Cork or Screw Cap

What matters is the wine on the inside of the bottle, right? Maybe long-term if the wine is good but I think the initial reason most people buy wines [especially on store shelves] is packaging. A bright-colored label will attract the attention of a consumer far more quickly than a dreary looking one, so market savvy is really important in the all competitive field of wine-making.

Perhaps the most contentious of these packaging issues is that of the way in which we seal our wines. Keep in mind that the type of closure used, can really affect the perception of the consumer to the quality of the wine [before they have even tasted it]

The romantic closure is no doubt cork, an impermeable material harvested from the Quercus Suber [the cork oak] which is endemic to Southwest Europe and Northwest Africa. Portugal produces roughly 50% of the cork harvested.

Once trees are 25 years old, cork is stripped from the trunks every 10 years with the trees being able to grow for roughly 200 years. There is approximately 2.2 million hectares of cork forest worldwide with over 30% again in Portugal.

The cork industry is generally regarded as environmentally friendly, with the sustainability and easy recycling of cork products two of its most distinctive aspects.  So far so good.

As a closure it is well suited, it is easily compressed and expands once inserted into the bottle to create a tight seal. This characteristic makes it perfect for a wide variety of bottle types and necks. So the question arises as to why more wine-makers and producers are looking at other forms of closures and moving away from cork.

There are natural flaws in cork, cracks in the bark make the cork highly inconsistent, and in a 2005 study [45% of corks showed gas leakage during pressure testing. The biggest negative of cork however, is that it can affect the quality of the wine, ever return a bottle at a restaurant because it was CORKED.

The cause of this problem 2,4,6-trichloroanisole [just checking to see if I spelled this correctly, yup] TCA can make a wine smell mouldy or like a wet dog, not exactly what you want to get from a wine. Everyone’s perception is different but generally is measured in part per trillion [a little goes a long way]. TCA is occurs when natural airborne fungi are presented with chlorophenol compounds [ironically enough, chlorophenols can also be a  product of the bleaching process used to sterilize corks].  So, I make a wine that is fruity, varietally correct and it becomes spoiled by cork, not only does that drive me bonkers, but imagine a consumer tries that wine for the first time, quite a first impression and not in a good way, so why I not immediately switch to a closure that protects the wine? Well, as mentioned, because of consumer perception, and the fact that a corks makes a pop when you pull it out of the bottle.

It is accepted that New Zealand Sauvignon Blancs are bottled under screw caps, but why not Opus One or Petrus. I would suggest that these fine wines would lose a lot of its luster if bottled under screw caps, and could they still command the prices they do on the market [food for thought]

Screw caps first and foremost are cheaper than cork, they provide a tight seal preserving the wines aromatic integrity and freshness and impart no TCA to the wine. But these wines might become reductive [the opposite of oxidation] and start smelling like rotten eggs or even in some cases like burnt rubber through a process called sulphidization. The winemaker needs to know what he/she is doing. So screw caps seem like a quick fix and viable option, but maybe not?

An often cited contradiction is the case of experiments conducted by Haute Brion in the 70’s where some of their wines were bottled under screw caps, the results. After about 10 years the screw caps became compromised and let air in, but I ask you, how many wines are being laid down for 10 years or more, but then again I do not have a cellar full of Haute Brion.

There is certainly a shift towards alternative closures to better protect the consumer against flaws which us wine makers have no control over. Will screw caps be taken seriously as a closure for fine wine, I challenge you to find 10 examples of wines above $100 that have screw caps, I can give you one though, Molydooker’s Carnival of Love, a 96 point wine also rated as a top ten wine in the world by the Wine Spectator.

Whatever your opinion on closure, may I suggest judging the wine by the quality of the wine, ultimately for me, that is what is important. Who cares if it is in a pink bottle with a blue cork, if the wine is good, I can live with that.

Man, this wine world is confusing, I have a feeling that I may never quite understand it

Maybe that is why I am so drawn to it



Winemaker for Keswick Vineyards


7 comments on “Cork or Screw Cap

  1. […] Stephen, Keswick’s winemaker, muses and informs about wine closures […]

