News & Updates

The cork closure has been around since the Roman days. There’s a whole mystique wrapped around pulling the cork out of a bottle of wine. What corkscrew to use, how to hold the bottle, do I look at or smell the cork and the list just goes on. Most of it is rubbish. The cork is there to seal the bottle and that’s just about it.

As well as corks leaking or drying out we can have the problem of a ‘corked’ bottle. Unfortunately there’s not much you can do to control this. Wine becomes ‘corked’ or tainted when a chemical called tri-chloro-anisole (TCA) combines with chlorine in the bleach used to sanitize the corks. TCA arises from moulds naturally occurring in the tree bark. It is virtually impossible to detect a mouldy cork before it’s put into the bottle. A severely corked bottle is easy to pick. It will smell like damp carpet or a flooded cellar. It gives that musty unpleasant smell. And this is fine because you can pick straight away that something is wrong with the bottle.

A lightly corked bottle presents a bigger problem. The wine will smell flat and taste dull. There’ll be no fruit nose and no fruit flavour. The average wine drinker will assume that this is how the wine is supposed to taste. The reputation of the winery suffers through something they have no knowledge of or control over. A no win situation. Wineries responded to this problem by using synthetic corks by the millions. The cork industry responded by spending millions on research to find the cause and cure for cork taint. A chlorine free cork treatment process was developed and this has helped greatly.

Anecdotal evidence says up to 8% of bottles had cork taint a few years ago. Now, that’s down to below 2% which is a great news!!!

It’s the natural properties of the cork that make it useful as a closure for wine bottles.

More specifically:

All from Cooke, G.B. 1961. Cork and the cork tree. Pergamon press, Oxford.

Most of the unique properties of cork relate to the cell structure, which is very different to other natural materials. The difference is that each cell is filled with air, is sealed and not internally connected to any adjacent cells. The individual cells are bonded together by a strong natural resinous substance, giving the cells strength. 

Cork is very unique and useful because it can be compressed, yet it remains resilient. Cork can be compressed by exerting pressure, and when the pressure is removed it will return to its original volume. When the piece of cork is put under pressure, the air in the cells is compressed, and when the pressure is removed the air expands to fill the volume it previously occupied such that the piece of cork will also return to the volume it previously
occupied. However if too much pressure is exerted the cells will collapse and the volume of
the piece of cork will be reduced. 

The cork is impervious to water and other liquids, including oil. This is because individual cells are not connected to each other therefore capillary action does not occur, as it does, for example in some types of wood. It is low density because the cells are filled with air and low thermal conductivity, again due to the cells that do not transmit energy well because they are filled with air. 

A High friction surface, so when the surface of a piece of cork is cut thousands of small cups are formed that create a vacuum when the surface is pressed against a smooth surface.

Finally, vibration and sound absorbency; This is because the air filled cells compress and therefore soak up some of the energy that is being transmitted through them.

Author: Lynda Walsh, Wine Cellaring Business Development Manager/ NSW Operations Manager.  Kennards Self Storage