Where does cork come from and where does it go?
Cork comes from the bark of the cork oak tree (quercus suber L) found mostly in the Mediterranean Basin. Trees are never cut down to make cork. It is harvested from trees that can produce up to 20 harvests over the course of their lifetime. The average lifespan of a tree varies between 170 and 200 years. Portugal is the source for over half of the world’s supply of cork, followed by Spain, Algeria and Italy. Remarkably, while only accounting for a small portion of cork production, the manufacturing of cork closures constitutes 70% of the industry’s income.
The world’s supply of cork is not running out there are over 963,300 acres of cork trees still not in commercial use, which will be available to provide high quality natural cork for generations to come.
Cork is used around the world in many functions. In 2004, France was the top importer of Portuguese cork, importing 21.8%. After France, the USA imports 16.4%, Spain imports 12.8%, and Germany imports 10.3% of the cork produced in Portugal.
Did you know?
Following the invention of the optical microscope in the 1660s, the British scientist Robert Hooke was the first to observe the structure of cork, for which he coined the term “cell”.
A cork cell is a minute, straight-sided pentagonal or hexagonal prism. About 80 per cent (in volume) of cork is gas enclosed in the cells. Suberose sacs make the cork cell membrane impermeable and the cell airtight. There are about 40 million cells per cubic centimetres of cork.
Suberin, a mixture of fatty acids and heavy organic alcohols, is the basic substance of cork. Impermeable to gas or liquid, it is also fire and insect resistant and unaffected by water.
The average chemical composition of cork is:
Suberin (45%) - the main component of the cell walls; responsible for the resilience of the cork
Lignin (27%) - the binding compound
Polysaccharides (12%) - components of the cell walls which help define the texture of the cork
Tannins (6%) - polyphenolic compounds responsible for colour
Ceroids (5%) - hydrophobic compounds that ensure the imperviousness of cork
Mineral water, glycerine, and others make up the remaining 4%.