With increasing layer thickness, the flow resistance of the filter cake increases. After a time, the filter cake has to be removed from the filter, e.g. by backflushing. If this is not accomplished, the filtration is disrupted because the viscosity of the filter cake gets too high; hence, too little of the mixture to be filtered can pass through the filter cake and the filter plugs. The specifications of the filter cake dictate the filtration method of choice.