a method of controlling rotation of a brush in a cleaning device of an image forming system . in the method , the brush is raced together with the photoreceptor which is in contact with the brush for a predetermined time in a warming - up period before the image forming operation starts , in an image - forming rest period , or when a new cartridge constituted by the photoreceptor and the cleaning device is set into the image forming system , so that the hairs of the brush which have been transformed during the rest of rotation are recovered into their original shapes .