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THE PRODIGAL SONBY PETER PAUL RUBENS

III. PAINTING TECHNIQUE AND RESTORATION

Susan Farnellwith additional comments by Nico Van Hout

The recent restorationThe Prodigal Son has just been restored. It was in good condition but the restoration was necessary because it was becoming increasingly difficult to see the painting through the layers of thick and discoloured varnish. Rubens must have intended the dramatic perspective of the view through the barn to give an added sense of depth to this composition while also experimenting with the effects of daylight and candlelight. The loss of transparency and the browning of the varnish had not only dulled the colours but had also greatly reduced the sense of space and light within the painting. The restoration has involved the gradual removal of the layers of varnish and over-painting from what is often a remarkably thin paint layer. There has been wide use made of brown glazes in this painting. In many areas the paint is applied so thinly that the underlying light ground can be seen through the brush-strokes. Fortunately the general condition of the paint layer was good with few important losses. The restoration has meant that we can now see Rubens’ painting clearly; we can appreciate the different sources of light, the free handling of the paint and the extraordinary sense of depth within the composition.

Technical studyThe restoration process provides an ideal occasion to observe a painting at close quarters and at the same time the opportunity to carry out technical and scientific documentation.1

The advantage of studying the technique of a recently restored painting is being able to see the paint layer rather than trying to imagine it, hidden under layers of dark and obscuring varnish. In the case of The Prodigal Son, the technique proved to be a great deal more spontaneous and the execution more rapid than it was thought to be prior to restoration.2

Technique

a. The supportThe Prodigal Son was painted on a well-constructed oak panel which measures 109.75 x 158.2 cm. It is composed of 5 horizontal planks which are butt-joined (ill. 1).

All the planks are quarter-sawn; the fourth plank is partly false quarter-sawn, where the medullary rays cross the annual rings diagonally. The wood came from the Baltic region and planks 2, 3 and 5 are from the same tree. Dendrochronology has been able to give an earliest felling date of 1613 for the fourth plank, giving the earliest possible creation date as 1615. However allowing a 15-year average for sap wood rings, the more probable date would be later, from 1621 onwards.3

1. 22 - 23 cm

2. 22 cm

3. 20.75 cm

4. 24.75 cm

5. 20.50 cm

Ill.1 The dimensions and position of the planks, recto side.

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Information about the construction of the panel is limited by the presence of a cradle (ill. 2) and a double layer of lead white paint applied between the elements of the cradle in1895.4

The panel must have been planed-down in order to attach the cradle. Under the vertical battens, we can see that areas of the panel were built-up by pieces of oak of

approximately 4 x 12 cm, glued side by side, presumably to create a level surface for attaching the fixed horizontal elements of the cradle (ill. 3).5

The panel has been reduced in size on all four sides but the presence of the vertical prepared but unpainted edges on the recto side, tells us that the amount may be slight as the painting proper is intact.The “unpainted edges” or margins correspond approximately to a rebate of between 3 -7 mm, cut at a right-angle into the vertical

edges on the reverse of the panel (ill. 4). This appears to be part of the original construction. We had thought that the rebates were related to the framing but it now seems probable that they were made to accommodate temporary grooved battens, or ‘channel edge supports’ that were slid onto the end-grain edges of panels to prevent warping.6 A similar rebate can be found on the reverse of the panel of “Christ and the Woman taken in Adultery” by Rubens in the Musée Royal des Beaux-Arts, Brussels.7 The ‘unpainted’ edges of The Prodigal Son have a ground layer (unlike the Brussels panel).

Ill.2 The cradle on the reverse of the panel

Ill.3 Detail of where a vertical batten of the cradle has been removed to show that the back of the panel had been built up before the cradle was attached.

