Stelvin® Closure: How It Works, Advantages, and Disadvantages

A Stelvin® closure is a screw cap that is used as an alternative to cork to seal wine bottles. Even though cork closures are still, to this day, the most popular wine bottle sealer, Stelvin closures have gained significant popularity in recent years, especially because they address some of the issues, such as cork taint, associated with traditional cork closures.

This article talks about these bottle closures, what they are, how they function, what their advantages and disadvantages are, and so much more.

What Is a Stelvin Closure?

A STELVIN® closure, commonly referred to as a screw cap, is a type of aluminum screw cap used to seal wine bottles, as an alternative to the traditional cork closure. It consists of a metal cap that screws onto threads on the neck of a wine bottle, with a metal skirt down the neck to resemble the traditional wine capsule ("foil"). Inside the cap is a liner, often made from Saranex™, which helps to create a tight seal that protects the wine from oxygen exposure and potential cork taint, while also making the bottle easier to open and reseal. These liners are integral to maintaining wine quality, offering distinct levels of oxygen permeability that are critical for the wine's aging process. They preserve the wine's aromas, flavors, and freshness. 

When Was the Stelvin Closure Developed?

The journey of Stelvin started in the 1960s in Chalon-sur-Saône, a city nestled in Burgundy, France. The first Stelvin closure was developed in its final form in 1964, and the brand was formally established in 1976.

Where Is a Stelvin Closure Used?

Stelvin closures are used worldwide in the wine industry for sealing wine bottles. Initially adopted in countries known for innovation in wine packaging, such as Australia and New Zealand, their use has since expanded globally. These closures are used across a broad spectrum of wine types, from everyday table wines to premium and boutique vintages. They are used in wine-producing regions around the world, including: Australia and New Zealand, the United States (e.g., California, Oregon, and Washington), Europe (France, Italy, and Spain), South Africa, and South America (Chile and Argentina).

How Does a Stelvin Closure Work in Wine Bottling?

The Stelvin closure significantly improves upon traditional cork closures by incorporating several key features designed to preserve the quality of the wine. This closure system (see Figure 1 below) is not just a simple cap but a carefully engineered solution aimed at enhancing the wine's integrity from bottling until it's opened:

The heart of the Stelvin closure's effectiveness lies in its closure liner. This liner is critical as it directly seals the product within the bottle. It sits snugly between the closure and the bottle's rim. Winemakers can tailor the closure to suit the specific aging and flavor preservation needs of the wine by selecting appropriate liner materials. 

The knurl is a design feature that enhances the consumer experience by providing a better grip on the closure. This textured surface around the cap makes it easier to open the bottle without the need for additional tools. Support beads provide structural integrity to the closure during the application process. They ensure that the closure does not deform or break when being applied to the bottle.

The skirt is the extended lower portion of the capsule provides an area for custom-designed printing. Wineries can use this space to include branding, product information, or decorative elements. Tamper-evident bridges are small, uncut sections that join the top (head) of the closure to the skirt. When the closure is first opened, these bridges break, providing a clear indication that the bottle has been opened.

What Are the Advantages of Stelvin Closures Over Traditional Corks?

Stelvin closures have the following advantages over traditional corks:

1. Provide a consistent seal, reducing bottle variation compared to natural corks, which can vary in density and quality. This consistency ensures each bottle of wine is sealed under similar conditions.
2. Eliminates cork taint, caused by TCA (2,4,6-trichloroanisole), a compound that can impart an undesirable musty flavor to the wine. Since Stelvin closures are not made from cork, they eliminate the risk of this type of contamination.
3. The liner within a Stelvin closure can be engineered to allow precise control over the oxygen transfer rate (OTR). This enables winemakers to manage the wine's exposure to oxygen more effectively.
4. Are easy to open and reseal without the need for a corkscrew. This ease of use also eliminates the risk of cork breakage.
5. Can better preserve the wine's intended flavor profile and freshness. Even for wines with aging potential, screw caps can provide a suitable aging environment.
6. Can vary in price depending on the quality. However, generally speaking, they tend to be cheaper than natural cork.

How Does Stelvin Closure Impact the Wine Aging?

The Stelvin closure impacts wine aging primarily through its control over the oxygen transfer rate (OTR) to the wine. The tight seal of Stelvin closures limits the amount of oxygen that can enter the bottle over time. Oxygen is a crucial factor in the aging process; too much can accelerate oxidation, leading to premature aging and loss of fruitiness and freshness. The controlled OTR of Stelvin closures can slow down these oxidation processes, potentially leading to a more gradual and predictable aging process.

