Should closure influence my purchasing?

Another cork debate?

From what I’ve been able to surmise, the idea that oxygen transpiration through a slightly permeable cork is a major factor in proper aging (as opposed to simple oxidation) is specious at best.

Nate - it is not specious, it is simply false. A perfect cork seals perfectly. Oxygen does not go thru the cork. It is already in the cork, the wine, and the headspace. The problem with cork is that it’s variable and many are not perfect because they are not built to spec. So you can get some probabilities regarding a bag of corks, but you can’t say one is exactly the same as another and consequently, you’ll likely end up with variable bottles over time.

With manufactured closures OTOH, you can make sure they’re all the same. So if you want some air transmission, you can build your closure accordingly. Someone else might want none and you can build that closure accordingly.

And yeah, it’s a bit much to say that synthetic closures eliminate TCA. I’ve had tainted wine that came in bottles with synthetic closures. It happens less often than with cork perhaps, but it happens nonetheless.

Pretty much evey Aussie member of the board has been banging on about the virtues of screwcaps for years now, sometimes to very deaf ears.

Good to see the tide is starting to turn!

I am happy w screw caps but won’t buy Ponsot’s wines w his closure.

I’ve never seen one study, not a single one, that has cork as sealing perfectly…it might be very close but oxygen does come in…All of the ones I’ve seen have allowed some ingress oxygen…but they also show the variability you’re talking about.

If you have a source, it would be interesting to read…

Synthetic closures eliminate TCA that comes from the closure, but obviously it doesn’t remove TCA from a wine that’s been contaminated in the winery. Doesn’t happen often but it does happen; obviously the winery contamination is easy to spot because the whole lot will be off, not just bottles.

I did. I seem to recall reading this article, and seeing those pictures, at least a couple years ago. I want to know what each of the closures in that picture is. In particular, I’d like to know which closure is used on the bottle that is the second bottle from the left, as it appears that wine has the lightest color of all pictured bottles in the 125 months picture. The lack of details in this article makes it come across more as a screw-cap advertisement than it does a scientific study.

Looking at the photos again, the two bottles on the left side are indeed really close in color. The black of the screw top will mess with perception though.

A couple of things to note here:

This study was conducted by the AWRI nearly 10 years ago.

The Aussies conducted the study because they HAD to do something about closures since they were having TCA rates of 25%+ on a consistent basis.

  • The closures available at the time were used, but since then, other closures have been ‘created’, including newer generations of synthetics and the DIAM closure as well.

  • The wines immediately next to the screw cap wine are cork closure wines - the highest quality ones they could find at different cork lengths IIRC.

  • Overall findings - the screwcaps permeation rates were similar to the best cork rates BUT cork had a high degree of variability (naturally) which screw caps did not have.

Hope that helps to clear some things up. It would be great to continue to see studies like this done, including a ‘sensory’ aspect as well, just to either reinforce or challenge our beliefs about closures and long term aging.

And full disclosure - I’ve only used screwcaps for my label since I started it in 2006 . … .


I’ve seen way too high of an oxidation rate with synthetic stoppers beyond about 3 years from bottling, and the oxidation has been variable, so I won’t buy anything under those circumstances anymore.

I was going to post the same article.

There are studies. The idea that cork lets air in and that’s a good thing is one of those old myths that won’t die. How do you account for a metal capsule? Plastic capsule? Do those let air in as well? Will a cork w/out a capsule behave the same as one with a capsule?

From 1976 -
… the quantities of oxygen that normally penetrate into the bottles are negligible if not zero. Oxygen is not the agent of normal bottle maturation.” J Ribéreau-Gayon et al (1976), “Traité d’Oneologie – Sciences et Techniques du Vin” Vol. 3

Amorin, the biggest cork producer in the world, with a real interest in the matter, said “Cork is not permeable to atmospheric O2”.

Peynaud also noted the same thing numerous times. I don’t feel like digging thru his book at the moment but you can probably Google something about him and cork.

This next isn’t exactly on point, although they do note that after a few months, the loss of SO2 by cork and screwcap is the same, indicating “. . . both types of closure presented a similar effective barrier to gas movement.” Here’s the abstract, you have to pay for the entire study:

Anyway, if oxygen did go throught the cork, how does it actually do so? There are 2 possibilities, one would be through the passageways between cells of the cork, and it can enter that way, but mostly it’s by way of the interface between the cell walls and the bottle. That’s because of the properties of cork. A long cork, with tight cell structure, isn’t going to let a lot of gas through. But cork cells are like little balloons and they compress. When against a rigid material for a long time, they tend to harden and don’t hug the wall as tightly.

