What is Cork?


Cork is one of nature’s most versatile materials and has a wide range of applications from the corks in your wine bottles to flooring panels that can insulate your home. Cork’s versatility comes from its unique structure.  Cork consists of a honeycomb of microscopic cells filled with an air-like gas, which gives it a range of interesting qualities, such as being a great thermal and acoustic insulator.

Cork is also a fully sustainable and environmentally friendly resource, thanks to the unique nature of its gathering. In fact, cork is one of the greenest alternatives out there and is 100% natural, renewable and recyclable.

At SPD UK we believe that cork is the perfect material, versatile, sustainable and endlessly useful. That’s why we have written this handy guide to answer any and all questions you might have about cork.


Cork bark detail

Where does cork come from? 

Cork comes from the bark of the cork oak tree, known as Quercus suber L. for those of you who speak Latin. This means that all of our cork products come from 100% natural plant tissue. 

Unlike other wood products, cork is harvested from the cork tree and doesn’t result in the tree being cut down. In fact, the harvesting process is entirely sustainable and doesn’t harm the cork oak tree at all.

Where do cork oak trees grow?

Most cork trees grow in the western Mediterranean, where the climate is ideal. Cork trees require a lot of sunshine, high humidity and low rainfall to grow well.

Portugal is the world’s main exporter of cork, however, other countries like Spain, Algeria, France, Tunisia and Morocco also grow and export cork.


  • How is cork harvested?  

The specially designed axes have a wedge-shaped handle that is then used to pry each cork panel from the tree. With the amount of bark that is removed during harvesting, the cork oak is the only tree that could survive the process. This makes cork oaks a very special and unique tree.

Cork can only be harvested by hand and requires a dedicated and skilled workforce. In fact, cork harvesters are the highest paid agricultural workers in the world. 

These harvesters make use of small, specially designed axes or hatchets to harvest the bark.  These axes are incredibly sharp and slice through the outer layer of bark without damaging the actual trunk of the tree. The harvesters then cut horizontal slices across the base of the trunk of the tree, and at the top, just below the lowest branches.


  • When is cork harvested?

cork tree must grow for 25 years before it can be stripped for the first time. Cork trees are only harvested during the summer, between May and August. This is when the tree is going through its most active growth phase which makes the bark much easier to strip without damaging the trunk of the cork tree. 

  • How often can cork be harvested?

    After the initial period of 25 years, a cork tree can be stripped and harvested every 9 years. This can continue during the cork trees entire 200-300-year average lifetime. This means a cork tree can be stripped and harvested many times during its life.

    It is only after the third harvest of cork, which is known as Amadia, that the cork takes on the high standard of quality that is required for producing cork stoppers. The first two harvests are used to make flooring, insulation and other cork products.

    • How is cork made?

    After harvesting, the cork planks are stacked outside to cure for up to six months. A combination of fresh air, sun, wind and rain causes chemical changes that improve the quality of the cork. The curing process transforms the cork planks and causes them to flatten out and lose around 20% of their original moisture.

    The cork planks are then steamed in boilers to eliminate any contaminants or bugs. This process also separates the outer layer of bark and softens the cork, making it much easier to work with.

    The cork is then placed in dark cellars and once again allowed to cure for up to 3 weeks under carefully regulated temperatures and humidity.  

    How is Cork Flooring or Cork Sheets made?

    Once the cork sheets have been cured for the second time, they are ready for use.

    The sheets are taken and first used to make wine stoppers. This is done by punching out the stoppers from the sheets, leaving the cork sheets full of holes.

    There is virtually zero waste with cork, however, as every part can be recycled and used.

    This is shown when after the wine stoppers have been punched out of the cork sheets, the leftover sheets are used to make cork flooring.

    The sheets are ground up and made into larger blocks that are then baked in ovens. They are then sorted by colour, and made into planks or tiles, ready to be used.




    Can Cork be Recycled?

    Cork is :

    • 100% natural
    • Biodegradable
    • Renewable
    • Recyclable


    There are fantastic organisations in the UK, USA, France, Portugal and other countries, such as ReCork, that recycle cork into a variety of amazing products.

    Cork can also be recycled and re-used during the manufacturing process. As we mentioned, all of the material that is taken from the cork tree is used and there is virtually no waste.

    Portugal is actually the world’s 4th largest importer of cork, which is then processed, recycled and re-made into new cork products that are then subsequently exported to other countries.


    Is Cork Sustainable?

    Cork is one of the most renewable and sustainable resources on the planet. In fact, a cork tree can be harvested multiple times in its 200-300-year lifespan, supplying cork for many generations.

    The process of harvesting cork actually has a fairly small ecological footprint compared to other sustainable resources, this is due to cork being both recyclable and biodegradable.  

    Cork harvesting neither cuts down or harms the cork tree itself, meaning it continues living and is incredibly eco-friendly. In fact, cork harvesting actually helps clean the air and undo the damage caused by greenhouse gases. Cork harvesting is a truly green process and should be fully supported.

    How Cork helps fight Global Warming

    Harvesting cork is not just a sustainable process, but it also helps fight against global warming. After a cork oak has been stripped, it proceeds to capture carbon dioxide from the atmosphere to aid with the bark regeneration process. In fact, a cork oak tree will absorb more CO2 each time it is harvested. A regularly harvested cork tree will absorb and retain five times more CO2 than those that aren’t.

    Estimates suggest that cork forests absorb and retain up to 14 million tonnes of CO2 each year thanks to cork harvesting. This is a sizeable contribution to reducing greenhouse gas emissions, the main cause of climate change.

    Cork Forests & Biodiversity

    Cork oak forests support one of the highest levels of forest biodiversity in the world, second only to the Amazon rainforest, and provide long term habitats for hundreds of animal and plant species. This included incredibly endangered species like the Iberian Lynx and Barbary Deer.



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