Emerald Green Degradation in Masterpieces Revealed: Light and Humidity as Culprits

The study, led by the European Synchrotron Radiation Facility (ESRF) with partners, investigates emerald green copper arsenite pigment in James Ensor's The Intrigue (1890). Using macro-scale analyses and micro-scale X-ray techniques, researchers show that humidity promotes brittle arsenic oxide formation while light drives surface darkening through arsenic oxidation. The work outlines preservation strategies and non-invasive museum techniques, including external reflection infrared spectroscopy, to detect degraded areas and guide targeted sampling. Published in Science Advances, 2025, the research offers actionable guidance for conserving emerald green paintings across collections.