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The Wall Paintings at St Stephen’s Chapel, Westminster Palace: Recent Imaging and Scientific Analysis of the Fragments in the British Museum

Recent imaging, examination, and analysis of the few surviving fragments of wall painting from St Stephen’s Chapel have revealed new data relating to the original technique and aspects of workshop practice in the production of these important mid-fourteenth-century wall paintings. Infrared imaging of the paintings provides clear evidence for the presence of an under-drawing and of extensive modification of the design in situ at an advanced stage of the painting process. There are marked differences in the character of the under-drawing on the various fragments studied, which are likely to relate to different hands and may be indicative of workshop practice. In addition, the presence of an original varnish is strongly suggested, the red dyestuff employed for the red lake pigment has been identified, and the complexity of pigment mixtures and stratigraphy of the paint layers has also been elucidated. This information will be discussed in the context of the documentary sources and of analytical results from the investigation of contemporaneous polychromy.


Introduction
When the Society of Antiquaries donated the painted and architectural fragments from St Stephen's Chapel to the British Museum in 1814, its collection of medieval antiquities was practically non-existent. 1 There was little desire on the part of the museum to collect and display European medieval material; the acceptance of the donation can be seen to be at odds with the prevailing-or at least developing-institutional Zeitgeist. 2 Why the museum accepted the fragments, and why the society gave them away needs addressing. It is the aim of this short introduction to set out the evidence for the removal of the fragments from St Stephen's after 1800, their donation to the British Museum in 1814, and the context of their first public redisplay in 1852. 3 The Department of Antiquities had been set up in 1807 and it was not until 1831, with the purchase of the Lewis Chessmen, that another substantial and important group of medieval objects would be added to the collection. The St Stephen's fragments are therefore the first considerable group of medieval objects to enter the museum. Their collecting history offers a glimpse into the status and perception of the medieval past at the British Museum.
had made his drawings in situ, or from fragments that had previously been removed from the walls. This mattered because a drawing made in situ was thought more likely to be accurate; removal created loss of paint and stone. Clarifying this will help in tracking when the fragments now at the British Museum might have been moved from St Stephen's and taken to the Society of Antiquaries. In his description of 1800, Carter mentions portions of the chapel "falling beneath the workmen's hammers". 9 Smith gives further evidence for the destruction of the interior in a description of his own working practices. He would begin at first light and work until nine o'clock, when those arriving to work on the renovation would start to remove what he had recorded earlier that morning. 10 Further, Smith's drawing of Cotton Garden shows it as a site filled with fragments from the chapel. It is a document for the removal of substantial fragments from the interior, including "a part of an inscription which was over one of the pictures, and another has on it a painting of two men, one of them in the inside of a gilt bull." 11 In a letter promoting his and Smith's publication, then in progress, Hawkins wrote to defend Smith's methods against Smirke's, suggesting that the latter had made his drawings after the fragments were removed from the walls. 12 Smirke refuted this statement and went on to clarify that certain fragments were moved subsequently into the best light, so that he was able to "make corrections, and discover many parts which, but for the removal, could never have been seen." 13

The Removal of the Fragments to the Society of Antiquaries
Several letters in The Gentleman's Magazine provide further evidence that a number of painted fragments had already been removed and taken to the Antiquaries before Smirke began his recording. Hawkins informs us that paintings from the first window "were taken down; some of them were conveyed into Mr. Groves's room, others into Cotton Garden among the rubbish, and others presented to the Antiquarian Society, long before Mr.
