A sophisticated method was developed for evaluating simultaneously and accurately both the average specific resistance and average porosity of the filter cake formed in unstirred dead-end ultrafiltration of nanocolloids such as protein solution and nanosilica sol. In the method, a step-up pressure filtration test was conducted by using a filter with a singlestage
reduction in the effective filtration area. The influence of the pressure drop across the cake on not only the average specific cake resistance but also on the average cake porosity of highly compressible filter cake was evaluated using only flux decline data in one dead-end filtration test, taking advantage of the decrease in the cake thickness caused by the pressure increase. As a result, the cake properties were easily determined for a variety of nanocolloids. Constant
pressure dead-end ultrafiltration data obtained under various pressures and concentrations were well evaluated based on the method proposed.