Polyvinyl alcohol is a water-soluble polymer. It is prepared by hydrolysis of a polyvinyl ester (polyvinyl acetate). It is used as a a starting material for the preparation of other resins. It can be used as a component of elastomers used in the manufacture of sponges. This polymer is used in sizing agents that confer resistance to oils and greases upon paper and textiles, to make films resistant to attack by solvents or oxygen. It is used as a component of adhesives, emulsifiers, suspending and thickening agents. In pharcuetical industry, Polyvinyl alcohol is used as a ophthalmic lubricant and viscosity increasing agent. It thickens the natural film of tears in eyes.