V. Materiality of a Vision: Unveiling the Complex Material Makeup of an Early Symbolist Work with Friable Media by Alfred-Napoléon Delaunois (Belgian, 1875-1941)

Introduction

Symbolism was a late nineteenth-century artistic movement that aspired to a higher ideal in both aesthetics and spiritual life, in reaction to the positivism and deep societal changes brought about by the industrial revolution.¹ Taking a step aside from reality and materialism, Symbolist artists explored subjects drawn from literature, theology, mythology, and music. Their works paved the way to later twentieth-century abstraction and Expressionism, opening gateways into imagination, spirituality, and the inner world.

It has been noted that the Symbolists achieved a remarkable convergence of means, form, and content in their artworks. Indeed, in their endeavour to “make visible the invisible,” they crafted ways to embody intangible ideas in colours and shapes, realised through careful choice and manipulation of artistic (notably, drawing) techniques.² Such techniques included friable media—chalk, charcoal, pastel. With its inherently insubstantial nature, pastel became a favourite medium with Symbolist artists. Through the unique properties of this technique, they could materialise their dreamlike visions, in subdued colours and with hazy effects.³ Symbolism was particularly prominent in Belgium, with champions such as Fernand Khnopff (1858–1921), Jean Delville (1867–1953), and Léon Spilliaert (1881–1946). All of them used pastel and other friable techniques to create drawings intended as stand-alone artworks. Belgian Symbolism has received sustained scholarly attention, at home and abroad, for four decades, in the wake of the seminal Belgian Art, 1880–1914 exhibition at the Brooklyn Museum in 1980. Yet, while Khnopff, Delville, and Spilliaert have been the focus of extensive art historical research through several monographs,⁴ technical aspects of their works have not been covered so far in the literature. More broadly, art technical studies of late nineteenth- and early twentieth-century materials often remain centred on a specific artist’s drawing materials and practices—Edgar Degas (1834–1917), Odilon Redon (1840–1916), Edvard Munch (1863–1944), and Umberto Boccioni (1882–1916) are notable examples.⁵ Materials-based approaches in technical studies can be found nonetheless, with important historical surveys of nineteenth-century graphic techniques tackling wet and dry media. More recently, the catalogue of the 2016 exhibition Noir: The Romance of Black in Nineteenth-Century French Drawings and Prints offered a comprehensive investigation of black drawing media integrating art historical and technical perspectives.⁶ As for nineteenth-century pastel, it was lately showcased in two exhibitions, L’Art du pastel de Degas à Redon (Paris, Petit-Palais, 2017) and Pastels, de Millet à Redon (Paris, Musée d’Orsay, 2023), evidencing the growing interest for this material and this period. The present case study aims at bringing into focus the specific intersection of Symbolist aesthetics and friable media. It is set within the broader framework of the multidisciplinary FRIABLE research project (2022–26), hosted by the Royal Museums of Fine Arts of Belgium.⁷

Part of the fin de siècle generation, the Belgian artist Alfred-Napoléon Delaunois (1875–1941) was born in Brussels to a family originating from Ghent (Fig. 1). His father, a decorative painter, was the head of a successful atelier in Brussels at the time. Alfred was seven when the family moved to Leuven, a city east of Brussels. According to Crab and Van Buyten, he would have become a house painter if not for the intercession of his elder brother Edgard-Séraphin (1873–1949), a decorative arts teacher at the Academy of Fine Arts in Leuven.⁸ Following his encouragement, the young Alfred enrolled at the academy in 1891. His remarkable talent was also noted by the famous painter and sculptor Constantin Meunier (1831–1905), who was teaching there at the time.⁹ More recent writing on Meunier has tended to focus on his social realism—namely, his depictions of the industrial world—neglecting the part of his oeuvre that reflects his religiosity, as expressed in his scenes of monastic life.¹⁰ Meunier’s inspiration, together with a general trend seen in the subject matter favoured by the Symbolists, could explain the fact that religious subjects feature so prominently in Delaunois’s entire output. Vision de Moine (A Monk’s Vision), preserved in M Leuven, is no exception (Fig. 2). In line with Symbolist aesthetic ideas, Vision de Moine displays the otherworldly qualities of a mystical experience.

Dated to 1897, Vision de Moine entered the collection of the Stedelijk Museum Leuven (the municipal museum known today as M Leuven) in 1957, as part of a vast bequest of the artist’s works by his brother Richard.¹¹ Delaunois was recognized in his lifetime as a prominent Leuven artist, a leading figure of the art scene in his capacity as the director of the Academy of Fine Arts, exhibiting regularly in Belgian galleries and several times at the Venice Biennale.¹² A vast body of art historical writing exists for Delaunois dating from the first half of the twentieth century.¹³ However, compared to the renown he experienced during his lifetime, later and more recent research on the artist remains relatively obscure.

Like much art historical writing from this period, technical commentary remains limited due to the absence of advanced analytical techniques that are more commonly used today, and to a lesser interest in material aspects of artworks. Except for a brief mention,¹⁴ technical descriptions of his works are virtually nonexistent—especially in exhibition catalogues—with authors and researchers mainly focusing on other forms of art historical analysis such as iconography. In a rare occurrence, Henri Lavachery, one of his biographers, does allude to the peculiar materiality of Delaunois’s works:

The skillful richness of the matter contributes to perfecting this realisation, because Delaunois is a magician of nuance. Thanks to skillful overlays of impressions, in his etchings, thanks to sumptuous highlights, in his drawings, he manages to endow them with the muted richness of tortoise shell, of lacquer and enamel. Faces, glowing mysteriously like ivory leaf laid on gold.¹⁵

Written in 1931, this testimony of Delaunois’s way of working captures the decorative qualities of some of his works, and his mastery of various artistic techniques. This observation is exemplified by Vision de Moine, with its complex combination of drawing (mostly pastel) and painting media, handled so as to achieve a variety of visual effects. Situated at the intersection between several artistic categories, the work blurs the lines between fine and applied arts, its unique materiality a testament to the young artist’s experimental and intuitive approach.

This mixed-media artwork also raises a number of questions, the first being the artist’s original intention, which in this instance refers to his material choices and how he used them to fulfil his aesthetic goals. In addition, the work’s highly finished appearance further leads us to wonder how Delaunois prepared and carried out his work. Finally, distinctive degradation patterns apparent on the work’s surface suggest a complex layering of various media that needs to be locally understood so as to deconstruct its full material structure.

