Acoustic Emission has been employed as a method of non- destructive testing for evaluating structural changes in works of art and for planning a program of conservation. Experiments have been carried out on the bronze doors of S. Zeno in Vernoa, contemporarily with microclimatic measurements of surrounding environment. The method enables us to establish a close relationship between the plastic deformation of the metal structure and some parameters such as the radiating solar energy and the humidity content of the door's wooden support.