Cork Bark Explained

The thing that makes cork unique as a renewable resource is that it can be harvested without destroying the tree. Other renewable resources such as bamboo, rattan, water hyacinth and coconut require the destruction of the tree or plant to harvest the resource. Below are a few details about cork bark.

The cork oak has to grow for 25 years before the first bark can be harvested. The harvesting of the cork bark is a skilled process done by hand. It is important to remove the bark while not damaging the inner layer of bark which remains on the tree providing protection to the tree against insect and fungal attack. The first bark that is harvested is known as 'virgin bark'. It has a rough uneven exterior and is of low quality. Usually virgin bark is ground down and used for cork insulation. Another use of virgin bark is for ornaments and for use in reptile habitats.

After nine years the cork oak tree has re-grown its outer bark and is ready to be re-harvested. Second and subsequent cork barks are called 'refugo' bark. Unlike the virgin cork refugo cork has a smoother surface and is brown in color.

The second harvest of cork bark is still not good enough to make cork floring and is again often ground up to make insulating material. The third harvest, however, is normally more even with fewer and more tightly closed pores. This is the best material for making cork flooring tiles.

Once the cork has been harvested it is left in the forest to dry for a few days. And then it is taken to a factory where it is boiled to remove the woody outer layer and to make the bark more elastic. Then the finest pieces of bark are selected to be used for cork flooring.