We will first shed light on the work’s genesis, based on archival and material evidence, to anchor Vision de Moine within both Delaunois’s early oeuvre and the broader artistic context of his time. Then, we will dive deeper into the materiality of the artwork. In order to gain insight into Delaunois’s idiosyncratic working method, we carried out close examination of the work’s surface with the naked eye and with a headband magnifier, and subsequently collected more precise data through a number of noninvasive imaging and analytical techniques (high-resolution visible-light photography, photometric stereo, microscopy, narrow-band multispectral imaging, macro X-ray fluorescence; see Appendix 1). This data helped us better evidence the range of materials Delaunois used, the ways in which he implemented them, and how this can explain damage patterns. Subsequently, we will look underneath the surface for traces of the artist’s working process, through the close study of the surface topography coupled with chemical imaging and microscopy. Finally, revisiting our first discussion point on the artist’s original design in light of the technical and documentary data collected, we will reflect on the work’s afterlife and the special status it enjoyed with the artist until his death.

Through this technical case study, we hope to provide a concrete example of the subtle interplay of materiality and aesthetics in the Symbolists’ works. These artists remained all but silent about the specific materials and studio practices that enabled them to create such a haunting visual legacy, but evidence thereof lies embedded within the artworks they created, for us to unlock. Additionally, the technical imaging protocol performed on Delaunois’s work was intended as a test for the analytical workflow that would be carried out on nine works with friable media from the FRIABLE project’s research corpus.

Unraveling the Work’s Genesis: A Preparatory Work for a Decorative Cycle

A label in Delaunois’s handwriting pasted onto the verso of the work is inscribed: Vision de Moine / (pour fresque murale) (“A Monk’s Vision / [for wall fresco]”) (Fig. 3).¹⁶ Although the inscription in red in the lower left corner is now partially effaced (Fig. 4), the top part is an earlier signature flanked with the date 1897, and the bottom line can still be read as Le Songe des Moines (“The Monks’ Dream”). The work’s documentation at M Leuven does not provide any further indication that could shed light on these inscriptions. However, the most explicit mention of a project titled Le Songe des Moines, and of this very artwork, can be found in art historical writing on the artist. Indeed, in his 1935 monograph on Delaunois, Robert de Bendère wrote that:

[Delaunois] created a whole series of projects that would make up a fresco titled “Le Songe des Moines.” This project,¹⁷ only partially realised, comprises fragments of astonishing technical value… Some of these panels, already shown in a number of exhibitions of Alfred Delaunois’s works, were destined, according to the artist’s design, to decorate the chapel of a Dominican convent or a church of the same order. Among the fragments of this decorative suite, we should mostly mention some pieces of beautiful idealisation and romantic feel such as “The Monk with a Lily,”¹⁸ in which he synthesised the gentleness and naiveté of a monk’s mask, young still, … expressing admirably the monk’s contemplative and dreamy attitude… This “Songe des Moines,” too little known, would deserve to be realised, but who will be the patron who will endow a chapel with this jewel among the most admirable of modern religious art?¹⁹

It appears, therefore, that this project was Delaunois’s own initiative, a young painter’s ambitious attempt at demonstrating his talent as a decorative painter while celebrating the religious heritage of his hometown. The envisioned destination, a Dominican institution, is clear from the monk’s tonsured skull. The exact desired location, however, if Delaunois had any in mind, is not known.²⁰

Another uncertainty lies within the term fresque murale seen on the pasted label. The authors of related exhibition catalogues use the denomination fresque and décoration murale (wall decoration) interchangeably to describe preparatory studies such as this one.²¹ It is therefore unclear which technique Delaunois would have eventually implemented to realise this cycle at full scale, perhaps a technique of working directly onto the wall, or even using mounted panels.²² The young artist’s familiarity with decorative painting techniques, learnt from his father and elder brother, could explain his affinity with wall painting and fresco-like procedures. This hypothetical choice should also be contextualised within the so-called Fresco Revival.²³ Observed from the mid-nineteenth to the early twentieth century in countries such as England, France and Germany, it was spurred by the Pre-Raphaelite and Nazarene schools, the Arts and Crafts movement, as well as early Symbolist painters such as Pierre Puvis de Chavanne (1824–1898) in France.²⁴ This renewed appreciation for the technique proceeded directly from the Tempera Revival,²⁵ which sought to break away from academic art and the medium it was most associated with—oil paint. In reaction to the glossy finish of varnished oil paintings, artists turned to materials with a matte appearance, such as tempera, distemper, pastel, and crayons.²⁶ This aesthetic trend is reflected in the studio practice of Paul Gauguin and the Nabi painters Edouard Vuillard and Pierre Bonnard, among others. Odilon Redon exemplifies this trend as well, in his drawings combining pastel and distemper to create large finished artworks with an unvarnished surface.²⁷ Both matte painting materials and subdued colours used in modern wall paintings served the aesthetic goal of re-engaging with the “austerity of the primitives.”²⁸ Against this backdrop, Delaunois’s choice of techniques such as pastel, used extensively in Vision de Moine, could be interpreted as the artist’s attempt at transposing onto paper the visual effect of the a fresco technique, the matte and chalky texture of soft pastel lending itself perfectly to this purpose.

A Complex Material Makeup and Distinctive Degradation Patterns

Close examination of the artwork reveals the wide array of techniques used by Delaunois. Soft pastel can be identified over most of the surface, applied in layers of various colours blended together, in adjacent touches, or in strokes, oftentimes allowing the paper colour (a light pink) to show through to build subtle mid-tones.²⁹ The pastel was stumped into a remarkably smooth layer on the monk’s face. The figure’s sharp outline and hair were drawn with an iron-rich pigment,³⁰ both in the form of a dry medium (chalk or crayon), and mixed with an aqueous binding medium applied with a thin brush.³¹ Faint lines consisting of a black dry medium are also visible in the lilies. Paint (gouache and watercolour, oil) was also used in many passages,³² mostly in combination and layering with pastel—notably in the lilies, in the figure’s white cloak and veil, and in thin brushstrokes in his hair, with varying degrees of transparency and thickness.³³ In some parts of the veil, Delaunois appears to have blended pastel colours together using a wet brush.

Observation in raking light shows the striking three-dimensionality of the work’s surface. Thick white oil paint (Fig. 5) was applied using an impasto technique (Fig. 6) that Delaunois further carved into using a blunt tip.³⁴ He also carved similar details into the paint layer of the left sleeve of the monk’s cloak. The effect achieved calls to mind the way his master and teacher Constantin Meunier would carve lines and hatchings into clay to create background texture in some of his models for high-relief friezes.³⁵ The MA-XRF calcium map further evidences that a layer of white pastel or chalk was applied in several instances on top of the lead-containing white paint that the artist used in the veil, contributing to the overall matte effect (Fig. 7).

