Abstract: Apparatus for evaluating physical properties of suspensions, particularly the tendency of the solid and fluid portions of a suspension to separate under pressure. The apparatus comprises a pressure vessel having an input port, a bleeder port and a pressure measuring port. A piston is slideably mounted within the pressure vessel and has a head portion which is exposed through a retainer ring for contact by the force applying apparatus. Depending upon the design of the piston, the apparatus may be used either for the separation test described above or for a density evaluation test.