Smirke was engaged." 14 His account that numerous fragments had already been taken down and transferred to the Antiquaries is corroborated by a letter from R. Wynne, who recalled a visit to Cotton Gardens on 21 October 1802. Wynne provides a description of the condition of the fragments still present in the garden: "This inscription is similar to the fragments in the possession of the Antiquarian Society, which were mostly taken down from the South side of St Stephen's chapel long before Mr. Smirke began his drawings." 15 By 1803, the Society of Antiquaries had possession of at least some of the paintings from St Stephen's Chapel, which it must be assumed are the pieces that were eventually donated to the British Museum. If the letters by Hawkins, Smith, and Wynne are correct, then the Antiquaries would have received them between 11 August and the 23 September 1800. There is unfortunately no information in their council meeting minutes to confirm this suggestion. The bulk of the antiquarian effort was dedicated towards preserving the paintings via drawing and publication. It would seem that little effort was made to salvage the majority of the fragments remaining in Cotton Garden. It was surely not a question of time, as Wynne's letter makes clear that the Cotton Garden fragments were still there in 1802, and were being taken by members of the public to be reused as building material. A fragment showing Queen Philippa was preserved and drawn by John Carter, but its whereabouts are now unknown. 16 Other architectural fragments do survive, although some in poor condition. Two fragments from a moulded mullion were acquired by the British Museum in 1883; 17 and Sir John Soane's Museum holds four heavily weathered stone architectural fragments and a cast from a heraldic shield. 18

Technical Examination and Analysis of the Fragments
Although the British Museum's development of an interest in medieval antiquities was protracted, the work of Carter, Smith, and Smirke was pioneering. This innovation was mirrored in the analytical investigations undertaken on the St Stephen's Chapel fragments by the London doctor John Haslam in 1800. 30 His work on the fragments included the first recorded analysis of paint samples ever undertaken, and marked the beginning of an interest in this field by leading scientists in Europe at the turn of the century.
Haslam's ground-breaking work provided a remarkably accurate preliminary overview of the pigments and binding medium employed in the scheme of fourteenth-century wall painting. It was another 170 years before further examinations and analysis were carried out, in advance of the conservation and remounting of the surviving fragments at the British Museum in 1973. 32 Aside from these instances, a few other minor phases of analysis have been undertaken to answer particular technical queries, and a summary of the previous studies is given in the Appendix below. 33 Following discussions with researchers on the AHRC-funded project 'St Stephen's Chapel, Westminster: Visual and Political Culture, 1292-1941' (2013, and with other scholars at a seminar hosted at the British Museum, the decision was made in 2015-2016 to undertake a limited phase of further examination. 34 In light of more recent research on related material, this set out to resolve a small number of outstanding technical questions and included undertaking technical imaging, some further sampling, and re-examination of the 1973 samples with analytical techniques which were not available at that time. Primary research questions focused on: the evidence for the setting out of the paintings, such as the use of incision or under-drawing; the type of dyestuff used in the preparation of the red lake pigment; evidence for original finishes, including further investigation of the mordant gilding; and whether there are any remains of original varnish.
Constrained by the restricted access afforded by the fixed display of the majority of the fragments in glass-fronted cases, only a limited amount of infrared and ultraviolet imaging, examination, and sampling was possible in 2015. Despite the constraints, much useful new information relating to the painting methodology and workshop practices has been assembled, and these results are detailed below. However, perhaps the single most significant advance, which has been made as part of the recent study, is the production of a new set of high-resolution images of the paintings, undertaken by the British Museum in 2017. These images will make detailed study of the fragments possible for all and thus revolutionise the accessibility of these important fourteenth-century wall paintings by exploiting a system of display appropriate for the twenty-first century.

Infrared Examination
Infrared reflectography (IRR) was undertaken on those fragments accessible in the 2015 examination to investigate the possible presence of underdrawing. 35 The resulting infrared images have provided new information relating to the preparatory methods used in setting out the paintings.
Although only a portion of the original scheme survives, the few remaining fragments provide clear evidence that a number of different hands were involved in both the drawing and painting phases of the production of this once-extensive cycle of images.
A scene from the Book of Job, reveals an under-drawing in a fluid medium, but rather thickly and stiffly applied (Fig. 2). Both the exterior outline and interior folds of the drapery are indicated, but they are rather awkwardly and crudely drawn, with broad stiff lines.
View this illustration online The infrared image from the Turret Scene reveals a drawing that is similar, in that all of the folds of the drapery are suggested, but here the drawing is much less stiff, with more confident and flowing brushwork. This can be seen particularly clearly in the fluid freehand drawing of the female figure's hair (Fig. 3), and in the flowing curly interior details of the drapery at the bottom left (Fig. 4). It is also apparent that the lines setting out the architecture have been ruled, as evidenced by the overrun of the line at the bottom of the scene. Ruling against a straight edge would explain this type of overshoot (Fig. 4). The infrared image also shows that the architecture was very carefully planned out in advance of painting, and that the drawing was followed very closely in the subsequently applied paint layers.