Due to its complex material makeup and layer buildup, Vision de Moine displays unusual degradation patterns. We will focus here on two areas presenting severe delamination and medium loss. One of the lilies is particularly damaged: the oil paint layer has cracked, lifted, and flaked off. The concave deformation of the cardboard backing caused undulations of the primary support particularly visible in raking light from a 0º angle.³⁶ Mechanical stress therefore probably partly explains this flaking phenomenon. However, observations of these lacunas under a Hirox microscope revealed the presence of faint traces of yellow and red pigments still sitting on the paper, in areas where accidental smudging is very unlikely to have occurred (Fig. 8).³⁷ This shows that the paint was applied over a friable medium layer, the particular combination contributing to the overall instability of this interface. It is probable that the fallen paint flakes lifted off most of the original pastel layer that had adhered to them.

The second severely damaged area is located in the monk’s hairline. Interestingly, the flaking corresponds to parts of the MA-XRF lead map, suggesting a relationship between the local makeup of this area and its fragility (Interactive figure I). ³⁸ Microphotographs provide further insight into the layer buildup of the painting (Fig. 9). It appears that Delaunois first drew in pastel—reddish and yellow pigments are visible as a cohesive layer in the lower and right part of the main lacuna—then he likely applied the same lead-containing white paint as in the other damaged area, and finally reworked in pastel on top of this layer. Therefore, both damage patterns should be attributed to the same cause: the layering of paint on top of a friable medium.

Retracing Delaunois’s Working Process

The highly finished appearance of Vision de Moine leads to the question of just how much the artist prepared his work, and whether traces can be found that evidence the early steps of his creative process. The presence of an underdrawing, for instance, is not clearly visible to the naked eye, owing to the thick layer of pastel applied throughout, although a few lines in red dry medium appear through the thin paint layer on the left wrist, together with the aforementioned black dry medium tracings, partially covered with paint, in the lilies. However, incised lines appear in some passages, most visibly in the area above the lily close to the face (Fig. 10), in the top left corner, along the top part of the halo (short parallel hatchings in all three cases), and along the right hand, in long lines running roughly parallel to the outline of the wrist. A powerful complement to raking-light imaging, the white-light Microdome allowed for a deeper investigation of these shallow traces from all angles. These observations showed that the relationship between these lines and the markings in the pictorial layer was not directly obvious. We therefore propose to view them either as a very early stage of Delaunois’s creative process—from which he eventually drifted considerably—or as elements from another composition that he subsequently drew over.

Another remarkable element of this composition is the golden halo around the monk’s head. Delaunois occasionally worked on a gold background and/or with gold highlights.³⁹ This is the case for other drawings in the collection of M Leuven that are stylistically and technically very close to Vision de Moine.⁴⁰ Examination in raking light confirmed the halo was made with metal leaf, and MA-XRF mapping revealed that the metal present is copper, with traces of zinc.⁴¹ A nod to Italian Quattrocento painting, it provides an interesting contrast with the otherwise matte surface overall. Evidently, the outer part of the halo has darkened throughout, while the inner part has not (Fig. 11).

Chemical data collected in this area is fragmentary, since the copper leaf that makes up the halo has a shielding effect. It is therefore not possible to ascertain what kind of ground layer it was applied onto, and whether the darkening could be attributed to contact corrosion with the underlayer.⁴² However, the MA-XRF maps for lead and mercury reveal discontinuous outlines underneath the halo—although interestingly, these lines do not overlap with each other (Interactive figure II). This could hint at the presence of two distinct sets of preparatory tracings and provide further evidence of extensive reworking in the area. Similarly, the lead map shows a dotted line under the chin, which the artist tried to erase, probably using a diluent, causing a leaching of lead in this area (Interactive figure III).⁴³

Furthermore, raking-light photography shows the presence of underlying texture in the outer part of the halo, also clearly visible in the zinc and calcium maps, which could reveal an earlier stage of Delaunois’s working process (Interactive figure IV). Indeed, another panel shows a very similar pattern, with broad touches of gold paint freely applied all over to create a background (Fig. 12).⁴⁴ It is therefore probable that he experimented with a comparable solution in Vision de Moine but changed his mind and applied metal leaf to homogenise the aspect of the halo.

Finally, the zinc map shows that the eye was originally drawn slightly higher than its current position, and also more slitted in shape (Interactive figure V), while the pupil was first drawn with a copper-containing pigment (Interactive vewier VI). Both the lead and the zinc maps reveal the extent of Delaunois’s reworking in the area encompassing the eye up to the forehead and hairline. As discussed above, he reapplied a thin layer of lead-containing paint as a ground to work on top of the previous layer, paying special attention so as not to disturb the overall smoothness of the surface.⁴⁵

Working with such elaborate colour buildup, the artist was also able to implement reductive or subtractive techniques such as sgraffito (“scratched”). For example, he used a sharp tool to scratch out fine lines and hatchings in the pastel layer to expose the lighter tone underneath and create subtle modelling as a finishing touch.⁴⁶ This is particularly visible in the face, the hair, and the hands (Fig. 13).

Reconstructing the Work’s History: From Preparatory Study to Stand-alone Artwork?

A lighter halo is visible to the naked eye around the inscription in red, in the lower left corner (Fig. 4). Principal Component Analysis performed on a stack of multispectral images reveals the extent of Delaunois’s efforts when it came to erasing and reworking this area (Fig. 14). Visible- to near-infrared imaging proved unsuccessful at bringing out the effaced inscription in its entirety,⁴⁷ nor did MA-XRF mapping produce conclusive results in this respect.⁴⁸ Nonetheless, even if the original inscription remains illegible using current methods, the erasing and reworking alone are a good indication of a change in Delaunois’s intention with regards to the painting’s final destination. When it became clear that his project for a decorative cycle titled Le Songe des Moines would not materialise, the artist likely decided to suppress the mention of this previously envisioned destination. The fact that both the inscription in red and the monogram appear to be part of an earlier stage in the work’s material history is also evident through the observation that they were later covered with various pastel colours, some clearly visible on top of the red paint in the monogram (Fig. 15).⁴⁹ Once he was done reworking this corner, the artist signed it again and drew a circle around the monogram in a blue coloured pencil. The only mention in an exhibition catalogue that could potentially identify this artwork dates back to 1917—which judging from available written records was also Delaunois’s very first exhibition—where it is listed under no. 41 as the Moine au Lys (Monk with a Lily) among other “Fragments of Decoration (Studies for wall fresco).”⁵⁰ It is therefore possible that the artist later reworked his drawing in preparation for this exhibition, or at an unknown earlier date. It should be noted, however, that without further details, the listing in this catalogue can only provide a limited level of confidence, mostly owing to the fact that the work’s title is the same as the one found in the De Bendère’s 1935 monograph mentioned earlier. Yet, in the absence of more precise technical descriptions—let alone reproductions of the works—we cannot be absolutely certain that the described work is, indeed, the one at the M Leuven. This further illustrates the challenges posed by vague descriptions in catalogues from that period when attempting to trace back an artwork’s history.

