Cork is one of the resources owned by a few countries on the earth. It mainly grows along the Mediterranean coast and is one of the existing ancient tree species in the world, with a history of about 60 million years.
As the saying goes, "Trees are afraid of peeling.". After peeling off the bark, many trees will soon die because they cut off the supply of water and nutrients. However, there is also a kind of tree that is not afraid of peeling in the vast forest sea. This is the music of cork. Cork is the bark of Cephellodendron. Because its material is similar to wood and soft, it is commonly called cork.
Cork is an excellent material. The growth of Xanthocellole is slow, and the bark thickness only grows about 2 mm per year. When Cephellodendron grows to 25 years old, it can pick and peel the bark, which is called "native cork" or "virgin bark". After that, they were stripped every 9 years until they were 300 years old. If well maintained, a tree can be stripped for 10 times, and the weight of bark collected can reach 1000 kg. The bark of Cephellodendron is not only soft, but also thick, usually 4-5cm, and the softwood can reach about 10cm.
Summer is the season to pick and peel the bark, because at this time, the bark has absorbed rich nutrients. Cork can not be used immediately after being stripped from the tree, but is stacked in the open air and exposed to the sun and rain for at least 6 months. The purpose is to remove the green color, make the color darker and the internal structure more dense. Then bundle the cork and put it into 100 ℃ boiling water, and steam it for about 90 minutes. This process is very important, which can remove the salt, tannin, gum in cork, and eliminate pests and bacteria. Cook the cork and let it dry naturally. At this time, the cork becomes straight, soft and elastic, which is convenient for product processing.
Portugal is located on the Atlantic and Mediterranean coasts, providing good natural conditions for the growth of Cephalospylla. Portugal is a cork producing country with an area of more than 800000 hectares, accounting for half of the world's cork area. The annual output of softwood is nearly 300,000 tons, accounting for more than 56% of the world's total output. Every year, softwood or softwood products are exported to more than 100 countries, and foreign exchange income is considerable. Therefore, Portugal is known as the "Kingdom of Cork". Cork is now regarded as a "national treasure" and enjoys the reputation of "soft gold".