Cork is the bark of the Cork Oak tree (Quercus suber L). It is a completely natural raw material, with unique properties which give it an unrivalled character. It is light, impermeable to liquids and gases, elastic and compressible, provides thermal and acoustic insulation, it is a fire retardant and highly abrasion-resistant. Furthermore, it is completely biodegradable, renewable and recyclable.
Chemical composition of cork:
Cork is stripped from the trunk of the Cork Oak every nine years, without damaging the tree. The largest areas of cork oak forest (montado) are in Western Mediterranean countries: Portugal, Spain, Italy, France, Morocco, Tunisia and Algeria.
Cork can be compressed up to half its size without losing its flexibility. Then it resumes its original form. This is due to its extraordinary "elastic memory"”.
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).
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 airtight 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 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. When transformed into stoppers, its insulation properties contribute to making it the best protection for wine and spirits against temperature variations or contamination and possible negative effects from storage and transport conditions.
In construction, it has clear advantages in regard to the quality of buildings, indoor air and comfort, and may be used in the waterproofing of infrastructures, foundations and underlays, in acoustic and thermal insulation and the final coverings for floors, walls, ceilings, facades and roofs.
Biodegradable, recyclable and renewable
Cork is a natural raw material which is 100% biodegradable, recyclable and renewable.
Cork consists of suberin cells in the shape of tiny pentagonal or hexagonal honeycombs, a complex fatty acid and 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.
It is the air which fills the cells in the cork that makes it an excellent thermal insulator. The same protective principle can also be found in other natural products, such as wool and feathers, and in industry, such as double glazed windows, for example. However, none of these materials have such a high level of insulation as cork.
Not necessarily. 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.
Yes. At Corticeira Amorim, over 60% of energy needs are met 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.