A Multi-disciplinary Analysis of the Portrait of Philip the Good in Dijon

VIS-NIR multispectral reflectography When analysing the multispectral cube, particular attention was drawn to the composition of the dark blue-green background, which consists of various zones painted at different times and with different pigments. Immediately around the face and the headdress, the background becomes translucent at 1050 nm, while the outer parts only become visible at higher wavelengths (Fig. 4). The various optical properties were visualised in a colour composite image based on principal component analysis (Fig. 5), suggesting that a seemingly untouched original background is only present in the immediate vicinity of the figure. The (presumed) overpainting was executed from the edges inward. At the top, left of centre, there is a spot with a different composition, most probably a retouching. This retouching only became translucent at wavelengths between 1830 and 1940 nm. The original or non-original character of the different paint passages in the background will be clarified by the pigment analysis based on the MA-XRF scans (see below). In contrast to the troubled background, the figure itself, particularly the facial features, appears conspicuously unaffected by retouching. Comblen-Sonkes noted in 1986 that the delicate modelling of the face had been well preserved [14]. This is in line with restoration practices in the first half of the twentieth century, when background areas were considered non-essential and suitable for radical overpainting. A well-known example is Rogier van der Weyden’s Virgin and Child in Tournai, which was treated by a controversial restoration by Jozef Van der Veken around 1924 [29]. Infrared reflectography at a wavelength of 1600 nm has rendered the paint layers of the face and the immediate background completely transparent. In this image, we see the underdrawing of the face, consisting of remarkably sharp, confident lines. The neck and tip of the cornette (the cowl) are also outlined (Fig. 6a). This linear sketch, without hatching and with a continuous line free of hesitations, is characteristic of a copied sketch [14; 30; 31]. Where the face appears as a confident, almost mechanical copy, we see a very different image in the hands. The underdrawing indicates hesitation and adjustment by the painter. Initially, the fingers were narrower towards the tips, and the nail of the index finger pointed upwards: two anatomical errors that were corrected during painting. The ring around the index finger was initially shifted further towards the palm and was only provided with a gemstone during painting (Fig. 6b). The fingers, initially too short, were lengthened during painting, and the space between them was reduced to a line, resulting in a more realistic depiction of the fingers (compare Fig. 6b and 6c). Three parallel fingers with a V-shaped space between them, only visible in the inferior underdrawing here, are also seen with the painted hand in the Vienna portrait of Philip the Good. The upward-pointing nail and the too short fingers are mistakes also observable in the Bruges Philip the Good (Fig. 6d). These observations seem to suggest that the painter carried out a copying process while improving the inferior execution in his version. Synchronous macro XRF and hyperspectral reflectance scanning The original colour palette consists of a limited number of hues. Where the presence of tin correlates with that of lead, lead-tin yellow pigment was used, notably conspicuous in the Order of the Golden Fleece chain and, very faintly, in the cross-shaped pendant and the ring (see the Sn-K and Pb-L maps in Fig. 11). This pigment has been documented since the fourteenth century but has not been identified after 1750 [32]. Its presence convincingly attests to the authenticity of this panel, quite confidently eliminating the possibility of a modern copy or falsification. The original blue mostly consists of copper-containing pigment (Cu-K map in Fig. 7), identified as azurite by HR scanning (Fig. 8), predominantly found in areas of the background closely surrounding the head and chaperon of Philip the Good. On the peripheries of the panel, the original blue has been overpainted with modern cobalt-based (blue) and chromium-based (green) pigments (Co-K and Cr-K maps in Fig. 7). The distribution of azurite based on its NIR spectral features (combination bands at 2351 and 2390 nm, and OH overtone bands at 1496 nm, [33]) is reported in Fig. 8 and matches the distribution of Cu in the MA-XRF map. The red pigment used is cinnabar, based on mercury sulphide (HgS). It was observed in the flesh tones, but particularly vibrant in the gold of the Order of the Golden Fleece chain, the central ruby in the cruciform pendant, and the ring (See the Hg-L map in Fig. 7). This is explained by the traditional technique of creating the illusion of gold: a red underlayer is heightened with a semi-transparent yellow paint. Lead white was extensively used, both in white areas (for instance, in the shirt and the scroll) and mixed with other pigments to produces different tonalities, such as in the face and hands, or even in the background where it was mixed with azurite (See the Cu-K and Pb-L maps in Fig. 7). We observe a minimal amount of lead over the entire surface of the painting (excluding the added