Fragment of a panel painting rendering female bust(s), winged griffin, and two minor deities.

Summary

The fragment described here is the left part of a panel painting. Two adjoining boards of different widths are preserved, and assembled vertically. In the top register of the panel, human figures can be seen that are preserved in their entirety, including a man with a double axe, a griffin of Nemesis (facing towards the centre of the painting), and the remains of what are identified as the busts of two female characters.

Description of object

This fragment constitutes the left part of a panel painting. Two adjoining boards of unequal widths are preserved, assembled vertically. The board to the right is preserved in its entire height and width, while only the upper and right part of the left board is preserved. Along the preserved part of the painting to the left and along the upper edge is an unpainted band, corresponding to the original frame, which is now lost. Two pegs, oriented at a 45-degree angle are preserved in the right side of the right most board, attesting to the attachment of a third board to the right (now missing).

The paint is very flaky and has disappeared from a large part of the central part of the panel, which makes it difficult to understand the original iconography. Overall, the composition renders a bust, probably of a woman/female character centrally placed in the panel, accompanied by two secondary/smaller deities placed in the upper left corner. The background is light grey.

In the top register of the painting are depicted to human figures, preserved in their entirety. To the left is a male figure holding a double axe and to the right a female figure, represented in s smaller scale. The man with the double axe is depicted frontally with his feet shown in profile as if he is walking. He is clad in a long-sleeved yellow tunic, which reaches to just above his knees and belted at the waist. The tunic is decorated with borders (some of them light grey in colour) at the biceps, wrists, and two horizontally above the knees. He wears light grey, tight trousers underneath the tunic as well as ankle-length black boots/shoes. Finally, he wears a pink mantle fastened on his right shoulder, reaching until his mid-calves. His left arm has largely disappeared, but he holds a thin, black staff (a spear?) in his left hand, which is partly preserved. The right arm is bent, and he holds a double axe, which rests on his right shoulder. His face is broad, and he has black hair and beard, which is rendered as a dark band encircling his lower face and accentuated with black accents representing curls. Finally, he wears a wreath, which is still visible at his right temple. The presence of a wreath is confirmed by the fillets (dark lines) visible on both sides of the neck. Moreover, a light grey area/shape around the left side of his head could indicate the presence of a sort of head covering, possibly a pointed cap with side “flaps” (Rondot 2013, x). Yet, this light grey colour is not visible at the right side of his head, which makes this interpretation unlikely.

In the mid-register is the griffin of Nemesis, facing towards the centre of the painting. Only parts of the griffin are preserved, including the head, beak, neck, some of the back, the udders under the belly, part of the right hind leg as well as most of the wings. The body of the griffin is light beige, the wings are dark blue, while the outlines of the beak, udders, and the hind leg is rendered in black.

At the lower register of the painting are the remains of what is probably the busts of two female characters, placed offset from each other, one behind and above the other. The upper most bust is recognisable from the right shoulder. She is clad in a pink tunic with a grey clavus. Above, to the right of the two minor figures in the top register are the remains of her hairdo, with visible strands of black hair arranged in a bun. Just below her hair is a preserved patch of skin colour, probably of her chin or earlobe.

Just below this bust is possibly another bust, also only recognisable from the right shoulder. She is dressed in a similar pink garment but decorated with an additional white fringe at the neckline.

Moreover, she wears a gold necklace in two, twisted rows. Alternatively, it is also possible that this part of the painting renders the arm of a female bust, clad in a pink garment with a white fringe, and that the gold jewellery is rather an armband.

Most of the central part of the painting has been lost, and thus only parts of the female bust(s) in the centre of the painting are discernible, which makes a certain identification of the subject impossible, although it is most probably a goddess. In contrast, the two figures in the top left corner are well-preserved enough to allow a tentative identification. The male figure to the left holds a double axe and is dressed in military garb. He is probably one of the armed gods, rendered in several other panel paintings in the corpus of Roman Egyptian panel paintings (Rondot 2013, 317-318). The god might be Heron. This military god was imported into Egypt from Thrace or the Near East in Ptolemaic times and is often depicted in contemporary Egyptian painting, sometimes together with the griffin of Nemesis as in ÆIN 711.8 The smaller female figure to the right of the armed god has a lunar crescent above her head, which might indicate her status as a goddess, but a firmer identification is not possible.

Choice of methods

Visual examination

• Macroscopic

Technical imaging

• UV
• VIL
• IR
• Raking light

Sampling

• Cross section
• Microscopy
• XRF
• FT-IR
• UV-VIS
• Raman
• Radiocarbon (14C) dating, wood analysis, shotgun liquid chromatography tandem mass spectronomy.

