Cellophane is a transparent, impermeable or semipermeable film of cellulose used primarily in packaging, first developed by J. E. Brandenburger (1911). Wood pulp is soaked in sodium hydroxide, shredded, aged, and reacted with carbon disulfide to form a solution of viscose sodium cellulose xanthate. This is extruded through a slit into an acid bath, where the cellulose is regenerated as a film. It is dried and given a waterproof coating. If the viscose is extruded through a minute hole, rayon is produced.