A Synchrotron Photoluminescence Microscopy Study into the Use and Degradation of Zinc White in ‘The Woodcutters’ by Bart van der Leck

Bart van der Leck, as a member and co-founder of the artistic movement De Stijl, is well-known for his abstract color plane compositions, set on extensive white backgrounds. The white background in The Woodcutters (1928, oil on canvas), which comprises the brightly luminescing semiconductor pigment zinc white, was noticed to exhibit unusual luminescence behavior under UV light. Based on the observation of three distinctly different intensities of green luminescence, it was possible to differentiate between regions within the white background. This observation raised the question whether photoluminescence could be used as a tool to gain insight into different stages of the paint process and the condition of the different paint layers. This study was conducted on the microscale, on three paint cross-sections taken in the differently luminescing regions of the zinc white background. Optical microscopy and scanning electron microscopy – energy dispersive X-ray spectrometry (SEM-EDX) were used in combination with a synchrotron-based multispectral photoluminescence micro-imaging technique to examine the stratigraphy of each cross-section and reveal the photoluminescence behavior of each layer. The submicron spatial resolution and deep-UV excitation energy allowed resolution of individual zinc white particles, as well as thin surface layers which are thought to be caused by the reaction of zinc white with atmospheric contaminants. The results demonstrate how photoluminescence micro-imaging can be used to differentiate between zinc whites from different sources in the multi-layer build-up of a paint cross-section, and explain the origin of the luminescence behavior of The Woodcutters at the macroscale.