St. Joseph with the Child by Gian Lorenzo Bernini: A definitive artwork or a preparatory drawing? A multidisciplinary study of the only autograph painting of the Artist, preserved at Palazzo Chigi of Ariccia (Rome)1
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St. Joseph with the Child” by Gian Lorenzo Bernini: A definitive rtwork or a preparatory drawing? A multidisciplinary study of the nly autograph painting of the Artist, preserved at Palazzo Chigi of riccia (Rome)
artina Romania, Lucilla Pronti a,∗, Marco Sbrosciab, Francesco Petrucci c, mbretta Tarquinid, Gianluca Verona-Rinati e, Maria Antonietta Riccib, Armida Sodob, arcello Colapietrod, Marco Marinelli e, Augusto Pifferid, Mariangela Cestelli-Guidia
INFN-Laboratori Nazionali di Frascati, via Enrico Fermi 40, 00044 Frascati, Italy Dipartimento di Scienze, Università degli studi Roma Tre, Via della Vasca Navale 84, C.N.R., I-00146, Italy Palazzo Chigi, Piazza di Corte, 14, 00040 Ariccia, (Rm), Italy Istituto di Cristallografia – Area della Ricerca Roma 1, Via Salaria Km 29300, 00015 Monterotondo Roma, Italy INFN-Dipartimento di Ingegneria Industriale, Università degli Studi di Roma Tor Vergata, via del politecnico 1, 00133 Roma, Italy
a r t i c l e i n f o
rticle history: eceived 31 January 2020 ccepted 5 August 2020 vailable online 11 September 2020
a b s t r a c t
The artwork “St. Joseph with the Child”, preserved in Palazzo Chigi of Ariccia (Rome), is today the only paint- ing signed by Gian Lorenzo Bernini. In this work, for the first time, an integrated spectroscopic imaging and analysis approach was performed to study and characterize Bernini’s wall painting. Complemen- tary in situ analyses, imaging in the UV–VIS–NIR–SWIR range, FT-IR spectroscopy, Raman spectroscopy,
eywords: ian Lorenzo Bernini all painting ultispectral Imaging
laser-induced fluorescence and XRF were performed to obtain information on the state of conservation, the execution technique and the composition of the materials of the painting investigated. The results achieved were discussed and delivered to the conservator of Palazzo Chigi, to plan further restoration treatments and conservation programs. In conclusion, preliminary considerations are presented to define
prese
. Introduction
The mural painting “St. Joseph with the Child”, executed by Gian orenzo Bernini in 1663 for the chapel of Palazzo Chigi di Ariccia Rome, Italy), still represents one of the most studied works in the eld of cultural heritage [1], as it is the only signed work of the rtist [2].
Considering the great importance of the painting, for the first ime a dedicated and detailed diagnostic plan was performed, using n integrated approach of imaging and spectroscopic analysis.
Our approach is focused on the characterization of Bernini’s xecution technique, and in particular to try to resolve the ques- ion related to this painting if “Saint Joseph with the child” can be
onsidered a definitive artwork or represent a preparatory drawing.
Should be mentioned, that the results obtained from the iagnostic investigations cannot give a definitive answer to this
∗ Corresponding author. E-mail address: lucilla.pronti@lnf.infn.it (L. Pronti).
https://doi.org/10.1016/j.culher.2020.08.003 296-2074/© 2020 Elsevier Masson SAS. All rights reserved.
nts a definitive painting or a preparatory drawing. © 2020 Elsevier Masson SAS. All rights reserved.
question, but they can provide important information on the exe- cution technique, the materials used, which can be useful to art historians for their consideration in this regard.
To this end, the presence of “pentimenti” and preparatory drawings was studied using IR reflectography, while the state of conservation of the materials, due to previous restoration treat- ments, was studied by UV fluorescence [3,4].
Starting from the imaging results, spectroscopic analyses (FT-IR, Raman, XRF and LIF) have been used to provide the molecular and elemental characterization of the materials used by the artist [5,6].
2. Materials and methods
2.1. “St. Joseph with the Child” by Gian Lorenzo Bernini
The mural painting studied in this work was created using
different execution techniques, intermediate between drawing and painting. Indeed, it realized directly on the rough plaster and presents elements made with sanguine, gouache paint and chiaroscuro effects obtained with the help of the fingers. The frame
F ting b U
2
( a o l b r
ig. 1. (A) The painting “St. Joseph with child”, (B) Photo rendering of Bernini’s pain VF image, (C) LIF measurement’s position.
round the painting was made in plaster painted as “fake marble” in 771 by Luigi Baldi on commission from Prince Sigismondo Chigi. B.A.V., A.C., n. 20794).
