The theory of colloidal filtration in slip casting of ceramics as developed by Aksay and Schilling for incompressible cakes has been extended to compressible materials. The rate of cake deposition in the mold depends upon the capillary pressure and permeability of the mold. Assuming that the capillary pressure is inversely proportional to an average diameter typifying the mold and that the permeability is directly proportional to the square of the diameter, an optimum diameter exists for production of maximum pressure drop across the cake and maximum rate of deposition.