By Will Lyons, Wall Street Journal

In a temperature-controlled cellar with little damp, a good cork will be able to protect wine for several decades. The problem arises on those rare occasions when it doesn’t. Anyone who has built up a collection of fine wines over, say, 40 years will know that perhaps the biggest factor in maintaining their quality is the longevity of corks. At what age does one wear out and have to be replaced?

The answer lies in the quality of the cork. There are three main types. Regular corks are made from bark that’s stripped, without harm to the trees, from the cork oak, found in Portugal and the western Mediterranean. They come in a range of lengths, with the finer wines opting for a longer cork. Second is the agglomerated cork, made of fragments of ground-up cork bound together, either by the bark’s natural resins, released by heating, or with some added adhesive. Thirdly there are synthetic corks, made of plastic foam: Like screw caps and glass closures, these are really only used for wines with a short life-span.

Cork is an excellent material for stoppering wine. The Romans knew a thing or two about viticulture, and cork was used to seal amphorae throughout the Roman Empire. It’s impervious to liquid, long-lasting and doesn’t rot. There is, of course, the problem of cork taint. This arises, usually, through the contamination of the cork with a chemical compound called TCA (2,4,6-trichloroanisole). TCA is produced in the cork when airborne fungi encounter chlorophenols (perhaps deposited by industrial pollution), and it imparts to the wine an unmistakable pungent, moldy odor that I have heard described as anything from mustiness to a dank swimming pool.

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