Particles in a slurry often form a solidified layer at the bottom of its container, making the slurry no longer useable in material fabrication processes. In order to analyze the mechanism of solidification of a sediment, we observed the gravitational sedimentation behavior of various slurries prepared by changing the slurry pH and measured the height of the solidified layer after settling by inclining the test tube. We conclude that the height of the solidified layer has a close correlation with the maximum repulsive force calculated by the DLVO theory, but not with the potential barrier. In addition, we can express the final height of the solidified layer using a very simple model. (c) Koninklijke Brill NV, Leiden and Society of Powder Technology, Japan, 2008.