Several mural paintings (15th/16th centuries) located in churches in the North region of the country being subject to environmental fluctuations where no measures of preventive conservation took place, disclose a chromatic alteration in the form of dark stains. The removal of the pigmentation hasn’t been successful or much tested so far. To characterise its composition and achieve pigment removal, innovative methodologies will be tested both in vitro and on prototypes of granite and mural painting executed with similar materials to those used in the north of Portugal at the time. The development of cleaning gels and a film-based layer for inhibition of the microorganisms growth after cleaning used singlehanded or with essential oils will also be tested. An all-inclusive preventive conservation plan will also be developed for all selected case studies. This is a pioneer work, from which may emerge a set of patentable solutions for mural paintings. The team is led by researchers of CBQF (ESB-UCP) and includes researchers from CITAR (EA-UCP) and CICECO (U.A). The project has institutional support of Regional (North) Directorate of Culture and of the Bragança-Miranda Diocese. At the international level, it has the support of the mural painting expert Pilar Roig Picazo of the Polytechnic University of Valencia (Spain).