Ill.4 Detail of rebate along the vertical edge

It seems that ‘channel edge supports’ may have been put on in the studio, during the painting process, presumably when the panel began to warp. This could explain why some paint can be found on the unpainted edge but a distinct margin, or limit to the paint layer, was made once the battens were in place.

b. The frameWe have no information about the original frame. The frame in which that The Prodigal Son is currently shown is of English origin, dating from the 19th century.

c. The groundThe panel was prepared with what looks like the traditional chalk glue ground (ill. 5). It is off-white, thinly applied and is smooth and hard. Very few samples were taken and in the cross-section (ill. 8) the ground appears to be absent.

The ground continues to the edge of the panel where the sharpness of the outline confirms that the panel has been trimmed. The “unpainted” but prepared edges of the vertical sides of the panel were obviously intended to be covered later by the frame.No isolation layer was visible. Because much of the paint layer was thinly applied, the white ground influences the final painting by allowing light to reflect through even the darker areas, adding luminosity and transparency.

Ill.5 Detail of the “unpainted” edge or margin.The white ground can be seen where the frame has rubbed away the overlying paint layers

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d. The imprimaturaA pale grey stripey imprimatura is present but not easily detected. Stripey imprimatura is characteristic of Rubens panel paintings but it is most commonly seen in his sketches on panel, such as the recently restored

Triumphal Chariot of Kalloo (KMSKA, inv. no 318), where the imprimatura is ochre rather than grey. It is often less apparent in his finished paintings, as is the case here. It can be seen, however, in the gap between the painted contours of the wooden post and the sky and through the transparent brown paint of the post (ill. 6). The imprimatura can be seen more clearly with infrared photography (ill. 7) where it appears to have been roughly applied with a wide bristle brush in horizontal and diagonal directions (2.), changing to a vertical direction along the vertical edges.

The stripey imprimatura may have acted as an isolation layer preventing the oil of the paint layer from sinking into the porous white ground. It was also a device to give a tonality to the ground without losing its luminosity.

e. The underdrawingNo underdrawing was visible or detected by infra-red photography. It is, in any case, unusual to find underdrawing in Rubens’s finished paintings, although more common in his sketches. An example, however, can be found in The Farm at Laeken, (London, The Royal Collection), where “lines of

Ill.6 The grey stripey imprimatura can be seen in the gap in the paint between the post and the sky. Rubbed away the overlying paint layers.

Ill. 7 The grey stripey imprimatura is visible under the transparent paint layer of the tree and the wooden post.

underdrawing are visible in the arm and face of the standing woman in the centre”8

f. The paint layer PigmentsAnalysis: a number of inorganic pigments have been identified by using PXRF, a non-destructive method of analysis.9 Organic pigments frequently used by Rubens, such as red and yellow organic glazes, indigo, Cassel earth and bitumen, cannot be identified by this method of analysis.The following pigments were identified: white lead was identified in the 29 places that were analysed; sienna or possibly umber in the browns with occasional traces of vermilion; vermilion probably in combination with red earth for the reds; in the yellow highlights of the hay, lead-tin yellow with probably a yellow earth. The greens were composed of a mixture of yellow, probably lead tin yellow and a copper containing pigment, such as azurite, or blue or green verditer. The blues used for clothing contained copper indicating the use of azurite or blue verditer. However the blue for the sky could be identified as either indigo or ultramarine / lapis lazuli. Very few samples were taken from the paint layer. Two samples were taken from the grey paint on the margin of the left edge. This was to identify the large white grains that occur throughout the paint layer but predominantly in the dark area of the roof, on the left side of the picture. Another sample was taken in the sky to identify the blue pigment that could not be determined by PXRF.The ubiquitous white granular pigment was identified as lead white. The sample taken to analyse the blue pigment in the sky can be seen in cross-section (ill.8) where ultramarine/ lapis lazuli was identified. The under-lying grey layer contains chalk and lead white. Originally we believed it to be the ground layer but now see it as an intermediate layer and that the ground layer is missing.10

Ill.8. Cross-section, taken from the sky with part of a leaf. The blue pigment was identified as ultramarine / Lapis lazuli.

(Photograph, Antwerp University).