The inscription, in the lower part of the painting (Fig. 1A), estab- ishes the date of its realization (1663) and confirms the autograph nequivocally characterized by the stylistic evidence of the author: EQVES IO LAVRENTIVS BERNINVS FAC: YEAR DNI MDCLXIII”.
.2. In situ analyses
To study the state of conservation of the analyzed surface, razing light was performed. Then multispectral imaging, in the V–VIS–NIR–SWIR range, was performed to verify the presence of
ynthetic consolidants, the conservation state of the materials used n previous restoration treatments, the behavior of the materials in he selected spectral range and the presence of under drawings. inally, to spectrally characterize the pigments used by the artist, n integration of molecular and elemental spectroscopic analyses FT-IR, Raman, XRF and LIF) was performed.
.2.1. Grazing light The study of the pictorial surface through the observation in
razing light was performed by illuminating the sample on one ide using a halogen lamp with angles of incidence at 20 to the ormal analyzed surface.
Multispectral Imaging in the UV–VIS–NIR–SWIR range: The ultispectral imaging in the UV–VIS–NIR was performed by using
NIR converted camera (Nikon D7100) equipped with a long pass lter at 1000 nm (Edmund Optics).
To record image in the SWIR range was used an IR camera XENICS “Xeva-1.7-640”) equipped with an InGaAs sensor oper- ting between 900 and 1700 nm. The VIS-SWIR acquisitions were
btained by using two halogen bulbs while for UV analyses an UV amp (370 nm) was used. A radiometric calibration was performed y using a diffuse reflectance standard a spectralon withe diffuse eflectance standard by Edmund Optics).
efore the restoration treatments, (C) VIS image obtained by using grazing light, (D)
2.2.2. Mid-IR portable spectroscopy In situ analyses were carried out using the portable ALPHA-R
FT-IR spectrometer (Bruker Optics) equipped with a DTGS detector (7500–360 cm−1), using 4 cm−1 of resolution and 32 scans.
2.2.3. Raman spectroscopy Raman spectroscopy has been applied for in situ investiga-
tions using a Renishaw In-Via Reflex micro-Raman spectrometer equipped with a solid state diode laser source (785.5 nm). Excita- tion light has been driven to the sample by an optical fiber and focused using a portable Renishaw head equipped with a 20× objective and a color video camera. Backscattered light has been collected by the same objective and driven to the spectrometer through a second optical fiber, coupled to a Leica 10× objective mounted on a DMLM microscope. An edge filter provided rejec- tion of elastically scattered light. The inelastic contribution has then been dispersed by a diffraction grating with 1200 grooves/mm and recorded by a Peltier cooled 1024 × 256 pixel CCD, to reduce dark counts. Spectral range of 100–4000 cm−1 has been accessed with a spectral resolution of about 2 cm−1. To prevent radiation damage, laser power was set to 20 mW. To achieve suitable statistics, two to five accumulations of 10 s each have been collected. Renishaw Wire 5.2 software has been used for spectral collection and elaboration.
2.2.4. Laser induced fluorescence The system is composed of a pulsed laser with an excitation
wavelength at 266 nm. The pulse duration is about 2 ns with a rep- etition rate of 10 kHz. The laser beam is focused on an optical fiber driving the radiation to the specimen with a spot of about 300 m in diameter. The spot size on the sample is about 1 mm2. The investi- gated spectral range was 400–700 nm. To reduce the large number of variables of the acquired emission bands, the LIF data was ana- lyzed by means of principal component analysis (PCA) performed
on the first derivative spectra. A decomposition of the acquired spectral data into a linear combination of the original spectral data (PCs – principal components), was operated. In this way a reduced set of factors is produced. Then, using the PCs obtained from PCA
M. Romani et al. / Journal of Cultural Heritage 46 (2020) 283–288 285
F pectra L aman f
i w c
3
3
c e
m
ig. 2. (A) Principal component analysis obtained onto the first derivative of LIF s IF spectra of frame, (C’) first derivative spectra of frame, (D) FT-IR spectrum, (E) R orehead (FRG and FRG2).
t is possible to grouping samples with common spectral features hich tend to aggregate in the score plot of the first two or three
omponents [7].
