As part of the 2018 Girl in the Spotlight project, reflectance and molecular fluorescence imaging spectroscopy (RIS, FIS), and macroscale X-ray fluorescence scanning (MA-XRF) were performed on Johannes Vermeer's Girl with a Pearl Earring (c. 1665, Mauritshuis) with the goal of obtaining a comprehensive understanding of the distribution of pigments. Prior analysis of cross-sections in the 1990s, and their recent (re)-examination identified many of the pigments present in the painting. The results from all three imaging methods, along with site-specific fibre optic reflectance spectroscopy, confirmed Vermeer's limited palette and determined how and where each pigment was used. RIS and MA-XRF found the blue region of the headscarf was painted with natural ultramarine and varying amounts of lead white. The yellow part of the headscarf was painted with yellow ochre and lead white, and the border of the headscarf additionally contained ultramarine and lead-tin yellow. The lit side of the jacket was painted with yellow ochre, lead white, and ultramarine, whereas the darker, ruddy blue-green areas that are in relative shadow contained yellow ochre with ultramarine. FIS also mapped a red lake in portions of the shadowed areas at the back of the jacket. The Girl's skin was painted using earths (ochres), lead white, vermilion, and some red lake. Fluorescence emission from red lake was strongest in the lips, where vermilion was also found. The pearl earring was depicted using a scumble and highlight of lead white. In the dark background, the RIS data cube allowed the determination of the visible spectral shape even though the overall reflectance intensity was low (1 to 3%). A reflectance inflection point at ~ 700 nm indicated the presence of indigo, whereas lack of a reflectance peak at green wavelengths in most areas indicated degradation of the yellow pigment previously identified as weld. Some small green areas in the background (i.e. reflectance maximum at 525 nm) were found; these coincided with areas previously protected by old retouchings, and are thus better preserved. The combination of all three spectral imaging modalities provided a more complete understanding of how the colouration of the painting was achieved.

The initial steps that Johannes Vermeer took to create Girl with a Pearl Earring (c. 1665) are, partially or completely, hidden beneath the painted surface. Vermeer's painting technique involved applying underlayers that vary in colour and thickness, on top of which he applied the upper paint layer(s). To investigate the painting's genesis, the Girl was examined using non-invasive scientific imaging as part of the project The Girl in the Spotlight (2018). This was complemented by the re-examination of existing paint cross-sections using microscopic analytical techniques, including focused ion beam-scanning transmission electron microscopy (FIB-STEM). The weave of the canvas, visible in the X-radiograph, was examined using a new computer-assisted thread-level canvas analysis algorithm to measure the thread spacing and thread angles. The canvas was primed with a warm light grey ground, although probably not by Vermeer himself. The tinted ground provided neutral base tone upon which he began to lay in areas of light and shade in his composition, and some outlines around the figure. Multispectral infrared reflectography( MS-IRR) images in four spectral bands spanning the spectral range from 900 to 2500 nm were collected of the painting at high spatial resolution (50 µm/pixel). Visible 3D digital microscopy visualised the underlayers where Vermeer left them visible around the perimeter of the figure as a contour, and where the upper paint layers are thin. These infrared reflectograms and visible micrographs identified three distinct preparatory phases of Girl with a Pearl Earring: the ground, fine black outlines, and underlayers. Some pentimenti were also detected, including a change in the position of her ear. The combination of examination methods showed that the materials beneath the surface played an important role in establishing the three-dimensional space, fall of light, and the eventual colour in different areas of the painting.

