Natural corks remain the most popular and frequently used closure; and while synthetic closures and technical corks remain the most widely used alternatives, screw caps continue to make healthy inroads, according to results from Wine Business Monthly's 2006 Closure Survey.

Usage of screw caps has been boosted by an increasing impression among winemakers that consumers' opinions of the closures are improving. And although natural corks remain the most widely used closure-82 percent of responding wineries use natural cork for at least part of their 750 ml bottles-alternatives are being used more for low- and mid-priced wines, and are now even being considered for use with wines at price points of $25 and above.

This is the first year we asked about oxygen transmission through the closure into the bottle. The importance of oxygen ingress through the closure after bottling has been a much debated aspect of closure performance, but with little independent research yet available, winemakers appear to have widely differing views as to the need for, and correct amount of, oxygen transmission. More than half of the respondents thought that some oxygen transmission through the closure was important while slightly more than a quarter of the respondents held the contrary view.

Oxygen transmission

Renwood CEO Robert Smerling argued that the industry's real problem is the lack of knowledge regarding closure performance. "The process of aging occurs in the space between the closure and wine. If you eliminate the cork, then you triple the amount of space between the closure and the wine. What effect will this have on aging? This needs to be studied. This has nothing to do with the transmission of oxygen. I do not believe a closure properly sealed transmits oxygen. The aging process occurs in a contained space. Thus, in red wines, a screw top is an unknown in the effects of aging."

Our interest in this topic mirrors Smerling's comments. Oxygen ingress has been a much debated aspect of closure performance, but the subject is rarely peer-reviewed with published research. Despite this, many winemakers appear to have strong, if empirically derived, opinions on the subject (Chart 1). Twenty-six percent of respondents answered that oxygen ingress through the closure was not important for wine development in the bottle while 56 percent followed the traditional perception of bottle aging and answered that oxygen transmission through the closure was important for the development of wine in the bottle.

Stephane Vivier of Hyde de Villaine Wines in California provided one of the most succinct arguments in favor of oxygen transmission through the closure. "Let's have an older Grand Cru Burgundy and I will tell you why. Some wines need some aging to show a different facet, and oxidation is part of it."

Scott Ratcliff, owner of Bend, Oregon's Volcano Wine Company, agreed. "Aging for reds is the reason I'd like to have some ability to transmit oxygen to the wine but not much, mind you. Traditional cork lets small amounts of oxygen in over time, which I believe helps with aging. There hasn't been enough long-term data since the newer synthetic closures have not been around long enough. I think any data I have reviewed is 20 years old, at best, which doesn't reflect the latest technology."

Tom Larson, owner of Larson Family Winery in Sonoma, California, said, "I believe the screw cap is the best closure and the oxygen permeability of corks to not be a good thing."

Jim Gullett of Plymouth, California's Vino Noceto winery added, "We want a positive seal on our Frivolo, a Moscato di Asti style wine, and our Rose, Rosato di Sangiovese. In both cases we want to preserve freshness as much as possible."

Referring to research like that from the Australian Wine Research Institute (AWRI), Shaun Richardson from Clos Pegase in Napa, noted, "If the closure transmits a large amount of oxygen, there is the risk of spoilage. There is research that indicates that a screw cap is on a par with the best sealing cork."

It appears that at least some of this disagreement between the respondents is because of a paucity of independent research. Oxygen transmission through the closure has been something of a hot topic since AWRI released its preliminary findings in their long-term closure study. This was only amplified by the "Science of Closure Seminar" at last year's ASEV annual meeting. Despite being held several years subsequent to the AWRI study's initial publication, the seminar had little other peer-reviewed and published research on which to draw (see sidebar, page 18).

Perhaps it is not terribly surprising that most of the winemakers rated closure consistency as a very important attribute (Chart 2). Eric Laumann of the Monterey Wine Company spoke for the majority of the respondents when he noted, "Closure consistency is important so the wine ages uniformly from bottle to bottle."