.2.5. X-ray fluorescence The analyses were performed with tungsten (W) X-ray source,
Peltier cooled Silicon drift detector complete with its amplifier- eeder and multi-channel (Amptek MCA 8000A). The detector esolution is 140 eV at 5.9 keV (Mn K). The analyses were car- ied out by powering the X generator with a voltage of 38 kV and
current of 350 A. A qualitative analysis was performed in order o identify the elements at the points examined. The collected data ere analyzed with the PyMCA program.
. Results and discussion
.1. Monitoring of the conservation state
Considering the great importance of the investigated artwork, he first objective of this study concerned the characterization of ts conservation state. Specifically, we focused our attention on
onitoring the state of conservation (presence of fractures or inho- ogeneity), evaluating the effectiveness of previous restoration
reatments over time, assessing the presence of a possible biological ttack and/or humidity.
It is known that the Bernini’s wall painting was object of a
onservative restoration treatment in 1998, in the occasion of the xhibition “L’Ariccia del Bernini” [8].
As documented in the restoration schedules, conservative treat- ents involved filling the cracks on the painted surface. These
, (B) LIF spectra of red pigments, (B’) first derivative spectra of red pigments, (C) spectra, (F) LIF spectra of two areas: Child’s arm (FR0 and FR1) and St. Giuseppe’s
cracks were caused by a window underneath the artwork, which was closed during the restoration to avoid future damage. An improvement in the rendering of the cracks, in the features of Bernini’s drawing and signature, was carried out on a photo acquired before the restoration (Fig. 1B).
A comparison of this photo with the one acquired in the VIS spectral range, obtained by the grazing light observation, showed an amplification of the three-dimensional aspects of the surface (Fig. 1C). It has been noticed that the surface is rather uneven and has some cracks. Therefore, some previously filled cracks seem to have repeated since the grazing light produces shadows in certain areas (baby’s arm, calf, and ribs). This means that monitoring the pictorial surface, simply by using grazing light, is highly recom- mended to supervise their behavior over the years.
The UV fluorescence image (Fig. 1D) showed the presence of three different colors of fluorescence (purple, blue and green), sug- gesting the presence of at least three different materials. The first (purple) is found on almost the entire surface of the background preparation layer, the second (blue) appears to be located in dark shades, while the third (green) is mapped to specific areas corre- sponding to some healed crack (i.e. the arm of the Child) and around Bernini’s signature.
From the literature [9,10] it is known that calcite has a fluo- rescence emission in the violet-blue spectral range, while gypsum in the green one, the presence of these colors in the fluorescence image, could be attributable to the presence of such materials.
However, since the color of the fluorescence could be influ- enced by the sensitivity of the human eye, LIF spectroscopy was performed in some selected areas shown in Fig. 1E. The results obtained were analyzed by the analysis of the main com-
286 M. Romani et al. / Journal of Cultural Heritage 46 (2020) 283–288
tail o
p s
a t t T a i f p t s t d t
( o m s
a a a i F t
Fig. 3. (A) VIS image, (B) IRR image at 1000 nm, de
onents (PCA) in order to find areas with similar fluorescence pectra.
The scores plot (Fig. 2A) shows some groups of data. All the red reas analyzed are grouped in the blue circle, but a point related to he Bernini signature (FM) is the only red pigment different from he others; indeed, in the PCA it seems to be separated from them. his behavior is also observed in the fluorescence spectra (Fig. 2B) nd in its first derivative (Fig. 2B’) in which the spectral signature s different from the other red pigments. However, considering the act that in this case, we are not able to uniquely characterize the igments of the signature only by observing the LIF spectra, fur- her analyses were performed such as IR reflectography and Raman pectroscopy in order to understand if the different behavior spec- ral observed (for the point called “FM”) is due to the use of a ifferent pigment for the signature or to a greater contribution of he background.
As for the fluorescence spectra relating to the marble frame Fig. 2C), all the points analyzed, acquired on three different areas f the surface of the frame and named as C0, C1 and C2, showed a aximum band at about 520 nm, also confirmed in the first derived
pectra (Fig. 2C’). The PCA scores of C0 and C1 correspond to areas character-
zed by a similar color rendering in the UVF image (1D), while C2 as acquired in a dark area of the UVF image, with low fluores-
ence emission, as shown by its minor intensity in the spectrum mission.
