Bottle corks are made of the cork oak, which grows mostly in Portugal and Spain. These two countries produce about 70% of the world cork production. Over 80% of its capacity consists of oxygen and nitrogen. Thanks to these gases cork can be freely squeezed in almost any way, after which it will go back to its original shape and size. For that reason corks are squeezed, pushed into a bottle’s neck and left so that they can go back to their natural shape. As a matter of fact, cork does not let any liquids out. It allows only very slow, delicate “wine breathing”, so that it could mature.
