Ever considered where cork from your wine bottle, your bulletin board or cork yoga mat comes from? Read on to find out more about the harvesting process of this fantastic sustainable material.
Cork is a bark found on the Cork Oak tree. It is harvested using ancient techniques from highly specialized harvesters using only axes and their bare hands to separate the cork from the trunk and branches before getting shipped to a production facility. It is a practice that occurs every nine years of a Cork Oak’s life from May-August.
Where Does Cork Come From?
Cork comes from the bark of the Cork Oak which is endemic to northwest Africa and southeast Europe and thrives where there is plenty of sunshine, low rainfall, and high humidity.
What is Cork?
Cork is the outer bark of the Quercus suber and has a thicker layer than other trees as it’s evolved to protect itself from the harsh conditions. This has made it resistant to fires, rot, and termites as well as being impermeable to gas and liquid, creating water-resistant cells that are soft and buoyant.
How Often is Cork Harvested?
A Cork Oak is harvested every nine years and will be used up to fifteen times during its lifespan. The Cork Oak can live anywhere between 150 – 200 years with it taking at least 25 years to become mature enough to harvest.
To produce cork that is profitable the tree will be harvested once it reaches a circumference of 70 cm and reach 1.3 metres above the ground.
When Is Cork Harvested?
From mid-May to the end of August the outer bark of the Cork Oak’s trunk and the major branches are delicately stripped by experienced cork strippers: the descortiçadores.
The descortiçadores use an ancient process using only specialised cork axes to split the bark. No mechanical devices are allowed, to avoid damage and to ensure the tree can continue to produce for years to come.
What Are The Cork Harvesting Stages?
Cork harvesting is performed in six stages:
The descortiçadores create vertical cuts into the bark. As they cut, the edge of their axe is used to twist and separate the outer bark from the inner bark.
The piece of cork is then separated from the tree by inserting the axe in between the inner and outer pieces of bark.
Horizontal cuts are then added to dictate the size of the plank that will be removed from the tree and what will stay. During the dividing stage, the inner bark can get marked, these impacts can sometimes affect the tree, altering the geometry of the trunk.
The plank is then removed from the tree carefully so it does not split. This is repeated over the whole trunk.
After the planks have been extracted, some small pieces of cork can still remain on the base of the tree. To get rid of any parasites in these “pockets” or “wedges”, the descortiçadores will give it a few taps with their axe.
The final step is to mark the tree with the last number of the year in which it was harvested so that the cycle can begin again in nine years.
The Quercus suber is unique as it is the only tree that can support and flourish from this harvesting process with it improving the trees overall health and vigour.
What Happens To Cork After The Harvesting Process?
Once the bark is harvested it is taken away from the forest and left outside to be dried by the sun for six months. This weathering process improves the quality of the cork with it then being handled and sorted by its condition and size.
After this, the cork bark is distributed to go into the first stage of cork production: boiling. The planks of bark are boiled to clean them as well as soften.
After the boiling process, the planks are flatter and more pliable so that they can be graded and cut into more workable pieces. The material can then be used to make things like expanded insulation corkboard and cork stoppers to supply the 13 billion-plus needed in the world’s alcohol industry annually.
What Happens With The Leftover Cork?
When the best cuts have been used for its retrospective products the remaining cork, also called ‘blocker waste’ is then ground up and processed to be used in other items like cork and rubber compounds and agglomerated cork. These products can be found in everyday items such as decorations and bulletin boards to more specialized areas like constructions and gaskets.
During the production process of cork, nothing is wasted. Anything leftover is sent to the beginning of the production line to be reused in other products.
Cork harvesting and its production are one of the most sustainable business practices on the planet. It is a fantastic material that provides employment and economic purpose for many communities across the globe while maintaining ancient techniques and practises that have proven to stand the test of time.