How is cork flooring made and how is it a green product?
Cork flooring is becoming more and more popular in Westchester County, especially for Kitchens. My customers love that it”s soft on their feet and it’s green. But many ask, how come cork is green? What makes it green? Where does cork come from? How is cork made? Have you ever wondered?
Where does cork come from?
First, let me explain that to some extent, virtually every tree has an outer layer of cork bark. But, the cork that is used for cork flooring, as well as cork wine stoppers, primarily comes from the cork oak (Quercus suber). Most of these are grown in countries around the Mediterranean Sea where the climate is ideal for them – plenty of sunshine, high humidity and low rainfall. Portugal is the primary exporter of cork, but other counties such as Spain, Algeria, France, Tunisia and Morocco grow these trees as well.
What makes the cork oak extra special is that it has a thicker layer of cork than other trees. So, the next logical question is Why? And, of course the answer is evolution – these trees evolved to survive the harsh conditions of the Mediterranean forests which have frequent droughts and as a result brush fires. In addition, there are large temperature fluctuations. Well cork is a rather unique substance – it’s made with water-resistant-cells that separate the exterior bark with the interior of the tree. it’s unlike any other natural material – it’s lightweight, termite and rot resistant, resistant to fires, and it’s soft and buoyant…how cool is that?
What is cork made of?
Cork is made of dead cells that accumulate on the outer surface of the cork oak tree. Because of its honeycomb-like structure, cork consists largely of empty space. Therefore, cork’s density is one-fourth that of water. There are millions of these empty cells per cubic inch of cork making it like microscopic bubble wrap. As a result, cork is a great cushioning material and it’s great for life preservers and buoys. The large amount of dead-air space makes cork an effective insulation material for both temperature and noise and that’s another reason we often use it in flooring – either as the actual floor or an underlayment underneath hardwood (often used in condos and coops when there are tenants below and restrictions on the type of flooring that can be used.
How is cork made?
A cork tree must grow for at least 25 years before you can harvest the bark. The cork grows back, so it can be stripped every 8-14 years throughout the whole rest of the tree’s lifetime. The trees are not harmed by this process, and they continue producing cork for an average of 150 years.
Using a specially designed hatchet, the harvester slices through the cork layer on the trunk of the tree. They are careful not to damage the living portion of the tree. Horizontal cuts are made at the base of the trunk and just below the lowest branches. Using the wedge-shaped handle of the hatchet, the harvester strips each panel of cork from the tree.
The cork planks are then stacked outdoors and allowed to cure for a few weeks to six months. The fresh air, sun, as well as rain foster chemical changes that actually improve the quality of the cork. By the end of the curing process, the planks have flattened out and hey tend to lose about 20% of their original moisture content.
The cork slabs are then boiled to separate the outer layer of bark. This process also softens the cork and makes it easier to work with. The cork is then scraped (they take off about 2% of it) and placed in dark cellars and allowed to dry and cure for a few weeks under carefully regulated temperature and humidity.
Then, they take the slabs and punch them to make bottle stoppers. (By the way, these stoppers are impermeable to water and gas due to natural waxy substance called suberin. Also, some more trivia – cork stoppers have been used for over 400 yrs).
This leaves the cork slabs full of holes and the scrap cork is used to make cork flooring. The scrap is ground up and made into larger blocks and then baked in ovens (this is also how cork boards are made).
So, why is cork flooring green?
Well not only is the process of harvesting the cork non-detrimental to the tree, but in addition, because cork flooring uses the left over scrap after cork stoppers are punched out, it’s actually doubly green as the material is recycled to make the flooring. In addition, cork is usually a floating floor that clicks into place and therefore does not require additional adhesive or nails.
There is actually a lot more I would love to write about cork, but I will need to save that for another flooring post.
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