is the bark of an oak tree known botanically a QUERCUS SUBER. It is an evergreen
which grows in commercial stands only in areas bordering the Mediterranean Sea.
Of the important cork producing countries, Portugal supplies approximately 50%,
Spain 25%, and the balance is divided between Algeria, France, Morocco, Italy
and Tunisia. As early as 2,500 BC cork was used as fishing floats in ancient
Egypt, and in 400 BC cork was also commonly used as stoppers for containers as
well as soles for shoes. One of the many famous users of cork was, according to
history, conqueror Alexander the Great. A cork piece once saved him from
drowning when crossing a turbulent river.
In these days of increasing concern for the environment, cork remains the only
tree which can regenerate itself after each harvest. The cork bark is stripped
off 2/3 of the tree. The first time is when the tree is approximately 20 years
old. A thin layer protective inner bark gives the cork oak the unique ability to
protect itself from the debarking process. The stripping requires great skill as
the inner bark must not be damaged by the specially designed hatchet used for
The first bark is called "virgin" bark. It has a very irregular
exterior surface of grayish color. This bark is suitable for grinding into
various granule sizes used for cork insulation and composition cork, but it has
also become very popular for the manufacturing of decorative items.
The subsequent strippings of the tree will take place every nine years until the
cork oak is approximately 150 years old and is replaced by a young one. The bark
which grows out after the "virgin" bark has been stripped is called
"refugo" bark. It looks entirely different as it has a much smoother
surface which is brown. The first crop of "refugo" is mostly used for
grinding purposes. The following strippings consist of better qualities with
fewer and more closed pores (grains) and the major part is used for the
production of cork stoppers or other items requiring a better quality or finer
After the stripping process, the bark remains in the forest for some days to dry
or perhaps to be inspected by potential buyers. To purchase cork bark is not an
easy task as the quality does not only vary from forest to forest and from tree
to tree, but from the same tree depending on the exposure to sunlight.
Once in the factory area, the "refugo" bark is boiled to make it
easier to scrape off part of the woody outer layer and to make the bark more
elastic in order to flatten it out for boiling - should it be sold later on.
Thereafter, the bark is sorted into various thicknesses which in their turn are
sorted into many different qualities to determine a sale price and/or suitable
Cork is a unique natural product with remarkable properties unmatched by any
other natural material. One cubic inch of cork consists of not less than 200
million completely enclosed air cells each measuring l/1000" in diameter.
Each minute cell is 14 sided to avoid empty spaces between cells.