A method for manufacturing a film, wherein said film has a basis weight of less than 50 g/m2 and wherein the density of the film is higher than 750 kg/m2 comprising the steps of: providing a suspension comprising microfibrillated cellulose (MFC); forming a web of said suspension on a porous wire, microfibrillated cellulose (MFC); surface sizing said web, wherein the web, at the beginning of the surface sizing step, has a moisture content in the range of from 10 to 50 wt-%; drying said surface sized web to a final moisture content of between 0.1-20 wt-% to form said film.