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g. Method of paintingOne of the most remarkable aspects of the technique of this painting is the apparent speed and spontaneity of its execution. The following description is an attempt to describe the technique, by which way Rubens succeeded in executing a complex, often thinly painted but detailed composition while at the same time demonstrating an extraordinary liveliness in his painting.

Establishing the composition:It is difficult to know to what extent Rubens had developed the composition for The Prodigal Son before transferring it to panel. In the absence of any important changes of composition and the fact that areas were reserved in the paint layer, we should conclude that it was carefully planned. The composition, in any case, would have been underpinned by detailed drawings taken from nature, such as his study of A Man Threshing beside a Wagon, Farm Buildings Behind, ca 1617-18 (J.P. Getty Museum, Los Angeles). In it we see an identical wagon in front of a similarly thatched farm building.11

There is no detectable underdrawing. One of the methods of transferring a composition to its final support may have been with a material such as black

or other coloured chalk. The following description may offer an explanation of why we see no trace. “..it would seem from the De Mayerne MS that it was customary to erase, or nearly so, the initial rough drawing in black chalk before or during the painting process.”12

If we look at Rubens’s sketches on panel, he often used thin grey or warm brown paint as a brushed drawing over the imprimatura. This method allows alterations to be easily adjusted while the composition is being developed and does not disturb any final

transparent or thinly applied paint layer. Another method used by Rubens to place figures was by painting into a scumble or opaque wet paint.13 An

example of the former type of laying in or placing details in The Prodigal Son, can be seen in the brown lines of the sow’s hind legs and, at a later stage of the painting, where a cow’s horns have been provisionally placed using thin brown fluid paint (ill.9).While an example of the latter, wet paint method, can be illustrated by the painting into the wet paint around the woman feeding the pigs, where she was originally placed more to the left and her shoulders have finally been made less broad (ill.10).

Apart from the laying in of the structure of the barn and principle elements of the composition, it would have been important for Rubens to establish the areas of light and shadow cast by the different sources of light, daylight and candlelight. This would have to be done in the early stages. The unusually grainy texture of the paint surface that is so noticeable on the left of the picture, in the dark, thinly-painted rafters, is caused by large grains of lead white pigment. They come from an underlying paint layer that may have been used to lay in the composition. We do not yet know if the opaque grey paint visible along the left vertical margin belongs to this laying-in stage but, if so, it seems plausible that it was used to establish areas of light and shadow. (A detail of the grey paint on the left margin can be seen in ill 5).

The painting technique:Once the composition was in place, the painting of the background must have been executed at great speed judging by the broad brush strokes in the central rafters (ill.11), and by the thin and transparent brown washes applied along the beam that catches the light (ill.12).

Ill.10 Painting into the opaque wet paint of the background to place the woman feeding the pigs. She was originally more to the left and had broader shoulders.

Ill.9 The cow’s horns have been provisionally placed using thin brown fluid paint.

Ill.11 Infra-red photography gives a clear image of the broad brush strokes and rapid execution of the beams and rafters in the background.

Ill.12 The beam was rapidly executed using thinly applied transparent brown washes.

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By comparing a finished detail of the barn with an infrared photograph of the same detail, we are able to see the spontaneous brush strokes that underlie some of the final paint layer (ill.13, 14). The hurriedly-applied dark horizontal brush stroke to the left, near the top edge of the panel, crossing under the light-coloured roof supports, may have been intended

as another beam. The fact that it is now so easily visible in the light areas underlines the artist’s command of his technique elsewhere in the painting. As much as three-quarters of this composition was painted using tones of brown paint. Much of it was applied very thinly and transparently as we can see even in the dark areas of the roof. 14 The middle and foreground are much lighter in tone and in the immediate foreground

the paint is often so thinly applied that the white ground itself is barely covered. An idea of how the painting stage developed can be seen by a slight change of position in the skirt of the old woman holding a candle.15

Originally she was painted advancing further into the barn. A few highlights corrected the position, but the firm linear brush strokes of her original skirt remain clearly visible (ill.15).

