Wine Bottle Closures

A "closure" is nothing more than the object that seals or closes your bottle of wine. In this page, we present our ideas and observations on these closures, much of it based on reading and research throughout the years but also quite a bit of first-hand testing and exposure. Ideally, we would also discuss the bottles that are used because, inherently, they are a portion of the success or failure of any given closure. For instance, a bottle that has an oval opening may still work well with a cork but not with a screwcap. And a bottle with a narrow neck may work well with a ZORK but not a technical cork. Not to mention the quality issues that seem to be affecting wine bottles these days, not to forget mentioning the bottles that are coming from China. Still, such a discussion is out of the realm of why we specifically chose screwcaps for our Sauvignon Blanc. Also, we should note that this page is not meant to be an exhaustive dissertation on the various closures, histories, or industries. All we wanted to do was provide a brief overview and explain where we stand with each of them. There are several classes of closures, namely:

    - Corks
    - Screwcaps
    - Synthetic "corks"
    - ZORK
    - Vino-Seal


Cork comes mostly from Portugal although Spain, Italy, and North Africa are also producers. Rumor has it that China has vast cork oak forests and so we might expect to start seeing Chinese corks one of these days. There are two main classifications of cork: natural and technical. A natural cork is punched, or cut, out of the bark of a cork oak tree, washed, sometimes printed with food-grade ink, and coated. The coatings agents typically used for natural corks are block paraffin (basically drop some paraffin in a huge tumbler with corks and let it spin for a few minutes) although this is not very common anymore, and emulsions of paraffin and silicone. In this case, the emulsions are sprayed, paraffin first and then silicone. The paraffin puts a protective layer over the cork in order to minimize any potential transfer of off-odors or spoilage agents that may be in the cork such as TCA (tri-chloro-anisole). The silicone, for its part, acts as a lubricant and allows for the easier extraction of the cork.

Technical corks are also made of natural cork but of pieces instead. During the punching out of the natural from the bark, a lot of good cork material is left behind but is too small to form a cork. So, it can be chewed up into small pieces which are then reconstituted using glues and latexes and formed into the shape of a cork. Some of these corks are made up entirely of chewed up bits of cork while some have one or two disks of natural cork on each end, thus giving the possible impression or feeling to the consumer that it is a natural cork. No one is trying to deceive anyone here but, rather, just trying to preserve a specific impression. The wineries are motivated to use technical corks because they preserve part of the image of natural corks but are substantially cheaper.

In terms of coating, technical corks are usually coated with an elastomer, one example is CAF--imagine a latex glove on the cork. As you can see, all coatings are petroleum by-products and, although technically inert and food-grade, the reality is that they can impart chemical flavors to the wine. Whether they come from the glues, latexes, or coating, we have seen (well, smelled) chemical overtones to white wines when we conducted trials. Also, the coatings do not always work 100% of the time and it is possible for cork (or wood) odors to be imparted to the wine. For a red wine this is much less of a problem but, for a white wine, the odors or flavors from wood or petroleum can be definitely be noticed on occasion.

There are other things that can be done to corks such as painting them in order to cover ugly blemishes, or filling in large cracks with cork dust and glue. Those happen rarely in the American market and so we will not go into detail here.

Lastly, a comment about coloring: you will sometimes notice that corks are quite pink and, other times, they are quite white. Natural cork, as it comes off the tree, is pink; actually, it can be quite brown. However, over the years, wineries have found that customers prefer white corks and, therefore, during the washing process, the color is removed. Up until the 1990's, the cork producers used bleach which they then neutralized with oxalic acid. In the early 1990's, due to a demand from a large British importer, they ceased using oxalic acid without realizing that bleach is actually a precursor to TCA. So, many corked bottles later, they decided to switch to other chemicals such as hydrogen-peroxide. Some wineries still insisted on natural-looking corks although the majority seem to prefer white. Either way, the color doesn't affect the performance of the corks.

For our Cabernet Sauvignon, we are committed to natural cork and will continue conducting exhaustive trials in order to make sure that the supplier we use has provided us with lots that are not contaminated and will not impart off-odors, as best as we can. We believe that natural cork complements the experience that our customers expect when opening a bottle of our Cabernet Sauvignon.