strips), even in the black areas. A possible explanation for this could be the presence of a monochromous preparatory layer or imprimatura, based on lead white, which isolates the pictorial layers from the ground layer. This technique, also employed by Jan van Eyck, has been observed in many other Netherlandish panel paintings [33; 34; 35]. By comparing the Pb-image and the Ca-image, we can identify areas where lacunae were retouched: where the lead is locally absent, the calcium signal appears much brighter (Ca-K and Pb-L maps in Fig. 7). The iron-containing ochre was not used in the flesh tones but rather in the brown marten fur of cuffs, fur collar, and mantle lining. The absence of heavy elements (apart from Pb) in the black areas suggests the presence of carbon-based black pigments (for instance, charcoal or bone black). This is also evidenced by the fact that the black zones absorb radiation at every infrared wavelength (Fig. 4). The original palette is thus composed of lead-tin yellow, azurite, cinnabar, lead white, ochre, and carbon-based black, demonstrating a relatively limited range of pigments. The MA-XRF images provide a clear view of the retouched paint layers and restorations. The vertical cracks, two parallel lines (a short and a longer one) passing through the ear and a long line located to our right of the face, were filled with a barium-containing pigment after 1850 (Ba-K map in Fig. 7). A third crack, more towards the left, was restored at a different time (also after 1850), with the presence of titanium, iron and manganese detected here (See Ti-K and Fe-K in Fig. 7). In the black areas (the pourpoint and hood), local lacunae have been filled with newer paint in some places. However, the most notable are several overpaintings in the dark blue background, as already suggested by the VIS-NIR multispectral reflectography. These were executed when the panel was enlarged with additional edges, and a greenish dark blue was painted well beyond the old background from the new edges. The cobalt-containing pigment was identified by HR scanning to be cobalt blue, also known as Thénard’s blue (Fig. 8) (near-infrared d-d transition of cobalt (II), [36]). The chromium-based pigment, instead, could be either viridian or chromium green. Although some spectral features in the visible range highlighted by HR scanning hinted at the usage of the first, a clear identification of the pigment cannot be achieved without further complementary analysis. These are pigments that were not used before the end of the eighteenth century [37, p. 119]. A notably distinct retouching in dark blue is situated to the left of the upper edge, which was seen translucent at wavelengths between 1830 and 1940 nm in reflectography. A small spot measuring 20 mm wide and 5 mm high consists of cobalt stannate, a compound of cobalt and tin (see the Co-K and Sn-K maps in Fig. 7) and a primary component of cerulean blue (near-infrared d-d transition of cobalt (II) as for the previously mentioned cobalt-based pigment, [36]). This pigment was introduced only after 1860. Lastly, the repainted lower edge also exhibits a markedly different chemical composition, with notably high concentrations of iron and calcium (Fig. 7). Furthermore, the scans in the elements lead, copper, and calcium provide insights into an intriguing line in the original, overpainted background. Approximately 20 mm from the right edge, we observe in the lead scan a vertical boundary line in the background. The area near the right edge clearly exhibits less lead, causing the calcium from the ground layer to appear brighter in that area. Additionally, a noticeable lacuna in the lead image, between Philip’s left shoulder and the right edge of the image plane, highlights the underlying calcium. In the original background, now invisible because of the overpainted cobalt blue paint, there must have been a 20 mm strip with a lower concentration of lead. This is further corroborated by the copper image, which shows a discontinuity along the same line (Fig. 7). The vertical 20 mm strip certainly does not represent an added piece of panel. The added pieces are clearly discernible in the lead scan, where they create lead-free black edges. The strip where the presence of copper and lead is reduced must have been a distinct colour zone in the original background. We can claim with some confidence that the original, hidden background had a different colour effect in the areas left and right of the vertical boundary line (Fig. 8). Given that in Pieter Cristus’s Portrait of a Carthusian (Fig. 9), dating from 1446, we see a similar vertical boundary between two colour zones in the background, positioned halfway between the face and the right edge of the image plane, creating the illusion of a corner in an interior, it is highly plausible that a similar corner effect was intended in the original background of Philip the Good’s portrait. However, later overpainting of the background has obscured this subtle tonal difference to the naked eye. It is not inconceivable that originally there was also a horizontal zone at the top with a difference in colour, thus suggesting a ceiling plane. Indeed, we can distinguish a thin 16 mm strip where both the lead and copper concentrations are reduced and calcium is highlighted. However, the top 11 mm are not authentic; here, the lead