View this illustration online  In the Destruction of Job's Children, a rather different character of underdrawing is evident, and again this is likely to relate to the various hands present in the workshop (Fig. 5). For the preparatory drawing of this fragment, only the external outlines of the drapery are indicated, none of the internal folds are shown. Further, it is clear that the architecture was drawn in first, and then followed by the horizontal lines of the table. The position of the front of the table was subsequently altered considerably, indicating that the planning of the overall composition was still relatively fluid at this stage, and that certain major compositional changes were made to the drawing on the wall. The drawing of a spoon extends over the first line of the table front, suggesting that at least some of the items of tableware were added after changes in its position were made. However, other objects had already been sketched in at an earlier stage, and so were moved forward at the same time as the table front, such as the platter (just to the left of the glass, in the centre of the image in Figure 5), which was repositioned and refashioned as a dish.
View this illustration online A number of objects are more distinct in the infrared image than in the painted fragments, such as the knife and bread roll on the left side of the table (Fig. 5). Examination of Smirke's drawing of this scene, made in 1800, confirms that a row of three bread rolls was originally positioned along the front of the table, as it was still visible then (Fig. 6). The IRR image also shows that the glass vessel at the centre of the scene was initially drawn in an upright position. It is clear that the repositioning of this object was made at a very advanced stage of the painting process, as the tumbled vessel has been painted over the final flesh paint of the hands of the figures on the right side of the scene (Fig. 7).  By comparison with the crude and stiff under-drawing of the first fragment described, which may suggest copying, here the drawing has been refined and developed in situ and, like the Turret Scene, was undertaken in a fluid, confident freehand technique. By contrast, with the Turret Scene, this draughtsman did not indicate the inner drapery folds.
Examination of the IRR image of the Blinding of Tobit (Fig. 8) reveals a drawing that is different in character to those described above. The features of the bearded figure of Tobit on the right-hand side of the scene have been carefully and skilfully drawn with minute attention to detail. The final flesh painting partially masks the preparatory drawing, but examination of a detail taken at high magnification in normal incident light shows that the preparatory drawing has been undertaken in brown paint, rather than the black fluid material used elsewhere. In the IRR image, we see through the overlying paint, allowing the under-drawing of the face and beard to be easily seen. The final paint layers of this particular fragment have also been exceptionally finely painted. Here, we have a very skilled hand, evident both in the brown under-drawing and in the fine detail of the final paint layers (Figs 9, 10 and 11).
View this illustration online    Examination of the Blinding of Tobit reveals another significant change in the composition-again undertaken at an advanced stage of the painting process (Fig. 12). Here, a broad vertical architectural feature in the original background goes directly through the body of Tobit's wife. Further, the green paint of the original background is evident beneath the pink of her drapery, and shows through where the pink paint is worn or damaged, indicating that Tobit's wife was painted in her present position after the completion of the green background (Fig. 13). It appears likely that this figure was originally shown emerging from a doorway, or was partially masked behind an architectural feature, but was subsequently moved to a more dominant position in the composition. This new finding has been significant in relation to Jane Spooner's recent interpretation of the iconography of this scene. 36 View this illustration online  The IRR images suggest that a number of painters drew freehand in situ, developing their compositions on the wall. This is consistent with the evidence of the fabric accounts. 37 They confirm that Master Hugh of St Alban himself was involved in the drawing process, since the entry for the week beginning 27 February 1352 records that he was paid for two days' working, "on the drawing of images in the same chapel". 38 The stiffness of some other areas of drawing may suggest that subsidiary artists were copying from models (perhaps on paper), which in all likelihood were also prepared by the master painter, as suggested by an entry in the accounts for the week beginning 30 April 1352, in which Master Hugh of St Alban is paid for "directing the drawings for the said painters". 39 The accounts also provide evidence for the purchase of paper, which may have been used for this purpose, in the week beginning 2 January 1352, "To John Lambard for two quires of royal paper bought for the designs of the painters 20 d.". 40 In addition to the use of preparatory drawing, lines were finely incised into the lead white paint layer for setting out the inscriptions (Fig. 14). Ruled or snapped vertical and horizontal lines for guidance in the overall setting out are also visible in one case below the white paint layer (Fig. 21).

