Cork material is produced
Cork material is produced from the bark of cork oak, which grows in the Western Mediterranean and on the Atlantic coast at an altitude of up to 1,400 meters above sea level. The bark of this tree is very thick and durable. Its outer layer after removal is restored in a certain time in a natural way.
Although the cork bark appears even on young shoots, however, the first removal of the outer layer occurs only after 15-25 years. Subsequent layers, which are called feminine or reproductive, can be removed every nine to ten years. The life of cork oak averages 160 years. Therefore, from one tree you can get about 15 harvests of bark.
Over half (about 60-65%) of the world’s reserves of valuable raw materials are located in Portugal, where the first processing plant was founded. And although nowadays other countries of the world are engaged in the production of cork material and products from it, Portugal accounts for over half of the world’s cork products.
Cork material is used in construction for heat and sound insulation, as well as to protect against vibration. In addition, it is used as a finishing material in the form of wall and floor covering. Cork stoppers for wine bottles are produced from the bark of cork oak. Cork is considered to be quite a valuable raw material, therefore it is used as efficiently as possible in the production of floor coverings. To minimize the cost of raw materials in processing for the manufacture of cork coating is granulated cork (for example, residues from the production of corks for wine bottles).
The honeycomb structure of cork wood, which contains a huge number of closed air bubbles of various sizes, gives the unique properties of this natural finishing material. They are tightly pressed together and impregnated with natural cork substance – suberin. Each element of the honeycomb cork structure acts as a thermally insulating component and an acoustic absorber. Therefore, corkwood floor coverings have excellent heat and sound insulation characteristics and have good cushioning properties.
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When a cork floor is affected, for example, by a short-term (heel pressure) or long-term (from heavy furniture legs), it absorbs and returns to its original shape. The cork from champagne or wine also works. Additional properties of cork include water resistance (even with direct exposure to moisture, such a coating retains its original appearance), sound insulation, antistatic and bactericidal properties, resistance to household chemicals, slip resistance and ease of maintenance.
So, cork for wine, floor and wall coverings, boards for information are made from corkwood. The first and second “yields” of cork are considered to be of insufficient quality. Such cork bark is used only for the preparation of cork crumb (in the process of processing and grinding). The third and subsequent harvesting of bark is of the necessary quality for the production of coatings and other products.
The bark is removed exclusively in the hot season (from June to August), when she herself departs from the trunk of the tree. This procedure requires the utmost care and attention from the collector. When applying a circular notch on the trunk (this operation is called “create a crown”) it is very important not to damage the tree itself. Then the cork is divided in the longitudinal direction with a special thin hatchet. The cork is removed by its edges, and with the help of the handle the bark is separated from the tree at a certain angle. Then, the removed cork pieces are laid out on the open space under the scorching sun, where they dry for several months (up to half a year). After drying, they are sorted for the first time, with the result that the cork, which is suitable for commercial use, is sent to the factory.
When entering production, the cork is digested, which makes it more elastic and durable, is cleaned and classified according to the quality of the material and the thickness of the cork sheet. Before the production of the cork coating itself, the bark of the oak is kept for a month at a certain temperature in a dark room.
Let us consider in more detail the production technology of closures. Champagne cork must withstand a pressure of 5-6 atmospheres, so special trees are selected for its production. The thickening of the cork leaf depends directly on the place where cork oak grows – on the landscape and the quality of the soil. The slower a tree grows, the stronger and thinner the leaf will be. The leaf that is used to make corks is digested in clean boiling water. As a result of this procedure, the softness, strength and elasticity of the material is significantly increased, most of the mineral salts and tannin, which is included in its composition, are removed.
