Why Are Corks Used to Seal Wine Bottles?

Many Wine Corks

Wine is a unique beverage in many ways. It undergoes a complex production process, comes in numerous styles, and offers a wide variety of flavors. And it comes in cork-sealed bottles. Why is this the case in a world of plastic packages? Why Are Corks Used for Wine Bottles?

Corks are used for wine bottles because they create a tight seal. At the same time, they allow a little bit of oxygen to get into the bottle so the wine can breathe. This oxidation process produces more delicate flavors, smoother tannins, and a more balanced drinking experience.

In this article, we will discuss the history, production, and purpose of corks in detail. And we will learn about the advantages and disadvantages of corks over other types of bottle closures.


Bottle stoppers from cork have been around for thousands of years. Even before the invention of glass bottles, some winemakers sealed their containers with cork. Archeologists found remains of cork stoppers in old Egyptian tombs, but also ancient Greece. Nevertheless, it was a rather unusual way to seal containers.

In medieval, it became a common practice to make both bottles and bottle stoppers from glass. While this combination was a safe way to keep the liquids inside the container, it was hard to open it. It was quite normal that an attempt to remove the glass seal resulted in a broken bottleneck. Alternative solutions like oil-soaked rags also had their downsides.

In the 17th century, winemakers found a better solution. As glassblowing became a more refined art, artisans could create standardized bottle designs with more narrow necks. And with cork stoppers, it was possible to seal these bottles safely and open them easily. One of the first people to use cork stoppers was Dom Perignon. The Benedictine monk, famous for inventing Champagne, used cork together with wire to seal bottles of sparkling wine.


Cork is a natural material that comes from the bark of oak trees. More specifically, it is made from the bark of Quercus suber, an evergreen tree that is native to Spain, Portugal, and some parts of North Africa.

This bark has a unique honeycomb-like cell structure that contains around 90% air. This structure makes it light and elastic. Nevertheless, it is non-permeable and qualifies as an excellent material for bottle sealing.


It takes between 15 and 25 years until Quercus suber trees are ready for harvest. Workers peel the bark from their trunks with axes or machetes without cutting them down. It is important to mention that the trees do not take permanent damage from this procedure. They regrow their bark and are ready for another harvest in 7 to 10 years. With each growth cycle, the cork gets better in quality. In fact, trees that are about 100 years old produce the best cork.

Workers Harvesting Bark from Cork Oak Tree
Worker harvesting Bark from Cork Oak
Source: Nocampo / CC BY-SA

After the harvest, the workers boil the bark to remove impurities and sterilize it. Next, they dry the material until it has the optimal texture and cut it into the typical cylindrical shape. Usually, high-quality stoppers result from manual labor, while machines cut out lower-quality corks.


As indicated earlier in this article, cork stoppers provide some crucial benefits for winemakers. But they also have other gains. Let us find out about them.

Improving Flavors

Most types of wine benefit from breathing. When they are exposed to oxygen, they develop more complex aromas, and their tannins get less dominant. In some cases, aeration also can help get rid of unpleasant flavors. As a result, the wine becomes more balanced and more enjoyable. But too much oxygen can harm wine and cause it to spoil. So the right dose of oxygen is vital to improve a wine.

With its porous structure, natural cork provides the right conditions for optimal airflow. It lets about one milligram of oxygen per year into the bottle. With this small amount, wine can rise to its full potential without going off.

Sealing Safely

With changing temperatures, liquids like wines expand and contract. This can become a problem, especially when it happens repeatedly. A wine that regularly expands and contracts can damage a solid stopper or push it out of the bottle ultimately.

The elastic structure of the cork allows it to adapt to the wine’s expansion and contraction to some extent. Thus, it reduces the risk of a leak significantly. It cannot lower it to zero, though.

Environmentally Friendly

Cork is a natural product from a renewable resource. Its production does not harm the environment.

Also, corks are 100% recyclable. Like other plant matter, you can simply compost them. They need a couple of years to compose, but they will without any remainings. Alternatively, you can use them to craft wine-related decor for your home.


Although natural corks are highly beneficial for wine and great for the environment, they have some faults.

No Cork Is Like the Other

We have already discussed that the quality of corks depends on the age of the trees. But there are a couple of other factors that contribute to their quality and, in particular, their porousness.

With the different levels of quality and porousness, winemakers face the challenge of finding the right corks for their wines. The process of finding those that match a specific type of wine best can be long and hard. And it always includes the risk of choosing the wrong one and harming the wine.

Cork Can Promote Taint

You might have experienced wine that smells moldy, like a wet newspaper or a damp cardboard box. This smell is the outcome of taint or TCA. TCA is the abbreviation for 2,4,6-trichloroanisole. This strong chemical forms when plant phenols, chlorine, and mold interact with each other.

TCA can be present in the bark of cork oak trees even before the harvest. But it is also possible that it originates from barrels, storage boxes, or other wooden materials.

If a cork stopper that contains TCA gets in contact with the wine, it will impart its aggressive smell to it over time. This wine will not be a health risk for consumers, but it won’t be enjoyable anymore, either. The only thing you can do with this “corked” wine is to pour it away.

Cork Is Fragile

Due to its porous structure, cork is fragile. When it dries out, cork pieces can break off a cork stopper and fall into the wine. The same can happen when you try to open the bottle with a metal tool. Drinking wine with cork particles is not a great experience, and neither is fishing them out of your glass.

For this reason, you should store wine bottles with a cork seal lying on their side. In this position, the wine stays in contact with the stopper. It keeps the cork moist and prevents it from drying out.

