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Dual mode standoff imaging spectroscopy documents the painting process of the Lamb of God in the Ghent Altarpiece by J. and H. Van Eyck

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Science Advances  29 Jul 2020:
Vol. 6, no. 31, eabb3379
DOI: 10.1126/sciadv.abb3379
  • Fig. 1 The Ghent Altarpiece by the Van Eyck brothers (1432, Cathedral of Saint Bavo, Ghent, Belgium) with the wings opened.

    The white rectangle indicates the area featuring the Lamb of God, the central motif of this polyptych and subject of this paper. Color image taken after the 1950s treatment and before the 2019 treatment (© Lukasweb.be - Art in Flanders vzw).

  • Fig. 2 Detail of the head of the Lamb.

    Color image (A) before the removal of all 16th century overpaint and (B) after the removal of all 16th century overpaint, revealing the face of the Eyckian Lamb. The dotted lines indicate the outline of the head before treatment (© Lukasweb.be - Art in Flanders vzw). MA-XRF elemental maps showing the distribution of (C) gold, (D) copper, (E) mercury with a red arrow indicating the position of the Eyckian Lamb’s nostrils and (F) lead. (G) Colorized composite MA-XRF elemental map showing the elemental distribution of copper (in green), mercury (in red), gold (in yellow), and lead (in gray). (H) Composite false-color infrared RIS image (B, 1000; G, 1350; R, 1650 nm) shows underdrawn lines, indicating the position of the facial features of the Eyckian Lamb. The white arrow indicates the nostrils, whereas the black arrow indicates the jawline. All chemical images were collected after varnish removal but before 16th century overpaint removal.

  • Fig. 3 Paint microsample extracted from the body of the Lamb.

    The scheme on the left illustrates the stratigraphy observed in the paint cross section collected in 1950 to 1951 and reanalyzed here. An area of the cross section is shown on the right, recorded with three different methods (from left to right): (A) Backscattered electron image recorded with a scanning electron microscope (SEM-BSE) and (B) lead distribution image recorded with an SEM equipped with an energy dispersive x-ray spectrometer (SEM-EDS-Pb), followed by (C) an optical microscopy (OM) image. The uppermost “varnish and retouching” layer, but not the overpaint, was removed before imaging spectroscopy was done. Size of micrographs: 95 μm by 42 μm.

  • Fig. 4 The Lamb of God.

    (A) Color image of the Lamb before removal of all 16th century overpaint; the location of the paint sample discussed in Fig. 3 is indicated by a white reticle. (B) The Lamb after removal of all 16th century overpaint in 2019 (© Lukasweb.be - Art in Flanders vzw). (C to E) MA-XRF elemental maps recorded before removal of all 16th century overpaint showing the distribution of (C) lead (in white), (D) copper (in green), and (E) mercury (in red). The yellow arrows in (D) indicate the edge of the larger altar. (F) False-color infrared RIS image (B, 1000; G, 1350; R, 1650 nm) revealing underdrawing that denotes the size of the smaller version of the Eyckian Lamb’s back and tail, more rounded hindquarters, repositioning of the hooves, and the larger size of the altar. The white arrows indicate underdrawing lines defining a smaller body, whereas the black arrows point to wavy underdrawing lines applied for torso modelling and fleece texture.

  • Fig. 5 Detail of the angel to the left of the Lamb.

    (A) Color image after 2019 cleaning and during retouching (© Lukasweb.be - Art in Flanders vzw). The brown and black arrows indicate the position of the underdrawing lines shown in (C). (B) IRR image (http://closertovaneyck.kikirpa.be, © KIK-IRPA, Brussels) revealing the infrared-absorbing underdrawing. (C) The corresponding false-color infrared RIS image (B, 1000; G, 1350; R, 1650 nm) allows further distinction of the types of underdrawing: (i) Brown arrows indicate the finer lines of the first stage of underdrawing, which appear brownish in the RIS image, and (ii) black arrows show the thicker lines in a liquid medium from the second stage of underdrawing, which appear blackish in the image. The yellow color in the background is a result of partial penetration of copper-containing green paint in the infrared.

  • Fig. 6 RIS images and map of the Lamb derived from processing the infrared reflectance image cube.

    (A) Infrared RIS false-color image (B, 1000; G, 1350; R, 1650 nm) and (B) associated average infrared RIS spectra collected from the colored dashed shapes shown in (A). (C) RIS lead white map derived from processing the infrared RIS image cube. Brighter areas of the map indicate stronger absorption from the –OH group of lead white. (D) X-ray radiograph detail (http://closertovaneyck.kikirpa.be, © KIK-IRPA, Brussels) after removal of all 16th century overpaint in 2019. The white arrows indicate where the body of the Lamb was revised, whereas the black arrows point to fleece texture.

Supplementary Materials

  • Supplementary Materials

    Dual mode standoff imaging spectroscopy documents the painting process of the Lamb of God in the Ghent Altarpiece by J. and H. Van Eyck

    Geert Van der Snickt, Kathryn A. Dooley, Jana Sanyova, Hélène Dubois, John K. Delaney, E. Melanie Gifford, Stijn Legrand, Nathalie Laquiere, Koen Janssens

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