Czech modern mosaics represent a specific tradition in the European context but are still underestimated as objects of the national cultural heritage. The submitted project deals with materials composition and degradation processes of Czech late 19th and 20th century (modern)mosaic mortars. These materials have not been sufficiently investigated so far but the knowledge on their composition and durability could help their better restoration and conservation treatment. The project ́s goal is to characterize authentic samples of Czech mosaicmortars and their degradation products and to develop a standardized methodology to characterize composition and degradation in these materials. This research will also bring usefulresults concerning mosaics ́ technology and hopefully answer some questions regarding the provenance of anonymous works. Moreover, model samples imitating historic materials and test mosaics will be prepared to check the materials durability and potential use. The obtained results will enable to design more effective restoration and conservation strategies and materials.