However, even though consistency is highly rated, we see that elsewhere in this survey the most inconsistent closure, natural cork, remains the most widely used closure. This is most likely because, although consistency is a desirable attribute, other factors like image and perceived long-term performance actually outweigh its importance.

Richardson of Clos Pegase viewed consistency as a very desirable trait. "I like the consistency of the screw cap."

About two-thirds of respondents thought it was important to match the winemaking process to the intended closure (Chart 3). Eric Laumann explained that these adjustments are usually kept to a minimum. "We may fine-tune our winemaking to accommodate a certain closure, but we require the impact of any closure, or closure-related adjustment, to be minimal on the wine's character. I'm a believer in screw caps but sentimental for cork. Plastic stoppers work well in certain situations, but with so many new, alternative closures being developed, their market share may diminish. The Monterey Wine Company recently purchased a screw cap machine to keep pace with the demand for that type of closure."

Mark Chesebro of Chesebro Wines provided his insight. "In order to predict wine development, SO₂ levels and potential reduction problems, winemakers need to know what the oxygen transport is like in relation to the cork standard. Although corks vary, winemakers are familiar with their general effects and results, and everything new needs to be related to that."

"If you are using a synthetic cork, which will allow more oxygen into the wine than a natural or screw cap, then you may want to treat the wine less oxditively prior to bottling and probably add a little more SO₂ at bottling," said David Forsyth, general manager for The Hogue Cellars in Prosser, Washington. "The wine will continue to receive O₂ through the cork at a fairly high rate (relative to natural and screw cap), and the wine will age (oxidatively) quicker than the alternatives; so you want to set yourself up a bit more reductively going into the bottle and protect from oxygen (N₂ sparging at bottling and higher SO₂). Conversely, in putting a big red wine into a screw cap you will want to make sure that you take into account that this wine will only receive a fraction of the oxygen during aging versus a cork or synthetic; you will want to ensure that it is at a proper oxidative state going into the bottle. Also less SO₂ is required."

However, many respondents "match the closure to the wine" rather than matching the wine to the closure. Bonny Doon's (Santa Cruz, California) Jillian Johnson explained how this approach works in practice. "With white wines, we like the tightest closure, and with reds that are intended for aging, we also like the tighter closure. However, with early-release reds we sometimes use the looser closure."

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Oxygen Transmission and Recent Research

The Australian Wine Research Institute (AWRI) long-term closure study has reignited interest in closure performance with regard to oxygen transmission. In part, this is due to the dearth of available data. Although a great deal of ongoing research has been conducted by the various closure manufacturers, little closure research is actually peer-reviewed and published. There has been a peak in interest in such research in the wake of the "Science of Closures Seminar" held during the last ASEV annual meeting.

More recently, Allen Hart and Andrew Kleinig conducted an interesting, if extremely limited, study on "The Role of Oxygen in the Aging of Bottled Wine." Their conclusion was that "oxygen was not a vital component for the ongoing evolution and maturation of these red wines after bottling." Hart and Kleinig found that "the access to small but measurable amounts of oxygen (e.g., synthetic closures, approximately 4 CC O₂/bottle/year) will accelerate the evolution and maturation of red wine through oxidative reactions. However, red wine will continue to evolve without measurable oxygen ingress via a closure, primarily through what is assumed to be anaerobic reactions. Some bottled wine may express 'reductive' characters in such an anaerobic environment, in contrast to the wine developing oxidized characters in a more aerobic environment." (Hart & Kleinig, 2006)

According to recent, but as yet unpublished, research by Susan Ebeler, the primary benefit of oxygen ingress into the bottle appears to be to oxidize thiols, which can be produced during bottle aging under anaerobic conditions. These thiols can cause the "rubber" or "struck flint" aromas that are most associated with "reductive" or "reduced" wines. Additionally, as mentioned by the AWRI's Ella Robinson at the "Science of Closures Seminar," research appears to indicate that increasing the initial oxygen in the headspace, either through head-space size or oxygen concentration, just oxidizes the wine rather than forestalling thiol formation.

