Abstract: Process for the manufacture of a biodegradable hydrophobic and transparent film, comprising the following steps:(a) producing a mixture including an alginate of algal origin the algae being chosen from the group consisting of, chlorophyceae, rhodophyceae, or phaeophyceae, or a synthetic equivalents thereof an aqueous solvent and a plasticizer which is miscible with the alqinate and the solvent;(b) forming a film from this mixture;(c) drying the film thus obtained;(d) treating at least one face of the dry film with a solution of tanning material selected from the group consisting of an alum, a tannin or a chrome tanning solution and then with a solution of a compound capable of ensuring the gelling of the alginate, said compound being chosen from the group consisting of calcium carbonate, calcium or zinc chloride, calcium or zinc sulfate.