Development of a NDT toolbox dedicated to the conservation of wall paintings: Application to the frescoes chapel in the Charterhouse of Villeneuve-lez-Avignon (France)

One of the main issues in the conservation of wall paintings is to understand the origin of the degradation and to detect the deterioration patterns before any loss of material occurs. A toolbox of Non Destructive Techniques (NDT) has been developed. It aims to establish a precise conservation diagnosis according to two approaches: a campaign in the field using multianalytical techniques and data compilation in a multidimensional database. Several NDT techniques were used to analyze Giovannetti´s wall paintings in La Chartreuse (Villeneuve-lesAvignon, France) in an experimental mission. Some of the techniques give information about the inner and the outer surfaces of the mural and wall while others inform on structural aspects which mainly concern the mortar. Thus, LIBS, digital images of material fluorescence under UV light, photogrammetric results and maps of deterioration patterns have been created from analysis of the painted surface. Investigations on the inner defects and surfaces included stimulated IR to provide additional information to aid conservation strategies. In a second step, all the information was compared including old images and documents from previous restoration campaigns. Finally, all the documentation is inserted in a specific database which allows the superposition and comparison of images arising from different origins. The paper discusses the choice of appropriate NDT tools and the importance of being able to cross-reference the data from a conservation perspective by using of a multidimensional database. This combination of a NDT toolbox with a specific database enables enhanced interpretation of the degradation mechanisms, essential to understand outdoor masonry or the impact of past restoration acts on the wall painting. In addition, it is able to show the evolution of these deterioration