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Cork Myths and Curiosities

Did you know that a single cork stopper can capture up to 392g of CO2?

And that cork was used in Ancient Egypt and can be used to produce energy? Did you know that scientific research consistently proves that consumers associate cork with high-quality wines?

Find out everything you’ve always wanted to know about cork.

Cork is the bark of the Cork Oak tree (Quercus suber L). It is an all natural raw material, with unique properties which give it an unparalleled character. It is light, impermeable to liquids and gases, elastic, compressible, provides thermal and acoustic insulation, a fire retardant and highly abrasion-resistant. Furthermore, it is completely biodegradable, renewable and recyclable.

Cork is stripped from the trunk of the Cork Oak every nine years, without damaging the tree. The largest areas of cork oak forest are in Western Mediterranean countries: Portugal, Spain, Italy, France, Morocco, Tunisia and Algeria.

The world's production of cork is 340,000 tonnes per year, 55% of which is from Portugal.

No. The extraction of cork is a controlled process and does not required the cork oaks to be felled - on the contrary, it contributes to their regeneration. It is the cork industry which makes the continuity of the cork oak forest viable, by contributing to the maintenance of forests and the populations that depend on them. A recent estimate forecasts that only in Portugal, where there is the world's largest cork oak forest area, shall the harvestable cork be enough to meet market demand for the next 100 years.

Cells were discovered in 1665 by Robert Hooke. On observing a sliver of cork under a rudimentary microscope, the English scientist discovered that it was made up of multifaceted cavities, which he called cells (from the Latin cellula, small room).

Each tonne of thick cork planks can provide, on average, 66,700 cork stoppers.

Yes. Being a 100% natural product, cork stoppers are biodegradable and do not pollute the atmosphere if they are thrown in the rubbish bin. However, they are completely recyclable and reusable. Although recycled cork shall never be used in stoppers again, it can be used in coverings, insulation, memo boards, high competition kayaks, badminton rackets, tennis and cricket balls, car and aircraft components, design and fashion items and a multitude of other uses.

Environmental motivation is one of the most important factors in recycling. Cork stoppers absorb CO2 particles that have been retained by the bark of the cork oak. If they are decomposed or incinerated, they release the CO2 into the atmosphere, thus contributing to global warming. Recycling enables the CO2 retention capacity of cork to be extended. In each tonne of cork stoppers, around 1.07 tonnes of CO2 is retained, which, once they have been recycled, this capacity is ensured forever, as the reuse of this raw material is unlimited.

On the other hand, by recycling used cork stoppers you are also contributing to enabling the reuse of a raw material and the decrease of the costs associated with the production of other high added-value products.

Amorim is a pioneer in promoting the recycling of cork stoppers, developing collection programmes in Portugal, the USA and Canada, France, Italy, the United Kingdom, South Africa and Australia.

Learn about the cork stopper collection projects in:

Lightness
Cork is a very light raw material, weighing just 0.16 grams per cubic centimetre, and can float.

Flexibility/compressibility
Each cork stopper is made up of around 800 million watertight cells. Among them is a gaseous mixture which allows it to be compressed to around half its thickness, without losing any flexibility, and to be decompressed and return to its original shape. This is what is called an elastic memory. Cork is the only solid which when compressed on one side, does not increase in volume on the other. This feature enables it to adapt to variations in temperature and pressure, without compromising its integrity as a stopper.

Impermeability
Thanks to the suberin and ceroids, it is practically impermeable to liquids and gases.

Decay resistant
Cork is highly resistant to moisture, and therefore to subsequent oxidation and decay.

Insulation
Cork is an excellent thermal, acoustic and vibration insulator. In relation to wine, the insulating properties of cork contribute to cork stoppers being the best protection against variations in temperature.

Biodegradable, recyclable and renewable
Cork is a natural raw material which is 100% biodegradable, recyclable and renewable. A recycled cork stopper is never used to manufacture a new stopper, but its recycling has endless uses, from materials for construction, fashion, sport, art, the aeronautics industry, among others.

Cork consists of suberin cells in the shape of tiny pentagonal or hexagonal honeycombs, a complex fatty acid and is filled with an air-like gas, which makes up 90% of its volume. It possesses an average density of around 200 kg/m3 and low thermal conductivity.

Each cubic centimetre of cork may contain around 40 million cells. There are around 800 million cells in a single cork stopper.

There are some remnants of the use of cork by the people of Ancient Egypt and in Roman civilisation. In France, amphorae from the 3rd century BC were found full of wine considered to still be in good condition. The use of cork at pre-industrial level dates back to the end of the 17th century.

Stripping is the ancient process of extracting the bark of the cork oak - the cork. This work is done by specialised professionals, with absolute precision, who use just a single tool: the axe.

This delicate operation takes place between May and August, when the tree is at its most active time of growth and it is easier to remove the bark from the trunk. Harvesting cork is the world’s best paid seasonal agricultural job.

Over the course of its lifetime, a cork oak may be stripped around 17 times, at intervals of at least nine years, which means that the harvesting of the cork will last 150 years, on average.

The first stripping is called "desbóia" from which the virgin cork is obtained, which has a highly irregular structure and hardness that make it difficult to process.

Nine years later, when the second stripping takes place, the cork, known as "secundeira", has a regular structure which is not as hard.

The cork from these first two harvests is not fit for the manufacture of stoppers and thus used in other applications for insulation, flooring, decorative items, among others.

From the third and following strippings the "amadia" or reproduction cork is obtained. This cork has a regular structure, with a flat front and back and the ideal characteristics for the production of natural, quality cork stoppers.

The first stripping takes place when the cork oak is 25 years old and the trunk has reached a perimeter of 70 centimetres, measured 1.5 metres from the ground. Subsequent strippings take place at intervals of at least nine years.

No. Stripping is carried out manually and the trees do not have to be cut down. In fact, the cork oak undergoes a self-regeneration process of the bark, which gives the activity of cork harvesting a uniquely sustainable nature.

No. After stripping, the planks are stacked into piles in structures and shall remain outdoors for at least six months for the cork to stabilise. This process is governed by the strict compliance of the Code of Cork Stopper Manufacturing Practices.

Nothing is wasted from the cork oak, all its components have a useful ecological or economic purpose:

  • The acorn, which is the fruit of the cork oak, is used to propagate the species, as animal fodder and in the manufacture of cooking oils;
  • The leaves are used as fodder and a natural fertiliser;
  • The material from tree pruning and decrepit trees provides firewood and charcoal;
  • The tannins and natural acids contained within the wood from the tree are used in chemical and beauty products.

Thanks to the thermal and weak combustion properties of cork, cork oaks are more fire-resistant than other trees. The slow combustion of cork makes it a natural fire retardant, forming a barrier against fires. Its combustion does not release smoke or toxic gases.

This is due to the high level of expertise necessary to harvest the cork without damaging this precious resource.

No. The Quercus suber L genome is the same, therefore there are no significant differences according to origin. There are, however, individual differences from tree to tree.

When in contact with wine, the cork stopper forms antioxidant and anti-carcinogenic compounds that may reduce the risk of heart and degenerative disease. Furthermore, waste from the cork industry gives rise to composites which are used in vaccine adjuvants to enhance immune system response.

Yes. Cork dust can be used in the cogeneration of electricity, making a valuable contribution to improving energy efficiency. Amorim meets over 60% of its energy needs by using cork dust (biomass), which is a CO2 neutral source of energy.

Due to the lightness and acoustic and thermal insulation capacity of cork, it is also used in wind turbines.

The name Quercus suber L. derives from Linnaeus, who was the first botanist to describe the species.

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