The time‐dependent transient values of the stress, strain, and dielectric susceptibility tensors were measured in a circular disk made of a rheologically simple material and subjected to two equal pairs of diametric loads oriented at right angles. The instantaneous application or release of each pair of loads was programmed at different time intervals so that the loading configuration was suddenly transferred from a four‐load rheologic equilibrium situation to a transition state with only one pair of diametric loads. In this way the isotropic point (stress, strain, or birefringent) existing at the center of the disk for the four‐equal‐load configuration split into a pair of isotropic points moving along the diameter of the disk towards its circular boundary as the recovery process in the viscoelastic material developed. The velocities of movement of this pair of isotropic points along the diameter of the disk in the recovery process allowed the study of the phase lag between the stress, strain, and optical principal axes. The material chosen for the experiments was a strongly plasticized epoxy polymer, designated as C‐100‐60‐8, which presented a strong viscoelastic behavior at room temperature. However, the study extended along the whole viscoelastic spectrum of the material from its glassy to its rubbery state, by applying the principle of reduced variables. Important results were revealed for the mechanical and optical viscoelastic behavior of rheologically simple materials extensively used in photoelasticity.