Three Phases, One Masterpiece: Conserving the Altarpiece of the Mystic Lamb 1432 by the Van Eyck Brothers (2012–2026)

Abstract

ABSTRACT The Altarpiece of the Mystic Lamb 1432 by Hubert and Jan van Eyck is a landmark of Early Netherlandish painting whose appearance has been significantly shaped by centuries of structural interventions and overpainting. Since 2012 a major conservation campaign led by the Royal Institute for Cultural Heritage (KIK-IRPA) has re-examined the altarpiece through an interdisciplinary framework, integrating conservation practice, advanced imaging, scientific analysis and collaborative decision-making. To balance treatment needs with continuous public access at Saint Bavo’s Cathedral in Ghent, the project was organised into three phases: conservation of the exterior shutters (2012–2016), the lower interior register (2016–2019) and the upper interior register, currently in progress and scheduled for completion in 2026. This paper traces the development of the project and evaluates how phased treatment strategies supported the preservation of the ensemble’s visual and structural coherence. Mapping of historical overpaint and retouching, as well as the condition of the original paint layers, relied on close studio examination combined with integrated analysis of high-resolution photography, IRR, X-radiography, MA-XRF, MA-XRPD, 3D microscopy and the reassessment of historical paint samples. These complementary techniques clarified the materials, working methods and complex restoration history of the altarpiece. The removal of extensive early overpaint uncovered remarkably well-preserved original surfaces, yielding new insight into the Van Eycks’ technique and workshop practice, while illuminating centuries of interventions that have shaped the work’s condition and appearance. The project underscores the importance of sustained interdisciplinary collaboration, evidence-based treatment and transparent decision-making in the conservation of large, historically layered heritage ensembles.