Technical imaging

Multispectral imaging was performed with a modified Canon EOS 5D Mark IV camera body and a Canon EF 50mm f/2.5 Compact Macro lens. The following filters were used for image acquisition: XNite CC1 from MaxMax.com for visible light photography (VIS), XNite CC1, PECA 916, and Tiffen Haze 2E for ultraviolet induced visible fluorescence imaging (UVF), as well as a Schott RG830 for infrared photography (IRR) and visible light induced infrared luminescence imaging (VIL). A Midwest Optical Systems BP324 filter in combination with XNite CC1 yielded ultraviolet reflectance (UVR) images. The subtraction of an image at 635 nm shot with a Midwest Optical Systems BP635 filter from one at 735 nm (Midwest Optical Systems BP735) uncovered information about the presence of indigo as described by Webb et al 2014 and Bradley et al. 2020. For this imaging mode the abbreviation MBR (multi band reflectance image subtraction) is used. Light sources employed were incandescent tungsten lamps in combination with soft box diffusers, Excled LED RGB lamps (470 nm, 525 nm, and 629 nm), and Hoenle UVA SPOT 400/T lamps filtered with a Schott UG2A glass. The X-Rite Color Passport 2, Target-UV™ from UV Innovations, and a 99% Spectralon® diffuse reflectance standard were included in all images.

Other types of investigation

Fourier transform infrared (FTIR) spectroscopy

FTIR spectra were recorded with two different instruments. At the Center for Advanced Bioimaging (Copenhagen University), the samples were flattened onto a diamond window and analyzed in transmission mode between 600 and 4000 cm−1 using a Nicolet Continuum infrared microscope (Thermo Fisher Scientific Inc., Waltham, Massachusetts, U.S.) equipped with a liquid nitrogen cooled mercury cadmium telluride detector. The collected spectra were compared with reference libraries for compound identification.

Raman spectroscopy

For Raman measurements two spectrometers were also involved. In Copenhagen, at the Center for advanced Bioimaging (University of Copenhagen), the spectra were acquired on scrapings with an alpha300R Confocal Raman Microscope (WITec Oxford instruments, Ulm, Germany) equipped with two lasers emitting at 532 nm and 785 nm, respectively. The excitation laser power was on the order of 1 to 5 mW. A Zeiss EC Epiplan-Neofluar 50x lens and 300 and 600 g/mm gratings were used. The data was processed with WITec Project Five software, version 5.0.15.55, and compared with reference spectra. Raman spectroscopy on the cross sections was carried out in Boston. The different layers in several sections were examined with a DXR3 Raman microscope (Thermo Fisher Scientific Inc., Waltham, Massachusetts, U.S.), operated by Thermo OMNIC for Dispersive Raman software version 9.12.1002. All analyses from Boston were carried out with a 785 nm laser, 25 μm pinhole aperture, and 50x objective giving a spot size of approximately 1.0 μm. The standard grating that was utilized acquires data in the range 3374-32 cm-1, with resolution between 2.3 and 4.3 cm-1. Number of scans, scan time, and laser power were adjusted for each acquisition.

X-Ray Fluorescence (XRF) spectroscopy

XRF spectra were acquired with a handheld Tracer 5i XRF spectrometer equipped with a Rhodium tube (Bruker, Billerica, MA, USA). Two measurements at 15kV, 15 µA, with no filter and 40 kV, 7 µA, with a Ti/Al filter were taken for each location optimizing the detection of low and high Z elements, respectively. The data was processed with the Bruker Artax software Spectra, Version 8.0.0.476.

X-Ray Diffraction (XRD)

XRD data were collected using a PanAlytical Empyrean diffractometer equipped with focusing mirrors for Cu Kα radiation (λ = 1.541 Å) and a capillary spinner 8 (Malven Panalytical, United Kingdom). A Ni beta filter and a pair of 0.04 rad soller slits were used. The sample was ground in an agate mortar, placed in a 0.3 mm diameter quartz capillary, mounted on a rotating stage and measured in transmission geometry. Evaluation of the spectra and phase identification was carried out with the software X’Pert Highscore Plus v.4.8 (Malven Panalytical, United Kingdom) using the ICDD PDF 4+ database. Rietveld refinement was performed using the software TOPAS v.6 (Brucker AXS, Karlsruhe, Germany) with reference structures for Gypsum (ICSD 000210816), Anhydrite (ICSD 000371496), Bassanite (ICSD 010742787), Calcite (ICSD 000050586), Alunite (ICSD 010759141). Atomic positions and stoichiometry were fixed, while lattice parameters, average crystallite size and scale factors were refined.

Cross sections and microscopy

Samples for cross sectional analysis were mounted in Technovit 2000 LC resin (Kulzer Technik, Wehrheim, Germany) cured with blue light (Technotray Power, Kulzer Technik, Wehrheim, Germany). A two-step process was used for including a label resulting in 8 mm diameter cylinders. The final polishing was executed on an EcoMet 30 manual twin from Buehler (Lake Bluff, IL, USA) with 6 μm and 1 μm diamond suspension. Images of the polished cross sections were recorded with a Leica research microscope (Leica Microsystems GmbH, Wetzlar, Germany) in bright field mode with crossed polarizing filters and under UV illumination detecting the induced visible fluorescence.

