Ullage (from the French ''ouillage'') is a winemaking term that has several meanings but most commonly refers to the headspace of air between

wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...

and the top of the container holding the wine. It can also refer to the process of

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

that creates the headspace itself or it can be used as a

past tense The past tense is a grammatical tense whose function is to place an action or situation in the past. Examples of verbs in the past tense include the English verbs ''sang'', ''went'' and ''washed''. Most languages have a past tense, with some hav ...

verb A verb () is a word (part of speech) that in syntax generally conveys an action (''bring'', ''read'', ''walk'', ''run'', ''learn''), an occurrence (''happen'', ''become''), or a state of being (''be'', ''exist'', ''stand''). In the usual descri ...

to describe a wine barrel or bottle that has gone through the evaporation process (''to be ullaged'', etc.). The headspace of air is a mixture mostly of

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

and

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

s with

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

that is a by-product of the

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

process. In containers that are not completely

air-tight A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers, but as technology advanced it applied to a larger categor ...

(such as an oak wine barrel or a

cork Cork or CORK may refer to: Materials * Cork (material), an impermeable buoyant plant product ** Cork (plug), a cylindrical or conical object used to seal a container ***Wine cork Places Ireland * Cork (city) ** Metropolitan Cork, also known as G ...

-stoppered

wine bottle A wine bottle is a bottle, generally a glass bottle, that is used for holding wine. Some wines are fermented in the bottle while others are bottled only after fermentation. Recently the bottle has become a standard unit of volume to describe sal ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

can also seep into this space. While some oxygen is beneficial to the aging process of wine, excessive amounts can lead to

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

and other various

wine fault A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine ...

s. 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. After-market resellers and

wine auction A wine auction may also auction other alcoholic beverages than wine. There are two basic types of wine auctions: ''first hand wine auctions'', where wineries sell their own wines, and ''second hand wine auctions'', arranged by auction houses or ot ...

houses will often inspect the ullage levels of older

vintage Vintage, in winemaking, is the process of picking grapes and creating the finished product—wine (see Harvest (wine)). A vintage wine is one made from grapes that were all, or primarily, grown and harvested in a single specified year. In certa ...

s to determine the potential quality and value of wine.J. Robinson (ed). ''"The Oxford Companion to Wine"'' Third Edition, pp. 270, 702 & 718. Oxford University Press 2006 .

In the barrel

At the winery, the natural process of evaporation creates ullage in the barrel by causing some of the alcohol and water particles to escape as

vapor In physics, a vapor (American English) or vapour (British English and Canadian English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critic ...

s, a loss sometimes referred to as the " angel's share". If the wine is in a container that is not completely air-tight, these vapor molecules (along with carbon dioxide) will

diffuse Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

out of the container through openings in the wood and around the

bung A stopper or cork is a cylindrical or conical Closure (container), closure used to seal a container, such as a bottle, tube or barrel (storage), barrel. Unlike a Lid (container), lid or bottle cap, which encloses a container from the outside wit ...

and be replaced with oxygen molecules. While some oxygen is beneficial in the maturation and break-down of some phenolic compounds such as

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' (from Anglo-Norman ''tanner'', ...

, excessive amounts of oxygen can interact with ''

Acetobacter ''Acetobacter'' is a genus of acetic acid bacteria. Acetic acid bacteria are characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. Of these, the genus ''Acetobacter'' is distinguished by the ability to oxidize ...

'' present in the wine and start the process of turning the wine into

vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to et ...

. To prevent this possible oxidation and spoilage wineries will regularly "top up" the barrels by replacing the lost liquid with new wine. The exact method and timing of topping up a wine barrel is determined by the individual wineries and can depend on the type of wine or

grape variety This list of grape varieties includes cultivated grapes, whether used for wine, or eating as a table grape, fresh or dried (raisin, currant, sultana). For a complete list of all grape species including those unimportant to agriculture, see Viti ...

that is being produced. A barrel can be topped off anywhere from once a week to every month and a half. The position of the barrel can affect the speed and degree of evaporation and the need for topping up. If the barrel is sitting with its bung hole on top,

aeration Aeration (also called aerification or aeriation) is the Systems engineering process, process by which air is circulated through, mixed with or solvation, dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration proces ...

and evaporation occurs more quickly. If the barrel is turned to the side in the ''bung over'' position, the bung is kept moist with the wine and aeration occurs at a slower pace. The wine that is replaced during the topping up is usually the same wine taken from another smaller container (such as a

carboy A carboy, also known as a demijohn or a lady jeanne, is a rigid container with a typical capacity of . Carboys are primarily used for transporting liquids, often water or chemicals. They are also used for in-home fermentation of beverages, ...

) with the barrel filled to the very top to where the reinsertion of the bung causes some spillage.

In the bottle

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

. During the

bottling Bottling lines are production lines that fill a product, generally a beverage, into bottles on a large scale. Many prepared foods are also bottled, such as sauces, syrups, marinades, oils and vinegars. Beer bottling process Packaging of bottle ...

process, most wineries 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. If the wine is stored on its side, in contact with the cork, some wine will also be lost by

absorption Absorption may refer to: Chemistry and biology * Absorption (biology), digestion **Absorption (small intestine) *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which ...

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. This is why auction houses and retailers of mature wines pay close attention to the ullage levels in determining the resale value of the wine. The ullage level can also give insight as to the type of care and storage condition that the wine was kept in. Wines that have been kept at ambient

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

levels and in temperatures between 50–59 °F (10–15 °C) will experience evaporation and diffusion at a slower rate than wine kept in lesser conditions and will thus have a lower ullage levels. Ullage levels are generally important to the likelihood of almost any wine being in good shape. Vintage Port might be slightly less prone to damage since it is fortified, but the only wines that can not be damaged by oxidation are Madeira wines, which are already oxidized. There are standard descriptions used by wine merchants and auction houses for the fill levels (ullage levels) of wine. The fill levels descriptions are different for Bordeaux and Burgundy wines due to the different shape of the bottles from those two regions.

Broadbent's ullage guide

In the late 1980s,

Master of Wine Master of Wine (MW) is a qualification (not an academic degree) issued by The Institute of Masters of Wine in the United Kingdom. The MW qualification is generally regarded in the wine industry as one of the highest standards of professional knowle ...

and senior consultant of

Christie's Christie's is a British auction house founded in 1766 by James Christie (auctioneer), James Christie. Its main premises are on King Street, St James's in London, at Rockefeller Center in New York City and at Alexandra House in Hong Kong. It is ...

auction

Michael Broadbent John Michael Broadbent, MW (2 May 1927 – 17 March 2020) was a British wine critic, writer and auctioneer in a capacity as a Master of Wine. He was an authority on wine tasting and old wines. Career Broadbent was born in Yorkshire. He was ed ...

developed a guide for evaluating the ullage levels of matured wines. While the focus of his guide was primarily on Bordeaux, it has been generally accepted and widely used in the wine market as an evaluation tool for all sorts of wine. The terms are used to describe the levels of wine in a wine bottle. They are commonly used to describe old wine bottles offered for sale in

s and by dealers in rare wine. Due to the guide's popularity, Broadbent has been quoted as regretting his decision not to

copyright A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, education ...

it.G. Harding. ''"A Wine Miscellany"'', p. 33, Clarkson Potter Publishing, New York 2005 .

References

{{Winemaking Bottles Fermented drinks Oenology Viticulture Wine packaging and storage Wine terminology