These spectral features could be attributed to plaster [9,10]. This spect confirms what is reported in the conservative schedule of the rtwork, produced by the Conservator of Palazzo Chigi. Other points
re distinguished into two groups which present different spectral ntensity (400–480 nm); the representative spectra are shown in ig. 2F. This behavior could be related to mixtures of compounds hat we are not able to clearly identify due to that fact that fluores-
f the VIS image (C) detail in the InGaAs image (D).
cence emissions of heterogeneous materials could be influenced by subtractive and additive effects (quenching) [10].
To overcome these limitations, FT-IR and Raman analyses were performed (Fig. 2D and E). FT-IR spectra have detected the presence of bands at 1410, 880, 720 cm−1 related to calcite, and the ones of gypsum 1150, 1620, 3330–3500 cm−1 [10]. These results were confirmed by the Raman spectra collected in the same area that identified a mixture of calcite (157, 282, 711 and 1086 cm−1) and gypsum (178, 412, 491, 617, 670 and 1006 cm−1) [11,12].
At this point, it was possible to say that the composition of the preparatory layer is a mixture of calcite and gypsum.
For the scope of this work, the identification of gypsum is extremely important because it could cause the deposition of sul- phates which, if not checked, could cause esthetic and mechanical damage to the surface [13]. Therefore, a spectroscopic characteriza- tion of its state of conservation is recommended to prevent possible future damage.
3.2. Characterization of the drawings
At this point we focused on the characterization of the materials used by the artist for the realization of the mural painting. The pur- pose of these analyses was both to characterize the chemical nature of the pictorial materials, in order to preserve them correctly, and to try to understand if the work had been conceived as it appears or if it was a preparatory drawing.
Since the drawing is realized with a red pigment, it is possible to assume its partial or total transparency in the IRR images (Fig. 3B and D). However, this characteristic spectral behavior did not occur
here. This suggests the presence of an underlying drawing made with an IR opaque material, such as carbon-based compounds, or the use of a material in which an IR opaque compound is mixed with an IR transparent one. To solve this problem, an elemental
M. Romani et al. / Journal of Cultural Heritage 46 (2020) 283–288 287
F analy ( and
a b p t t p
r o r b a w
R s g n u C a h I t f b l p c
fi a t b a J
ig. 4. (A) In situ acquisition with the Raman spectrometer, (B) magnification of the D) magnification of the analyzed black pigment, (E) Raman spectra of amorphous C
nd molecular characterization of the pigments was performed y XRF and Raman spectroscopy. XRF measurements showed the resence of calcium and sulfur, due to the preparation layer, while he presence of strontium, could be related to gypsum [14], finally he presence of iron is indicative of the use of a of an iron-based igment.
As a matter of fact, the main drawing was made using a bright ed pigment that appears compact and homogeneous under the ptical microscope (Fig. 4A and B). Moreover, Raman spectra from ed areas reveals the use of high purity hematite identified by the ands at 226, 293, 405, 497, 602, 1300 cm−1 (Fig. 4C) [11]. From the nalysis of these materials, the execution techniques result in line ith that foreseen for a sanguine [15].
Since the artwork is characterized by a fine use of “chiaroscuro”, aman spectra were acquired also onto gray areas: these show the pectral signature of amorphous carbon [16] along with calcite and ypsum, revealing the use of a charcoal pencil. Interestingly, this is ot the only allotropic form of carbon found. Indeed, a black stroke nderneath the red layer was identified, close to the belly of the hild. Under the microscope, it resulted highly compact, suggesting
higher spatial ordering of atoms. (Fig. 4D and E) This suggestion as been confirmed by Raman spectra of this black layer (Fig. 4E).
ndeed, the Raman spectrum shows the fingerprint of graphite with he sharp G band (E2g symmetry) characteristic of this ordered orm of carbon, centered at 1580 cm−1 [17], superimposed onto the roader charcoal spectrum. On the other hand, we can exclude any
aser induced graphitization, since this process is activated at tem- eratures much higher than those accessible in our experimental onditions.
