In 1966, the University of Illinois, Motion Picture Service interviewed campus janitors about their work. "To do a really top notch piece of work, you've gotta do more than just dust and sweep -- you've gotta really color it clean." From the description at Archive.org:
Shows the detailed steps necessary to achieve a high standard of cleanliness in a public restroom and presents the opinions, attitudes and personal feelings of the men who do the job, giving voice in particular to a janitor in a university building. Director: James W. Hall. Janitor: Hance Nelson.