A method for determining changes of a site, wherein the site is treated with an aqueous dispersion having at least one binder, at least one substance emitting visible light on UV exposure, at least one binder and, optionally, a dispersant and the site thus treated and/or untreated adjacent sites are exposed to UV light and the deviation of the light intensity of the emitted light of a partial area of the site from the mean light intensity of the emitted light of the site area and/or the light intensity of the emitted light of a part of the adjacent, untreated area from the mean light intensity of the emitted light of the adjacent untreated areas and/or the light intensity of the emitted light of the site immediately after the treatment with the composition from the light intensity of the emitted light at a later time and/or the light intensity of the emitted light of the adjacent untreated area immediately after the treatment of the site with the composition from the light intensity of the emitted light of the adjacent, untreated area at a later time are determined.