Used by humankind for more than 5,000 years, Cork is waterproof, buoyant and fire resistant. In fact it is one of the most versatile natural materials you can find.
Cork is the outer layer of bark on the cork oak tree. It has the unique ability of being able to rejuvenate itself and so can be collected without felling or killing the tree it comes from. The trees reach maturity between 20-25 years – and can then be harvested for their bark every nine years after that.
There are two species of cork oak. They grow mainly in the Iberian and Mediterranean regions. Indeed, around half the cork produced worldwide comes from Portugal.
Cork trees aren’t harmed during harvesting and it is in the interests of producers to allow the trees to grow for as long as possible because the best quality cork comes from older trees which are also vital for local wildlife. The Iberian lynx, native to a large part of the main cork producing regions, is endangered and depends on the habitat provided by these trees.
Cork’s honeycomb structure is what makes it so light and flexible. It can be moulded into almost any shape and will not be eaten by insects or affected by rot. It has been found in Egyptian tombs and was used by ancient Greeks and Romans for fishing nets, soles of sandals and stoppers for bottles. It was also used in housebuilding for flooring and insulation.
Cork is mainly taken from tree trunks but it can also come from the lower branches of older, larger trees. Specially designed axes are used to harvest it. Horizontal and vertical cuts are made through the bark with no damage being done to the living part of the tree. Layers of cork are then taken from under the bark with the wedge-shaped side of the axe.
These layers, or slabs, are left outside for up to six months, to cure naturally. This makes them stronger and flatter. They are then cleaned and heated to soften them and make them more flexible.
- About 70
- Large pieces of cork are used to make footwear, furniture, interior decoration and flooring.
- Ground pieces of cork can be heated and compressed to make extremely hardwearing floor and wall tiles which are great for sound and heat insulation.
- Powdered cork can be added to concrete, reducing its weight and improving thermal insulation.
- Cork is so good at resisting heat it was used as thermal protection on the space shuttle’s external fuel tank.
Those are just some of cork’s uses – the challenge is ON to find a new one!
