Natural cork provides a very good seal for a wine bottle, but a screwcap is potentially better still. There are pros and cons for each of them.
- Cork has a unique cellular structure which allows it to be compressed, and then spring back to its original shape. This provides a very good seal to prevent wine from seeping out. It can still seep out if the bottle is overfilled, the cork damaged, or because of poor storage.
- Screwcaps prevent any wine from seeping out.
- Cork. Oxygen can slowly diffuse through the cork into the wine. Some corks are more porous than others, and some have defects; this allows more rapid diffusion of oxygen into the wine, and more rapid ageing.
- Screwcaps. The original screwcaps allowed almost no oxygen into the wine, and this may cause unpleasant odours to develop. Different seals are now available which allow controlled amounts of oxygen into the bottle.
- Corks can be contaminated with TCA, a very small amount of which makes the wine undrinkable. Refer to this earlier post for details. This is cork’s biggest disadvantage.
- Screwcaps do not contaminate the wine.
- Cork. Bottles have to be stored with the wine in contact with the cork. If not, the cork dries out, and becomes a less effective seal. Rapid temperature fluctuations can cause a cork to move within the bottle neck, which can also cause sealing problems.
- Bottles sealed with screwcaps do not suffer from these problems.
- Cork has been used as a wine closure for centuries, and there is plenty of evidence that a good wine, with a good cork, stored in a good cellar, ages gracefully.
- Screwcaps have been around for decades, and there is evidence that some wines age well. However, plenty more trials will be needed over many years, before everyone is convinced.
The scientist in me says that a screwcap with the right seal, is the perfect closure. No bottles will be contaminated, and every bottle in a batch will mature the same way. My heart however, would rather see a cork pulled from a fine bottle of wine, rather than someone crack open a screwcap.