Ebeler's work seems to indicate that the thiol production of a given wine has more to do with the nutritional status of yeast during fermentation rather than the particular hermetic properties of a given closure. When yeast are stressed, they appear to produce certain thiol-precursors as sulfur compounds accumulate in them as a result of inadequate assimilable nitrogen. This has led to a fair amount of disagreement among winemakers as to the role of oxygen during bottle-aging. Fully one-third of the respondents replied that oxygen ingress was "very important" for the development and aging of a given wine despite the fact that this opinion appears to run somewhat contrary to the findings of researchers like Hart, Kleinig, and Ebeler. wbm

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Survey respondents rated screw caps as having the lowest oxygen transmission (Chart 4). Natural corks were rated at the opposite end of the spectrum as having the highest oxygen transmission. Technical corks and synthetic closures occupied the middle ground, with respondents rating technical corks as having slightly more oxygen transmission than synthetic closures.

However, the overall ratings were somewhat at odds with the views of some winemakers. Winemaking consultant George Vierra noted that, "Some closures, agglos and polys, have been shown to allow more air into the bottle, and therefore the wines 'age' faster and lose their freshness. The independent studies I have seen show screw tops are best at protecting the wine from oxygen pick up. Standard corks are second."

In-bottle oxidation was a hot topic among the respondents. The results of our survey indicated that winemakers believe screw caps are the best closure for preventing unwanted oxidation (Chart 5). Many responded anecdotally that they have had oxidation problems with pretty much every type of closure other than screw caps. Conversely, several respondents noted that they thought wine developed better if the closure allowed minute amounts of oxygen into the bottle. This, of course, is the traditional view, but perceptions aside, what the small amount of peer-reviewed research seems to indicate is that while the oxygen that passes into the bottle in this "in-bottle micro-oxidation" mainly just binds with sulfur dioxide or any thiols that have formed, it doesn't appear to be involved in some of the slow reactions, like the polymerization of polyphenols, usually thought to be characteristic of bottle aging. Of course, the oxidation of thiols is important in preventing the development of "reduced" aromas (see sidebar, below).

Tom Meadowcroft, winegrower for Magito Wines in Sebastopol, California, opined that the issue was really more complex than might have been implied by the question in the survey. "I view that the oxidation created by the closure will affect the development of the wine. Synthetic corks create the greatest opportunity for oxidation, and screw caps are the best at keeping a wine free of oxidation. Therefore, the type of closure greatly affects the development of the wine. If a winemaker wants oxidation to be part of their wine style, then they should be aware of what the closure will or will not do for them. I grant that few winemakers would choose oxidation as a tool in winemaking; yet by choosing a synthetic cork and a real cork, winemakers are choosing to oxidize their wines at rates that are faster than with a screw cap. So if winemakers are choosing closures that oxidize their wines faster, then they are making a deliberate choice to purposely oxidize their wines and, therefore, affect the development of their wines."

We asked respondents to rate each of the closure types in terms of preventing unwanted reduction in an attempt to address one of the more frequently voiced winemaking concerns about screw caps. As we can see from Chart 6, taken as a whole, the respondents did not view screw caps as being any more likely to lead to reductive odors than any other closure. Some winemakers voiced strong opinions as to the reductive nature of bottling under screw caps, but an essentially equal number tended to view the question of unwanted reduction in the bottle as a winemaking issue rather than as a closure issue.

David Forsyth of Hogue Cellars discussed both oxidation and reduction by noting, "The winemaking process is not done when you put the wine into the bottle." Forsyth went on to note that some wines, like Sauvignon Blanc, seem to benefit from slightly reductive conditions whereas for a big red wine, a winemaker "might have to allow the wine to move further along [in development] before bottling."

