What is Cork and Why is it Used to Close Wine Bottles? | VinePair

What is Cork and Why is it Used to Close Wine Bottles?

2 minute Read


Cork

Unless you drink boxed wine to the exclusion of all others, cork has played a role in your wine journey. Whether getting the reputation as a “world-class cork breaker” sent you running for screw caps, or hearing the delightful “pop!” transformed you into a wine enthusiast, your wine memories involve at least a little cork. But cork is more than the recalcitrant barrier between you and your booze. It’s a critical element of winemaking history and a fascinating organism to boot. And though new advances in winemaking technology mean that screw caps and artificial corks can work as well as the natural stuff, cork trees and their history are critically important, especially as climate change affects wine regions, growing seasons, and life cycles globally.

Though cork harvesting has been a practice since the ancient Greeks, it wasn’t used in glass wine bottles until much more recently. Like wine, cork comes from a living, breathing organism: Quercus suber, or the cork oak. Amidst the frenzied yearly cycle of the wine industry, these evergreen oaks move like sloths, slowly expanding and growing the bark, known as orange cork. With an average lifespan of 200 years, each tree can provide thousands of bottle stoppers when cared for properly.

The short version of the cork life cycle goes like this: Happy cork trees grow to age 25 in semi-arid forests surrounded by other animal and plant life on the Iberian peninsula and North Africa. After that, skilled cork harvesters use axes to slice off the outer bark of the tree, leaving its inner wood intact and undamaged. Then, the planks of cork bark are dried, sorted, and processed. To make the bottle stoppers we know so well, slices of cork are boiled to remove impurities (like the chemicals that cause cork taint) and dried until they reach the optimum texture to be pressed into bottles. Over nine years, the outer bark slowly regenerates before the next harvesting cycle begins.

Cork oaks are the only oak whose bark regenerates in this fashion, making Quercus suber a very special tree. On a cellular level, cork looks like a honeycomb of air pockets. These pockets make cork both buoyant and fire resistant, which is why it’s quickly becoming a popular home insulation material. This is the same reason cork works so well to age wine — its molecular structure makes watertight seals easy, but lets tiny bits of air move in and out, allowing the flavor and aroma molecules of wine to evolve and become more complex over time.

Only high-quality cork bark can be made into bottle stoppers, so repurposing lower-quality bark actually makes the industry more environmentally friendly (go ahead and buy that cork purse on Etsy!). Lower-grade or crumbled cork material can sometimes be used in composite corks, like the ones in many sparkling wine bottles. Today, those bits are used in everything from shoes to flooring.

Shoes are critical, of course. But the cork forests of Portugal, Spain, Morocco, and Tunisia play an important environmental role, too. In arid landscapes like the Moroccan desert or Portugal’s Alentejo region, these forests hold soils together, preventing the desertification of large swaths of land. At the same time, these forests provide a critical habitat for endangered species like the Iberian lynx and imperial eagle.

Despite what screw-cap manufacturers would have you believe, there’s no shortage of Quercus suber trees, and the generations of farmers tending them plan to keep doing so. The largest forests in Portugal have been protected by law since the 13th century, so it’s safe to say the stewards of these lands know the value of what they have. In 2007, a study conducted by PricewaterhouseCoopers and Ecobilon concluded that natural cork production was actually more environmentally sound than the production of aluminum and plastic closures.

Know what that means? More drinking, cork crafting, shopping, and building that’s conveniently and naturally earth-friendly. Now, get some glitter and drink up!

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