Chemical Mapping by Macroscopic X-ray Powder Diffraction (MA-XRPD) of Van Gogh's Sunflowers: Identification of Areas with Higher Degradation Risk.

The discoloration rate of chrome yellow (CY), a class of synthetic inorganic pigments (PbCr1-x Sx O4 ) frequently used by Van Gogh and his contemporaries, strongly depends on its sulfate content and on its crystalline structure (either monoclinic or orthorhombic). Macroscopic X-Ray powder diffraction imaging of selected areas on Van Gogh's Sunflowers (Van Gogh Museum, Amsterdam) revealed the presence of two subtypes of CY: the light-fast monoclinic PbCrO4 (LF-CY) and the light-sensitive monoclinic PbCr1-x Sx O4 (x≈0.5; LS-CY). The latter was encountered in large parts of the painting (e.g., in the pale-yellow background and the bright-yellow petals, but also in the green stems and flower hearts), thus indicating their higher risk for past or future darkening. Overall, it is present in more than 50 % of the CY regions. Preferred orientation of LS-CY allows observation of a significant ordering of the elongated crystallites along the direction of Van Gogh's brush strokes.

[1]  E. Hendriks,et al.  Raman study of different crystalline forms of PbCrO4 and PbCr1−xSxO4 solid solutions for the noninvasive identification of chrome yellows in paintings: a focus on works by Vincent van Gogh , 2014 .

[2]  H. Tan,et al.  Nanoscale investigation of the degradation mechanism of a historical chrome yellow paint by quantitative electron energy loss spectroscopy mapping of chromium species. , 2013, Angewandte Chemie.

[3]  Demetrios Anglos,et al.  Mitigation strategies for radiation damage in the analysis of ancient materials , 2015 .

[4]  E. Hendriks,et al.  Digitally reconstructing Van Gogh’s Field with Irises near Arles. - Part 2 : Pigment Concentration Maps , 2018 .

[5]  M. Cotte,et al.  Synchrotron-based X-ray spectromicroscopy and electron paramagnetic resonance spectroscopy to investigate the redox properties of lead chromate pigments under the effect of visible light , 2015 .

[6]  K. Janssens,et al.  XRDUA: crystalline phase distribution maps by two‐dimensional scanning and tomographic (micro) X‐ray powder diffraction , 2014 .

[7]  Koen Janssens,et al.  Examination of historical paintings by state-of-the-art hyperspectral imaging methods: from scanning infra-red spectroscopy to computed X-ray laminography , 2014, Heritage Science.

[8]  Koen Janssens,et al.  Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods. 2. Original paint layer samples. , 2011, Analytical chemistry.

[9]  H. Effenberger,et al.  Four monazite type structures: comparison of SrCrO4, SrSeO4, PbCrO4(crocoite), and PbSeO4 , 1986 .

[10]  M. Cotte,et al.  Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of spectromicroscopic methods. 4. Artificial aging of model samples of co-precipitates of lead chromate and lead sulfate. , 2013, Analytical chemistry.

[11]  Koen Janssens,et al.  Evidence for Degradation of the Chrome Yellows in Van Gogh's Sunflowers: A Study Using Noninvasive In Situ Methods and Synchrotron-Radiation-Based X-ray Techniques. , 2015, Angewandte Chemie.

[12]  M. Menu,et al.  Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of spectromicroscopic methods. 3. Synthesis, characterization, and detection of different crystal forms of the chrome yellow pigment. , 2013, Analytical chemistry.