Preserving Modern Art Materials in Historic Gardens: Biodeterioration and Conservation of Epoxy Resin and Cementitious Niobid Replicas at Villa Medici (Rome, Italy)

Historic gardens represent complex systems in which vegetation, artistic and architectural elements all require equal protection. This becomes particularly challenging when considering the dual role of vegetation between bioprotection and biodeterioration. This study addresses the conservation issues associated with the modern sculptural group of the Niobids, located in the historic garden of Villa Medici. The group presents critical issues related to the materials used in its creation (i.e., white-cement- and epoxy-resin-based composites) and the limited literature documenting the effectiveness of cleaning methods for this type of artwork. To address this knowledge gap and provide a basis for a low-intensity maintenance plan, investigations were carried out to identify the different components of the biopatinas, as well as higher vegetation in direct contact with the statues. In this context, the efficacy of a protocol based on water micronisation for biopatina removal was also assessed. Clamydomonas spp. was a frequent phototrophic element, along with Candelariella species, Xanthoria parietina, Flavoplaca flavocitrina, and Verrucaria nigrescens. The cultivable fungal fraction evidenced the substantial presence of Parengyodontium album and melanised strains belonging to the genera Chaetocapnodium, Exophiala, Scolecobasidium and Coniosporium. Vegetation cover was characterised by the frequent presence of Grimmia pulvinata on the sculptures and Acanthus mollis in their surroundings. These findings raise significant conservation concerns, as the observed taxa suggest an advanced stage of ecological succession driving pedogenesis. The water micronisation protocol produced noteworthy results, highlighting its potential for treating new materials and as a maintenance technology within planned conservation. Indeed, regular monitoring and low-intensity preventive actions can prevent the need for late restorative interventions and, above all, transform emergency management from the rule into the exception.