Research ArticleCHEMICAL PHYSICS

Macroscopic x-ray powder diffraction imaging reveals Vermeer’s discriminating use of lead white pigments in Girl with a Pearl Earring

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Science Advances  30 Aug 2019:
Vol. 5, no. 8, eaax1975
DOI: 10.1126/sciadv.aax1975
  • Fig. 1 Comparison of various macroscopic imaging techniques.

    (A) Visual photograph of Girl with a Pearl Earring marked with the areas scanned with transmission (T) and reflection MA-XRPD (R). The locations where the paint cross sections X39 and X40 were taken are marked with a circle. (B) MA-XRF distribution for Pb-L and (C) MA-XRF distribution for Pb-M. (D) NIR reflectance imaging spectroscopy distribution displaying the integrated area of the narrow ─OH absorption feature associated with hydrocerussite, centered near 1447 nm, in reflectance units. (E) Pseudo absorption of the narrow ─OH absorption feature. Photo credit: René Gerritsen, Art & Research Photography and Mauritshuis.

  • Fig. 2 Crystalline phase distributions obtained by μ-XRPD for two paint cross sections collected from the Girl’s face.

    For hydrocerussite and cerussite, the weight fractions were calculated in every pixel of the image. For calcite, palmierite, and cinnabar, a scaling parameter is displayed instead to improve the qualitative readability of the maps. Brighter areas indicate a higher weight fraction or scaling parameter value. The intensity was scaled independently for each image to improve readability: Intensities should not be directly compared. The scan parameters and size of the scanned areas are shown in table S1.

  • Fig. 3 Results obtained with MA-XRPD reflection mode.

    (A) Optical photograph of the analyzed area. (B to F) Distribution images obtained with reflection MA-XRPD showing the scaling parameter for every pixel. Higher scaling parameter values are represented by a brighter color. (B) Hydrocerussite, (C) cerussite, (D) calcite, (E) palmierite, and (F) cinnabar. (G) Histogram for the wHC/(wHC + wC) ratios. The black dashed line represents the combined contribution of both Gaussian curves. (H) Corresponding RGB image for (G). (I) Histogram for the average depth of hydrocerussite relative to the average depth of cerussite. (J) Corresponding RGB image for (I). Images were scaled independently of each other: Intensities should not be directly compared. Photo credit: René Gerritsen, Art & Research Photography and Mauritshuis.

  • Fig. 4 Results obtained by MA-tXRPD.

    (A) Optical photograph of the analyzed area (B to D) Distribution images obtained with MA-tXRPD showing the scaling parameter for every pixel. Higher scaling parameters are represented by a brighter color. Images were scaled independently of each other: Intensities should not be directly compared. (B) Hydrocerussite, (C) cerussite, and (D) calcite. (E) False color image and (F) Histogram showing the wHC/(wHC + wC) ratio. Photo credit: René Gerritsen, Art & Research Photography and Mauritshuis.

  • Fig. 5 Combined results of macro- and micro-XRPD.

    (A) Proposed stratigraphy for the lead white paint and ground layers based upon the MA-XRPD (transmission and reflection) and μ-XRPD data for the shadow flesh tones, bright flesh tones, and dark background. In each layer, the corresponding wHC/(wHC + wC) ratio is indicated. Layer thickness is not to scale. (B) 3D image showing the relation between wHC/(wHC + wC) ratio (ranging from 0 to 1, black indicates areas without lead white) and the relative depth of hydrocerussite compared to cerussite based on the MA-rXRPD data. A larger height indicates a smaller to no measured difference in depth between hydrocerussite and cerussite (and thus the presence of a homogeneous lead white mixture at the surface), while a lower height indicates the presence of a larger difference between hydrocerussite and cerussite (and thus the presence of a hydrocerussite-rich layer below a cerussite-rich layer).

  • Table 1 Overview of the wHC/(wHC+ wC) ratios for every layer (or set of layers) analyzed with μ-XRPD, MA-tXRPD (transmission), and MA-rXRPD (reflection).

    For MA-XRPD, an error of ±2σ is used; for μ-XRPD, a relative uncertainty value of ±10% is cited (see Materials and Methods).

    AreaTechniqueLayer(s)wHC/(wHC + wC)
    Bright flesh
    tones
    μ-XRPDUpper (a3)0.65 ± 0.07
    Lower (a4)0.79 ± 0.08
    Ground (b1)
    MA-tXRPDAll layers0.75 ± 0.05
    MA-rXRPDSuperficial0.65 ± 0.06
    Shadow flesh tonesμ-XRPDUpper (a1)0.48 ± 0.05
    Lower (a2)
    Ground (b2)0.83 ± 0.08
    MA-tXRPDAll layers0.82 ± 0.06
    MA-rXRPDSuperficial0.37 ± 0.20
    BackgroundMA-tXRPDAll layers0.88 ± 0.04
    MA-rXRPDSuperficial0.37 ± 0.20

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/8/eaax1975/DC1

    Fig. S1. Overview of the MA-XRPD scanning instrument.

    Fig. S2. NIR reflectance spectra for cerussite (lead carbonate powder) and hydrocerussite (lead white cremnitz).

    Fig. S3. Extracting depth information with MA-XRPD.

    Fig. S4. XRPD data treatment procedure.

    Table S1. Overview of the scans performed with μ-XRPD and MA-XRPD.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Overview of the MA-XRPD scanning instrument.
    • Fig. S2. NIR reflectance spectra for cerussite (lead carbonate powder) and hydrocerussite (lead white cremnitz).
    • Fig. S3. Extracting depth information with MA-XRPD.
    • Fig. S4. XRPD data treatment procedure.
    • Table S1. Overview of the scans performed with μ-XRPD and MA-XRPD.

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