Fig. 7
From: Visible and infrared imaging spectroscopy of paintings and improved reflectography
Detail images from Madonna and Child with Four Angels, c. 1290. Samuel H. Kress Collection, 1961.9.77, National Gallery of Art, Washington, DC. a Color detail. b Detail from broadband infrared reflectogram (1000 to 1700 nm) which provides little material information. c False-color image (R = 1650 nm, G = 1400 nm, B = 1050 nm) showing distinct material differences. The region under the eyes is likely a conservation fill and corresponds with the red spectrum in (d) that has a strong absorption at ~1415 nm, possibly talc. The brown regions in the false-color image show brushstrokes likely associated with verdaccio, an underpainting that is probably original to the artwork. This region corresponds with the black spectrum whose absorption between ~1450 and 1550 nm indicates the presence of gypsum