Casket for the Reliquary-Crown of the Holy Thorns: Study and Conservation of a Thirteenth-Century Masterpiece from the Treasury of the Cathedral of Saint-Aubain in Namur (Namur Diocesan Museum)

The casket of the Reliquary-Crown of the Holy Thorns, housed in the treasury of Saint-Aubain Cathedral (Namur, Belgium), is a 13th-century masterpiece designed to hold the cathedral’s most revered relic. The octagonal wooden box is covered in leather and decorated with enamel medallions. Over the centuries, the casket has experienced material deterioration, prompting a conservation project supported by the Wallonia-Brussels Federation.An interdisciplinary study led by the Royal Institute for Cultural Heritage in Brussels (KIK-IRPA) examined its construction and materials. Dendrochronology confirmed a terminus post quem of 1197 for the wood. The analysis of the enamels, when combined with comparisons to other enamel productions and caskets, could suggest a date in the first third of the 13th century, when two types of enamel compositions coexisted. However, neither the enamel composition nor the stylistic comparisons allow for a definitive decision on whether it is a Limoges or a northern European (?) production. Textile dating identified the red damask lining as being from the mid-17th century.Conservation treatments included anoxia, stabilisation of leather and textiles, metal cleaning, and enamel consolidation. Preventive conservation, guided by the ArtGarden project, assessed environmental risks to ensure the long-term preservation of this complex, mixed-media artefact. This study enhances our understanding of medieval church objects and emphasises the importance of collaborative research in cultural heritage conservation.