The investigation into wet grinding, with the forced movement grinder, RSK LAB 10-25 MATTER PARTNER proved the efficiency of this grinder. The essential parameters are the rotor and the feeding speed. The population balance method showed that the coarse particles display a first order grinding reaction and a non linear grinding according to time duration while the finest particles don＇t display a first order grinding reaction, but a linear grinding according to time. The energy study indicated that Bond＇s law applies to the first grinding cycle(s), subsequently Rittinger＇s law is confirmed. A dimensioning method, derived from the Mac Cabe and Thiele method, was used. This construction offers the advantage of anticipating the number of cycles needed for a predetermined size distribution.