Where does cork come from?
Corks are made out of… well, cork. It is harvested from a tree called “Quercus suber“, Latin for oak cork (chêne liège in French). These trees have a life expectancy of two to six hundred years. They primarily grow in countries that run along the coast of the Mediterranean Sea. This oak tree’s particular feature is its very thick bark (2 to 7 inches).
Those trees evolved to protect themselves from the harsh conditions of the forests near the Mediterranean sea. These forests experience frequent droughts, brush fires and temperature fluctuations. The outer bark is actually made of water-resistant cells that protects the delicate interior bark. It has a unique set of properties not found in any other naturally existing material. It is lightweight, rot resistant, fire resistant, termite resistant, impermeable to gas and liquid, soft and buoyant.
Starting around the 3rd century, its usage was already well known by the Egyptians and the Greeks who proudly used cork to seal their amphoras. The cork was then covered with resin or jute and locked in place with a wooden peg. The cork disappeared for a while once the Celts invented the barrel. The cork was no longer necessary as barrels used a round piece of wood covered with jute and wax. The cork came back around the 17th century, once glass became technologically viable for transportation and usable on a consumer level. It went through quite a few makeovers, in order to adapt with new various containers. It’s only in 1728 that it started being used for Champagne.
How are corks made?
A cork oak tree must be at least 25 years old before its bark can be harvested. Its cork can then be stripped every 9-15 years (depending on the region) for as long as the tree lives. Yes, the bark grows back which makes natural cork completely sustainable. The cork is stripped off during July and August using a long-handled hatchet to cut sections out of the bark. These sections are then pried away from the tree. Workers must be careful not to damage the inner layer of the bark, otherwise the bark won’t grow back. The cork slabs are then boiled and the rough outer layer of the bark is stripped away. Boiling the cork also softens it, making it easier to work with. From the slabs of cork, holes are punched out to make that notorious bottle stopper called cork. The corks are now treated and washed, a delicate procedure that requires most attention. The stoppers can at this time be printed or branded with names or logos before being shipped to their proud owners.
This fabrication method leaves leftover slabs full of holes. This scrap is ground up, molded into large blocks and baked in ovens to make other cork products, such as roof insolation material, cork tile flooring, cork message boards, and more.
Cork contains a natural waxy substance called suberin. This substance makes cork impermeable to liquids and gas, and prevents the cork from rotting. However, based on the type of fabrication, a cork will let certain gases get in contact with the wine, a necessary symbiosis for proper aging. I’d like to see a screw cap do that! Well actually, it does… Grrr!! Modern screw tops are so precise that the winemaker can adjust the tightness of the seal to allow more or less outside air to enter, without the risk of cork taint.
A cork is not just a cork. The engineering and thought process behind its fabrication is quite complex and requires a group of engineers, chemists, and years of practice. Certain types of corks will be used for certain types of wine. It is important to determine precisely the needs and choose the right cork based on the following:
– wine type (white, red, or rosé)
– aging duration
– bottle characteristics
– bottling conditions
– shipping and stocking methods
– commercialization type
There’s literally a cork for every type and every usage. You want it? They have it.
Who makes corks?
There are quite a few companies from around the world that fabricate corks. The largest and most notorious group is located in Portugal. With more than 31 production units in the world, Amorim has been manufacturing corks since 1870. They proudly produce 3 billion corks per year. Another company called Portocork (also located in Portugal) focuses on producing only natural corks. Portugal is by far the largest producer of corks in the world. The country counts 45 companies that produce an average of 30 million corks per day! Nomacorc is an American company that produces 2 billion corks per year, though all synthetic.
Cool fact #2: Once upon a time, cork’s astringent characteristic became useful in medicine. The bark was used to stop the bleeding of wounds. Also, when burned, the ashes mixed with egg oil were an excellent remedy against hemorrhoids.
Check out Wine Cork Story [Part 2], where I explain the fundamental differences between the three primary closure styles!