Nail marks are visible at regular intervals along the four edges, evidence of old mounting and/or framing. In fact, we know from two photographs taken in Delaunois’s home, from an album dated to 1955, that the drawing was originally mounted together with a smaller one (Figs. 16, 17).⁵¹ This framed ensemble featured prominently in the artist’s living room.⁵² The room itself has the look of a small private museum,⁵³ where a selection of the artist’s works mingled with an eclectic collection of architectural fragments, sculptures and sculpted decoration, frames, and furniture. The styles of the various objects span from the Gothic era to the twentieth century.⁵⁴

The fact that Delaunois kept this early work in the room where he also displayed a wealth of objects dear to his heart, likely as sources of inspiration and for their sentimental value, attests to the special status of the drawing as a work particularly enjoyed by the artist himself. The objects surrounding it further shed light on the visual references from which Delaunois drew throughout his career.⁵⁵ They reflect the same eclecticism that Delaunois demonstrated in choosing the artistic techniques and processes he brought together in his Vision de Moine.

Conclusion

The research carried out on Delaunois’s Vision de Moine helped us understand the breadth of the technical skills he mastered in his early career, and the freedom with which he combined techniques and materials to create this singular work. The degradation patterns investigated in this study have proven to be directly linked to this unrestrained way of working—in particular, his application of paint highlights and impastos over a friable medium layer to create contrasts in textures. Closer examination revealed that this artwork’s apparent spontaneity hinges both on careful preparation (as shown by underlying tracings) and the artist’s ability to easily rework passages utilising the properties of soft pastel, namely, its blendability or ability to create soft transitions between different passages of colour and to mix colours together.

This case study testifies to Delaunois’s experimental technique and his bold—yet carefully weighted—choice of materials. The other works by him we were able to see in the M Leuven collections for this research all stood out by their very distinctive material and visual effects, stemming from the broad array of media and techniques he combined. Although art historical writing published in his lifetime only succinctly touched on the materiality of his artworks, we demonstrated that this aspect deserves closer scrutiny; an observation that also holds true for Symbolist artists more broadly. It is our hope that this research will spur further investigation into Delaunois’s studio practice, through close examination and comparisons across his drawings, prints, and paintings. This survey would be interesting from a (technical) art history perspective, in leading to the rediscovery of an artist whose unique talent is situated at the crossroads of tradition and modernity. It would also be very valuable from a conservation and collection management standpoint, by mapping the use of materials across his oeuvre, their fragility, and the damage patterns resulting therefrom.

In the present technical case study, the combination of methodological approaches that complemented each other proved to be a successful strategy. Archival and art historical research contributed by filling in gaps in the work’s provenance and exhibition history, while also establishing the broader context of its creation. Various imaging techniques, as well as optical and non optical analytical techniques, have each compensated for the other’s limitations. We have therefore also aimed to demonstrate the efficacy of noninvasive and nondestructive techniques when it comes to tackling research questions on artworks with a complex material makeup such as Delaunois’s Vision de Moine. In this endeavour, an innovative visualisation tool such as the Curtain Viewer has played an instrumental role by allowing for seamless comparisons across imaging modalities, peeling off—so to speak—the artwork’s layers to understand its buildup, the nature of the various medium-to-medium interfaces, and also their relationship with each other. In particular, the examination of surface features, as evidenced through high-resolution raking-light photography and Microdome imaging, coupled with chemical mapping, emerged as a powerful tool to understand local variations of material buildup, albeit concealed beneath the surface.

As such, the technical-imaging workflow performed on this artwork was deemed satisfactory enough to be applied to the FRIABLE project’s research corpus, consisting of nine artworks from the collections of the Royal Museums of Fine Arts of Belgium, including friable media alone or in combination, dating to the late nineteenth- to the early twentieth century. This corpus was imaged during the summer and fall of 2023 by the KU Leuven-VIEW and the KIK-IRPA teams, following the standardised procedure tested on Delaunois’s work, with practical adjustments and the addition of micro-Raman spectroscopy to complement the Ma-XRF data. Building upon the results obtained, a future avenue of research could entail the systematic correlation of spectral and chemical data for modern pastel pigments,⁵⁶ extenders and binders, in order to build a more granular understanding of the materials used and how to best characterise them with simple imaging equipment.

Appendix 1: Technical Imaging Performed and Instrument Specifications

• High-resolution (1200 dpi) even illumination and raking-light photography: Phase One IQ3 100MP camera, f/11, 1/125 sec., ISO-100, Schneider Kreuznach 120 mm LS Macro f/4.0 “blue ring.”

• Narrow-band multispectral imaging (NBMSI): Phase One IQ4 150MP Achromatic camera with filter wheel, 350 to 940 nm, 800 dpi,⁵⁷ data acquisition with the Spectral XV software, normalisation and Principal Component Analysis (PCA) performed with the ImageJ software.

• Portable Light Dome (Microdome) white-light photometric stereo imaging of areas of interest: GX 6600 (6576×4384 px) 35 mm CCD, f/11, shutter speed 150 ms, image scale 84.3342 px/mm (=11.85 μm/px), 100 mm lens.⁵⁸

• Microscopy: Hirox RH-2000.

• MA-XRF mapping of selected areas of interest with Bruker M6 Jetstream, spot size 550, step size 500 mm, dwell time 15 ms (unless otherwise specified); data processing with PyMca.

The research took place at the KU Leuven Core Facility VIEW: Imaging Lab (KU Leuven Libraries) and Book Heritage Lab (Faculty of Theology and Religious Studies). MA-XRF scans were performed at IPARC, Kampenhout, Belgium.

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La Nasa, Jacopo, Brenda Doherty, Francesca Rosi, Chiara Braccini, Frederique T. H. Broers, Ilaria Degano, Jordi Moles Matinero, et al., “An Integrated Analytical Study of Crayons from the Original Art Materials Collection of the MUNCH Museum in Oslo,” Scientific Reports 11 (March 30, 2021): 7152. https://doi.org/10.1038/s41598-021-86031-6.

Laoureux, Denis. Jean Delville (1867–1953), maître de l’idéal. Paris, 2014.

Lavachery, Henri. Exposition de l’oeuvre graphique du maître Alfred Delaunois. Brussels: Galerie des Artistes Français, 1931.

Lluveras Tenorio, Anna, Jacopo La Nasa, Barbara Ferriani, Maria Perla Colombini, and Francesca Modugno. “The Chemistry of Pastels: Investigation of the Organic Materials in a Drawing by Umberto Boccioni.” In “Modern and Contemporary Art,” edited by Francesca Caterina Izzo and Patrizia Tomasin, Journal of Cultural Heritage 35 (January 1, 2019): 235–41. https://doi.org/10.1016/j.culher.2018.12.009.

Moréas, Jean. “Manifeste du Symbolisme.” Le Figaro, 18 September, 1886. https://www.berlol.net/chrono/chr1886a.htm.

Powers, Alan. “The Fresco Revival in the Early Twentieth Century.” Journal of the Decorative Arts Society, 1850–the Present, no. 12 (1988): 38–46.

Sargant Florence, Mary. “The Influence of Material on Style.” Arts and Crafts Quarterly 1 (1920): 13–22.

Stratis, Harriet K. Stratis. “A Technical Investigation of Odilon Redon’s Pastels and Noirs.” Book and Paper Group Annual 14 (1995): 87–103.

Timmermans, Felix. “Alfred Delaunois.” Van Onzen Tijd, no. 23 (1913–14): 357–63.

———, and Henri Lavachery. Graphische Werken van Alfred N. Leuven: Akademie van Schone Kunsten, 1936.

Townsend, Joyce H. “Analysis of Pastel and Chalk Materials.” Paper Conservator 22, no. 1 (1 January 1998): 21–28.

Tricot, Xavier. Fernand Khnopff: Catalogue Raisonné of the Prints and the Enhanced Platinotypes. Antwerp, 2018.

Tummers, Anna, and Robert G. Erdmann. “The Eye versus Chemistry? From Twentieth to Twenty-First Century Connoisseurship.” In Analytical Chemistry for the Study of Paintings and the Detection of Forgeries, edited by Maria Perla Colombini, Ilaria Degano, and Austin Nevin, 3–45. Cham: Springer International, 2022.

Vaeyens, Christiane. “Le sac de Louvain (1914) in de grafiek van Alfred-Napoléon Delaunois (1875–1941).” Master’s thesis, KU Leuven, 2012.

Vanzype, Gustave. Exposition d’une partie de l’oeuvre d’Alfred-N.. Brussels: Galerie Georges Giroux, 1926.

———. Nos peintres. 3 vols. Brussels: Paul Lacomblez, 1905.

Watteeuw, Lieve, and Hendrik Hameeuw. “Art Technical Research on Manuscript Heritage with the White Light and Multispectral Portable Light Dome System (Multi Light Reflectance Imaging).” In Immaginare la Commedia, edited by C. Perna and G. Ferrante, 225–37. Rome: Salerno, 2022.

1. For an overview of (Belgian) Symbolism, its ethos and aesthetics, see Jean Moréas, “Manifeste du Symbolisme,” Le Figaro, 18 September 18, 1886; Michael Botwinick, Sarah Faunce, and Francine-Claire Legrand, Belgian Art, 1880–1914, exh. cat., Brooklyn, The Brooklyn Museum, 23.04 1980 - 29.06 1980 (New York: The Brooklyn Museum of Art, 1980); Michel Draguet, Le Symbolisme en Belgique (Antwerp: Fonds Mercator, 2004); Vivien Greene, Jean-David Jumeau-Lafond, and Kenneth E. Silver, eds., Mystical Symbolism: The Salon de La Rose Croix in Paris, 1892–1897 (New York: Guggenheim Museum Publications, 2017); Ralph Gleis, ed., Decadence and Dark Dreams : Belgian Symbolism (Berlin: Nationalgalerie SMB and Hirmer, 2020). ↩︎

2. Sharon L. Hirsh, introduction to Symbolism and Modern Urban Society (Cambridge: Cambridge University Press, 2004), 3–6. ↩︎

3. Thea Burns and Philippe Saunier, “The Symbolist Pastel,” in The Art of the Pastel (New York: Abbeville, 2015), 339–54. ↩︎

4. See, for instance, Michel Draguet, Fernand Khnopff (Brussels: Fonds Mercator, 2018); Xavier Tricot, Fernand Khnopff: Catalogue raisonné des estampes et des platinotypes rehaussés / Oeuvrecatalogus van de prenten en de gehoogde platinadrukken / Catalogue Raisonné of the Prints and the Enhanced Platinotypes (Antwerp: Petraco-Pandora, 2018); Denis Laoureux, ed., Jean Delville (1867–1953), maître de l’idéal  (Paris: Somogy, 2014); Brendan Cole, Jean Delville: Art between Nature and the Absolute (Cambridge: Cambridge Scholars, 2015); Anne Adriaens-Pannier and Leila Jarbouai, eds., Léon Spilliaert (1881–1946): Lumière et solitude (Paris: Éditions de la Réunion des musées nationaux–Grand Palais, 2020); Anne Adriaens-Pannier, Léon Spilliaert: De oorsprong van het beeld (Antwerp: Stichting De Reede, 2022). ↩︎

5. Michelle Facini et al., “Technical Exploration of Edgar Degas’s Ballet Scene: A Late Pastel on Tracing Paper,” in Facture: Conservation Science Art History, vol. 3, Degas (Washington, DC: National Gallery of Art, 2017); Harriet K. Stratis, “A Technical Investigation of Odilon Redon’s Pastels and Noirs,” Book and Paper Group Annual 14 (1995): 87–103; Jacopo La Nasa et al., “An Integrated Analytical Study of Crayons from the Original Art Materials Collection of the MUNCH Museum in Oslo,” Scientific Reports 11 (30 March 2021): 7152; Anna Lluveras Tenorio et al., “The Chemistry of Pastels: Investigation of the Organic Materials in a Drawing by Umberto Boccioni,” in “Modern and Contemporary Art,” ed. Francesca Caterina Izzo and Patrizia Tomasin, Journal of Cultural Heritage 35 (1 January 2019): 235–41. ↩︎

6. Lee Hendrix, ed., Noir: The Romance of Black in 19th-Century French Drawings and Prints (Los Angeles: Getty Publications, 2016). ↩︎