Considering the high purity of the red pigment and the identi- cation of a carbon-based material, we confirm that two drawings re superimposed: one realized with carbon pigment (prepara-
ory drawing) and one with hematite. This finding is very peculiar, ecause sanguine usually represents a preparatory drawing itself, nd more important this result supports the hypothesis that “St. oseph with Child”, could be considered a finished artwork.
zed red pigment obtained by optical microscope, (C) Raman spectrum of hematite, graphite.
3.3. Bernini’s signature
Finally, the pigment used for the Bernini’s signature is analyzed and spectrally characterized.
The UVF image showed an area characterized by both green and blue emissions, while the Raman spectra collected in the white background close to the inscription revealed the almost total absence of gypsum.
Furthermore, an intense fluorescence background prevents the collection of informative Raman spectrum of the pigment, despite its high concentration compared to that of the main drawing.
Our hypothesis is that this pigment is probably an iron oxide- based mineral, but not as pure as the one of the main drawing, considering that coarse ochres are weak Raman scatterers. This hypothesis is confirmed by considering the IRR (Fig. 6B), where in the SWIR (Short Wavelength IR) range the pigment showed a dif- ferent behavior, resulting opaque in this range respect to the one of the drawing.
4. Conclusion
In this paper, the artwork “St. Joseph with Child”, the only one signed by Gian Lorenzo Bernini and conserved at Palazzo Chigi of Ariccia (Rome), was characterized for the first time by using an integrated approach of imaging and spectroscopic analysis.
The integrated approach allowed to obtain a complete charac- terization of the analyzed artwork. In fact, observation in grazing light made it possible to characterize the state of conservation of the wall paint, while the absence of “pentimenti” and prepara- tory drawings were studied by IRR in the NIR and SWIR range. The conservation state of the materials used in previous restora-
tion treatments, were studied by using UV–VIS imaging analysis. Thus, spectroscopic analyses (FT-IR, Raman, XRF and LIF) have been used to provide the molecular and elemental characterization of the materials used by the artist.
2 ultura
t h c t w e a t m i
t o w r
A
88 M. Romani et al. / Journal of C
The obtained results allowed to establish that the preparatory ayer is composed by calcite and gypsum. As previous discussed, the dentification of gypsum is extremely important because it could ause the deposition of sulphates which, if not checked, could cause sthetic and mechanical damage to the surface.
Moreover, it was demonstrated that Bernini realized a prepara- ory drawing by using graphite and refined the drawing by using igh purity hematite and charcoal (amorphous carbon) for the hiaroscuro. This discovery strongly supports the suggestion of he conservator of Palazzo Chigi, according to which the art- ork showed a complete and autonomous character, allowing to
xclude the possibility that it was a true “sinopia” or trace for fresco. Finally, our analyses suggest that the inscription with he signature of Bernini was realized with different and less pure
aterials with respect to the red pigment used for the draw- ng.
All the results here discussed cannot give a definitive answer to he question if the studied painting represent a definitive artwork r a preparatory drawing, but they provide important information hich can be useful to art historians for their consideration in this
egard. This study was carried out within the ADAMO project, whose
bjectives included the application of diagnostic techniques for the onservation and restoration of cultural heritage in different sites in he Lazio region. The results presented here are part of a large cam- aign carried out at Palazzo Chigi of Ariccia. All the results obtained re now collected and delivered to the conservator of Palazzo Chigi nd could be used to plan future conservation strategies.
cknowledgments
The authors wish to acknowledge the Regione Lazio for founding he ADAMO project (2.10.2018–1.01.2020). The project is financed ithin the Center-of-Excellence (CoE) of the District of Technolo-
ies for Culture (DTC) by Regione Lazio. Thanks to the Arch. Francesco Petrucci (Conservator of Palazzo
higi of Ariccia) and Dr. Roberta Fantoni (ADAMO project coordi- ator).
Thanks to Dr. Fernanda Benetti (INFN-LNF) for her collaboration, r. Pio Alfonso Russo for technical support and Professor Mauro issori (leader of in situ measurements WP of ADAMO project). In situ Raman measurements were feasible thanks to the collab-
ration of Renishow S.r.l. and in particular to the helpfulness and echnical support of Dr. Riccardo Tagliapietra.
ppendix A. Supplementary data
[
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1 Introduction
2.1 St. Joseph with the Child by Gian Lorenzo Bernini
2.2 In situ analyses
3.2 Characterization of the drawings
3.3 Bernini's signature