• the empty space in a wine bottle or barrel between the bottom of the cork or top and the surface of the wine. In a barrel or cask this space must be kept to a minimum by topping up with wine to prevent oxidation, though in some wines such as the vins jaunes of Jura a flor develops and protects the wine. In a bottle, old wine can develop a big space through natural evaporation, but in younger wines it could indicate a faulty cork.

Origin & History of “ullage”

Ullage denotes the amount of unfilled space in a wine bottle or barrel. It goes back ultimately to Latin oculus ‘eye’ (a distant relative of English eye), in the metaphorical sense ‘bung-hole of a barrel’. As the word passed into Old French as oeil, this meaning followed it, and it formed the basis of a varb ouiller ‘fill up a barrel to the bung-hole’. from this was derived ouillage, which English acquired via Anglo-Norman ulliage as ullage.