Jillian Johnson described her protocol for predicting the reductive tendencies of particular wines. "We do bottling trials with our reds in different closures, with and without homeopathic copper additions before bottling the wine. The trials can show us if a wine has a tendency to go reductive in a certain type of closure. The copper part of the trial will also help us to see if there is a reduction tendency in the wine."

Brook Williams, winemaker for Santa Barbara, California's Zaca Mesa Winery, noted that his concerns were somewhat determined by the varietals from which he makes wine. "My concern is that my main product is Syrah. Syrah is a reductive varietal and can get stinky in an oxygen-free environment. I need oxygen to transmit during the bottle aging process."

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Oxidation and Reduction

Oxidation and reduction are terms that are often thrown around when the discussion turns to closures. I apologize to all those people whose eyes glaze over at the mere mention of chemistry, but it is pretty much impossible to describe a chemical process without reverting to the language of chemistry. I should also apologize to all chemists since my attempt at explaining these processes grossly oversimplifies what's really going on.

Oxidation

The term "oxidation" literally means "combined with oxygen," and the oxidation of metallic iron (Fe) to rust (iron oxide or Fe₂O₃) is the classic example. Another common example is oxidation ethanol (CH₃CH₂OH) to acetaldehyde (CH₃CHO). In this oxidation, two hydrogen atoms (actually hydrogen cations: positively charged ions) are removed, one coming from the CH₂ and the other from the OH portions of the molecule. This allows the carbon and oxygen to form a double bond, thus transforming the ethanol into acetaldehyde. This is, of course, exactly the oxidation referred to when one describes a wine as "oxidized."

Reduction

Reduction seems to confuse a lot of people, but it is exactly the opposite of oxidation. Thus, although a gross oversimplification, the term can be thought of as roughly meaning "reducing the oxygen in a compound," as in the reaction where iron oxide (Fe₂O₃) is reduced by carbon monoxide (CO) to yield metallic iron (Fe) and carbon dioxide (CO₂). In truth, however, what is really being reduced is the molecule's oxidation state; in this case the charge of the iron ion (Fe₃₊) in iron oxide is reduced from a plus-three charge to a neutral charge in metallic iron (Fe0). Therefore, the actual amount of oxygen in a molecule can in fact remain the same. For example, the final step of the metabolic cycle used by yeast during fermentation reduces acetaldehyde to ethanol by adding hydrogen across the carbon-oxygen double bond (C=O) in the acetaldehyde and is thus the counterpart to the above oxidation.

Oxidation, reduction and closures

As noted above, when discussing closures, the main oxidation reaction with which we are concerned is production of acetaldehyde from ethanol. The "reductive" aromas that sometimes occur in wine are almost exclusively reduced sulfur compounds like thiols (the term "mercaptans" is synonymous if somewhat outdated). Thiols, and therefore mercaptans, are the sulfur analogs to alcohols. Instead of possessing an O-H group, thiols have an S-H group.

Thiol precursors, including dimethyl-disulfide (CH₃-S-S-CH₃; IUPAC: (CH₃)₂S₂) and diethyl-disulfide (CH₃CH₂-S-S-CH₂CH₃), appear to be formed by yeast under nutrient-deficient conditions. The disulfides are apparently produced because the yeast cells lack sufficient substrates to complete the metabolic pathway, leading to the formation of the amino acids methionine and cysteine. The production of disulfides is therefore apparently somewhat different in origin from the production of H₂S during fermentation due to the presence of elemental sulfur on the grapes at harvest even though both routes lead to thiol/mercaptan production.

Since there are sensory thresholds for detecting thiols, it has been proposed that one way to minimize the production of "reduced aromas" is to ensure that the production of disulfides and thiols is minimized by good yeast nutrition during fermentation.

