[Greek]. Rheopexy is a property shown by some non-Newtonian fluids and describes the effect of increasing viscosity at a constant shear force. The opposite behaviour of decreasing viscosity at a constant shear force is called thixotropy. Rheopexy and thixotropy are time-depending effects. In view of the above, the viscosity does not return immediately to its original value after removing the shear force, but after a certain time of relaxation. An example for rheopexy is a plaster (gypsum)-water mixture with approx. 40 % plaster.