Scanning electron microscopy (SEM) coupled to energy dispersive x-ray spectroscopy (EDS)

Cross sections of the paint samples were examined without carbon coating in a JEOL JSM-IT500 low-vacuum SEM (JEOL, Tokyo, Japan). The instrument was operated at 20 kV, with a beam current of ca.1 nanoampere. The chamber pressure was set at 50 Pa. EDS analyses were carried out with an Oxford Instruments X-MaxN spectrometer with 80 mm2 detector area, operated by Oxford ‘Aztec’ software, version 4.2 (Oxford Instruments, Abingdon, United Kingdom). The measurements included back-scattered electron images, individual point analyses, EDS maps, and line scans.

Shotgun liquid chromatography tandem mass spectrometry

The sample was processed, along with a protocol blank, following the protocol described in Mackie et al. (2018)1. Briefly, protein residues were extracted from the sample using a lysis buffer, and enzymatic digestion was performed with LysC and Trypsin. The resulting peptides were immobilised on C18 Stage-Tips and analysed by nano-liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS). The MS/MS spectra were identified with the MaxQuant software, matching them against a reference database containing all the publicly available sequences of proteins contained in the most common proteinaceous artistic materials: collagens, egg proteins, and milk proteins. In order to investigate the presence of protein residues originating from other sources, the spectra were then matched against a larger database (SwissProt, from UniProt), containing all publicly available and manually reviewed protein sequences. The matches were against fully tryptic peptide sequences, with no taxonomic restriction.

Proteins are considered confidently identified if at least two unique non-overlapping peptides are observed, unless otherwise specified. Peptides were considered species-diagnostic when, after BLAST search against the entire nrNCBI protein database, they were assigned to a single species, or to a limited number of species among which only one can be considered plausible, based on: (i) the nature of the samples, (ii) the geographic origin of the sample, and (iii) the dating of the sample. Peptides assigned to recurrent contaminant proteins were filtered out and not considered further. Contaminants include primate keratins (likely from the laboratory space or through human handling of samples), excess trypsin, and Bovine Serum Albumin (a common laboratory reagent)

Wood analysis

Because of the three-dimensional nature of wood anatomy, each tiny wood sample, irrespective of its size, was fractured manually to show transverse, radial longitudinal, and tangential longitudinal sections (TS, RLS and TLS). Each TS, RLS and TLS wood section was then mounted, uncoated, onto aluminum stubs. Examination of the wood samples and comparative reference specimens prepared and mounted using the same method was undertaken in a variable pressure scanning electron microscope (VP SEM), Hitachi S-3700N, using the backscatter electron (BSE) detector at 15 kV, with the SEM chamber partially evacuated (40 Pa). Magnifications ranged from x65 to x650. The preferred working distance was circa 14 mm but was raised or lowered from 11.1 mm to 15.7 mm as required. With the BSE detector, 3D mode (rather than Compositional) was preferentially selected to maximize the opportunity to reveal diagnostic features for identification. These details, along with the scale bar in microns (μm) can be seen on the data-bar on each of the three SEM images in the Results section. Further details on wood identification methods and techniques can be found in Cartwright 2015 and Cartwright 2020.

Radiocarbon (14C) dating

14C measurements of the panels and the organic binder were conducted at the Laboratory of Ion Beam Physics (LIP) at ETHZ (Switzerland). The wood samples underwent first a Soxhlet extraction (Bruhn et al. 2001) for removal of conservation treatments, which consisted of consisted of a round of 3 solvents starting with hexane (60°C, 1h), acetone (55°C, 1h) and ethanol (65°C, 1h). After which, the cellulose content of the wood was extracted by applying a modified base-acid-base-acid-bleaching method for cellulose extraction (Němec et al. 2010; Brehm et al. 2021) as follows: 1M NaOH (60°C, overnight), 1M HCl (65°C, 30’), 1M NaOH (65°C, 1h), 1M HCl (65°C, 30’), before being bleached with NaClO2 5% +0.1 ml 0.5M HCl (70 °C, 45’) and freeze-drying overnight. The selected paint material was chosen following an already established workflow (Hendriks et al. 2018), which highlights the need to characterize all paint components and ensure the presence of inorganic pigments only. The selected paint samples were cleaned by an acid wash (0.5M HCl, 60°C, 30’).

Bibliography

References: Rondot 2013, 149-151, 317-8; Parlasca 2004, 329, n. 12 + p. 332, fig. 9; Schmidt 1899, 415, no. A499; Schmidt 1908, 640-641, no. E816.