Chrome Yellow DeteriorationChrome Yellows (CY), sometimes known as Van Gogh Yellows, refer to a family of synthetic lead chromate pigments widely used in the 19th century and often mixed with lead sulphate to obtain different yellow hues. Van Gogh famously used them in many paintings, such as the Sunflowers series, and some of these have suffered darkening of once bright yellow areas. Some types of chrome yellow, such as PbCrO4, are lightfast, while others, such as PbCr1−xSxO4 are known to darken. The darkening of lead chromate yellow pigments is found to occur on the surface of the paint layer, indicating that it is caused by a photo-induced reduction of the native Cr(VI) (chromate) ions to Cr(III) compounds. Recent advanced spectroscopic analyses have proved that this process of darkening occurs mostly where the pigment presents a sulphur-rich orthorhombic phase of a PbCr(1−x)SxO4 solid solution, while chromium-rich monoclinic phases are lightfast. Therefore, sulphur is implied to play a key role in the degradation process. Degradation of model samples were found to require irradiation with either UV-visible, UV or blue light, while red light has been found to be insufficient to trigger the process.
Chrome Yellow DeteriorationMonico L., Janssens K., Miliani C., Brunetti B.G., Vagnini M., Vanmeert F., Falkenberg G., Abakumov A., Lu Y., Tian H., Verbeeck J., Radepont M., Cotte M., Hendriks E., Geldof M., van der Loeff L., Salvant J., Menu M., 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, in: Analytical Chemistry, 2013, vol. 85 (2), pp 851-859
Monico L., Janssens K., Vanmeert F., Cotte M., Brunetti B.G., van der Snikt G., Leeuwestein M., Plisson J.S., Menu M., Miliani C., Degradation Process of Lead Chromate in Paintings by Vincent van Gogh Studied by Means of Spectromicroscopic Methods. Part 5. Effects of Nonoriginal Surface Coatings into the Nature and Distribution of Chromium and Sulfur Species in Chrome Yellow Paints, 2014, in: Analytical Chemistry, 2014, vol. 86 (21) , pp 10804-10811
Monico L., Janssens K., Hendriks E., Vanmeert F., Van der Snickt G., Cotte M., Falkenberg G., Brunetti B.G., Miliani C., 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, in: Angewante Chemie vol.54 iss. 47, pp13923-13927
Monico L., Janssens K., Alfeld M., Cotte M., Vanmeert F., Ryan C.G., Falkenberg G., Howard D.L., Brunetti B.G., Miliani C., Full spectral XANES imaging using the Maia detector array as a new tool for the study of the alteration process of chrome yellow pigments in paintings by Vincent van Gogh, 2015, in: Journal of Analytical Atomic Spectrometry vol. 30, pp 613-626
Monico L., Janssens K., Hendriks E., Vanmeert F., Van der Snickt G., 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, in: Angewante Chemistry 2015 vol. 127 (47), pp 94-103
Munoz-García A.B., Massaro A., Pavone M., Ab initio study of PbCr(1−x)SxO4 solid solution: an inside look at Van Gogh Yellow degradation, 2016, in: Chemical Science 2017 Nr. 7 , pp 4197-4203