Mordant Gilding
Examination of the surviving painting fragments at high magnification revealed that many of the fine linear details, which now appear white, for example, the decorative borders of drapery and the edging of the tablecloths, were once gilded. Remnants of the original gold leaf remain on the surface in the Blinding of Tobit, and traces are evident on other fragments, such as the Destruction of Job's Children (Figs 15,16,17,31 and 32). The published antiquarian sources confirm that more extensive remains of gold leaf were evident at the end of the eighteenth century. Describing the Destruction of Job's Children, it is stated that "the borders and ornaments of all the dresses are gilt". 41   Although very little of the gold leaf itself now survives, the fine white lines that are the remains of the original white mordant used to adhere the metal leaf to the surface are still apparent. This new finding is significant, since white mordants were generally reserved for the application of silver leaf. The only other roughly contemporary example of a white mordant for gold leaf is that used for the fine linear details on Christ's drapery in the late fourteenthcentury Judgement scene in the Chapter House of nearby Westminster Abbey (Figs 18 and 19). 42   The use of a warm-coloured mordant to lend a deeper golden tone to the subsequently applied gold leaf is far more common and has been found elsewhere on the St Stephen's fragments, for example, for the borders of text (Fig. 21), and also on the tin-relief (background) decoration, which was mordant gilded after being applied to the surface of the painting   Recent instrumental analysis of the constituents of the yellow-coloured mordant reveal that it comprises a drying oil, 46 combined with a yellow earth pigment, a lead pigment (lead white or red lead, or both), a few large inclusions of chalk and quartz, and a few particles of a brilliant red earth and vermilion (Fig. 23). 47 A mordant closely comparable in overall colour and constituents was used in late fourteenth-century wall paintings in the Byward Tower, Tower of London (Fig. 24). 48 Analysis suggests that the oil did not have much chance to dry before the gold leaf was applied, and this of course is the whole point, that the mordant was sticky enough to hold the metal leaf on the surface. 49 There is little doubt that the two different coloured mordants, white and yellow, were used with the intention of producing distinctive and different optical effects in the subsequently applied gold leaf.
It seems likely that silver leaf itself was employed elsewhere, as it is mentioned in the accounts for the chapel-although entries for it are much less frequent than for gold leaf and tin foil. 50 Haslam's analysis confirmed that silver leaf was used, the specimen of painted glass you lately sent me consists of verdigrise prepared with varnish, painted to the glass; immediately over which silver-leaf is laid, and upon that a cement, to fasten it to the niche wherein it was laid. 51 Examination of the surviving fragments, suggested that silver leaf was used for a number of items of tableware, such as the two goblets, cutlery, and platters in the Destruction of Job's Children (Figs 5 and 7). Indeed, they are described as such in the early nineteenth-century accounts. 52 Unfortunately, due to limited access, it was not possible to sample any of these areas to confirm the nature of the metal leaf, or to determine the constituents and overall colour of the mordant employed. Though silver leaf would originally have been glazed or varnished to prevent tarnishing, the metal leaf in these areas now appears dark and degraded.
Examination of the surface at high magnification also suggests that silver leaf may have been employed to render the tumbled glass vessel at the centre of this scene. A green glaze seems to have been applied over metal leaf to produce the appearance of liquid in the type of greenish transparent glass that would have been available at the time (Fig. 7). 53

Red Lake Pigment
Two samples of red lake paint were analysed: one from the pink robe of the female figure at the far left side of the Destruction of Job's Children (1973/S7; Figs 5, 25 and 26) and the other from the red drapery of the female figure in the Blinding of Tobit (Fig. 12). High-performance liquid chromatography (HPLC) analysis in both cases confirmed that the lake pigment was made from dyestuff extracted from the lac insect Kerria lacca Kerr. The presence of erythrolaccin, an alkali-soluble dyestuff component suggests that the lake was prepared by alkaline extraction of sticklac. 54  Gas chromatography-mass spectrometry (GC-MS) analysis of the sample taken from the Destruction of Job's Children (1973/S7) suggests that the dry lake pigment was combined with a heat-bodied drying oil, likely to be linseed or walnut oil, a mixture of the two, or indeed different oils in the different layers. 55 The paint cross-section prepared from this sample shows that the red lake pigment was applied in two layers over an underpaint of lead white combined with red lead, yellow earth, and a few black particles (Fig. 26). The lower of the two red lake-containing layers contains particles of red lead and lead white, which would not only have increased the opacity of the layer, but would also have aided drying. Over this, a translucent red lake glaze layer has been applied to model the drapery. This layer additionally contains a few particles of red lead and lead white, probably incorporated to function as driers.
