Salts are one of the most dangerous degradation agents of artworks, especially in the environment of industrial pollution of 20th century. Salt damage in artwork causes not only mechanical changes by crystallization pressure, but also chemical and mineralogical alteration of its painted surface. That deterioration is especially serious on porous systems such as wall paintings. Salt removal by appropriate cleaning procedures is one of the principles of their restoration. For its optimal choice, it is crucial to know what salt is present and what its source is. The main aim of the project is diagnosis of salt attack on wall paintings using non-destructive analysis of microsamples, identification of the attacking salts, and explanation of the alteration of Cu- and Pb-pigments. The work will be performed in collaboration with three artistic institutions. Results of laboratory experiments with porous materials, pigments, and salt solutions will be compared with analyses of real artworks.