Natural Cork Is Expensive

With all the manual labor involved in producing them, natural cork stoppers are cost-intensive. And with prices between 0.50 and 1 USD, they can be up to three times as expensive as bottle stoppers from other materials. Winemakers have to factor in these extra costs. Therefore, vintners that produce high-end wines are more likely to use natural cork than those who make affordable wines.


Besides natural cork, winemakers use some other materials to seal their bottles. These alternatives include reconstructed cork, synthetic cork, and screw caps. In comparison to natural cork, they have individual advantages and disadvantages.

Reconstructed Corks

Reconstructed cork is basically recycled natural cork. This material is made by gluing together the remaining pieces of the production of high-quality cork stoppers. It is also possible to use grounded old corks for this purpose.

Because it is made of natural cork, reconstructed cork has a similar structure and comparable characteristics as natural cork: It allows the wine to breathe and is a reliable seal. It is significantly cheaper to produce, though. Thus, producers of low-cost wines tend to prefer it over the expensive natural alternative.

Unfortunately, reconstructed corks have similar disadvantages as natural corks: They can contain TCA and cork a wine, and they also can break apart. Because of the glue they contain, these risks are relatively low, though.

Synthetic Corks

Of course, there is a synthetic alternative to natural cork stoppers. These plastic seals are made from polyethylene, just like milk bottles or garbage bins. They offer several advantages over natural or reconstructed cork:

  • Depending on the manufacturer’s preferences, they have a consistent and reliable structure optimized for a specific level of aeration. So winemakers do not need to go through the try-and-error process to find the proper bottle stoppers.
  • They are immune to TCA, so the risk of corking wine is almost zero.
  • Synthetic corks are more affordable because producing them is a less time- and cost-intensive process than making natural cork.
  • For the environment, synthetic corks are significantly worse, because they do not decompose over time. Despite this disadvantage, especially producers of low-quality wines tend to prefer synthetic corks.

Screw Cap Closures

Screw caps for wine bottles emerged around the late 1950s. But it was not until the 2000s that commercial winemakers began using them instead of traditional corks. This switch to screw caps began in New Zealand and Australia but expanded worldwide. Nowadays, wines with screw caps often are considered low-quality wines. But actually, many high-end wineries utilize them as well due to the benefits they offer:

  • One of these benefits is their ease of use. It is much easier to open a bottle with a screw cap than a cork. No tools like bottle openers are necessary, and it is almost impossible to break screw caps.
  • As they do not contain plant matter, screw caps are not prone to TCA. Thus, they minimize the risk of accidentally corking wine for winemakers.
  • Screw caps are made from aluminum, so they are air-proof. For young, crisp wines that do not need much aeration, this is a crucial feature, because it prevents overoxidation.

On the other hand, it means that bold wines cannot benefit from exposure to a bit of oxygen. So the typical aging process that improves flavors and softens tannins will not occur.

Finally, screw caps are not very eco-friendly because they are not compostable. They are recyclable but only through energy-intensive procedures.


Screw caps are not fundamentally better or worse than cork stoppers. Winemakers have to decide which type of bottle closure they use based on the wine they want to seal:

  • Screw caps are the right choice for light wines that are meant to be drunk when young. To conserve their freshness, air-proof bottle seals are necessary. Most white and rosé wines belong to this category.
  • Cork stoppers are the proper solution for complex, full-bodied wines. As these wines benefit from exposure to oxygen, cork is the right material for them. Thus, many red wines, as well as some oaked whites, come in cork-sealed bottles.


As mentioned above, fragility is one main issue of cork stoppers. They are likely to crumble when consumers try to open the bottle.

But it is possible to minimize the risk of breaking a cork by following some simple rules:

  • Store Your Wine Properly. As mentioned before, you should store cork-sealed wine on their side. This position ensures that the wine stays in contact with the cork and prevents it from getting dry and porous, so it does not break as easily.
  • Use the Right Corkscrew. Depending on the age (and value) of the wine, you should use a different corkscrew. A basic model is right for the majority of wines. You should consider using a two-pronged bottle opener only for old vintages or very expensive bottles. It is a little harder to handle these openers, but they minimize the risk of breaking the cork.
  • Use the Corkscrew Properly. When using a standard corkscrew, make sure to place it in the center of the cork. Deviating for just half a centimeter increases the risk of breaking the cork. Twist the corkscrew into the cork slowly. Stop when about one twist is left, so the corkscrew does not go all the way through the cork. Pull it out carefully without shaking the bottle and the corkscrew too much.


Even with proper care, pieces break off the cork and fall into the wine sometimes. But if you realize it and take action immediately, this will not be a big problem.

Pour the wine through a proper filter into a decanter. As a filter, you can use a coffee filter from paper or a piece of cheesecloth. If the cork pieces in the wine are not too big, a fine cullender might be an option as well.

Having the right decanter for your wine is key. If it exposes the wine to too much oxygen, it might cause overoxidation.

In case, you do not own a decanter, pour the wine directly into glasses. Because the glasses have a wider opening than a decanter, this might be a bit tricky, though. You must pour very slowly and ensure the filter does not get out of place. It might be a job for two people.


For many people, wine corks are a fancy tradition that makes wine stand out from less fancy beverages. For others, they are an annoying obstacle on their way to a good glass of wine. With the knowledge from this article, you know better than all of them. Cork stoppers actually serve a meaningful purpose for wine by contributing to its taste and smell. Next, try to experience the differences yourself. Can you sense the differences between wine with a screw cap and cork-sealed wine?

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