Diam and Cork closure

Diam cork, and other alternative closures

Some will have noticed that we have been moving to Diam Kork for 3 years. How did it come, what has the screwcap to do with it and were the corks around 2000 really so bad?

“DIAM corks guarantee wine without any cork taste

From the cork granulate, all the wood parts are first sieved out and then cleaned in the diamond process by harmful chloranisols. Cleaning is done without chemicals.

The microbial load is also decreased and stabilized without affecting important elements such as e.g. Waxes. Another advantage is that no solvents or adhesives are used. Instead, the cork granules are stirred and baked under pressure and heat with food-borne polyurethane to form a mash. ”

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This is what Diam says, lets look closer.
Back to the initial question: Yes! Around 2000, the cork quality in Austria finally collapsed. One had to reckon with up to 10% failure by TCA. Another problem was the shrinking flexibility of the corks by new cork treatment agents in the fight against TCA. And phenolic problems. (The more refined our wines got, the more we felt the cork tannins, sometimes positive sometimes negative) So we began to look for alternatives and tried to close our wines with screw caps since 2004.


Around 2004 we were in conversion to organic viticulture and the vineyards had to fight with a lot of green cover crops competition. So during the fermentation little yeast-available nitrogen was present and our wines were thus very reductive.

A challenge, this phenomenon is actually found in all organic biodynamic winery in their conversion time. In some cases it arrives early in some cases it arrives later. Simply taste a producers wines in the this time.

Bottles with corks, the problem was not so prominent,  because the oxygen passage and the oxygen present in the cork oxidized the reductions gradually. A further complication was that here in Austria we took the screw caps from Germany. There a tin foil or aluminum foil was installed in the screw caps (the germans got this from the Australians, at this time with the idea to fight oxygen transmission), in order to grant even less oxygen transmission. In the old world, screw closure when used, where Saranex. This is the material that is also used in crown corks (eg beer). And this material has a transfusion rate 1/10 of a cork but still 1/10 more then the tin foils.

Tin, Saranex, Saran,...
Tin, Saranex, Saran,…

For a long time we tried to manage the matter in the cellar: lowered sulfur, more oxygen in front of the bottling, … We tried a lot, but had the feeling that we lose quality. especially we lost finesse. You can find more details in this article by Schneider. (its in german but google translate is you friend 🙂

It was exciting for me to find out that our wines from the stony soils (oxygen-rich soils) had much fewer problems with this reduction in screw caps than the wines from the loamy soils (low oxygen soils).

What made it even worse was, that we have been operating without sterile filtration since 2000, so we always have tiny bit of yeasts in our wines, these keeps the wine young as we say. This minimal reduction i enjoy a lot at blaufränkisch, so the wine can unfold fully in the glass or in the decanter, and ages nicely.

Now it could be countered that there are newly developed screws with different oxygen transmission rates. So I could follow my style of wine also with screw caps. Yes i could. But there are still some “soft facts” which I would like to mention here.

Cork is a soft material. It is balancing things out, takes pressure and releases it again. These properties can also be seen in all areas of the wines:

For example at the bottling plant. If the screwcap machine is just little bit of this can lead to considerable problems. The contact pressure has to be correct otherwise produces bottles in the worst case dribble, or oxygen can pass. It can also happen that the screwcap does not “crack” when opening.

Another possible source of error is packaging in the carton. If you are to fast and to bottles are hard touched and the screwcap gets a small dent, this can lead to the rapid oxidation of the bottle.

But the cork also balances the wine. Eg:

Reductive wine gets oxygen, clear. On the other side oxidation tending wine gets additional stability by the phenols of the cork. (Are not always positive but sometimes)

3 years ago I started my first experiments with diam. I got convinced as i tasted 10 year old wines closed with diam. Our first results were promising. We currently use Diam with the Horitschoner Blaufränkisch and also with special bottlings like Saybritz or Neckenmarkter Rotburger. From vintage 2015 onwards, we will also fill our Hochäcker with this closure.

As i heard that Domaine Leflaive with the end of last year completely converted to Diam, this strengthened us in our decision. And also here in Austria more and more winemakers choose this closure.


At the moment, I am absolutely happy with Diam, I “knock on wood” that this remains. For wines such as Dürrau and Kalkofen, we will start to use TCA single cork tests with biocertification.

And now i drink a bottle of Neckenmarkter Rotburger. Cheers.

I am Franz Weninger “Winzer” with passion. You want to know more about wine and philosophy, subscribe now:

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