Screw Caps vs. Cork Closure of the Debate

The quality of the wine was judged by its seal with natural cork, synthetic or screw caps. Wines that did not use cork were immediately deemed inferior.

So why would winemakers seal their wines with closures, you ask?

Natural cork

For thousands of years, natural cork has been the preferred wine seal. In the Pompeii ruins, remains of cork-sealed amphoras have been found. Cork is the most popular wine stopper in the ‘Old World. It makes up the majority of the modern-day cork. The oldest trade in Portugal is cork harvesting.

Semipermeable cork is what has made cork so valuable to the wine industry. This means that only a small amount of oxygen can penetrate wine. This is crucial for wines that are ‘fine’ as it helps with aging.

However, cork can also cause the wine to have unpleasant flavours. Wine consumers have always found cork taint to be a problem. Certain types of mould can, even though they are not visible, exist within the cork. The mould is found in the bark but can be released during bleaching. This can determine whether one wine becomes ‘corked’ from too much or little oxygen ingress. Cork taint can lead to wine being damaged.

One wine can become ‘corked’ because it doesn’t have the same consistency in size or density as another cork. Cork taint can lead to wine being damaged.

Synthetic and plastic cork

As an affordable and viable alternative to natural cork, synthetic or plastic corks are now available.

Although synthetic cork is a viable and affordable alternative to natural cork, its main problem is the inability to absorb oxygen into the wine. This makes it unsuitable for wines aged more than one year. Synthetic cork has the upside: it doesn’t cause cork taint. It’s also stable and resilient, so you won’t find any floating cork after opening the bottle.

Castelli cellar prepares the corks to be a bottle.


Screw caps are a new way to seal wine. Finding wine sealed under any other sealer in Australia or New Zealand is difficult. Cork quickly overtook it as the preferred sealer.

Two key points were the basis of initial arguments against screw caps:

  1. Screw caps were thought to indicate low-quality or poor wine quality;
  2. Screw caps are supposed to allow oxygen ingress.

Both of these arguments were proven false. The Australian Wine Research Institute published a study in 2010 that showed the same wine being sealed using each sealer and left to age for over a decade. The wine with the metal screw cap was the best preserved.

Screw caps can also prevent most wine faults from developing. Screw caps can eliminate faults such as TCA (Trichloroanisole). Screw caps are also much cheaper and more reliable than cork.

Stopper for glass

They are generally considered more effective at protecting wine than metal screwtops. The glass stopper is a very popular option for bottle sealing. It can prevent oxygen ingress and not cause cork taint. This is an elegant option. It can seal all sizes of bottles, making it an ideal choice for winemakers.

This solution has one major drawback: the high cost. Glass stoppers are more expensive and require special machinery, which limits their use.

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