#film  a thin coating or layer; "the table was covered with a film of dust"
  supertype:  physical_object__object  a tangible and visible entity; an entity that can cast a shadow; "it was full of rackets, balls and other objects"
  subtype:  oil_slick__oilslick  a film of oil floating on top of water (especially crude oil spilled from a ship)
  subtype:  scum  a film of impurities or vegetation that can form on the surface of a liquid
     subtype:  slag__scoria__dross__dros  the scum formed by oxidation at the surface of molten metals
        subtype:  basic_slag__basicslag  slag produced in making steel; low in silica but having large amounts of calcium phosphate; useful as fertilizer
  subtype:  soap_film  a film left on objects after they have been washed in soap

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