The dynamic simulator developed for the wet-end section and used for a fibrous pulp of a deciduous unbeaten pulp contg. TiO2, approached the effect of two unspecified com. retentants added to prep. a 75-g/m(2) paper enabled the electrokinetic potential to be predicted in the paper machine water loop. Zeta could reflect the effect of the retentants but could not help intercompare the efficiency of various polyeletrolytes.