An in situ microscopy method was employed to study the sediment volumes that result from batch settling of polymer-flocculated kaolin suspensions. Statistical methods were applied including chord length distributions, perimeter-based fractal dimension of the void areas, white area image ratio, and gray level co-occurrence (GLCM) features. Several GLCM features have a good linear relationship with aggregation state, and the parameters of aggregate and void chord distributions can be interpreted to help explain the flocculation results. The methods applied here are suggested for the measurement of the aggregation state or relative aggregate volume on bench or industrial scale when the settled suspension interface is not available, such as in a continuous process or reaction.