Ill.13 Detail of the barn in normal light

The old woman’s head is an example of painting directly into the dark background paint while it was still wet. It is also a remarkable example of rapid and sure technique. By adding a few strokes of brown glaze and white highlight he created her headdress and face. The whole is brought to life by the dramatic red highlights under her chin and nose from the

reflected light cast up by her candle (ill.16). Elsewhere, however, reserves in the paint layer were made to make use of the lightness of the white ground and to some extent, the effect of the stripey imprimatura. Examples of reserves in the foreground include the two pigs on the left, (but not the hind leg of the sow), the wooden supporting post of the barn and the Prodigal Son’s head and body. The tree trunk was reserved to the height of the first fork, after which the branches were painted over the blue sky. Even the belt of the bag hanging in the centre of the picture, over the cows, was carefully

reserved. The blue sky was painted up to either side of it, although the landscape had already been sketched in behind (ill.17). The belt is a device which, together with the

sight lines of the architecture of the barn, is intended to draw the onlooker’s eye into the picture, through the barn and out to the countryside beyond.16. The sense of depth was further enhanced by a glaze of natural ultramarine, a vivid blue, added to the sky line just above the trees to the right of the belt. The choice of ultramarine / lapis lazuli as the blue pigment for the rest of the sky is interesting as it was very expensive. Azurite, which tends to have a greener tonality than natural ultramarine, has been used as the blue pigment in the rest of the painting.17 Perhaps Rubens decided that only natural ultramarine could give the intense blue of day-light that he needed to contrast with the artificial and warmer candle-light in the barn.

Ill.16 The old woman’s head was painted into the wet paint of the background.

Ill.14 Infra-red photograph showing detail of the barn where the vigourous brush strokes of the underlying paint layer are clearly visible.

Ill.15 Shows, the firm linear brush strokes of an earlier position of the old woman’s skirt ( just to the right)

Ill.17 The belt was carefully reserved against the sky. The blue paint was added to either side of it.

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Much of The Prodigal Son was executed alla prima. The rapid execution, already noted in the broad-brush treatment of the background, can also be illustrated by the numerous examples of painting wet paint into wet paint. These include the cock’s tail painted with three rapid brush strokes into

the wet background paint (ill.18), working into wet impasto paint with the stub-end of the brush to imitate basket weave (ill.19), painting a branch through the impasto paint in the tree (ill.20) and the standing heifer’s rump, where the wet paint of the short diagonal brush strokes have been dabbed with a brush leaving round textured marks in the wet paint (ill. 21).

Of the many types of brush strokes that are clearly visible in the paint layer, a few examples are: in the thatch of the barn roof, where the brush strokes can be seen in the thinly applied, transparent paint (ill.22). The cock’s neck feathers, (ill.23) where white impasto paint has been applied with rapid strokes of a finely pointed brush, and the horizontal brush strokes in the barn, where a more flat-ended brush was used (ill.24).

Rubens has employed an almost graphic way of painting the cows and the pigs, where the diagonal brush strokes are similar to a hatching technique used in drawing. These lines follow the form and create a sense of volume using a minimum of material. The two horses were painted using a similar

Ill.18 The cock’s tail was painted with three rapid brush strokes into the wet background paint.

technique, but the areas of light and shade of the grey stallion were given more substance by the addition of a smooth and fluid paint layer, either of transparent brown in the shadow or pale grey in the light areas. The hindquarters seem to have been underpainted with a dark grey paint applied in irregular circular patterns, over which the lighter grey was added to produce a subtle dappled effect. Highlights were added in short diagonal strokes while white impasto paint completed highlights to the tail.Some parts of The Prodigal Son were painted with attention to detail, particularly in the centre while in areas that were less likely to be noticed the execution is particularly free and almost sketchy. Thus the central

Ill.19 “Drawing” into the wet impasto with the stub-end of the brush

to imitate the basket weave.

Ill.20 Painting a branch through the impasto paint in the tree.

Ill.21 The short diagonal brush strokes have been dabbed with the end a brush making round textured marks into the

wet paint

Ill.22 Brush strokes are clearly visible in the thinly applied paint of the thatch of the barn roof.

