Cork is the bark of the cork oak (Quercus Suber L.), which means that it is 100% natural plant tissue. It consists of a honeycomb of microscopic cells filled with a air-like gas and coated mainly with suberin and lignin. Other compounds are identified in its chemical composition, although in less quantity, such as polysaccharides, ceroids and tannins.
A single cubic centimetre of cork contains almost 40 million cells - around 800 million in a single natural cork stopper.
It takes each cork oak 25 years before it can be stripped for the first time and it is only from the third stripping (at 43 years of age) that the cork, then known as «amadia», has the high standard of quality required for producing cork stoppers. The first two harvests – the «virgin» cork and «secundeira» cork –, as well as that removed from the base of the tree, becomes the raw material for insulation, flooring and products for areas as diverse as construction, fashion, design, health, energy production and the aerospace industry.
The cork is harvested by specialised professionals, always between May and August, when the tree is at its most active phase of growth and it is easier to strip without damaging the trunk. The cork oak is the only tree whose bark regenerates, acquiring a smoother texture following each harvest. Over the course of its lifetime, which on average lasts 200 years, it may be stripped around 17 times.