Techniques including methods, apparatus and computer program products are disclosed. These techniques include computer instructions that are encoded on computer storage media for determining wettability. The techniques use a numerical aging computation process to provide a representation of a wettability alteration of a physical rock sample in the presence of at least two fluids is disclosed. The techniques include retrieving a representation of a physical rock sample, the representation including pore space and grain space data corresponding to the physical rock sample, calculating local curvature for each surface in the pore space, determining from the calculated local curvature whether water-film breakage will occur, and classifying the wettability of the physical rock based on the determination of water-film breakage.