Screwcaps have various names depending on who produces them but, in the wine industry, function basically the same: the consumer twists off the top portion of the closure and then re-seals it without any effort. Much discussion has taken place regarding the sealing ability of the screwcap and continual reengineering is taking place even now. The lining or disk that connects to the lip of the bottle can be made of various materials, anything from tin to foams. The idea is that these disks decide how much air goes into the wine. Corks allow air to come through which is what causes the aging of the wine. Technically, this is called Oxygen Transmission Rate (OTR) and a little is a good thing in red wines; in white wines it typically is not although, with no OTR, you run the risk of "reductive characters" which means that your wine can smell musty, like sulfur, or even have a chemical component. However, just swirl your glass a couple of times and the smells typically disappear. As mentioned, all the manufacturers are tinkering with the disk--or liner--materials in the hope of providing just the right OTR for wines. Our supposition is that it will take time for standards to be reached such that different OTR's are available for different varietals and styles of wine.

We felt that the screwcap was the best closure for our Sauvignon Blanc because it is easy to use, it does not impart any off-odors or taint, and has a growing consumer acceptance. We like the way the final package presents itself, and look forward to positive feedback from our customers.

As an aside, about five years ago we began hearing from consumers that, if you opened a screwcapped bottle, poured some wine, and then re-sealed it, the wine would be preserved. Of course not! Once the wine is exposed to air, it begins to oxidize (spoil) regardless of the closure used to re-seal the bottle. One can inject some inert gas that is heavier than air which will displace the oxygen and protect the wine, and that is the only truly effective solution to preserve the wine in an opened bottle. Even using pumps to extract the oxygen doesn't really work. But it was a funny rumor that someone circulated...

Synthetic "corks"

Synthetic "corks" are not truly corks but are called that because they are shaped as such and, quite often, are colored to look like corks. The varieties of plastics used to make these closures are broad and wide, and it would not be possible to provide a good overview here without going into a lot of details. The following can be easily said, though. All the synthetic closure manufacturers boast of different OTRs and apparently continue trying to improve the performance of their closures. However, from our point of view, the reason we will never use these is that the consumer typically has a negative perception of them, particularly for higher end and finer wines. Secondly, the vast majority of them are difficult to reuse--try re-sealing your bottle and see how difficult that is. Also, they are made of various plastics, all of which are petroleum by-products which, in our mind, increases the likelihood of off-odors. Finally, cost-wise, they don't offer a better solution than screwcaps or technical corks.


ZORK is an interesting closure because of it seems to have several advantages: a consistent OTR similar to nature cork, easy application and reuse, recyclability, tamper-evidence, and a popping sound upon extraction. It is made of a plastic similar to milk jugs and, therefore, should be recyclable, at least in many localities. The biggest difference is its look--you cannot avoid noticing it on the shelves. Unfortunately, it has some noticeable drawbacks: consumer acceptance is still a big question because it has not been around long enough, the possibility that it could be associated with cheaper wines since it is made of plastic, application cost (on the bottling line, it is put on by hand in most cases), and the per-unit cost (it costs more than technical corks and screwcaps).


The Vino-Seal and its predecessor, Vino-Lok, are truly amazing to us for the simple reason that they do not work. Basically, they are made of glass although we understand that a plastic version is coming out soon. There are special bottles that must be used since the standard wine bottles do not work. There is a plastic ring on the Vino-Seal that actually separates the wine from the outside; we have not been able to find any data on OTR regarding this ring. In terms of performance, our winemaker spent two hours on a bottling helping a friend apply them to his bottles: upon application they popped out of the bottle. If they didn't, they popped out the second two bottles bumped into each other on the bottling line. The only thing that kept them in place was the capsule that was applied on top; in the past, these capsules were glued in place (yes, with glue!). Lastly, we had the sad experience of drinking half a bottle of wine, putting the Vino-Seal back in, and placing the bottle horizontally in the refrigerator--a nice puddle of wine covered the floor in the morning. This being said, we can understand the, shall we call it, "snob appeal" of a glass closure. After all, the idea of glass-on-glass closures is appealing because it reminds us of the medicine bottles of the XIX century. However, we do not believe that they are structurally sound, nor have we been able to find any description of the plastic ring that actually seals the bottle (it's not a glass-on-glass seal). Finally, they are extremely expensive--not to mention the fact that they are applied by hand--and we would rather use natural corks, at the same cost, than the Vino-Seal.

An excellent book on closures in the wine industry is George Taber's To Cork Or Not To Cork. It is highly recommended for anyone who wants to know the problems that cork industry currently has, where screwcaps came from, and so on. It's easy to find it online and is a very entertaining and easy read.

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