a method for removing impurities from shredded plastic uses a device having a first and second cleaning disc with a first and second cleaning surface respectively . the cleaning surfaces lie opposite each other and border a cleaning gap between each other . the cleaning discs are rotated and liquid is fed into the cleaning gap . shredded plastic is fed between the cleaning discs and conveyed through the cleaning gap , and the shredded plastic is processed abrasively by the cleaning surfaces . the temperature difference of the liquid guided through the cleaning gap during entry into the cleaning gap and the temperature of the liquid as it exits the cleaning gap and / or at least one parameter characterizing this temperature difference is measured . the distance between the cleaning surfaces is set such that the measured temperature difference and / or the at least one parameter characterizing this temperature difference achieve a setpoint value .