In other areas, the red lake pigment was combined with ultramarine to produce a purple colour, as shown in the sample taken from the drapery below Tobit's wife's veil in the Blinding of Tobit (Figs 12 and 27). Here the red lake pigment has partially faded; it is now clearly visible only at the base of the paint layer. 56 Lake pigments were expensive. Indeed, records of the purchase of pigments for the chapel indicate that red lakes were among the most expensive materials a painter could buy. 57 The accounts for 1351-1352 include an entry for 1 lb cynople for 30s., while 2 lbs of vermilion-the most costly of all the other red pigments-was 3s. 4d., or about one-twentieth of the cost. 58 The documentary evidence suggests that several different types of red lake pigment may have been purchased for the St Stephen's Chapel scheme. One cyneple was priced at 17s. 3d. for 1½ lb, another cynople 20s. for 1 lb, while 2 lbs cynopre of Montpellier (de Monte Pessalono) cost 16s. 59 This price differential, with one of the lakes at twice the price of the others, must be due to a substantial difference in the quality, or to the lake having been prepared using a more expensive variety of dyestuff (such as lac or kermes lake, as opposed to madder, which would have been cheaper). 60 However, in the two samples taken, only lac lake has been identified. Indeed, recent analyses of lake pigments from Westminster of about this period have indicated that lac lake is the only red organic colorant employed in these high-quality commissions. 61 It seems likely that it was the only high-quality lake pigment available (though at a high price) until the last quarter of the fourteenth century, when the use of kermes lake (extracted from the insect Kermes vermilio Planchon) is confirmed in paintings for the first time. 62 Perhaps the earliest example of the use of kermes lake is in a sample taken from the frame of the tester over the tomb of the Black Prince in Canterbury Cathedral (d. 1376). Here, both kermes and lac have been identified in the same paint sample, along with a tiny trace of madder. 63 Among the other early identifications of kermes lake in England are the Apocalypse and Old Testament cycles  in the Chapter House of Westminster Abbey, as well as the portrait of Richard II, also in Westminster Abbey (dated to the last decade of the fourteenth century). On this, it was used in a mixture with a small amount of madder as a glaze over vermilion for the king's robe. 64

Original Varnish
A final question of this phase of analysis concerned the presence of original varnish. The documentary sources suggest that varnish was used in the original painting scheme, since the accounts for the decoration of the chapel mention the purchase of both red and white varnishes. For instance, between 15 August 1351 and 13 February 1352 white varnish is supplied three times and in much larger quantities than the red, which was supplied only once. 65 While the purchase of varnish is documented, the manner in which it was employed is less certain, although the sources again provide some information. Haslam's report begins with a description of the separation of the varnish layer and the media (that is, paint layers). It states: In order to examine these colours, I was obliged, after having carefully scraped them from the stone, to employ a quantity of impure aether (spiritus aetheris vitriolici of the London Pharmacopeia), to dissolve the varnish which had been laid over them, and also to separate the oil with which the colours had been prepared. 66 He went on to separate out the "oleaginous" matter, and noted that it, "had the peculiar smell of varnish and adhered as such to the sides of the phial. What the composition of this varnish may be, I can not precisely determine". 67 Haslam clearly describes a layer of varnish "laid over" the colours. However, it is not possible to be absolutely certain that the varnish he removed from the surface of the paintings was original. It could, for example, have been applied to protect the surface of the paintings before they were lost from view, some time before 1651. 68 Nonetheless, the notion of a later overall varnish layer seems unlikely in the light of Haslam's observation of two different types of varnish on the paintings. He states that the gold leaf was, "covered with a white or transparent varnish" and goes on to note that, "in some instances a brilliant lacker had been employed, the lustre of which is undiminished in the specimens before me". In an appendix to his analysis, Haslam also mentions the presence of verdigris in varnish over silver leaf. 69 The use of a translucent layer to modify the appearance of the surface in particular areas is supported by Smirke (1800), in his account of The Adoration of the Magi; St George, and Edward III with his sons, he describes what is likely to have been a varnish or a glaze for the purpose of making the floor recede: "it is glazed with transparent brown, which increases in strength as the floor approaches the diaper work" (Fig. 28). 70 The accumulated documentary evidence certainly seems to confirm the presence of a translucent layer, which varied in colour from area to area, and which functioned to modify the appearance of the surface. This layer may have been a varnish or a glaze layer, or potentially both. While a glaze is generally a translucent (usually) oil-based layer containing pigment (often a lake pigment), an oil-based medieval varnish would also have contained a resinous component. 71 The type of resin employed may have contributed to the overall colour of the varnish. 72 Broadly speaking, fourteenth-and fifteenth-century recipes for oil-based varnishes are of two types. In the first, the resin constituent(s) are heated together with the oil. In the second, the oil and resin are heated separately, and the resin is melted before the hot oil is added (for less easily soluble resins, this is a far more efficient method). 73 Whichever method was chosen for manufacture, analysis of their constituent components can be extremely challenging.
