A filter press contains a set of plates designed to provide a series of chambers or compartments in which solids may collect. The plates are covered with a filter medium such as canvas. Slurry is admitted to each compart ment under pressure; liquor passes through the canvas and out a discharge pipe leaving a wet cake of solids behind The plates of a filter press may be square or circular, vertical or horizontal Most commonly the compartments for solids are formed by recesses in the faces of molded polypropylene plates. In other designs, they are formed as in the plate and frame press shown in Fig. 30.5, in which square plates 6 to 78 in. (150 mm to 2 m) on a side alternate with open frames. The plates are to 2 in. (6 to 50 mm) thick, the frames to 8 in. (6 to 200 mm) thick. Plates and frames sit vertically in a metal rack, with cloth covering the face of each plate, and are squeezed tightly together by a screw or a hydraulic ram. Slurry enters at one end of the assembly of plates and frames. It passes through a channel running lengthwise through one corner of the assembly. Auxiliary channels carry slurry from the main inlet channel into each frame. Here the solids are deposited on the cloth-covered faces of the plates. Liquor passes through the cloth, down grooves or corrugations in the plate faces, and out of the press After assembly of the press,