Abstract: An apparatus and a method for evaluating the stability of a disperse solid material against caking. The apparatus includes a chamber for storing a sample of the disperse solid material, the chamber having a diverging cross sectional area along a line of action of a compression load compressing the sample so as to cake a portion of the sample and an opening for enabling separation of the uncaked portion of the sample from the caked portion of the sample, a shutter for selectively sealing the opening during partial aggregation of the sample and a compression load mechanism for applying the compression load. The method includes the steps of providing a known weight of a sample of a disperse solid material, applying a compression load so as to cake a portion of the sample, separating an uncaked portion of the sample from a caked portion of the sample after partial aggregation of the sample and computing an index for the stability of the disperse solid material against caking.