Examination of one of the paint samples taken in 2015 at high magnification suggested the presence of an original varnish or glaze layer on the surface of the green paint (Fig. 29). This yellowish translucent layer is approximately 20 microns thick and exhibits strong fluorescence when viewed in ultraviolet light. There are drying cracks that go through both the green paint and the translucent layer on the surface, suggesting that they are likely to be coeval; if the uppermost layer had been applied later, it would be present within the drying cracks. The translucent upper layer was carefully separated out and analysed by GC-MS analysis, which confirmed the presence of a drying oil, but no resinous components could be detected. In case a polymerised resin, such as sandarac or amber had been used in the varnish, pyrolysis GC-MS was also performed. The analysis of the resinous components of original varnishes has generally proved extremely challenging, and it was not possible to detect any resin in this case. 74 This may be due to the fact that the proportion of resin dissolved in the oil to make these early varnishes was always rather low, but it may also reflect the changes undergone by these materials, both during the preparation of the varnish and in its subsequent ageing.
Though the layer is mainly composed of organic material, analysis in the scanning electron microscope with energy-dispersive X-ray analysis (SEM/ EDX) did confirm the presence of a few calcium-rich and silicon-rich particles (likely to be chalk and quartz), a little lead (likely to have been originally added as lead white, to function as a dryer), and a trace of copper. Copper salts are very mobile within oil-based paint layers and the small quantity present here is likely to have originated from the verdigris-based paint layer below. There is certainly insufficient evidence to suggest that this was a copper green glaze. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis was also undertaken, which confirmed the presence of metal oxalate and carboxylate salts, suggestive of a reaction between the lead and copper salts and the oil in the layer. 75 Re-examination and analysis of one of the samples taken in 1973, taken from an area of blue drapery in the Destruction of Job's Children, suggests the presence of a varnish layer over the ultramarine paint layer, although it was not possible to confirm the presence of a resinous component (Fig. 30). 76 In addition, the sample taken from Tobit's wife's veil in the Blinding of Tobit also seems to provide evidence of an original varnish, here used as an intermediary layer before the application of fine surface details. Figure 31 shows the fine linear details of the veil in white mordant, with a few tiny traces of the original gilding remaining on the surface. The paint crosssection shows the white mordant on the surface (Fig. 32). In UV light, the layer below the white mordant fluoresces. Although it was not possible to undertake analysis on this extremely thin intermediate layer, it seems likely that it is a varnish which was applied over the pale purple of the drapery before the fine linear details of mordant gilding were added on the surface. A varnish layer such as this would have provided a smooth and evenly absorbent surface on which to paint the final delicate details. 77  Varnishes that are considered to have belonged to the original paint schemes have already been identified at Westminster Abbey: on the Retable; on the Crouchback tomb; on the south transept figure of St Christopher; and possibly also on the sedilia. The type of resin incorporated in an original varnish has been characterised in only two cases in medieval English polychromy: an amber-containing varnish has been identified on the late fourteenth-century wall paintings in the Byward Tower, Tower of London; and a sandarac varnish has been detected on a mid-thirteenth-century engaged column with a stiff-leaf capital from Wells. 78 Both contemporary financial accounts and later descriptions of two differently coloured "varnishes" on the surface suggest the presence of an original varnish layer. The material evidence, when considered together (for instance, the drying crack that passes through both the paint and the translucent surface layer, the fluorescence of the surface layer, and its thickness and colour), all points to the presence of an original varnish on the St Stephen's Chapel wall paintings (Fig. 29). The fact that we have not been able definitively to confirm the presence of the resin here is likely to be a function of the difficulty of identifying the resinous component of such an aged material in the tiny sample available for analysis.

