CORK OAK TREE
Cork Is The Outer Bark Of The Cork Oak Tree (Quercus Suber L.).
Cork is a 100% natural raw material, that is 100% reusable and 100% recyclable. It is extracted from cork oak trees without ever harming the normal development of the specie and without damaging the tree. Actually, the cork extraction is not 100% harmless, it even contributes to the regeneration and healthy of the tree. This, because the cork oak is able to absorb much higher levels of carbon dioxide after the bark is harvested. So, harvested cork oak trees store three to five times more CO2 than those left unharvested. That’s a big plus for the environment.
The cork oak tree (Quercus suber), from which cork is extracted, is native to southwest Europe and northwest Africa. It’s one of the most common tree species in Portugal, being predominant in the coastal areas of Alentejo and the Algarve.
It takes each cork oak 25 years before it can be stripped for the first time and the first two harvests (at 25 and 34 years of age) the cork become the raw material for insulation, flooring, fashion, design, health, energy production, aerospace and other industries as it still doesn’t have the quality required for cork stoppers production. It is only from the third stripping (at 43 years of age) that the cork is qualified for those. At this time each trunk should reach a circumference of about 70 cm when measured and 1.3 metres above ground level.
The cork harvest is a controlled process made only by specialized professionals and it takes place always between May and August, when the tree is at its most active phase of growth, as it is easier to strip without damaging the trunk. Cork stripping is one the highest paid agricultural works in the world due to the high level of expertise necessary to harvest the cork without damaging this most unique and precious resource.
After each extraction, the tree is marked with the last number of the year in which it was last harvested. Then the cork oak will by itself produces a new layer of bark with the same thickness and properties for the following 9 years. At this time, it can be harvested again. Over the course of its lifetime, which on average lasts 200 years, it may be stripped around 17 times.
The cork planks are then stacked in piles in yards at a factory, as it needs to be outdoors exposed to atmospheric conditions like sun, wind and rain. This period is called “resting period”, follows specific rules defined by the International Code of Cork Stopper Manufacturing Practice – ICCSMP, so as to allow the raw material matures and cork stabilises and it goes for not less than six months.
Without the cork industry the continuity of the cork oak forest and their populations would not be viable.
Cork Oak Trees are not endangered in any way. Many people, in fact, think that there is a cork shortage, or that cork is at risk of extinction. This is not true. This myth came from the fact that in 1923, the Portuguese government began to protect the cork tree by law from improper or out of season harvest. Recent studies proved that actually there is enough cork in the forest of Portugal to last more than 100 years with a constant growth year over year due to the reforestation programs.
When it comes to it composition and characteristics Cork consists in 100% natural plant tissue with multiple layers of microscopic non-living cells that envelops the tree trunk and produces, each year, a 2- to 3-mm of a thick layer of the most pure cork. Each cell is essentially made of suberin, and lignin.
A single cubic centimetre of cork contains almost 40 million cells.
Those cells are filled with an air-like gas (identical to the air we breathe) which explains its extraordinary lightness. Cork can even float.
Elasticity and Resiliency:
The cellular membranes are very flexible, making the cork both compressible and elastic.
When cork is subjected to strong pressure the gas in the cells is compressed and reduces considerably in volume. When released from pressure cork immediately recovers its original volume, a property known as “elastic return”. I’m sure you have seen this in wine stoppers.
It is totally impermeable to liquids like water or alcohol and gases, thanks to the suberin and lignin present in the composition of cork cells. It’s resistance to moisture allowing it to grow old without getting rot and deteriorating.
Cork has one of the best insulating capacities with those 40 million cells in each cubic centimetre acting as a real decibel absorber, making it an excellent sound and vibration insulator.
Its molecular structure allows it to absorb heat and retain it for a long period of time.
Cork is a natural fire retardant as it burns without a flame and does not emit toxic gases during combustion.
Cork is also remarkably resistant to wear and has a high friction coefficient. Thanks to the honeycomb structure, it is less affected by impact and friction that other hard surfaces. It has a extraordinaire capacity for retaining its original conditions.
Cork does not absorb dust and prevents the appearance of mites, for that reason it does not cause allergies nor pose a risk to asthma sufferers.
Biodegradable, recyclable and renewable:
Cork is a natural raw material which is 100% biodegradable, recyclable and renewable.
Cork has a great hygienic value, as it releases no odours and has no taste.