Wine · Terminology

Ullage

The empty space between wine and closure — in a bottle, a barrel or a tank.

Ullage is the empty space in a container of wine — the gap between the surface of the liquid and the closure. It applies at every scale: the headspace under a bottle's cork, the few litres lost from a barrel to evaporation, the air left in a part-empty tank.

Ullage matters because that space contains oxygen. The larger it is and the longer it lasts, the more oxidation and the greater the risk of volatile acidity. Cellar work is largely a running battle to keep it small.

In practice

  • Barrels lose wine steadily to evaporation — the angel's share — so cellars top up regularly, traditionally weekly.
  • Tanks are blanketed with inert gas (nitrogen, argon, CO₂) to fill the space without oxygen.
  • In bottle, ullage grows with age as wine seeps past a tiring cork; poor storage speeds it up dramatically.
  • Some styles want it: Sherry's flor and Vin Jaune's voile both need a deliberately under-filled cask.

Where you'll meet it

  • Auction catalogues, where fill level is graded and priced.
  • Any discussion of cellar hygiene and wine preservation.
  • Fortified wines, where the rules are turned upside down.

Reading ullage on an old bottle

Fill level is the fastest read on how a mature bottle has been stored. The Bordeaux scale, from the base of the neck down:

Level Reading
Into neck Excellent — expected for wines under ~15 years
Base of neck / top shoulder Normal for 15–30 years, good storage
Upper shoulder Acceptable for older vintages; some risk
Mid shoulder Risky — likely oxidation, priced accordingly
Low shoulder Poor — usually a failed cork

Burgundy and Champagne bottles have sloping shoulders, so ullage there is measured in centimetres from the cork instead.

Why it drives storage advice

  • Store bottles on their side so the cork stays wet and swollen; a dry cork shrinks and ullage grows.
  • Keep the temperature steady. Wine expands and contracts with heat cycles, pumping air past the cork each time.
  • Once opened, a bottle is nearly all ullage — hence vacuum stoppers, inert-gas sprays and drinking the thing.
  • Oxidation — what ullage lets happen
  • Cork — the closure that governs it in bottle
  • Maturation — where topping up is routine
  • Flor — a style that requires ullage

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