The soft modelling of the skin tones in Vermeer's Girl with a Pearl Earring (Mauritshuis) has been remarked upon by art historians, and is their main argument to date this painting to c. 1665. This paper describes the materials and techniques Vermeer used to accomplish the smooth flesh tones and facial features of the Girl, which were investigated as part of the 2018 Girl in the Spotlight research project. It combines macroscopic X-ray fluorescence imaging (MA-XRF), reflectance imaging spectroscopy (RIS), and 3D digital microscopy. Vermeer built up the face, beginning with distinct areas of light and dark. He then smoothly blended the final layers to create almost seamless transitions. The combination of advanced imaging techniques highlighted that Vermeer built the soft contour around her face by leaving a 'gap' between the background and the skin. It also revealed details that were otherwise not visible with the naked eye, such as the eyelashes. Macroscopic imaging was complemented by the study of paint cross-sections using: light microscopy, SEM-EDX, FIB-STEM, synchrotron radiation µ-XRPD and FTIR-ATR. Vermeer intentionally used different qualities or grades of lead white in the flesh paints, showing different hydrocerussite/cerussite ratios and particle sizes. Lead isotope analysis showed that the geographic source of lead, from which the different types of lead white were manufactured, was the same: the region of Peak District of Derbyshire, UK. Finally, cross-section analysis identified the formation of new lead species in the paints: lead soaps and palmierite (K 2 Pb(SO 4) 2), associated with the red lake.

The background of Vermeer's Girl with a Pearl Earring (c. 1665, Mauritshuis) has, until recently, been interpreted as a flat dark space. The painting was examined in 2018 as part of the research project The Girl in the Spotlight using a combination of micro-and macro-scale analytical techniques. The stratigraphy of the background was determined from samples mounted as cross-sections, and its material composition was analysed using electron microscopy and chromatographic techniques. The underlayer contains mainly charcoal black, and the glaze contains two organic colourants-indigo and weld-and a copper drier. Deterioration of the glaze has made features in the background difficult to discern with the naked eye. Complementary imaging techniques were able to visualise Vermeer's signature, and the suggestion of folded fabric (possibly a curtain) on the right side of the painting. The distribution of the layer(s) in the background were imaged using: infrared reflectography (900-1100 nm), multi-scale optical coherence tomography scanning, macroscopic X-ray fluorescence and 3D digital microscopy. Vermeer applied the black underlayer vigorously with overlapping brushstrokes that varied in thickness. When he applied the glaze on top, it levelled out to make a smooth flat surface. The visual effect of the background contrasts the figure of the Girl and projects her forward in space, closer to the viewer.

A seventeenth-century canvas painting is usually comprised of varnish and (translucent) paint layers on a substrate. A viewer's perception of a work of art can be affected by changes in and damages to these layers. Crack formation in the multi-layered stratigraphy of the painting is visible in the surface topology. Furthermore, the impact of mechanical abrasion, (photo)chemical processes and treatments can affect the topography of the surface and thereby its appearance. New technological advancements in non-invasive imaging allow for the documentation and visualisation of a painting's 3D shape across larger segments or even the complete surface. In this manuscript we compare three 3D scanning techniques, which have been used to capture the surface topology of Girl with a Pearl Earring by Johannes Vermeer (c. 1665): a painting in the collection of the Mauritshuis, the Hague. These three techniques are: multi-scale optical coherence tomography, 3D scanning based on fringe-encoded stereo imaging (at two resolutions), and 3D digital microscopy. Additionally, scans were made of a reference target and compared to 3D data obtained with white-light confocal profilometry. The 3D data sets were aligned using a scale-invariant template matching algorithm, and compared on their ability to visualise topographical details of interest. Also the merits and limitations for the individual imaging techniques are discussed in-depth. We find that the 3D digital microscopy and the multi-scale optical coherence tomography offer the highest measurement accuracy and precision. However, the small field-of-view of these techniques, makes them relatively slow and thereby less viable solutions for capturing larger (areas of) paintings. For Girl with a Pearl Earring we find that the 3D data provides an unparalleled insight into the surface features of this painting, specifically related to 'moating' around impasto, the effects of paint consolidation in earlier restoration campaigns and aging, through visualisation of the crack pattern. Furthermore, the data sets provide a starting point for future documentation and monitoring of the surface topology changes over time. These scans were carried out as part of the research project 'The Girl in the Spotlight' .