October 16, 2006
The Cork Oak (Quercus suber) is one of the species of trees that has its bark “harvested” to produce the variety of objects that we use in our daily lives. Things like “corks” for wine bottles, floor tiles, wallboards, gaskets, coasters and sporting equipment, to name a few. The unique properties of natural cork are primarily the result of its specialized structure -- it's bark is composed of tiny cells, each a 14-sided polyhedron, with the intercellular space entirely filled with air. There are approximately 40 million of these cells in a single cubic centimeter of cork bark.
Cork is lightweight, rot resistant, compressible and expandable, fire resistant, impermeable, soft and buoyant too. It has been used for thousands of years by the Egyptian, Greek and Roman cultures. Cork oaks grow best in the Mediterranean climate of Portugal, Spain and Northern Africa. The commercial “stripping” of bark is tightly controlled to ensure a continued harvest of this valuable natural resource. The first bark is not harvested from a tree until it's 25-years old and then only every nine years afterward, on a rotating basis. This process allows a tree to be harvested for over 200 years. The cork is peeled off in large panels from the main sections of the trunk, including the large branches. About a third of the bark can be harvested from the tree at one time.
The above picture was taken of a tree that had been previously harvested and was in the process of growing new bark. This self-portrait was taken on a trip to southern Portugal in January of 2004. Portugal accounts for over 50% of the world’s cork production. While traveling through the Portuguese countryside it was hard not to notice these exceptional and highly prized trees.