In various industrial processes, it is important to prevent the solidi. cation in order to maintain the slurry properties. In order to predict the formation of the sediment and solidified layer, the gravitational sedimentation behavior of the slurries obtained by changing the slurry pH and the time change in the formation of sediment were observed. As a result, we can predict the solidi. cation time and precisely predict the formation of the solidified layer and determine suitable conditions for the storage of slurries. (c) 2008 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan.