The following characteristics of films prepared by various processes from Japanese lac were revealed: The films do not show sharp glass transition phenomenon and are durable as a protective coating over a wide range of temperature; The films from sugurome- processed Japanese lac have ample flexibility and considerable rigidity, ideally combined; During exposure to air, the films are oxidized with formation of polar group in polymer molecules. But cross-linking does not take place except in air-dried film of raw Japanese lac.