Abstract: A process simulator system for analyzing the forces imposed upon a mixing paddle of a predesignated configuration utilizes a rotary container with a curvilinear interior wall surface. A shaft extends into the container from above and supports a mixer paddle having a profile surface comprising side flanks of curvilinear configuration converging to an end surface concentric with the axis of the container which is immersed in the material adjacent the container wall surface. An indicator system provided with a zero force indicator and reactive to torque or bending forces imposed by the viscous material indicates the force imposed.