Conclusion
The red lake pigment has now been characterised as lac lake and a white mordant for gold leaf has been identified. In addition, the presence of an original varnish is strongly suggested.
Infrared imaging of the paintings has provided clear evidence for the presence of an under-drawing and of extensive modification of the design in situ at an advanced stage of the painting process. There are marked differences in the character of the under-drawing on the various fragments studied, which are likely to relate to different hands and may be indicative of workshop practice. The exceptionally high quality of a precious few sections of the under-drawing have been made visible for the first time. By revealing the quality of the drawing hidden underneath the paint layers, we have gained new insights into the delicacy and care with which this scheme was created, from the initial preparatory stages all the way through to the final paint layers, which points towards the overall quality of the scheme.
The present, damaged appearance of the many areas of the paint surface merely reflects their violent physical history. Perhaps the most significant outcome of this study is that the new high-resolution images will make the surviving fragments of one of the finest schemes of English medieval wall painting accessible to all. The Gentleman's Magazine 73 (1803), I: 31-32: "the drawings for the Society were not begun till after the 24th of September, as I am well informed; at which time the originals had been removed from their first station; so that the artist never saw them as they stood placed in the House of Commons, but was obliged to copy them as so many detached subjects".  Haslam's work was followed by that of Jean Chapel (1809) and Sir Humphry Davy (1814), who analysed pigment

Footnotes
The cross-section shows the white mordant used to adhere the fine linear detailing in gold leaf over the rich red of the drapery in the Judgement scene, in the Chapter House of Westminster Abbey (Fig. 20). The style of the brooch visible at the left side of Figure 19 is also closely comparable to that in a Scene from the Book of Job (BM 1814.0312.2d; Fig. 18 Analysis was undertaken using GC-MS (conventional and following low temperature pyrolysis using a thermal separation probe) and FTIR spectroscopy (transmission and ATR-FTIR imaging), see Catherine Higgitt, "Organic Analyses, St Stephen's Chapel, Westminster Palace", unpublished report, Scientific Department, National Gallery, London, 2017.
SEM/EDX analysis confirms the presence of lead (Pb) within the mordant and FTIR analysis indicates the presence of lead carboxylates (lead soaps) within the sample. However, the nature of the lead-based pigment, which may have been added as a drier to the oil or mordant, cannot be determined. Jane Spooner, "Royal Wall Paintings in England in the Second Half of the Fourteenth Century", unpublished PhD thesis, Courtauld Institute of Art, University of London, 2016-2017; Jane Spooner, "An Admonitory Wall Painting at the Tower of London", Burlington Magazine 158 (2016): 940-949.
The sample examined was small but these results are suggestive of a rather lean oil-based mordant, with a high inorganic content, in which the oxidative drying processes were retarded by application of the gold, and in which metal-soap formation has occurred, see Higgitt, "Organic Analyses".
For example, on 22 April 1352, to John Lyghgrave and William Allemand, 400 leaves of silver for painting of the same chapel, at 8d. per hundred; Ayers, The Fabric Accounts of St Stephen's Chapel, no. 40, m. 18 (w/b 23 April 1352). It is also possible that part-gold (a composite metal leaf, in which gold and silver are beaten together) or tin foil are present here. Unfortunately it was not possible to sample this area of the painting, but future non-invasive XRF investigation may help to elucidate the elemental components of the metal leaf.