scan is black because a lead-free modern oak strip has been added to the panel. A Portrait of a Knight of the Golden Fleece, attributed to a follower of Pieter Cristus and dated around 1455, has exactly the same division lines dividing the background in two colour zones (Fig. 10) [38; 39, p. 130–131]. It is very possible that the latter portrait was executed after an earlier model featuring Philip the Good against a similar background. Finally, we were able to identify with reasonable certainty the areas where retouching was applied over the existing paint layers and the areas where the repaint was applied entirely from the ground layer up, due to paint loss. When the lead-map reveals gaps and the calcium-map highlights, the original paint layers have vanished, indicating that the entire present paint layer is a recent addition. Modern retouching areas are easily identifiable because they consistently contain zinc, chromium and/or titanium. The overpaint (transparent red) and repaint (opaque red) zones are illustrated in Fig. 11. This scheme clearly reaffirms what Comblen-Sonkes already claimed in 1986: the face and the hands are remarkably intact and untouched by restorations [14]. In summary, the MA-XRF scans have sharply delineated the retouched areas. These appear to originate from various restoration phases in the nineteenth and twentieth centuries and are located solely in the dark blue and black areas. The face and hands are nearly intact and, based on the pigment usage, were certainly painted before 1750. It appears that the original background on the right side of the image contained a 20 mm wide vertical strip with a distinct colour, and a similar but narrower strip on the top edge of the panel. Optical Coherence Tomography This technique can reveal subtle discrepancies in the surface texture. Twenty zones of 12 mm by 12 mm were selected on the front. Five of these will be discussed. The OCT tomograms presented in Fig. 12 show the paint layers, glaze layers and varnish on the surface of the painting into a depth of approximately 60 to 100 µm. Scattering layers are shown in false colours from yellow to blue, while transparent layers and deep structures not accessible for light are presented as black. The surface of the painting is seen as the uppermost strong line. Images are ten-fold vertically stretched for better readability and corrected for refraction with the average refractive index nR = 1.5. In every image, we observe a thin layer of varnish of approximately 10–15 µm, immediately below the reflective surface. Then, we observe at least two, but often three or four transparent layers interspaced by semi-transparent paint layers. On the left side of samples #6 and #8 (Fig. 12) it can be seen how these glaze layers are substantial in the flesh tones of the painting, while on the right side, we see much thinner glaze layers and more opaque paint layers when we move into the dark background or the black area of the headdress. Most striking this effect is in sample # 11 (Fig. 12) where the left part of the graphic corresponds to the gold of the Golden Fleece Chain, for which the painter has used relatively thick semi-transparent layers of paint in which glaze and paint alternate. Also, it can be observed how non-transparent textured paint is used as a preparation layer under the finishing golden colour glazes. Finally, in sample # 19, we observe a striking discontinuity at the point on the support where modern wood is adhered to the old panel. A similar effect is noted in sample # 20 (where the tomogram follows a vertical line). In the latter image, we see that the modern paint layer exhibits a distinctly different subsurface structure with more reflective paint with a smoother surface and without semi-transparent finishing layers. Historical and art historical analysis To confront the most important questions regarding this portrait, the technical results should be complemented with an historical and art historical analysis. To ascertain the date of origin of this portrait, we can draw support from descriptions in the accounts of the Burgundian court revealing that the black chaperon with large bourrelet was first introduced by the Burgundian duke in 1442 and abruptly went out of fashion shortly after 1456 [40, p. 133]. One of the numerous versions of this portrait appears in the presentation miniature of the manuscript Chroniques de Hainaut, dated 1446–1447 [41, p. 90]. Therefore, the Burgundian duke must have posed between 1442 and 1447 for the first portrait of this type. Luttervelt [11, p. 187–188] and Comblen-Sonkes [14, p. 229] both suggested that the first version of the portrait originated around 1445. Who was the painter for whom Philip the Good posed? The lack of a signature or documented commission makes it useful to analyse the historical context more closely. In the aforementioned period there were only two Brabantine or Flemish painters of renown, Rogier Van der Weyden and Pieter Cristus, who both have received commissions from the Burgundian duke or from his courtiers [42, pp. 130–132; 43, p. 196]. The ducal court travelled from city to city, and the court’s commissions were consistently directed to local suppliers and artists. For instance, during Philip the Good’s extended stay in Dijon in 1435, the local painter Jean de Maisoncelles was tasked with painting