Can the Stelvin Closure System Preserve the Wine Flavor and Aroma?

Yes, the Stelvin closure system can preserve wine flavor and aroma very effectively. The tight seal created by the screw cap prevents excessive oxygen from entering the bottle, which can lead to oxidation and deterioration of the wine's quality over time. By controlling the oxygen transfer rate (OTR), Stelvin closures help to maintain the wine's intended flavor profile and aroma for a longer period compared to some cork-sealed bottles.

Is a Stelvin Closure Made of Aluminum?

Yes, the Stelvin closure is an aluminum made closure. It consists of an aluminum cap that screws onto threads on the neck of a wine bottle. 

What Are the Disadvantages of the Stelvin Closure System?

While Stelvin closures offer numerous benefits for wine preservation and bottling efficiency, there are some disadvantages and concerns associated with their use:

1. The production of aluminum, the primary material used in screw caps, involves mining bauxite ore, which can have significant environmental repercussions. The process of converting bauxite into aluminum is energy-intensive and can lead to air and water pollution, generating substantial waste. 
2. The liners in most screw caps have traditionally been made from polyvinylidene chloride (PVDC), a type of plastic that raises sustainability and health concerns. PVDC is considered unsustainable and can release toxic chemicals if incinerated. Furthermore, some studies and regulatory bodies have raised questions about potential health risks associated with PVDC, leading to its ban or restriction in several Western European countries. Although Amcor has introduced a PVDC-free range of Stelvin closures to address these concerns, the use of PVDC remains a contentious issue in regions where it is still permitted.
3. Wines sealed with Stelvin closures may be prone to reduction, a condition characterized by the presence of undesirable sulfur compounds that can impart off-aromas, such as rotten eggs or onion. This issue is not directly caused by the screw cap itself but by the tight seal it creates, which can limit the wine's exposure to oxygen. Unlike cork, which is more porous and can allow for some oxygen exchange, the effective oxygen barrier formed by screw caps can exacerbate the reductive qualities in wine if sulfur dioxide levels are too high. 
4. Despite the growing acceptance of screw caps, there remains a segment of consumers and winemakers who prefer traditional cork closures due to their natural origin, traditional appeal, and perceived impact on wine aging. The perception of screw caps as a less prestigious option for sealing premium wines continues to be a challenge for some in the industry, although this is gradually changing.

What Are the Environmental Impacts of Wine Bottle Screw Caps?

The environmental impact of wine bottle screw caps involves several considerations related to their production, use, and disposal:

1. Aluminum, the main material for screw caps, is derived from bauxite ore, which is strip-mined. The extraction process can have significant environmental impacts, including: habitat destruction, soil erosion, and water pollution. These effects are particularly concerning in bauxite-rich regions where mining operations can disrupt local ecosystems.
2. The process of refining bauxite into alumina and then smelting it into aluminum is energy-intensive. It involves high temperatures and significant electricity use, contributing to carbon emissions and environmental pollution. The global aluminum industry is a notable consumer of electrical power, much of which is generated from fossil fuels in many parts of the world.
3. Aluminum production generates considerable waste, including red mud (bauxite residue), which contains various heavy metals and other toxic substances. Managing and disposing of this waste is a major environmental challenge, as it can contaminate water sources and soil if not properly handled.
4. The liners inside screw caps, often made from materials like PVDC, pose additional environmental concerns. PVDC is not sustainable and can be toxic when incinerated. Recycling screw caps with the liners still attached can be challenging, and not all recycling facilities are equipped to separate and process these materials properly.

What Is the Process of Stelvin Closure?

The process of applying a Stelvin closure to a wine bottle includes several key steps to ensure a secure seal and maintain the wine's quality:

1. Clean and sterilize wine bottles. Prepare Stelvin closures with their liners properly inserted.
2. Fill the bottles with wine, taking care to minimize oxygen exposure.
3. Equipped with a liner for sealing, screw the Stelvin closure onto the threaded neck of the wine bottle, typically using automated machinery.
4. As the closure is tightened, the liner compresses against the bottle rim, forming an airtight seal that protects the wine from oxygen and contamination.
5. Bottles undergo a quality check to ensure closures are correctly applied and sealed.
6. Finally, labeled and packaged bottles are ready for distribution.

How Are Stelvin Closure Caps Tested?

