Thermal effects can alter the physical and chemical parameters of the latent tracks and bulk material of dielectric track recorders, consequently those of the etched track pits too. A few characteristics of this thermal track-fading effect have been studied in various plastic track detectors irradiated with lightly and heavily ionizing nuclear particles. Experimental data are given for the influence of different annealing conditions on the diameter of etch pits and the bulk etch rate of plastics. The possibilities of the eradication of alpha-particle background and the selective thermal track discrimination in cellulose nitrate, cellulose acetate and polycarbonate detectors have been studied. Few practical applications of the thermal track fading are also presented.