This work reviews pertinent literature in modeling by considering the water movement in filter paper to measure capillary suction time (CST). Both the diffusion-like and piston-like approaches are described. In addition, liquid saturation profiles in the filter paper for pure water and some slurries are experimentally constructed. Experimental results indicate that the unsaturated flow in filter paper is unexceptionable in all tests. However, the CST correlations derived from either piston-like or diffusion-like approaches resemble each other in form, which is attributed to the s profile near the wet front resembling a power-law-type behavior.