-IR spectra. This could be explained by the fact that synthetic organic pigments are poor diffractors and are finely grinded [69,70]. Moreover, as they have good tinting strength, small amounts of pigment powders are diluted in a mixture including extenders and fillers, such as barium sulphate [69,70], so that their percentage may be very low. From the chemical point of view, PR49:1 is a lithol red and belongs to the sulphonated azo pigments. The molecule, patented in 1899, is obtained by the coupling of 2-naphtol and Tobias acid, neutralised by a counter-ion, in this case Ba, which makes the red hue slightly bluish [68,71–75]. Lithol reds are lakes, which originally were precipitated onto an inorganic carrier (e.g. barium sulphate [54]), but later the dried salts were used as pigments as well [63,71]. The identification of barium sulphate, confirmed by all the techniques, is likely related to the use of a precipitated lake, and to the use of extenders to improve the quality of the paint [54]. The main application for lithol reds has always been in the printing industry, for its properties of brightness, bleed resistance and low price [62,65,71,75]. Non-print applications encompass the plastic and paint industries. Durability was thought to be good in

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Fig. 9. Raman extended-range spectra of the red mastic SG-R3: 60 seconds, 2–5 accumulations. The bottom spectrum PR49:1 KIK IRPA is part of [64]. Ba: barium sulphate; Ma: massicot; Mi: minium.

the 1930s [72,76], but in the 1970s the pigments were used for student grade artists’ materials as their lightfastness appeared not to be optimal [71,75]. In fact, the poor lightfastness of these pigments is problematic from the conservation point of view, as especially highlighted by the cases of Mark Rothko’s Seagram (1958–59) and Harvard (1962) murals [70,71,77]. Table 2 overviews the occurrences of lithol red pigments in lithographic and painted artworks. The identification of PR49:1 in a mastic likely dated to the 20th century indicates an early use of the pigment as such, as well as an innovative use of this pigment, traditionally and widely employed for lithographic works. The identification of modern materials, such as PR49:1, as well as barium sulphate, in red and black mastics, is of particular significance for the purpose of dating and authenticating the sculpture of Saint-Germain-en-Laye. In fact, historical information on barium sulphate, found throughout the studied samples, indicates its extensive use in watercolours, as well as the development of a lake support in the US during the 19th century. It has to be noted that in 1950 barium sulphate was still used as a pigment (lithopone, blanc fixe, permanent white) and as a base for lakes [54]. Moreover, as the patent for the lithol red molecule was deposited in 1899, it poses a clear term post quem for the red mastic. Furthermore, seen the homogeneity of the polychrome decoration of the sculpture, and also considering that each sample is homogeneous on its surface and on the inside, it seems likely that the red and black mastics were applied all in one time, and not to restore a previously existing one, of which no trace could be found. The combination of PR49:1 patent (1899) with the oral testimonies (last trip to Italy of Mr. Duperrier in 1924) allows to define a limited timeframe for the creation of this stunning masterpiece, that is 1899–1924. If, on the other hand, the information in the donation letter is considered (sculpture in possession of the family since at least 1914), an even shorter timeframe can be put forward: 1899–1914. Seen the initial hypotheses, and the interdisciplinary research conducted, the chemico-physical information is a meaningful clue to place the creation of this work of art in the 20th century. Actually, in those years the activity of Alceo Dossena (Cremona 1878–Rome 1937) flourished [78]. He worked in an atelier in the Cathedral’s square in Parma between 1908 and 1912: he was active as a sculptor, producing high-quality imitations of ancient works, as well as original creations “in the style of”, which would later have caused him judiciary troubles, and his reputation as forger [3,78].

The production of Dossena is well known after the process of 1928, when he started signing his sculptures, but his earlier works are not documented. However, Ludwig Pollak (Prague 1868–Auschwitz 1943), who worked in Rome as a museum director and art critic, mentions in his diaries that Dossena, during his early career in Parma (1908–1912), had copied ancient masterpieces, such as the Deposition from the Cross by Antelami [79]. This historical record, which seems to point to Alceo Dossena as the author of the Deposition in Saint-Germain-en-Laye, is coherent with the chronological information gathered from oral testimonies and archaeometry, as well as with the utilitarian choice of materials used in the mastics.

4. Conclusions and perspectives The combination of archival, historical, art historical research with archaeometrical investigations on the material aspects of a sculpture attributed to the 12th century, finally allowed the definition of a modern timeframe (1899–1924 or 1899–1914) for the creation of the haut-relief. Further interdisciplinary research on the mysterious artist(s) and commissioner(s) behind this notable masterpiece benefitted from the chemical analysis, in the sense that the focus on the first quarter of the 20th century, allowed a targeted study of the artistic panorama in Parma, where the sculpture was likely executed, and to possibly identify the Deposition in Saint-Germain-en-Laye with the one attributed to Alceo Dossena by written sources, sculpted between 1908 and 1912.

Acknowledgements The authors thank the parish of St-Germain-en-Laye, Christian Barthe (Arts, Cultures et Foi) and all the participants to the “Symposium Bas Relief Antelami” for financial and logistic support through a crowdfunding action, as well as for the fruitful discussions. The heirs of the family Duperrier, namely Gérard Pages, are greatly thanked for their support in reconstructing the history of the sculpture; Hugues de Bazelaire for his help in the sampling process and for the identification of the rock; Prof. Marco Horak for the exchanges about Dossena; Ana Maria Cardoso for support in interpreting the FT-IR spectra. This research did not receive any specific grant from funding agencies in the public, commercial or non-for-profit sectors.

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