Abstract: Method of filtering wherein the filtration rate of and/or consumption rate of filter aid for difficultly filterable slurries is reduced for a plate and frame filter press having alternate solid plates supporting filter means, e.g. a composite clothpaper media and hollow frames for accumulation of filter aid and adapted for compression between a fixed half end plate and a movable half end plate by provision within said press of a chamber immediately adjacent to said movable half end plate, said chamber provided with at least one filtrate input and the sole means for exit of the filtrate from said press.