The Romanesque mural paintings of the Salzburg Nonnberg were endangered by pulverization of the paint layer and the growth of microorganisms. Although the interdisciplinary examinations carried out recently have not been completed, first urgent steps had to be taken to create the conservation of the mural painting in situ. A new method of a reversible consolidation with hydroxy propyl cellulose (HPC) Klucel LF has been developed, combined with the climatization of the site.