The reactions that produce thiols from disulfides are thought to occur relatively slowly in wine. However, if the amount of thiols present in the wine is already near the sensory threshold, there is a chance that the amount of thiol produced by this route would be enough to give the wine the detectible "burnt rubber" or "matchstick" odor associated with "reduction" in the bottle. wbm

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Overall Usage

Perhaps it is not terribly surprising that natural corks continue to be the most widely used closure. Eight out of 10 survey respondents indicated that they use natural corks for at least a portion of their 750 ml bottles (Chart 7).

It is notable, however, that screw caps have achieved parity with the other alternative closures, with one-quarter of the respondents noting that they use some screw caps to close 750 ml bottles. As we can see in Chart 7, by screw caps only, the number of respondents using screw caps has increased from just 3 percent in 2002 to 24 percent in 2006.*

According to David Guffy of The Hess Collection in Napa, "There is no one perfect closure for all wines. When you have a wine that is meant to be consumed in the near term, say two to three years from vintage date, you can use any closure; but I use [a synthetic] because, through trials and actual experience, they keep the wine fresh and guarantee that every bottle will be free of defects that natural cork can give. The same could be said about screw caps. I think it comes down to personal choice whether to use a synthetic cork or go to screw cap."

"First of all there is a marketing impression that certain closures convey to consumers, which I believe is rapidly changing," said Richard Bruno of Don Sebastiani & Sons, in Sonoma. "While many less wine savvy-consumers believe that screw caps convey cheapness based on past usage, more and more so-called wine aficionados are favoring screw-capped wines, possibly helped by the endorsement of some key influential wine reviewers."

Respondents from both small and mid-sized wineries reported slight declines in the proportion of natural corks being used, but natural corks still accounted for more than half of their overall production (Chart 8). Respondents from large wineries reported an increase in the proportion of natural corks, synthetic closures and screw caps used. Obviously, these increases had to come at the expense of the proportion of technical corks used. Respondents from mid-sized wineries reported an increase in the proportion of both synthetic closures and screw caps while seeing a slight decrease in the proportion of natural and technical corks. Small wineries reported small increases in the proportion of screw caps used and a correspondingly small decrease in the proportion of natural corks used. Also, slight and offsetting changes in proportions of both technical corks and synthetic closures were reported by the small wineries.

When these usages are broken out for red and white wines, we see that, as one would expect, the alternative closures are being used more frequently on white wines than on reds (Chart 9). The difference between the two is actually less than one would expect.

It is notable, however, that natural corks are still the most common closure for both. It is also notable that screw caps appear to have reached parity with the other alternative closures.

"We are returning to natural corks after trying 'technical 2-D' corks," said Pat Fallon of Eden Valley Orchards in Medford, Oregon. "Reports of difficult extraction, and our production staff becoming sensitized to the aroma of agglomerated corks while conducting QC trials, prompted the change. The aroma is not that of TCA but possibly the binder/adhesive that holds the granules together." Both Zaca Mesa winemaker Brook Williams and Don & Sons winemaker Richard Bruno noted that synthetic closures continue to have a place in their portfolios.

Tim Sauer of Livermore Valley Cellars noted, "Transmitting oxygen on white wines is not a great thing to do; it happens with cork and is okay, but not if you are intending to keep the bright and fresh qualities of a young white wine intact. Where it does come into play is with red wines. Oxygen transmission is a part of the aging process and allows the tannins to soften over time. Once again this is not important if you are making a big, fruit-forward red wine with soft tannins. But if you are making a wine that has a lot of tannins then oxygen transmission allows for its development and softening, so in time it can be enjoyed and the complex character of the wine can be discovered and enjoyed.

"Much of the red wine made today is made softer in style and is not meant to age for a long time, so oxygen transmission might not be a concern. If we were a much larger winery and could afford to inventory various types of closures, we would definitely investigate screw caps and synthetic corks. Since most of our production is red and can benefit from some oxygen transmission, we are sticking with cork for all of our wine (as of today, that is) even though it has its problems. All closures have their own little quirks and problems, so wineries just need to find what works best for them and use what they feel comfortable with. There is no wrong closure; some are just better for certain styles."

