Know Your Corks

Know Your Corks
All cork closures are not the same. Let me show you how to identify the type of cork in your wine bottle.

If nothing else it’ll help pass the time in a restaurant after the waiter has handed you the cork after opening your wine and your food arriving.
Historically wine closures are made from a solid piece of cork punched out from the bark of a particular type of oak tree. There are different grades of cork and wineries choose how much to pay for them.

Understandably more expensive wines usually have finer corks. A wine intended for long aging will have a longer cork than one for instant consumption. Cheap wines will have cheaper shorter corks so a look at the closure will indicate whether the wine for which you paid a fortune for in a posh restaurant is really worthy of its price..

Let’s consider the eight corks below.


If you are thinking I cannot count because there are nine corks, then look again. One of those closures looks like cork but in fact it is plastic.

The corks on the lower row are all solid cork. They vary in length and three on the left are of poorer quality as they have natural indentations, little holes in the cork. The two on the right are smooth and free of pockmarks. The one on the far right is perfect and has been treated with silicone to protect the cork from damage and to help it retain its moisture: I think this is the most expensive cork. It is the same length as the one second from left. That comes from a Bordeaux wine that will mature over a decade or more, but it is not one of the top wines from the region as we can tell because it has a less expensive pockmarked cork.

Did you spot the second from left on the upper row is plastic? It has been made to look like cork. The others on the top row are made from bits of cork; these are known as agglomerates. The cork on the left has discs of natural cork at each end so that wine in the bottle will won’t touch the agglomerate. They are known as twin-tops.

The closure on the far right is of a type known as a ‘technical’ cork. It looks like an agglomerate but whereas agglomerates are the cheapest cork closures this is something special and it’s expensive. The thing to look for is the name DIAM printed on it. Diam closures have been manufactured using a patented supercritical carbon dioxide cleaning process “which removes undesirable cork and wood flavours as well as microorganisms and pollutants. The resultant cork granules are then moulded into shape using a neutral food-grade binding agent that adds no flavour, aroma or taste.” Diam guarantees their closures are free of TCA, the agent that causes cork taint.

Take a smell. The Diam should be neutral, the others will smell of cork to some degree and that smell will be absorbed by the wine. My own preference is for a quality screwcap, because they are easy to open otherwise a Diam. When I see a wine with either I know the winemaker cares that I taste the wine the way it was meant to be.

Next time see if you can identify the type of cork in your wine.
Ask questions and talk about wine on our forum.

Peter F May is the author of Marilyn Merlot and the Naked Grape: Odd Wines from Around the World which features more than 100 wine labels and the stories behind them, and PINOTAGE: Behind the Legends of South Africa’s Own Wine which tells the story behind the Pinotage wine and grape, also available for the Kindle.

You Should Also Read:
Cork or Screwcap?
Understanding Restaurant Wine Service
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