What is cork? How is cork produced? « Back to Questions List

Cork is an extremely useful natural material. It is made from the bark of cork oak tree. Cork consists of dead cells accumulated on the outer surface of the tree. Cork has a unique set of properties not found in any other naturally existing material. It is lightweight, soft, resistant to fire, rot and insects, resistant to gas and liquid and highly buoyant because of low density. The fire resistant property of cork is derived from a hydrophobic substance contained in the bark. 

Because of these unique properties, cork has been used in various ways since time immemorial. Cork bottle stoppers have been found in Egyptian tombs dating back thousands of years.  The ancient Greeks used cork to make fishing net floats, sandals and bottle stoppers. The cork stoppers are widely used in wine bottles. For centuries, Mediterranean cottages have been built with cork roofs and floors to keep out heat and cold and provide a soft walking surface. Cork is used to make a variety of products. They include life preservers,   buoys and shoe insoles. They are also used for making cores for golf balls and baseballs and also for the production of badminton shuttlecocks. Fire resistant quality makes it useful for acoustic and thermal insulation. Cork is also used in woodwind musical instruments. 

Cork oak trees grow primarily in the Mediterranean coastal region. Portugal, Spain, Morocco  and  Algeria amount for major portion of cork forest. Worldwide, cork forest spans over 20,00,000 hectares.  Life span of cork tree is more than 300 years.  Cork harvesting occurs at nine year intervals. By that time,  the cork layer reaches thickness of 2 to 5 cm. Though corks are produced from the bark of trees, the industry is considered as environment friendly because cork tree is not required to be felled to produce cork.  During the period May to August, the cork can be easily separated from the tree without causing any damage to the tree.  A mature tree can yield up to 225 kg of cork.  The initial separation happens when the tree is aged around 25 years. The first product is of low quality. Even then it is useful for making flooring, insulation and other useful products. 
 

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