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Beyond the cork: different wine closures


This piece originally appeared on

long ago, a wine not sealed by cork was a signal to devoted wine lovers of a lower-quality, lower-priced bottle of vino. Thankfully those days of guessing a wine’s quality based on its closure are long behind us.

The perception of cork alternatives, such as screw-caps, is still lagging a bit behind their reality. Some of the wine world’s most exclusive (and priciest) wines are now sealed with alternatives to natural cork, with some high-end producers converting their entire product lines to technical corks, screw caps, glass stoppers, or synthetic corks – and making no bones about telling the wine market of their decision to do so. The technology behind these alternative closures have made the market much more competitive, to the point that traditional natural cork producers have also had to significantly up their quality game (along with their marketing efforts).

While it’s generally a bad idea to judge a wine by its closure, a little knowledge goes a long way in the wine-shopping experience, and it helps to know the benefits and the drawbacks of how you’re favorite wines are topped off. To help you make sense of all these alternatives (okay, and to help you sound more impressive at your next wine get-together), here’s the run-down on the most common wine closures and what makes them appealing to wine producers and wine lovers alike.

Natural Cork

Made from the bark of the Quercus suber oak (mostly grown in Portugal), cork has been used since at least ancient Egyptian times to seal vessels containing food and liquids meant to be preserved or transported. Cork is pliable, elegant, sturdy, and renewable, and we have hundreds of years’ worth of examples showing how well it can age a fine wine over many decades. But cork’s most appealing asset – that it’s a natural resource – is also its biggest drawback. Temperature and humidity changes can expand or contract cork, which can lead to premature aging of wine in the bottle. Cork is also susceptible to trichloroanisole (TCA), bacteria that can ruin a wine, dulling its flavors and giving it unpleasant off-odors (commonly known as cork taint). Finally, cork is unique in that it’s one of the few products that requires a specialized tool – a corkscrew – to extract it.


Technical Cork

In an effort to keep the benefits of cork while reducing that dreaded cork taint, companies like DIAM began making agglomerated corks that are specially treated to all but eliminate TCA bacteria. The result is a highly sturdy cork alternative that has many of the same benefits of natural cork, with far less cork taint and often less potential leakage. While there is less of an aging track record than with untreated cork, the risk is low given that it’s made of the same material. Of course, technical corks still require wrestling with a corkscrew when you want to get a bottle open.


Synthetic Cork

What if we could get the benefits of cork – the traditional corkscrew opening and oxygen transfer for slowly aging fine wines – without leakage and cork taint? That’s the driving force behind synthetic corks, which are usually made from synthesized plastic compounds. These corks are recyclable, they are often easier to extract from a bottle than traditional cork, and they usually offer very specific oxygen-transfer rates, so they can be matched to how long the wine they are closing is expected to age in the bottle. Some producers, such as Nomacorc, are now offering zero-carbon-footprint corks derived from sugar cane biopolymers. The downside, apart from still requiring a corkscrew, is that we don’t yet have a lot of examples of fine wines aged for long periods under these relatively new closures.


Screw Cap

In the 1970s, some forward-thinking Australian wine producers who were getting frustrated by the issues inherent in using natural cork began experimenting with closing their wines via screw caps. These closures consist of a metal cap with an internal liner that attaches to a metal “skirt” around the neck of the bottle. The perforation along the cap’s bottom edge allows the screw cap to be removed without the need of a corkscrew (or any other tool), although the best results are usually achieved by holding the cap and twisting the skirt rather than twisting the cap as one might when opening beer or soft drinks. Screw caps are almost totally immune to TCA infection, they handle temperature and humidity variations well, and they can be reused to temporarily store unconsumed wine while still in the bottle. They also don’t require bottles to be stored horizontally, which is necessary for keeping natural corks moist, and we have many examples of wines aging gracefully for long periods under screw caps. They can still leak if damaged, however.


Glass Stopper

Though not widely used in the United States, glass-stopper wine closures are popular in some areas of Europe, particularly Germany and Austria. With this closure, a glass (or sometimes plastic) plug with a flat top is used to close the wine bottle. An inert “O-ring” seal sits between the stopper and the bottle’s neck, creating an airtight seal that prevents TCA contamination and significantly limits oxidation (the exposure of wine to too much air, which can age it prematurely). Glass is, of course, recyclable, and the glass stoppers have an elegant look. They are also very handy for re-sealing a bottle of unconsumed wine so it can be kept for a few extra days after opening. The main drawbacks are that glass stoppers are heavy, adding additional weight to the wine bottle for shipping, and they are expensive for producers to use (which could mean a more expensive price tag for you).


At the end of the day, always remember to choose a wine based on personal preference! Regardless of how it’s corked, if you enjoy what’s inside, drink up!


By Joe Roberts, Food and Wine