But even so, if the cork stays moist, the cells are expanded and they block air ingress by both mechanisms. Basically where the oxygen comes from is from the cells of the cork itself, from the headspace and that’s why it’s important to be careful with the headspace pressure when you’re bottling the wine, and from dissolved oxygen already in the wine. In the study above, one suggestion was that some of the SO2 diffused into the cork over the first several weeks. When you put the cork into the bottle, you first compress it and it takes a while to decompress, and in doing so it sucks gas from somewhere - in this case the headspace.

Anyhow, if someone wants some air intake, closures can be and in fact they are built to allow exactly that. There’s not just a single type of screwcap - material science and engineering allow producers to make screwcaps of varying permeability, which is why I think there is no excuse for the variability caused by a Victorian-era relic of a closure. Cheers. [cheers.gif]


The capsule does absolutely nothing…That isn’t a reason.

Your quote from 1976 only confirms that it does allow some air in. It isn’t a lot btw…and I’m not even saying it NEEDS to be permeable (I don’t know) but all actual scientific tests (There are quite a few out there if you need me to put them here, I’m sure you’ve seen them) show that there is some ingress oxygen that comes in…

Won’t even comment on the cork producer…

Even the abstract you quoted…that doesn’t say what you think it says… Screwcaps I’ve seen allow a very small amount of ingress air…In all the studies that is the case…so if you’re saying they’re similar (as your source) that means corks allow some ingress oxygen…It is very very small amounts…

I’m not saying cork allows a lot of gas through…You seemed to suggest it allows ZERO which is something I don’t believe is the case. I don’t even believe this amount is high (except with bad corks). It is actually very low. Some might call it negligible…but it is not zero.

So here is what I’m saying…and maybe what you’re saying…

Screwcaps allow a very little amount of ingress oxygen which is similar to what we’ve seen for the best corks…Except without the variability of corks. That is what a previous winemaker on here said as well…and goes with all of the studies I’ve seen…

Here’s a resent presentation on it although I think it is quoting many of the same studies…

What about glass? Just opened a bottle of Calara that had a glass stopper under the capsule - really surprised me as I had never seen one before. Struck me as a clean/solid alternative to synthetics which can fail and, if optics count, more “upscale” than screw tops…

What is the view on these glass stoppers?

So far so good on the glass, but it’s an o-seal that is the actual closure.

Glass has been used for a number of years over in Germany, and is starting to gain more of a foothold here.

Advantages? Cool look; ease of opening and closing.

Questions? Long term aging potential; bringing down the cost of application during the bottling process;


hmmm, I had read that before and accepted it as fact until Don Cornwell corrected me (on that idea and a couple of others) by citing a study published by DIAM:

I now believe that it is true that even the best corks allow for a very slow transmission of oxygen over time. Maybe there are conflicting studies, but why would DIAM and Stelvin be trying to mimic what they think is the slow oxygen transmission of cork if it did not exist? They’ve both put some serious money into researching this stuff. I think the cork industry wants to claim zero OTR because it’s good for marketing. They misrepresent all kinds of other stuff, so I’m inclined not to trust them when multiple other sources refute this claim they’ve made.

Doug, are you suggesting that they under-report the number of corks affected with TCA/TBA? :wink:


Good question (-: The truth of the matter is that those who firmly believe in corks feel the rate is getting better, and the Cork Council of America continues to say that the rate is falling.

At the same time, you have more consumers than ever who truly don’t really know what a corked wine is. If a wine is ‘bad’, it is ‘corked’ to many of them. Therefore, my belief is that the numbers are truly ‘under-reported’ . . .



I couldn’t agree with you more. I get very little wine returned as ‘corked,’ and at least half of that isn’t corked at all, which means a) a lot of corked wine is not identified, and b) most consumers and many in the trade don’t know what the word means.

The problem is that I am pretty sure that people drinking corked wines know they aren’t good, and they think it’s the producer’s fault. The fact that they can’t identify the defect, or even know that it exists, doesn’t mean that it doesn’t change their experience.