A technique for the visualization of film coverage is described. The technique can be applied in instances where surface regions wetted by a flow need to be identified, but cannot be visualized in real time due to geometric considerations (difficult to reach or observe surfaces). The method introduces chemicals into a water how in addition to other chemicals on the surfaces on which the water film coverage is to be visualized. The chemicals react wherever the how is incident on the surfaces, leaving an identifiable pattern. The technique is applied in the study of silicon wafer rinsing, which is extensively used in microelectronics manufacturing.