Cellar worker tops off each wine barrel from another wine barrel.
Topping off a wine barrel
In this photo we see the meaning of “topping off a wine barrel.” Since wine barrels are made from wood, they breathe. A certain amount of evaporation will occur in the barrels and that space is filled with the air we breathe. In order to prevent oxidation of the wine in the barrel, that space of air called “ullage” must be replaced with wine. The wine must be the same as what is in the barrel. The cellar worker “breaks down” another barrel of the same grape and vintage. An inert gas like Argon or Nitrogen is used for pressure to move this extra wine juice through the hose to top off each of the wine barrels in this photo. Winemakers always try to limit the evaporation of wine in a barrel by having the correct “climate” in the barrel room. That means humidity and temperature control. This is one reason why winemakers love the wine cave. The natural conditions of the cave control the temperature and humidity all year around. This photo was taken at the Round Pond winery located in the Rutherford AVA in the Napa Valley on May 12, 2015.
The barrel is topped off, leaving enough room for the bung to close the barrel.