Wine · Terminology

Cork

The bark of the cork oak, shaped into a closure — still the default seal for wines meant to age.

Cork is the outer bark of the cork oak, Quercus suber, grown mostly in Portugal and Spain. The bark is stripped by hand every nine years or so without harming the tree, boiled, rested, then punched into cylinders. Its cell structure — millions of gas-filled compartments — makes it compressible, elastic and near-impermeable, which is what lets it seal a bottle for decades.

Cork's virtue is a slow, tiny oxygen transmission that suits long bottle ageing. Its vice is TCA taint, the reason a chunk of the wine world moved to screwcap.

In practice

  • Natural cork is punched from a single piece of bark; the best go to wines meant to age.
  • Technical corks (agglomerate, Diam, 1+1) are built from cork granules and binders, with the taint compounds extracted — consistent, and now very common.
  • Alternatives: screwcap, glass stopper, synthetic, crown cap — each with its own oxygen-transmission profile.
  • Sparkling corks are larger and multi-part, compressed into the neck; the mushroom shape forms afterwards.

Where you'll meet it

  • Every bottle you open, and every argument about closures.
  • Portugal, which supplies roughly half the world's cork.
  • In storage advice: cork is the reason bottles are traditionally laid on their side.

Choosing a closure

Closure Oxygen ingress Taint risk Typical use
Natural cork Low, variable Present Age-worthy reds and whites
Technical cork Low, consistent Very low Mid-market wines
Screwcap Very low to moderate (liner-dependent) None Aromatic whites, early-drinking wines
Glass stopper Very low None Premium whites, mostly Austria and Germany

The old assumption that screwcap means "cheap" has not survived contact with New Zealand Sauvignon Blanc or Australian Riesling, both of which age excellently under screwcap.

Storage and handling

  • On its side for natural cork, so the cork stays wet and swollen.
  • Steady temperature — heat cycling pumps air past the cork and grows ullage.
  • A crumbling old cork is a handling problem, not a fault; strain the wine while decanting.

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