7. This research is carried out within the framework of the BRAIN-be 2.0**/**Belspo FRIABLE project (2022–26) at the Royal Museums of Fine Arts of Belgium, Brussels,

   https://fine-arts-museum.be/en/research/research-projects/friable; and the 3Pi FWO Mid-Scale Infrastructure VIEW at KU Leuven (2018–24). ↩︎

8. Jan Crab and Leo Van Buyten, Alfred-Napoléon Delaunois (Leuven: [Stedelijke tentoonstellingszaal], 1976). The original Dutch term “bemiddeling” used by these authors can translate to “intercession”, or “brokerage”. Unfortunately, they do not provide any further explanation as to the broader family context in which the brother’s intercession took place. ↩︎

9. Alfred Delaunois would later become a professor in this academy and then, in 1920, its director. ↩︎

10. Delaunois paid homage to Meunier’s “deeply religious soul” in the catalogue published on the occasion of the hundredth anniversary of the Leuven Academy of Fine Arts; Alfred Delaunois, Fêtes du centenaire, 1830–1930: Exposition d’art rétrospectif et contemporain (Leuven: Akademie voor Schone Kunsten van Leuven, 1930), and again in a succinct monograph published shortly after the inauguration of the Meunier Museum; see Alfred Delaunois, “Valeur du peintre,” in Constantin Meunier (s.l., 1939), 19–21. ↩︎

11. The complete inventory—featuring an old numbering system that is now coupled with the museum’s current accession numbers—is preserved in the city archives. A typed version of this list features in Crab and Van Buyten, Alfred-Napoléon Delaunois (n.p.), in which the drawing is listed under no. 936 (bequest no. H 42), inaccurately titled Vrouwenkop (Woman’s Head) and described as a heightened drawing on paper, signed at the lower left. Delaunois’s significance for Leuven is best attested through a series of drawings made on the spot in the aftermath of the destruction by imperial Germany in 1914, at a time when Leuven was under German occupation and his sketching could have caused him in serious trouble. See Christiane Vaeyens, “Le sac de Louvain (1914) in de grafiek van Alfred-Napoléon Delaunois (1875–1941),” master’s thesis, KU Leuven, 2012. ↩︎

12. Gustave Vanzype (Exposition d’une partie de l’œuvre d’Alfred-N. Delaunois [Brussels: Galerie Georges Giroux, 1926], 5) noted that Delaunois achieved early fame: his first work to enter a public collection, a church interior titled Après vêpres (After Vespers), was purchased by the Royal Museum of Fine Arts of Belgium in 1901;

    https://fine-arts-museum.be/fr/la-collection/alfred-delaunois-apres-vepres. Other titles and distinctions include his membership at La Libre Esthétique, a Belgian avant-garde artistic circle that he joined in 1906; and at the Royal Flemish Academy of Sciences, Letters, and Fine Arts, where he was received a few months before his death in 1941. Crab and Van Buyten, Alfred-Napoléon Delaunois, n.p. Between 1907 and 1930 he exhibited nine times at the Venice Biennale. ↩︎

13. Mostly consisting of essays in gallery’ exhibition catalogues and press articles, in addition to Robert de Bendère’s 1935 monograph (Alfred-N. Delaunois [Brussels: J. & A. Janssens, 1935]), which is by far the most comprehensive publication. ↩︎

14. Only broad descriptors, such as “watercolour”, or “heightened drawing”, are used in the literature. ↩︎

15. “La richesse savante de la matière collabore à parfaire cette réalisation, car Delaunois est un magicien de la nuance. Par de savantes superpositions de tirages, dans ses eaux-fortes, par des rehauts somptueux, dans ses dessins, il arrive à leur donner la sourde richesse de l’écaille, des laques et des émaux. Des visages, mystérieusement lumineux comme une feuille d’ivoire superposée à l’or.” Henri Lavachery, Exposition de l’œuvre graphique du maître Alfred Delaunois (Brussels: Galerie des Artistes Français, 1931), n.p. (translated from the French by Marie-Noëlle Grison). ↩︎

16. Comparisons between Alfred’s handwriting and that of his brothers, on the basis of letters preserved in the M Leuven documentation, confirmed that he was indeed the author of this inscription. ↩︎

17. De Bendère (Alfred-N. Delaunois, 74–75) drew a direct connection between this project and a later one titled La vie bénédictine (The Benedictine Life), a cycle similar in its scope and theme. ↩︎

18. White lilies are a recurring feature in Delaunois’s oeuvre. Gustave Vanzype (Nos peintres [Brussels: Paul Lacomblez, 1905], 3:31), mentioned Delaunois’s depictions of monks, precisely drawn but idealised thanks to the artist having recourse to “accessories,” such as lilies. A drawing titled Pureté de lys is listed in Felix Timmermans and Henri Lavachery, Graphische Werken van Alfred N. Delaunois (Leuven: Akademie van Schone Kunsten, 1936), no. 168. The composition of a drawing from M Leuven, inv. no. G/973/D, also prominently features white lilies. Felix Timmermans (“Alfred Delaunois,” Van Onzen Tijd, no. 23 ([1913–14]: 363) describes a piece Delaunois was working on ca. 1913–14, with an apparition of the Virgin Mary in swirls of incense smoke and “a dream of lilies” with white-clad monks. ↩︎

19. De Bendère, Alfred-N. Delaunois, 73–75 (translated from the French by Marie-Noëlle Grison). De Bendère also makes special mention of the techniques with which Delaunois created some of the works for this project—distemper, pastel, watercolour, gold backgrounds. ↩︎

20. Dominican institutions in Leuven itself included at that time the Klooster der Predikheren on Sint-Annastraat (https://inventaris.onroerenderfgoed.be/erfgoedobjecten/73646[https://inventaris.onroerenderfgoed.be/erfgoedobjecten/73646](https://inventaris.onroerenderfgoed.be/erfgoedobjecten/73646)) and another complex on Ravenstraat (https://inventaris.onroerenderfgoed.be/themas/8294[https://inventaris.onroerenderfgoed.be/themas/8294](https://inventaris.onroerenderfgoed.be/themas/8294)). In addition, De Bendère mentions the church Our Lady of the Dominicans as a motif Delaunois depicted; Alfred-N. Delaunois, 26. ↩︎