  2. Now that I had my rant on concerns of the environment arguments, here are my real thoughts on Screw Tops. I am all for Screw-Tops. We are lucky enough to be selling wine on the East Coast where we have a plethera of wines from all over the world. Screw-tops are not new here and have gained acceptance because of New Zealand and Australia. We have now been 100% Screw Tops since 2007 and have had very little resistance. In California they have to battle their own wines. They hold a stronger market percentage which creates less wines in the market place with alternative closures and it is hard to change due to their own wines being the majority. The flaws as you states with Screw-Tops can be solves in the cellar. With Corks, they can’t. Also responsible winemaking with screw-tops will require less sulfites for the wine prior to bottling. That means as a young wine there should be less sulfites in the wine. However as it ages it will hold them more, so an aged wine will have less sulfites in most cork closed wines. There is definitely more consistency with screw-tops. If one wine is bad, you can guess the next bottle is bad. Same as if it is good, especially as the wine ages. With corks, the more the wine ages, the more you will have variability bottle to bottle since they are not a perfect closure. The perfect cork, is anaerobic. But as you stated 45% are structurally flawed. As for TCA it depends on threshold. Cork suppliers will state that is 6 ppb which will be less then 1% failure rate generally, but there are many people that can taste down to 1 ppb which increases that to 6-7% failure rate. It is all in the taster.

    Screw-tops are by no means the perfect closure, but I think they are the current best option. As for 10 year old wines, the big issue is maintenance. I have had several wines that are 10 years old under Screw-top (mostly Pinot Noir and Riesling, but also a good amount of Margaret River Cabs and Chards) that were stunning. I have also had some that have not aged well, but they all have the same problem. The top of the Cap had been dinged up. The main problem I find with screw-tops is that if you ever dent the top of the cap, especially along the corner, it can crack the seal.

    All and all, until another superior closure comes out, I am all for screw-tops.

    • Jordan
      Good points all round, there are arguments on both side of the proverbial fence. I sit in the middle, although I am not opposed to screw caps, and in many ways thinkk they are the superior closure at the moment. We use a technical Diam cork, with no issues of spoilage or leakage to this point after three years of use. Whatever your preference, the debate is an interesting one, would love to hear more about this from the consumer point of view
      Take it easy

  3. I am going to have to show two comments here. This one is just on the environmental side. We are solely screw-caps and when I made that choice there had recently been an article showing how there are in fact better. I will not argue one way or the other because, well…I am not smart enough and I don’t have enough time to do further research. I think it is interesting that the largest portion of Carbon Neutral Wineries in the world are in Australia and dominated by Screw Tops. Cullen is all screw-tops including their Diane Madeline which is close to $100.00. The process of manufacturing the cork is less then a screw-top for carbon emmissions, yes. But what about travel? The carbon footprint depends on where you are and what supplier you use. Is it direct? Is there a wholesaler? Are you corks Sardenga, Portugal, North Africs…? Are you a West Coast or East Coast winery? Corks have to travel across the Ocean. They are generally shipped to California, then back to the East Coast for East Coast Wineries. Screw-tops can be manufactured domestically so there is less Carbon emissions in the travel. Does it equal the process or more, I have no clue, but it does change the matrix. Then you can discuss the dyes on a cork, vs. the print on a cap. Which is worse and harder to manufacture. Then in Screw-tops you also have to question the insert of Serinex or Aluminum. There are too many variables to make a definite argument on the environmental side and I have heard it on both sides.

    When Toyota first came out with the Prius I read a very valid report on how the Carbon footprint of manufacturing the Prius outweighted its use benefits to the point where a Prius had a larger carbon footprint then a Hummer for the first 10 years of driving them. This was because Hummers were manufactured domestically and all in close by plants. Prius’s had parts manufactured all over the world. It is a crazy argument, hense I said from now on this is a subject for smarter people then me.

  4. katbarnard says:

    Great minds think alike I guess, another of my favorite wine blogs also had a post today on wine closures! This was a review of a book about wine closures- sounds like something you would enjoy reading!

  5. Bob Doan says:

    Have you considerd that cork is a renewable resource, while the screwcaps, although potentially recyclable, probably are not being recycled. Additionally, what is the carbon impact of screwtops versus cork. I believe that there may be very good environmental reasons for using cork over screwtops.

    But you are very correct–just give me a reliably good glass of wine and I’ll go away happy.

    • Bob
      Great comment. Carbon footprint is the measure of the amount of CO2 released into the atmosphere through the combustion of fossil fuels and other sources.
      According to tests conducted by Cairn Environment for Oeneo Bouchage in France, screwcaps give off 10kg of CO2 per ton compared to 2,5kg per ton for cork. The Diam cork fell in between the two with a carbon footprint of 4.3kg.
      Screwcaps do have the largest Carbon footprint compared to cork and other synthetic closures.
      Just as a fun facts, once recent environmental study founs that one individual cheeseburger has a carbon footprint of 3.06kg.
      Makes for an interesting discussion nonetheless
      Thanks once again for your comment, much appreciated

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