All forms of cellulose degrade before they melt but natural cellulose can be regenerated by the xanthate process to manufacture fibres, commonly called rayon or viscose, and film, commonly called by its earliest brand name Cellophane®. The latter films are plasticised by glycols and water to overcome their brittleness and are transparent, colourless and of moderate crystallinity. They were very widely used for packaging but have been substantially replaced by synthetic thermoplastics, especially polypropylene.They have very high permeability to moisture and, especially when dry, very low permeabiltiy to permanent gases. Their moisture content varies greatly with their environment reaching approximately 50% at 100% relative humidity. Not surprisingly, this causes many of their properties to vary considerably - so summarised values must be treated with considerable caution.Information provided by Goodfellow.