Cork is the outer bark of the cork oak tree, quercus suber, which grows mainly in the Mediterranean region. The bark is a vegetal tissue composed of an agglomeration of cells filled with a gaseous mixture similar to air and lined with alternating layers of cellulose and suberin.
Today, cork is a valuable resource for Portugal, representing one of its most important export products. The cork oak Cork oak forests cover approximately 2.5 million hectares across the Mediterranean region and most of them are located in seven countries: Portugal, Algeria, Spain, Morocco, France, Italy and Tunisia.
The tree has a life span of 250-350 years. Each cork tree must be 20 to 25 years old before it can provide its first harvest of Cork Bark, and this process takes about 10 harvesting cycles or more for each individual strip from the bark’s surface area transformation zone (STZ) which measures up over 100 meters tall in some instances! A typical tree produces several hundred kilograms of cork at each harvesting and will survive for many generations. The bark is stripped off the tree in sections by highly skilled men using special axes, a traditional manual skill that dates back many hundreds of years.
Cork is harvested on a sustainable basis and the stripping of its bark does not harm the tree in any way. A cork oak can be safely harvested up to 20 times during its life cycle, making it an inexhaustible natural resource with new plantations planted each year for sustainability purposes!
Portugal, the country that produces more than 50% of all corks in world has been particularly careful to safeguard this valuable resource. The cork oak tree is a living reminder of what can be accomplished with renewable sources. Every year, it regenerates itself after being harvested for its bark — leaving the majestic plant unharmed and ready to grow once again next season!
The bark of the cork oak tree has a unique honeycomb structure composed solely of cells. Each cell is an geometric polyhedron and they all contain air-like gaseous mixture within their inner space, which gives them incredible strength as well as waterproofing properties for any inhabitant that may want to make use out it! Because about 89% of the tissue of the bark consists of gaseous matter, the density of cork is extremely low, in the order of 0.12 to 0.20, a fact that bears witness to the huge disproportion between the volume and the weight of the material.
Cork is light and floats on water.
Elasticity and resiliency
Cork is a flexible material that can be compressed and expanded to its original shape. The cork membrane will return to its original form after being under pressure, almost instantly bringing back all lost volume.
Impermeability
The presence of suberin rmakes cork impermeable to both liquids and gases. As a result, it does not rot, making it one of the best seals available.
Insulation and fire retardant qualities
Cork’s low conductivity makes it ideal insulation material by preventing heat loss through conduction. This is because the gaseous elements it contains are sealed in tiny, impermeable compartments, insulated from each other by a moisture-resistant material. This endows cork with one of the best insulating capacities, both thermal and acoustic, of any natural substance.
Fire retardant qualities
Cork is also a natural fire retardantIt neither spreads flames nor releases toxic gases during combustion.
Resistance to wear
Cork is remarkably resistant to wear and has a high friction coefficient. Thanks to its honeycomb structure, it is less affected by impact or friction than other hard surfaces.
Hypoallergenic properties
Because cork does not absorb dust, it helps protect against allergies and does not pose a risk to asthma sufferers. It also has an unchangeable constitution that guarantees efficiency.