CONDITION ASSESSMENT OF THE MARBLE FUNERARY MONUMENT TO ANTONIO CANOVA IN THE BASILICA DEI FRARI IN VENICE: A NEW MECHANISM FOR MARBLE DECAY

In recent decades, the funerary monument dedicated to Antonio Canova in the Basilica dei Frari has suffered serious decay phenomena. The sharp increase in deterioration processes observed in different areas has caused the loss of large areas of marble detail from the surface of the statues. As there is an urgent need to stop the increasing rate of marble decay the authorities responsible for protection of the cultural and monumental heritage decided to start a comprehensive survey to identify the causes of alteration. Macroscopic observation of the marble surface showed different forms of alteration as well as the massive presence of salt efflorescence. A number of different types of alteration were observed macroscopically and in order to assess the deterioration mechanisms samples were taken from the decayed areas. ESEM observations together with EDS analyses have enabled us to explain the stages, each corresponding to different features, through which exfoliation and lamination of surface scales is taking place. A survey of the moisture content of the masonry structure under the steps of the monument has established that moisture from the ground is being transmitted by direct contact of the brick core with the marble. As a consequence capillary migration of water transports salt solution onto the marble surface, where it forms droplets. In order to stop the rapidly increasing rate of decay, observed over the last ten years, there is an urgent need for action to prevent any further capillary rising damp by inserting a damp proof course and at the same time to detach the statues from the base in order to remove the salts embedded in the marble.