The effectiveness of the capping process is tested through removal torque testing. This testing method ensures that the caps can be easily opened by consumers by measuring the force required to unscrew the cap from a sealed wine bottle. The process involves applying a predetermined torque to affix the cap onto the bottle during the bottling process, ensuring consistency and reliability in the seal. Subsequently, the removal torque test is conducted using specialized equipment that measures the amount of torque (force) needed to unscrew the cap.

How Are Winemakers Adapting to Stelvin Closure?

Winemakers are adapting to Stelvin closures by modifying winemaking and bottling processes to ensure wine quality and meet consumer preferences. This includes adjusting winemaking practices to account for the reduced oxygen ingress provided by screw caps, such as altering sulfite levels. They are also tailoring wines specifically for sealing with Stelvin closures, considering the impact on the aging process. Experimentation with different liner options allows winemakers to control oxygen transmission rates more precisely, influencing how the wine matures. Additionally, there's a focus on consumer education to shift perceptions and highlight the benefits of screw caps, including their ability to eliminate cork taint and preserve wine freshness.

What Does the Consumer Think About Screw Caps for Wine Bottles?

Consumer attitudes towards screw caps on wine bottles have shifted significantly from skepticism to acceptance and appreciation over recent years. Initially, screw caps were often associated with lower-quality wines, and the tradition of cork-sealed bottles was seen as a marker of high quality. This has changed over the years since winemakers started to incorporate screw caps more and more, including in premium varieties. The benefits of screw caps, such as preventing cork taint and oxidation, alongside the convenience of easy opening and resealing, have contributed to changing perceptions. Education and awareness efforts by the wine industry have also played a crucial role in highlighting the advantages of screw caps, including their environmental benefits, like recyclability. Moreover, demographic changes show that younger wine drinkers, who are less bound by tradition, are more open to accepting screw caps.

How Long Can a Stelvin Closure Last?

In general, wines sealed with Stelvin closures can be stored for several years, with many winemakers and experts suggesting a range of 5 to 10 years for optimal quality, although some wines may be suitable for aging beyond this range. The key factor is the oxygen transmission rate (OTR) of the specific liner used in the Stelvin closure, as different liners allow for varying levels of oxygen exchange, which can affect the aging process.

What Are Other Types of Wine Closures?

Beyond screw caps, the wine industry utilizes various other types of closures to seal wine bottles, each with its unique properties and applications:

1. Natural Cork: The traditional choice, made from the bark of cork oak trees, allowing minimal oxygen exchange beneficial for aging wine.
2. Synthetic Cork: Made from plastic compounds designed to mimic natural cork's appearance and function without the risk of cork taint.
3. Champagne Corks: Specifically designed for sparkling wines, these corks have a mushroom shape and are made to withstand the pressure inside sparkling wine bottles.
4. Agglomerate Corks (Composite Corks): Constructed from cork granules bonded together, suitable for wines intended for consumption within a few years.
5. Colmated Corks: Natural corks filled and sealed with cork dust to smooth out the surface, used for wines with moderate aging potential.
6. Multi-Piece Corks: Consists of two or more pieces of cork glued together, often used for sparkling wines and some still wines.
7. Vino-Lok™/Vinoseal: A glass closure with a plastic gasket for an airtight seal, offering an elegant and reusable option.
8. Zork: A plastic closure that combines the benefits of a screw cap and cork, providing a tamper-evident seal.
9. Helix: A twist-off natural cork design that engages with a threaded glass neck, allowing easy opening without a corkscrew.
10. Crown Caps: Similar to those used on beer bottles, used primarily for sealing sparkling wines during secondary fermentation.
11. Tasting Corks: Designed for temporary closure, making them ideal for use in wineries and tasting rooms for wines that will be consumed quickly.

Are Stelvin Closures Expensive To Make?

Yes, although Stelvin closures can vary in cost, depending on the quality, they are typically cheaper than other wine-closure options, especially natural cork. 

Can Stelvin Closures Be Anodized?

Yes, Stelvin closures can be anodized. Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts, in this case, aluminum, which is the material most commonly used for Stelvin closures. Anodizing can improve the corrosion resistance, surface hardness, and wear resistance of the aluminum screw caps, and it also allows for the addition of colored finishes.

To learn more, see our guide on Anodizing Closures.

Summary

This article presented Stelvin closures, explained them, and discussed how they work and their applications. To learn more about Stelvin closures, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

Copyright and Trademark Notices

1. STELVIN® is a registered trademark of Amcor Flexibles Capsules France SAS.
2. Saranex™ is a trademark of TRANSCENDIA, Inc.
3. Vino-lok™ is a trademark of Vinolok, a.s. (Preciosa Group, Czech Republic)

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