Usage by price point

It should be no surprise that the choice of closure is directly correlated to a wine's price point. In general, natural corks are used at higher price points while synthetic, technical and screw caps are used at lower price points (Chart 10). Seventy-eight percent of wine over $25 is sealed with natural corks while screw caps are used primarily for more inexpensive wine (21 percent of wineries use screw caps on bottles in the under-$7 category). Technical and synthetic closures are most widely used in categories under $14.

When we asked about closure usage according to price point, in the last three years, natural corks and screw caps have picked up while technical corks and synthetic closures declined in the under-$7 category (Chart 11).

Technical corks represented 36 percent of closures in this price range in 2004, but in 2006 this number decreased to 29 percent. Synthetic closures have been following a similar curve in this category and represent 30 percent of closures used at this price point in 2006. The use of natural corks has bounced back from previous declines, rising from 20 percent in 2005 to 31 percent in 2005. Screw caps have risen from 14 percent in 2005 to 23 percent in 2006 and are also inching up in popularity.

Technical corks and synthetic closures are most popular in the $7-to-$10 category. However, natural corks in this category have bounced back somewhat, going from 32 percent in 2004, dropping to 26 percent in 2005 and rebounding back up to 34 percent in 2006. Meanwhile, screw caps went from having a 3 percent share in this category in 2004, to 8 percent in 2005, to 20 percent in 2006 (Chart 12).

The bounce-back of natural cork with price points under $10 is one of the more interesting findings of the survey. Alex Cose, from the Purple Wine Company in Graton, California, noted that although they had been using corks in wines intended for the under-$10 price point, they were also seeing some of their brands move down into that sector as well. "It is a combination of both: I always use natural with some products under $10, and I upgraded one program to natural."

"Our production of fewer than 2,000 cases [of wine for the] under $10 per bottle price point allows us to spend the extra dime on lower tier natural corks, without raising red flags in the accounting department," said Pat Fallon of Eden Valley Orchards.

David Douglas, enologist for Murphy-Goode, noted, "When determining price points for the purposes of your survey, I use both the tasting room retail and the pricing I see in the marketplace in California. We are using screw cap closures on wines that are priced below $10, using both of these criteria. We are using natural corks in wines priced just over $10 at the winery, which can be found at larger retailers for just under $10. This decision has more to do with marketing than closure performance. Our screw cap line is independently labeled (Tin Roof) with the screw cap itself as part of the marketing package. The Murphy-Goode labeled wines are all cork finished, with the exception of the 375 ml bottles, which we are currently bottling. We have had contact from hotels and airlines requesting the screw caps, and thought that especially for the target market of the splits that it made sense both from a production standpoint and a marketing standpoint."

Natural corks remain the top choice in the $10-to-$14 category, but they have seen a decline from 57 percent in 2004 to 44 percent in 2006. Screw caps went from having a small, 3 percent presence in 2004 to 10 percent in 2005, reaching 22 percent in 2006. Technical corks have remained steady at 27 percent for the last two years. Synthetic closures have declined slightly over the last three years, falling from 34 percent in 2004 to 28 percent in 2006 (Chart 13).

Natural corks continue to hold a firm lead at the $14-to-$25 price point. Synthetic closures have stayed almost flat, rising from 18 percent in 2005 to 20 percent in 2006. Both technical corks and screw caps saw steady gains in this category, with screw caps jumping from 4 percent in 2004 to 17 percent in 2006 (Chart 14).

Wines priced at over $25 saw the least change as natural corks remained by far the favored closure. Natural corks declined from 91 percent to 85 percent while technical corks, synthetic closures and screw caps all remained flat or increased slightly at this price point (Chart 15).