Ill.23 The white impasto paint of the cock’s neck feathers, was applied with a finely pointed brush.

Ill.26 By comparison the hind legs have an almost sketchy execution.

Ill.24 Horizontal brush strokes, where a more flat-ended brush was used.

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heifer’s head is painted with a high degree of finish (ill. 25) while her hind legs, in shadow, have a more summary, almost sketchy execution (ill. 26).

This is a painting that can best be appreciated by standing at some distance. As we have seen Rubens employed a number of devices to enhance the element of space within this composition. The final brush strokes may well have been the rapidly applied highlights added to the fork in the foreground and some of the more hurriedly applied cobwebs in the rafters, again with the idea of drawing us into this remarkable painting.

Susan Farnell

Rubens is believed to have retouched The Prodigal Son later on in his life. The painting was, in any case, in his possession at the time of his death. Apparently the artist was unable to resist the temptation of making adjustments to the composition. Unlike the other faces in the painting, that of the stable hand on the far left is executed in very expressive, patchy brushstrokes. This style does not correspond with the smooth, calligraphic approach that is so characteristic of Rubens’s work from around 1618. The white horse also appears to have been retouched. Its head, unlike the rest of its body, was not kept in reserve, but sketched onto the brown background colour in a few quick light brushstrokes. The hind end and tail have been accentuated with some touches of white paint, so that the horse catches more light and thereby draws the viewer’s attention. Also, Rubens added some volume to the right flank of the brown horse. The purpose of these corrections was possibly to achieve a better balance in the composition. Without the alterations, clearly the most illuminated areas in the picture were on the right-hand side.

In the print after the painting by Schelte Adamsz Bolswert, one notices that the large deciduous tree in the farmyard was originally a rather measly

pollard willow. We were able to determine by means of an infrared image that Rubens reserved the shape of this pollard willow in the paint layer, as we notice the stripy imprimatura through the thinly applied paint of the trunk (ill. 7). This is however not the case for the rest of the trunk and the branches, which were painted over the greyish-blue sky. Perhaps Rubens chose to add a lush crown to soften the transition from the bright sky to the angular contours of the barn. Rubens is known to have retouched other paintings which he felt no longer tied in with his artistic aims. In quite a few cases, such corrections involved adjustments and sometimes enlargements of the support.18

There are hardly any other paintings of this size in Rubens’s oeuvre that have been painted as sketchily as The Prodigal Son. The explanation probably lies in the fact that the barn, which takes up most of the composition, is shrouded in twilight, and Rubens tended to provide far less detail in the darker areas of his paintings than in the brighter ones. The only comparable “cabinet picture” is The Calydonian Boar Hunt in Los Angeles (c. 1611),19 in which the boar as well as the foreground and background are also rendered rather sketchily. There are however a number altarpieces, including the Adoration of the Magi in Antwerp (1624), the St. Ildefonso Triptych in Vienna (1630-31) and the Adoration of the Magi in Cambridge (1633-34), which were executed with similar economy of means. The same holds for the monumental Hercules Drunk in Dresden (1613-14).20 Rubens executed these large paintings himself, quickly, alla prima, with medium-rich paints that he could apply thinly to the panels. As a consequence, the chalk glue ground is visible through the paint layer in many places in these works. As in The Prodigal Son, individual brushstrokes in the abovementioned paintings are visible

Ill. 7 The grey stripey imprimatura is visible under the transparent paint layer of the tree and the wooden post.

Ill.25 The central heifer’s head is painted with a high

degree of finish.

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mostly in the shaded areas. The technique of scratching into wet paint with the back of a brush, which Rubens applied in the basketwork in The Prodigal Son, is rather rare in his oeuvre (unlike in the work of Rembrandt, Jan Lievens, Aert van der Neer and Arent de Gelder).21

Nico Van Hout

1) The following documentation was carried out:Dendrochronology, see note 3.Infra-red Photography, (Adri Verburg).Infra-red Photography with false colour, (Adri Verburg).UV photography (Susan Farnell).Photographic documentation (Susan Farnell and Adri Verburg).Non-destructive inorganic pigment analysis (PXRF), see note 9.Cross-sections and analysis, see note 10.