a portrait of the Duke adorned with a crown and draped in a cloak of the Order of the Golden Fleece [12]. In essence, various painters received commissions from the Duke, and there was no exclusive court painter [44; 45]. We know that between 1444 and 1447, Philip the Good spent half of his time in Bruges and Brussels as his most frequented locations [46]. This historical context brings Pieter Cristus and Rogier van der Weyden, based in Bruges and Brussels respectively, into focus. However, the described period coincides with the onset of the copying tradition in the workshops of Flemish painters, situated around 1450 [47]. We can expect that Duke Philip the Good commissioned the copying of his state portrait in every city he visited. The portrait of a dignified, solemn Philip the Good represents a consciously chosen image intended for widespread dissemination, simulating his omnipresence [48]. There are several contemporaneous copies of this portrait, possibly executed by different painters. When a skilled painter executed a copy, it is nearly impossible to identify the painter’s hand. We now examine the previous attribution attempts of the Dijon portrait. In 1907, when several of these portraits of Philip the Good were first assembled for an exhibition about the Golden Fleece in Bruges, there were seven of the type “Philip the Good with black chaperon” [49]. Five of these portraits were cautiously attributed to an unknown Flemish or Northern French painter; the owner of the sixth panel felt no hesitation to attribute his painting to Rogier Van der Weyden. Another owner attributed his portrait version to Pieter Cristus. Conway believed in 1921 that most of the panels were copies and that Pieter Cristus was the most likely painter of the original portrait [44]. In 1934, Friedländer categorized all these portraits of Philip the Good as copies or imitations after Rogier Van der Weyden, without further elucidation [50]. In 1944, Michel also considered the Louvre version of Philip the Good’s portrait a copy of an original by Rogier Van der Weyden, while he acknowledged the very different style of the copy [51]. In 1946 the museum conservator in Dijon followed the same line and regarded the Dijon portrait as a copy after Van der Weyden [52]. Other scholars were more critical. Janssens de Bisthoven wrote that the attribution to Rogier Van der Weyden cannot be supported by facts [53] and Comblen-Sonkes does not believe that the Dijon portrait originated in his workshop [14]. De Vos preferred Jan van Eyck or Pieter Cristus as the most plausible author of the original portrait [54]. Thanks to the various technical analyses we are now much better armed to tackle this thorny attribution issue based on a stylistic analysis of the many previously hidden features. The author of the Dijon portrait demonstrates particular expertise in the subtle rendition of light and shadow within the flesh tones of his portraits. Particularly Pieter Cristus is known for this “cold yet soft and harmonious tones, with careful modelling and copious colour” [55, p. 145]. The painter of the Dijon portrait pursued a similar objective, striving for maximal realism through the nuanced variation of flesh tones. As we have seen on the OCT diagram of sample # 11, he used the same technique of glaze layers as Pieter Cristus to achieve this effect [43, p. 169]. However, we find a much more striking stylistic feature in the revealed original background, initially formed with colour strips at the right and upper edges. This “corner-space effect”, which is never observed with Rogier van der Weyden, is a distinctive characteristic of Pieter Cristus’s portraits circa 1446 [56, p. 28], as in his Portrait of a Knight of the Golden Fleece (Fig. 10). Similarly, in the Dijon portrait the combination of the copper scan and the hyperspectral image of azurite reveals a notable colour difference precisely in the same corner of the image. The resemblance is too striking to dismiss. A third notable feature is the size of the original panel, 21.3 cm by 29.6 cm, which is very similar to the dimensions of Pieter Cristus’s Portrait of the Carthusian in New York, 20.3 cm by 29.2 cm (Fig. 9). In the time period under study, it is best to avoid name-fetishism in attributions because numerous painters – workshop assistants, copyists, followers – worked in anonymity alongside the classical names, possibly at a high level of skill [57]. With this consideration in mind, it nonetheless appears reasonable to conclude that Pieter Cristus played at least an indirect role in the Dijon portrait. Perhaps a copyist painted it after his example, incorporating a Cristus-style corner into the background. Alternatively, Pieter Cristus may have painted this after a model, interpreting the background in his own manner and exhibiting his talent in the modelling of the face. The possibility that two different hands were at work, as has already been suggested for works by Pieter Cristus, cannot be ruled out either [43, p. 151]. In summary, the traditional assessment as “copy after Rogier van der Weyden” [58] has little or no factual support. The historical context in combination with the stylistic features, revealed by the recent technical analyses, clearly indicate that it was rather Pieter Cristus who played a significant role in the creative process of this portrait.