Survey of the State of Conservation of Detached Wall Paintings by Digital and IR Techniques. The Case Study of Verde Cloister in the Church of Santa Maria Novella, Firenze

The detachment of wall paintings was one of the most widely used techniques to preserve frescoes and discover the underlying drawings (sinopia) during the second half of the XX century. Today, their conservation is a challenge for restorers and scientists mainly due to the combination of two problems: the natural decay of the original parts (painted and preparation layers) and the decay of the support. These problems are related, but in practice conservation is often focused only on the painted part, while the support is disregarded. In this contribution, the authors highlight the problems related to the support and how these can reflect on the integrity of the painted surface. This problem is studied in the real case of the wall paintings of the Verde cloister, in the church of Santa Maria Novella - painted by Paolo Uccello in the 15th century - using the technique of IR thermography, laser scanner and photogrammetric surveys. The first stage of the conservation proces is the diagnosis of the structural integrity of the support. The recognition of the type of support (Masonite - wood and monolayer - fibreglass) can be achieved with a combination of IR thermographic survey and visual inspection. The structural integrity was completed by the investigation of deformations and loss of flatness through a laser scanner combined with photogrammetric survey. The analysis of the results allows the classification of the detached wall paintings with respect to the type of support, their deformation and structural stability (also the anchoring defect). This classification will be useful for planning an effective conservation programme.