21. A likely mention of this drawing features in Exposition d’une partie de l’œuvre d’Alfred-N. Delaunois (Brussels: Galerie Georges Giroux, 1917), under section C, “Fragments de décoration (Études pour fresque murale),” no. 41, “Moine au Lys”. “Le Mystique,” also a bust-length depiction of a monk related to a wall decoration, is illustrated in Albert Croquez, Exposition d’une partie de l’œuvre d’Alfred N. Delaunois (Bruges: [Galerie San Salvador], 1924); and Timmermans and Lavachery, Graphische Werken. Other examples of works related to such decorative cycles can be found in Lavachery, Exposition de l’œuvre graphique, under “Dessins et lavis,” cat. 137 D, “Étude pour décoration murale”; in Timmermans and Lavachery, Graphische Werken, cat. 85, “Fillette– Fragment pour fresque,” and in a section titled “Dessins originaux–Panneau 1: Étude pour décoration murale,” with no further detail. It is quite possible that some of these fragments were exhibited more than once, but the references in catalogues are not precise enough to identify them with certainty. ↩︎

22. Photographs taken in Delaunois’s home (the so-called “temporary museum”; see also note 53) after his death show examples of such mounted panels composing a landscape series, hung high on a wall; from a photo album dated 1955 preserved in the M Leuven documentation. His Belgian contemporary Jean Delville also ventured into monumental painted cycles for public spaces which he executed on large canvases intended to be mounted on the walls; see for instance Plato’s School, oil on canvas, 102 ²³/₆₄ x 238 ³/₁₆ in. (260 x 605 cm), Musée d’Orsay, https://www.musee-orsay.fr/fr/oeuvres/lecole-de-platon-158[https://www.musee-orsay.fr/fr/oeuvres/lecole-de-platon-158](https://www.musee-orsay.fr/fr/oeuvres/lecole-de-platon-158), and other examples in Emilie Berger, “Jean Delville et l’enjeu du « monumental » ”, Koregos – Revue et encyclopédie multimédia des arts, https://koregos.org/fr/emilie-berger-jean-delville-et-l-enjeu-du-monumental/[https://koregos.org/fr/emilie-berger-jean-delville-et-l-enjeu-du-monumental/](https://koregos.org/fr/emilie-berger-jean-delville-et-l-enjeu-du-monumental/). ↩︎

23. For a discussion of the historical and political implications of the Fresco Revival in Germany and Britain in particular, see Mitchell B. Frank and Mark Phillips, “Historical Distance and the Nineteenth-Century Revival of Fresco,” in History and Art History: Looking Past Disciplines, ed. Nicholas Chare and Mitchell B. Frank (New York: Routledge, 2020), 39–53. ↩︎

24. Puvis de Chavanne realised large decorative cycles in various public buildings, notably in Paris (City Hall, the Pantheon, and the Great Amphitheater at the Sorbonne), and the Boston Public Library. Some of these decors were executed in oil on canvas and stuck onto walls. Recent research determined that a preparatory work by Puvis de Chavanne (now at the Norton Simon Museum, Pasadena) was created using distemper on paper, and not gouache as is often mentioned in catalogues. ↩︎

25. Alan Powers, “The Fresco Revival in the Early Twentieth Century,” Journal of the Decorative Arts Society, 1850–the Present, no. 12 (1988): 38. ↩︎

26. For a more focused discussion of this subject, see Anthea Callen, “The Unvarnished Truth: Mattness, ‘Primitivism’ and Modernity in French Painting, c.1870-1907.” The Burlington Magazine 136, no. 1100 (1994): 738–46. ↩︎

27. See, for instance, Trees on a Yellow Background, oil, distemper, charcoal, and pastel on canvas, 97 7/16 x 68 1/8 in. (247.5 x 173.0 cm), Musée d’Orsay, https://www.musee-orsay.fr/fr/oeuvres/arbres-sur-un-fond-jaune-25623. ↩︎

28. Mary Sargant Florence, “The Influence of Material on Style,” Arts and Crafts Quarterly 1 (1920): 13–22. In fact, the iconography chosen here by Delaunois draws quite literally upon representations of the Virgin Mary of the Annunciation, with the presence of white lilies and the soft, veiled figure. Cf., for example, Fra Angelico’s frescoes at the San Marco convent in Florence. The time-honoured Italian fresco technique of wall painting onto freshly laid lime plaster was incompatible with the higher humidity of northern European climates, and therefore had to be adapted. Techniques such as Daniel Maclise’s water-glass medium and Thomas Gambier-Perry’s “spirit fresco” were developed to mimic the effect of a fresco painting while ensuring that their painted murals using these techniques would withstand England’s damp weather conditions. Powers, “Fresco Revival,” 38. ↩︎

29. Soft pastel sticks have a lower binder to pigment ratio, they are thus easier to blend and more friable than oil pastel sticks. ↩︎

30. As was revealed by the MA-XRF mapping of the iron (Fe-K) element. ↩︎

31. These lines appear shinier than the rest. ↩︎

32. We based our assessment of the paint materials on visual examination; no technical analysis of these materials could be performed for this research. ↩︎

33. Crackling and delamination of the oil paint layer is more pronounced in areas where it is the thickest; this is particularly visible in one of the lilies. ↩︎

34. The same oil paint that Delaunois used in the monk’s veil and as an underlayer in the left wrist, as seen in Fig. 5 (this shot was taken with the following settings: f/16, exposure time 25 sec., ISO-200, focal length 120 mm). ↩︎

35. Four of these models (ca. 1890), preparatory for Meunier’s Monument to Labour, are reproduced in Delaunois, Fêtes du centenaire, n.p. ↩︎

36. We use the convention that angles are measured counterclockwise from the x-axis. ↩︎

37. Our observations were compared with microphotographs of untouched paper taken in the same conditions to provide ground truth data. ↩︎

38. All these interactive figures make use of Erdmann’s web-based Curtain Viewer tool: (L. Hoogstede et al., Hieronymus Bosch, Painter and Draughtsman: Technical Studies (Brussels: Mercatorfonds, 2016); Anna Tummers and Robert G. Erdmann, “The Eye Versus Chemistry? From Twentieth to Twenty-First Century Connoisseurship,” in Analytical Chemistry for the Study of Paintings and the Detection of Forgeries, ed. Maria Perla Colombini, Ilaria Degano, and Austin Nevin (Cham: Springer International Publishing, 2022), 3–45; Marie-Noëlle Grison, Leila Sauvage, and Robert G. Erdmann., “Toward an Online Paper Study Toolkit: Developing Innovative Tools for Conservators and Researchers to Investigate the Materiality of Pre-Industrial Paper,” in Papers of the XXXV International Congress of Paper Historians 2021, (2023), 166*‒*179). Each of the imaging modalities was precisely stitched (where necessary) and co-registered, enabling arbitrary combinations of images to be displayed shown juxtaposed (sync mode), mixed (fading mode), or in a dynamic layered peel-away mode (curtain mode). Each configuration of mode, image selection, and zoom-in has a unique URL, enabling the precise specification of an exact views such as those presented here. ↩︎

