Carboy Headspace or Ullage

Once wine hits the carboy for some aging one has to watch how much headspace or Ullage there us. In case you were wondering what Ullage is, it's the air space between the wine and the airlock. Too much Ullage and your wine can oxidize.

The problem we winemakers encounter is having the right sized carboy to reduce the Ullage. One way to do this is to have enough similar wine on hand to top up your carboy. But sometimes the size of carboy doesn't match the amount of wine. What do you do then?

I have solved this problem by buying 3 and 4 liter used wine bottles. The openings to these bottles are large enough to accept a bung and airlock.

Check out the pics below to see what bottles I use to reduce carboy headspace or Ullage.

Carboy Airlock and Bung

Once the wine is in the carboy or secondary fermenter, it will need to be sealed with an airlock.

The airlock is stuck into a rubber bung which has a hole in it. Then the bung with the airlock is placed into the opening of the carboy. This allows the CO2 to escape and not let any air into the carboy.

Make sure you have the appropriate amount of water in the airlock to keep the air out.

Carboy - Secondary Fermenter

A carboy or a demijohn is where the wine gets racked over to from the primary fermenter.

Typically the size is 23 liters and is made of glass or plastic. Get a carboy that holds your wine with little or no space left over. Too much head space leaves too much air in contact with your wine and can cause oxidation.

Plastic or glass is your choice. The glass is clear and it's easy to see your wine and easy to see if it's clean. Plastic ones can discolour but when dropped they don't smash! I use glass ones.