This thesis encompasses conservation and restoration work done on the painting "Portrait of a Man", as well as the research into the influence of mold (fungi) on canvas paintings. During a visit to the depot of the Academy of Fine Arts, an unexpected fungal colonization has been found on numerous works of art inside the depot. The colonization is surprising, since the conditions inside the depot are within the defined norms for museum objects' conservation. While reviewing the professional literature, it was noticed that an identical situation occurs in depots all over the world, therefore it was necessary to prevent further colonization and remove the existing one. As part of the thesis, research was conducted with the aim of identifying fungi, including sampling fungi from the surface of three contaminated works of art, their isolation into pure cultures and identification through DNA sequencing. Although the measured relative humidity met the guidelines for the conservation of art objects, fungal colonies were distributed on all art within the depot. On the other hand, no fungal growth was found on the surfaces of the walls and ceilings. DNA sequencing from the direct source revealed high concentrations of fungi belonging to the species Aspergillus halophilicus. These are xerophilic fungi characterized by growth at low relative humidity; significantly lower than one established by the norms for the storage of art. As part of the research, it was mentioned how important it is to choose [BH2] an adequate substrate for the growth of fungi and how different results can be obtained with different procedures. Ultimately, the effectiveness of treating fungal colonization with essential oils of clove, thyme, lavender and sage was determined on the example of the painting "Portrait of a Man". This research is important for determining the identity of fungi that infest art, treating the infested object, and asking questions about traditional values for the conservation and storage of art. Natural-scientific research was carried out at the Conservation and Restoration Department of the Academy of Fine Arts in Zagreb and in collaboration with experts from the Ruđer Bošković Institute, Division for Marine and Environmental Research, Laboratory for Biological Diversity.