Enhancing Venetian traditional marmorino with TiO2 and ZnO for antimicrobial protection – A case study

Venetian marmorino is a traditional plaster that has been used since the 15th century, in several palaces in Venice and ancient villas throughout the Veneto region. While this material has considerable durability, it remains susceptible to various surface degradation processes. An effective means to mitigate such events is through the application of photocatalytic coatings. These coatings employ just oxygen from the atmosphere and light as energy source to degrade both organic and inorganic environmental pollutants, confer self-cleaning properties, and reduce bacterial attacks or fungal growth. In this work titania (TiO2) and zinc oxide (ZnO) were incorporated into the marmorino, both as top coating and within the mortar itself. The biocidal efficacy of these additives was assessed through optical microscopic observations of fungal colonies grown on the marmorino mock-ups with differing compositions or finish layers. Two Fungi Penicillium italicum and Cladosporium spherospermum were selected as reference microorganisms attacking wall materials in Venice. Hence, a more detailed analysis utilizing electron microscopy (SEM) was conducted to confirm the biocidal properties. The experimental results demonstrate that the development of a high-tech multifunctional marmorino capable not only of reducing environmental pollutants but of preventing surface degradation and inhibiting fungal growth. This inhibition leads to a reduction in biodegradation, resulting in a diminished ability to take root and lack of spore development.