Most of the entrenchment of natural corks at the higher price range appears to be due to tradition and perceived customer preference, though the long-term storage potential of natural cork compared to technical or synthetic is a factor as well.

Tim Pingelton of Westphalia Winery in Missouri noted that they are committed to using corks. "We are forefronting the 'Old World' image of wine and winemaking. The local area is populated by people with close relatives from Germany, Poland and other European areas. I had a hard time finding corks that didn't have the bleached, white look of most corks today; I wanted the darker, red oak color of natural cork. I fully appreciate the sanitary considerations of screw tops, but we still like the image of a guy on a grassy hillside pulling out an old laguiole and pulling out a cork for his gal."

"When you have a wine that can improve by cellaring five-plus years, I'll stand by high-quality natural cork as the best choice, even with the inherent issues natural cork may have," said Dave Guffy of The Hess Collection.

Considered Usage by Price Point

In addition to asking respondents what they currently use at each price point, they were also asked which closure they would "consider" using at each retail price point. Notably, screw caps are high on the consideration lists of many wineries: 43 percent would consider screw caps for their wine under $7, 38 percent would consider them for wines priced between $7 and $10, and 38 percent would consider them for wines between $10 and $14. And many wineries are now considering screw caps for higher price points as well: 32 percent indicated they would consider screw caps for wines priced from $14 to $25, and 26 percent would even consider them for wines priced at over $25, an interesting finding given that corks have traditionally dominated bottles at this price point (Chart 16).

Somewhat surprisingly, there was a significant increase in the number of wineries reporting that they would consider using natural corks at price points under $7. This trend is similar to the bounce back that we saw in the current usage of natural cork for the under-$10 price points. It appears that a number of factors have aligned to produce this result. Some wineries appear to be returning to natural corks after being dissatisfied with the performance of technical and/or synthetic closures. Additionally, a number of wineries appear to have brands that were always closed with corks but that have been drawn down to a lower price point by a competitive market.

An ever increasing number of wineries are considering screw caps for their wines priced under $7. In 2004, 43 percent of wineries reported considering screw caps for this price point, but in 2006, 74 percent are now considering screw caps. Consideration of technical and synthetic closures for this price point is down significantly in 2006, especially synthetic closures, which dropped from 58 in 2004 to 41 percent in 2006 (Chart 17).

An almost identical set of trends is seen at the $7-to-$10 range, with 67 percent of responding wineries compared to 41 percent in 2004 considering screw caps. Again, natural and synthetic declined in this price category while natural corks demonstrated a healthy gain (Chart 18).

The increase in consideration of screw caps in the $10-to-$14 category was even more pronounced than in lower price ranges. In 2004 only 41 percent of wineries considered screw caps for their $10 to $14 wines whereas in 2006 almost two-thirds of the respondents noted that they are considering screw caps. Again, we see a decline in respondents considering synthetic closures and a rise in those considering technical corks, with the percentage of those considering natural cork holding steady (Chart 19).

In the $14-to-$25 category, natural corks are the most considered closure, holding steady between 2004 and 2006. The percentage of respondents considering using technical corks in this price range rose slightly while those considering synthetic closures dropped by 11 percent to 22 percent. As we can see, screw caps demonstrated dramatic gains with almost twice as many respondents considering them in 2006 as in 2004 (Chart 20).

It is clear that many respondents still would only consider natural cork closures in wines priced over $25. Consideration of technical corks and screw caps remained almost constant at this price point, and synthetic closures dropped another percentage point (Chart 21).

When asked about the future for closures in the luxury segment, Richard Bruno noted, "The alternative closure I like best for the luxury segment (over $50) is the glass Vino Lock by Alcoa. Unfortunately, the organic image of the closure and bottle union at current must be hidden with a tamper-proof tin capsule and requires proprietary glass. Last I checked they were partnering with Vitro on molds, which may make the price more affordable, but in my opinion not as good a fit for the luxury segment as Saver. Until these problems are rectified, I predict screw caps and the traditional cork will remain the sole choices here."