X radiographs were not taken because of the lead white on the reverse of the panel2) John.Smith, Catalogue Raisonné, 11, 804; 1X, p.300, N° 205. “ …the picture is painted with extreme care..”3) P. Klein (Zentrum Holzwirtschaft an der Universität Hamburg), Report on the dendrochronological analysis of the panel, 17.3.2005.4) Archives of the KMSKA. The painting was acquired for the Museum in 1894, bought from Gauchez, Paris. The earliest treatment report that was found in the archives dates from 14th March 1895. It is a proposition by Maillard to re-glue the panel, to make a cradle and apply a double layer of ceruse to the back of the panel. (Archive dossier E 18f ). 1895 Maillard Archief, box E6,E8d, E8e. 1896 Maillard Archief, E8e. E18f 1937 No information, just reference. 1946 C. Bender, information, nothing specific. 1953 Just reference. 1977 Just reference. Also mentioned in two reports of Benders in 1994 and 1996.5) J.A. Glatigny, The support was treated in 2004. The sliding elements of the cradle needed to be unblocked prior to restoration, to prevent strain on the panel. The two horizontal breaks in the panel and all but one of the numerous short splits along the vertical edges were stable. 6) In many cases the ‘channel edge supports’ would have been in place before the ground was applied to the panel and only removed once the painting was to be framed; in that case the panel would have two unpainted and ungrounded edges and a ‘barbe’. I am grateful to Christina Currie for information concerning ‘channel edge supports’. For more detailed information on this subject see D. Allart et C. Currie, ‘Analysis of selected works by Pieter Bruegel the Elder and Pieter Brueghel the Younger’, Brussels, Royal Institute of Cultural Heritage, collection Scientia artis (forthcoming).7) This work was also painted on a panel constructed with horizontal planks. The recto side has two ungrounded-edges and a “barbe” indicating that the ground was applied when the vertical sides were held in ‘channel edge supports’. These must have been removed during painting as the paint layer overlaps the “barbe” onto the wood of the unpainted-edge. I am grateful to Hélène Dubois for this information; detailed information gathered during the Rubens Project of the Musées Royaux des Beaux-Arts de Belgique in Brussels, should be available at the end of next year, probably as a database/web site.8) C. Brown, Making and Meaning: Rubens’s Landscapes, exh. cat., London, 1996, p. 117. 9) Pigment analysis, using PXRF (Keymaster Tracer III-V), was carried out by Geert van der Snickt and Koen Janssens, Antwerp University, department of Chemistry. The identification of inorganic pigments by this method is made by a process of deduction: in this case, by comparing the chemical elements present in a sample of approx. ½ cm² with those of a comparable colour, from the limited number of pigments available to artists in the 17th century. Secondary colours such as green could be of a single mineral origin but were often made of mixtures of blue and yellow thus complicating the identification of the pigments used. XRF identifies elements through the depth of the paint layer and beyond, not just on the surface, which may lead to results that are difficult to interpret.10) Koen Janssens, G. van der Snickt, cited note 9, Cross-section and SEM and analysis by XRD.11) See also Study of an Ox, ca. 1618, Albertina, Vienna (8253); the central heifer in the Prodigal Son is very similar to this study but in reverse position. A similar ox appears in The Farm at Laeken, London, The Royal Collection, (RCIN 405333). In the same painting the position of the cow that is lying-down

