The conservation of wall paintings: the conflictual relationship with water

Enzo Ferroni wrote that the verb “to conserve”, according to its etymology, also means “to inhibit alteration, damage or corruption ... The mere storage of an object inside a case can not ensure its preservation in the sense that it will not be altered. The recognition of the value of a work of art is sufficient to justify the need of storing it. But, in order to avoid its degradation a deep knowledge of the materials constituting the object, and of their stability and reactivity, is strictly required”. Stability and reactivity of materials are concepts that inevitably recall the importance of scientists in the field of works of art conservation. The devastating flood that occurred in 1966 in Florence gave a strong impetus to research in the field of conservation and restoration. In those years the Institute of Chemical Physics, mainly in the person of Enzo Ferroni, gave a decisive contribution to the recovery of the XIV century mural paintings by Taddeo Gaddi in the refectory of Santa Croce church. The detachment of the paintings, in fact, could not be carried out due to the huge amount of nitrate salts impregnating the walls. Ferroni accepted a public invitation addressed by Umberto Baldini (who headed the restoration following the flood) to anyone who could make a contribution in order to solve the tragic problems of conservation, and proposed the use of tributyl phosphate (TBP) as a sequestering agent of nitrates. This solution allowed completing the detachment of paintings and their restoration, so to that they can be still admired today. This intervention was followed by the restoration of the XV century paintings by Fra Angelico in the Friary of San Marco (Florence), when an intense partnership was set between Enzo Ferroni and Dino Dini, a conservator and acute experimenter who contributed to the full development of the barium method, which consists of a pre-treatment with an ammonium carbonate solution followed by consolidation with barium hydroxide, so to counteract the dramatic effects of paintings sulfatation. In the followings, the XV century paintings in the San Francesco church in Arezzo (Legend of the True Cross’s by Piero della Francesca), and the Brancacci Chapel’s paintings, by Masaccio, Masolino and Lippi, in Florence were restored. Ferroni’s scientific and cultural legacy is now fully expressed by the research activity of the CSGI consortium that he has served as Honorary President until his death. The development of his insights, often sparked by intense discussion with his students, led to the formulation of innovative materials based on modern nanoscience such as microemulsions and micellar systems for removal of detrimental polymer coatings, and nanolimes for the consolidation of wall paintings.