The following study presents an improvement of previous techniques to determine critical flux in ultrafiltration. The data treatment allows having accurate values of the critical flux and the rate of irreversibility of the created deposit on the membrane. Measures of critical flux were run with different hydrodynamic conditions and were in accordance with the expected results (critical flux increases with hydrodynamics). To confirm this method, the experiments were run with stable suspensions of PVC latex in water with different ionic strength to induce a change in stability. A significant difference was noticed in the measure of critical flux showing the sensibility of the method.