The Degradation of Works of Art Materials

This chapter deals with the illustration of the main and general physicochemical properties of works of art materials strictly correlated to the processes leading to degradation and alteration phenomena. The principal chemical and physico-structural properties of the materials, both organic and inorganic, constituting a particular class of works of art, namely wall paintings, and easel paintings will be enunciated and discussed in relationship to the decay processes that will be treated in the following of the chapter. The mechanisms leading to the degradation of these works of art will be analysed classifying them in three big categories: natural weathering, pollution – indoor and outdoor – and general chemical, physical and mechanical stresses. The environmental conditions for the best conservation of indoor and outdoor works of art will be also discussed. Finally, the physical alteration associated with the combined action of light and oxygen from air will be treated in relationship to two classes of compounds particularly sensitive to these phenomena, which are drying oils and natural varnishes.