All About Cork

Ever wonder where cork comes from or when it was first used to seal wine? Here’s some interesting information we learned from the Portuguese Cork Association (APCOR).

What is cork?
Cork is the bark of the cork oak (Quercus suber L), a tree that grows in Mediterranean regions such as Spain, Italy, France, Morocco, Algeria and Portugal, where there are about 2,800 square miles of cork forests. The cork oak can live 150–200 years, despite its bark being stripped about sixteen times (at nine-year intervals) during its lifetime.

Cork is valued because of its unique combination of characteristics. It is very light, impermeable to liquids and gases, elastic and compressible, an excellent thermal and acoustic insulator, fire retardant and highly abrasion resistant.

What are the earliest known uses of cork?
By 3000 BC, cork was being used in fishing tackle in China, Egypt, Babylon and Persia. Artifacts from the 4th century BC, in the area that is now Italy, indicate that cork was used as floats, stoppers for casks, women’s footwear and roofing material. Also from that period is a reference to the cork oak, by the Greek philosopher Theophrastus, who referred in wonder to “the ability that this tree has to renew its bark after it has been removed.”

What is the first known use of cork with wine?
An amphora from the 1st century BC found in Ephesus was sealed with a cork stopper and contained wine. Also, in the ruins of Pompeii (1st century AD), wine amphorae sealed with cork were found.

When is cork harvested?
A cork oak trunk needs to have a circumference of about 28 inches when measured five feet from the ground before it is first harvested. It can take about 25 years until it reaches this size. The harvesting (or stripping) is carried out during the most active stage in the annual growth of the cork, from mid-May or early June to the end of August.

The first stripping produces cork of a very irregular structure which is hard to handle. This is known as “virgin cork”; it is not suitable for use as cork stoppers, but it is used as flooring and insulation. Nine years later, the second harvest produces material with a regular structure. This is known as “secondary cork.” Although it is less hard, it is still not suitable for use as cork stoppers. Cork with the best properties is obtained from the third and subsequent harvests. This cork is suitable for use as cork stoppers since its structure is regular with a smooth outside and inside. This is known as “reproduction cork.” From then on, the cork oak will supply good quality cork every nine years for about 150 years.

Source: The Portuguese Cork Association (APCOR). For more information, visit www.realcork.org.

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