39. Two framed drawings on a gold background are listed in Lavachery, Exposition de l’œuvre graphique, under nos. 99 and 198, the latter described as a monk’s face, seen from the front. De Bendère (Alfred-N. Delaunois, 74) also mentions that some of the preparatory works for “Le songe des moines” were executed on a gold background. ↩︎

40. Inv. nos. G/973/D, G/974/D, G/425/D, G/958/D. ↩︎

41. The jagged and slightly lifted edges of the leaf are visible under magnification. ↩︎

42. White paint does show corrosion patterns in several areas, including in the lilies and in the right wrist. ↩︎

43. A diluent can be inferred from the mottled aspect of the stain visible under the chin’s current outline. The Ca-K map shows a lesser concentration along the lower outline of the chin, where the pentimento is visible. Comparison with the background around the face—where the presence of chalk as an extender in lighter pastel colours shows as homogenous grey in this map—proves the artist’s intervention caused a change in the chemical makeup of this layer. On chalk as an extender, see Joyce H. Townsend, “Analysis of Pastel and Chalk Materials,” Paper Conservator 22, no. 1 (1 January 1998): 21–28. ↩︎

44. Also a preparatory fragment for a wall decoration, according to the label the artist wrote and pasted onto the verso. ↩︎

45. Only very minimal distortion of the surface is visible in this area under raking light from a 270º angle. ↩︎

46. This way of working is reminiscent of lithography techniques, whereby the artist scrapes out fine lines in the drawing on the stone with a sharp tip to create light accents and contrasting lines. Delaunois was taught printmaking techniques by Karl Meunier, Constantin’s son; Crab and Van Buyten, Alfred-Napoléon Delaunois, n.p. His printed oeuvre comprises etchings and lithographs. ↩︎

47. Since it was written in red and therefore starts phasing out from 600 nm onwards. ↩︎

48. This area was scanned with the following settings: spot size 100, distance 100 mm, dwell time 25 ms. ↩︎

49. The mercury-containing red paint has severely crackled and delaminated in two instances, revealing white paper fibres where the paint flakes have pulled the superficial layer. This is an interesting indication that the artist may have toned his paper in the light pink hue that can be seen in various areas. ↩︎

50. Exposition d’une partie de l’œuvre d’Alfred-N. Delaunois (Galerie Georges Giroux). This catalogue does not include any reproductions of artworks. ↩︎

51. The album is preserved in the Delaunois files at the M Leuven. The number H 42/A, inscribed twice on the verso of the artwork, suggests that the pendant with which it was mounted and framed might bear the number H 42/B. However, the typed inventory of the Delaunois bequest, which features in Crab and Van Buyten, Alfred-Napoléon Delaunois, does not list any drawing other than ours under the number H 42. We have not been able to locate this companion drawing so far. ↩︎

52. Another photograph from the same album shows two other drawings from the M Leuven collection (inv. nos. G/973/D and G/974/D; see also note 40) mounted and framed together in Delaunois’s house. ↩︎

53. Near the end of his life, Delaunois was in contact with the curator of the Royal Museum of Fine Arts of Belgium in Brussels about his project for a Delaunois museum in Leuven (Delaunois to M. Devigne, 20 December 1940, M Leuven documentation). After his death, his brothers Richard and Edgard repeatedly attempted to convince the municipality and the university of Leuven to create this museum, as can be seen through the correspondence kept in M Leuven, but this project never materialised. Eventually Richard bequeathed the collection kept in the house at 132 rue de Tirlemont in Heverlee, referred to in his testament (drafted 3 May 1949) as the “temporary museum” (musée provisoire), to the cities of Leuven and Heverlee, wary that it would otherwise be dispersed at auction. ↩︎

54. We can make out, for instance, a copy of the life mask of Beethoven, a bronze sculpture by his contemporary Georges Minne, and a copy of the winged head of Hypnos after a Greek original (which also features in Fernand Khnopff’s Blanc, Noir et Or (White, Black and Gold), https://fine-arts-museum.be/fr/la-collection/fernand-khnopff-blanc-noir-et-or[Brussels, Royal Museums of Fine Arts of Belgium, inv. no. 3707; [https://fine-arts-museum.be/fr/la-collection/fernand-khnopff-blanc-noir-et-or](https://fine-arts-museum.be/fr/la-collection/fernand-khnopff-blanc-noir-et-or))]{.mark}. ↩︎

55. Nods to Italian Renaissance ornamental vocabulary, as can be seen, for instance, in the low-relief hung at the bottom of a pedestal in Fig. 16, are particularly noteworthy in regard to the studied work. ↩︎

56. Thereby building on the research conducted for Degas’s pastels (Facini et al., “Technical Exploration of Edgar Degas’s Ballet Scene: A Late Pastel on Tracing Paper,” in Facture: Conservation Science Art History, Volume 3: Degas (National Gallery of Art, 2017); and Kathryn A. Dooley and Michelle Facini, “Revealing Degas’s Process and Material Choices in a Late Pastel on Tracing Paper with Visible-to-near-Infrared Reflectance Imaging Spectroscopy,” Journal of the American Institute for Conservation, no. 58 [2019]: 108–21) and complementing existing reference spectra libraries such as https://spectradb.ifac.cnr.it/ ; https://chsopensource.org/pigments-checker/; and https://webimgc.inrim.it/Hyperspectral_imaging/Panel3.aspx. ↩︎

57. For a complete description of the NBMSI setup and camera settings used for this case study, see https://zenodo.org/record/7410238#.Y-Ns03bMJPY. ↩︎

58. For more information about the development of the Portable Light Domes by KU Leuven and their application, see Hendrik Hameeuw et al., “The Painted Panels of the Early Sixteenth Century Mechelen Enclosed Gardens: Art Technical Examination with the Photometric Stereo; White Light and Multispectral Microdomes,” in Imaging Utopia: New Perspectives on Northern Renaissance Art; Papers Presented at the Twentieth Symposium for the Study of Underdrawing and Technology in Painting, Held in Mechelen and Leuven, 11–13 January 2017, ed. Lieve Watteeuw et al. (Leuven: Peeters, 2021), 20:165–75; Lieve Watteeuw and Hendrik Hameeuw, “Art Technical Research on Manuscript Heritage with the White Light and Multispectral Portable Light Dome System (Multi Light Reflectance Imaging),” in Immaginare la Commedia, ed. Ciro Perna and G. Ferrante (Rome: Salerno, 2022), 225–37; and https://portablelightdome.wordpress.com/. ↩︎