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is close to one in The Prodigal Son, but in reverse, as is the man on horse back, leading another horse to water.12) J.Plesters, ‘“Samson and Delilah”: Rubens and the Art and Craft of Painting on Panel’, National Gallery Technical Bulletin 7, 1983 p 38, note 21.)13) Both these methods can be seen in his sketch of the Triumphal Chariot of Kalloo, Koninklijk Museum voor Schone Kunsten, Antwerp, inv. no 318.14) However in some areas where dark brown or black paint was applied more thickly, premature drying cracks can be seen in the paint layer. This problem occurs in other paintings by Rubens and may be due to a bituminous content in the paint. See R. White, ‘Brown or Black Organic Glazes, Pigments and Paints’, National Gallery Technical Bulletin, 10, 1986, pp 58-71, p. 62, for problems caused by bitumen and aspheltum in the drying of oil film, and p.65, lignites and peats as principle source of Cologne earth, retards drying in oil films. J. Kirby, ‘The Painter’s Trade in the Seventeenth Century: Theory and Practice’, National Gallery Technical Bulletin, 20, 1999, p.38 on Cassel or Cologne earth, and other dark brown translucent pigments used by Rubens and Van Dyke; in same volume R. White, ‘Van Dyke’s Paint Medium’, pp. 84-88, esp. p. 84 with reference to paint film defects and also brown-black tars, pitches and bistre.15) A slight change of position can be seen in infrared photography where the winnowing fan, hanging on the wall, seems to have been smaller. There is a deformation in the panel near the top of the basket. We cannot be sure whether this is an old area of damage or perhaps an original repair in the panel. We are also not sure of the reason for losses in the paint layer of the skirt of the young woman feeding the pigs. Before restoration, they were thought to be due to flaking paint. This proved not to be the case but the paint has been damaged in localised areas.16) The perspective has been slightly corrected in the engraving of The Prodigal Son by Schelte à Bolswert (reproduced in M. Rooses, L’Oeuvre de P.P. Rubens, Antwerp 1888, vol. 11, pl. 89). There are a number of other variations, some of which include: the cows being carefully tethered, one of the mare’s forelegs is visible, the winnowing fan on the wall is smaller; the main tree is pollarded. The engraver has misunderstood the construction of the roof in the top corner above the manger, where a diagonal roof support has become a rafter.17) Kirby 1999, cited in note 12, pp 35-36.18) Cf. G. Martin, ‘Two closely related landscapes by Rubens’, in The Burlington Magazine, 757, CVIII (April 1966) pp. 180-184; R. Bruce-Gordon, ‘Rubens’s “Landscape by Moonlight”: technical examination, in The Burlington Magazine, CXXX (August 1988), pp. 591-596; V. Poll-Frommel, K. Renger, J. Schmidt, ‘Untersuchungen an Rubens-Bildern: Die Anstückungen der Holztafeln’, in Jahresbericht Bayerische Staatsgemäldesammlungen, 1993, pp. 24-35; K. Renger, ‘Anstückungen bei Rubens’, in Die Malerei Antwerpens: Gattungen - Meister -Wirkungen (Vienna, 1993), pp. 157-160; K. Renger, ‘Rubens-stücke. Die Anstückungen von Münchner “Silen” und “Schäferszene”’ Wallraf-Richartz-Jahrbuch, LV, Festschrift für Prof. Dr. Justus Müller Hofstede (Cologne, 1994), pp. 171-184; N. Van Hout, ‘A second self-portrait in Rubens’s “Four Philosophers”, in The Burlington Magazine, CXLII, 2000, pp. 694-697.19) Calydonian Boar Hunt, Los Angeles, The J.P. Getty Museum, inv. no. 2006.4.20) Adoration of the Magi, KMSKA, inv. nr. 298 (Jaffe 1980, no. 780); St. Ildefonso Triptych, Vienna, Kunsthistorisches Museum, inv. 678/ 698 (Jaffé 1980, no. 998); Adoration of the Magi, Cambridge, King’s College Chapel (Jaffé 1980, no. 1095); Hercules Drunk, Dresden, Gemäldegalerie Alte Meister, inv. no. 987 (Jaffé 1980, no. 215).21) See also Rubens’s St George Slaying the Dragon (Madrid, Prado, inv. no. 1644; Jaffé 1980, no. 69). Here, the hairs of the horse’s tail are also scratched into the dark paint. As a result, the beige underpainting comes to the surface.