Baroque stucco techniques of Baldassarre Fontana at Kroměříž Château

Abstract This study investigates the materials and construction techniques employed in the Baroque stucco decorations of the ground-floor halls at Kroměříž Château, executed by Baldassarre Fontana and his workshop. The material composition of sixteen samples was analysed using optical microscopy, SEM-EDS, XRD, thermal analysis, and acid dissolution. The results revealed the deliberate use of high-purity calcitic lime, sourced from Devonian limestone near Přerov and gypsum from the Ketř-Opava basin. Two mortar types were identified: a lime-gypsum-sand core modelling mortar and a lime-rich finishing stucco mortar, reflecting layered application techniques. The presence of crushed marble in certain decorations suggests recipe changes and indicates a multi-phase construction process possibly extending beyond Fontana’s supervision. Surface finishes were initially limited to white limewash, later overpainted with layers containing zinc white pigments. The findings highlight 17th-century stucco practices, provide a foundation for further conservation and historical research, and establish a benchmark for Central-European Baroque stucco studies.