Natural cork is still clearly the closure of choice, but the industry is seeing its share of flux in closure usage. While technical and synthetic closures have seen minor fluctuations the last few years, and remain solid choices at certain price points, screw caps have done nothing but increase in use.

Although proceeding from a small base, screw caps saw substantial gains in adoption to the point where fully one-quarter of all respondents are using screw caps on at least some of their wine. Perhaps even more telling is the fact that more and more wineries are considering screw caps at all price points.

Alison Crowe of Napa's Plata Wine Partners noted, "Many wineries, like Don Sebastiani & Sons, have made their closure choice a part of their alternative branding 'experience.' A perfect example is their Screw Kappa Napa line, which cleverly pairs Napa-appellated wines with screw caps, which probably helps allay customers' fears that wine under screw cap is 'cheap' or 'down market.'"

This is a point that was amplified by Don Sebastiani & Sons' director of winemaking Richard Bruno. "We are seeing wider acceptance than we anticipated by restaurants with screw caps and several who prefer it, especially bartenders. Similarly, Zork has been received well on-premise, particularly because the closure has some of the same features as cork. Namely, you must remove the tamper seal first; and when it is opened, a light popping sound may be heard which effectively is inclusive of the ceremonial aspect of wine service. This is a good choice for the $11 to $18 segment; however, I wouldn't be surprised to ultimately see it used in a $25 to $35 bottle. The only slight negative is that the Zork requires CETIE spec glass, [which is] standard in Europe [but not the standard in the US]."

Ken Albert from Shelburne Vineyard in Vermont noted that his closure choice was driven by his place in the overall wine market. "As a small winery in a state that does not have many wineries, I feel I have to use cork as the general public expects it in a 'genuine' bottle of wine. I fear my wine would not be respected if I used synthetics or screw caps. I feel that screw caps may well be the future for closures, but only a small fraction of the wine-buying public at this point in time view them as proper for quality wines."

"I think closure choice is most often a mix between the winemaker's feeling about what closure is appropriate for the wine and what the marketing department thinks their customer base wants and expects," said Crowe.

Survey Background

Wine Business Monthly's 2006 Closure Survey consisted of 14 questions related to purchasing, perceptions and usage of closures. Closures were defined for this survey as natural corks, technical corks (1+1, 2+2, agglomerate, composite cork, etc.), synthetic closures (100 percent plastic, extruded or molded) and screw caps.

Results were tabulated based on size of responding wineries. Respondents included 369 wineries from across the U.S. and abroad, notably: 197 from California, 30 from Washington, 22 from Oregon, 10 from Virginia, nine from New York and seven from Pennsylvania. Twenty-one of the respondents were from Canada, and an additional five were from elsewhere outside the U.S.

Respondents to the survey overwhelmingly were small wineries: 89 percent of the wineries that responded were small (fewer than 50,000 cases), 13 percent were mid-size (50,000-499,999 cases) and 4 percent were large (500,000+ cases) (Chart 23). Sixty-nine percent indicated their function as winemaking, 54 percent listed their function as president/owner/GM while 29 percent of the respondents indicated cellar/production. Other respondent functions included sales/marketing (23 percent), tasting room (10 percent), vineyard management/viticulture (23 percent), purchasing/finance (22 percent) and other (5 percent). Respondents could choose more than one function (Chart 24).

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* The Wine Business Monthly Closure Report measures total production and does not discriminate between different sales channels (such as on-premise or wines for export). ACNielsen research (see article) found that screw cap sales represent three percent of the market, but measures the wine sales in only one channel: food stores in 34 U.S. markets. Additionally, ACNielsen measures only what was sold between September 2005 and March 2006, not production that has yet to hit the retail channel. Accordingly, the 2004 and 2005 WBM Closure Reports are more accurate reflections of what type of closures are currently available in the food store retail channel.