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We would like to share with you a link to the study “Multi-analytical approach for the compositional and micro-structural study of Florentine Masters stucco devotional reliefs”, conducted by a group of scholars: Gianluca Gariani, Florian Beaugnon, Patrice Lehuédé, Yvan Coquinot, Monica Galeotti, Emmanuelle Gouillart, Gilles Wallez, Fabrice Goubard, Anne Bouquillon, and Marc Bormand. This is a valuable resource for the study of stucco as a material used in the artistic interpretation of religious subjects.
The study, developed as part of a research program supported by the Louvre, presents a multi-analytical methodology for examining the composition and microstructure of samples taken from twenty-six representative artworks — mostly held in French museums — attributed to seven Florentine masters. Its main objectives were, firstly, to identify and characterize the major and minor mineral components based on their structure and composition, and secondly, to investigate the technological aspects of stucco production.
The research revealed that the material characteristics were consistent across all works in the corpus. In every case, the reliefs were made using gypsum-based stucco. All analytical methods confirmed the relative purity of the binder, with no evidence of deliberate addition of mineral fillers. This indicates a stable workshop practice in Florence and supports the hypothesis that the stucco mixture used was a gypsum-based plaster (gesso) with very low levels of additional fillers.
The water-to-gypsum ratio also proved to be generally consistent across all works attributed to the different workshops examined in the study, further suggesting uniform production techniques for Florentine stucco reliefs. Only two reliefs in the corpus stand out as potentially produced by craftsmen using different techniques — either within a Florentine workshop under different circumstances, during work in another Italian center, or possibly in a workshop imitating or reproducing this highly popular model.
The overall quantity of secondary minerals in the samples was low; however, certain reliefs exhibited a relatively higher concentration of impurities — primarily clay minerals and associated elements such as titanium and rare earth elements. These include two “Nativity” casts attributed to Donatello and Bartolomeo Bellano, as well as three of the seven reliefs inspired by Antonio Rossellino. In contrast, other reliefs attributed to either Donatello or Rossellino did not differ significantly from those of other masters.
All analyzed works were created using gypsum plaster as a binder, in line with findings from previous studies. The plaster used for these devotional reliefs appears to resemble gesso plaster more closely than the lime-based plaster typically used in architecture. Most of these artworks share similar microstructural and compositional features. The consistency of results across reliefs attributed to different artists indicates a common practice within 15th-century Florentine workshops. Thus, the study highlights characteristics specific to Florentine stucco, which, when identified, can help link artworks to the Florentine school.
