Today’s letter is “U”, so we’ll talk about Ullage.
Ullage is also known as headspace, the unfilled space in a wine bottle, barrel, or tank. Derived from the French ouillage, the terms “ullage space” and “on ullage” are sometimes used, and a bottle or barrel not entirely full may be described as “ullaged”. It also refers to the practice of topping off a carboy or barrel with extra wine to prevent oxidation.
The headspace of air is a mixture mostly of alcohol and water vapors with carbon dioxide that is a by-product of the fermentation process. In containers that are not completely air-tight (such as an oak wine barrel or a cork-stoppered wine bottle), oxygen can also seep into this space. While some oxygen is beneficial to the aging process of wine, excessive amounts can lead to oxidation and other various wine faults.
This is why wine in the barrels is regularly “topped up” and refilled to the top with wine in order to minimize the head space. In the bottle, the ullage or “fill level” of the wine can be an important indicator of the kind of care and storage conditions that the wine was kept in.
The ullage level of a wine bottle is sometimes described as the “fill level”. This describes the space between the wine and the bottom of the cork. When you’re bottling your wine, you want to strive to have an initial ullage level of between 0.2–0.4 inches (5–10mm). As a cork is not a completely airtight sealant, some wine is lost through the process of evaporation and diffusion.
As a wine ages in the bottle, the amount of ullage will continue to increase unless a wine is opened, topped up and recorked. Here’s a good example of aged wine with various stages of ullage:
If the wine is stored on its side, in contact with the cork, some wine will also be lost by absorption into the cork with longer corks having the potential to absorb more wine (and thus create more ullage) than shorter corks.
Generally the greater the amount of ullage, the more potential that the wine has been exposed to harmful levels of oxidation. Ullage levels are generally important to the likelihood of almost any wine being in good shape. So pay attention to the wine levels not only during the fermentation, racking and aging process, but certainly when you bottle!
Here’s an even better visual on various stages of ullage:
- In Neck (IN) – a young wine or in exceptional condition.
- Base of Neck (BN) – the fill level for recent and older vintages. For wines over 25 years, this would indicate exceptional storage.
- Top Shoulder (TS) – standard for wines over 10 years. For wines over 25 years, this indicates excellent storage conditions.
- Mid Shoulder (MS) – about midpoint of the shoulder. Not unusual for wines over 30-40 years, but could suggest poor storage or early signs of cork failure in younger wines.
- Low Shoulder (LS) – below the midpoint of the shoulder. Normally a wine over 40 years of age.
- <2 cm – an excellent fill level for any wine age.
- <3-5 cm – standard for wines of 12 years and older. 3cm would be excellent for wines of 25 years or older.
- <5-7 cm – not uncommon in wines over 30 years.
(The Burgundy bottle shape does not allow for a level rating system and levels are described by measurements below the cork.)
So what does that mean for the home winemaker, and how full should we fill the bottles? The goal when filling, aside from the obvious, is to prevent oxidation. Bottles should be filled without splashing, to about one-fourth to one-half inch below the point where the bottom of the cork will be.
That’s where using a bottle filler is best – sink it to the bottom of the bottle and let wine fill up the bottle with minimum aeration. Some air space is needed should cellar temperatures rise and the wine expand, and a minute amount of air is useful in aging.
Winemaking is so much fun – at least for me – and am tickled every time I give the wine I make as gifts to friends and family who love drinking it as much as I love making it. While we go through this alphabetical series on winemaking, if you have any burning questions, be sure to ask them in the comments below, and I’ll reply there – and maybe even highlight your specific question(s) in a future post!
Thanks for joining me in this fun adventure!
Here are the links going backwards for your convenience, in case you missed any:
A for Aromas, Acidity and Appearance
B for Barrels, Bottles and Blackberry Wine
C for Color, Clarity, Carboys and Cherry Wine
D for Decanting and Decanters
E for Equipment
F for Fermentation
G for Glass and Grape
H for Harvest
I for Infusion
J for Jeroboam and Jug
K for Kabinett
L for Leaf, Label and Lees
M for Merlot, Muscat and Must
N – the Nose has it!
O for Oak and Oxidation
P for Palate and Press
Q for Quality
R for Racking and Riddling
S for Sweet and Sanitary
T for Taste and Tasting