Ullage

Ullage is a winemaking term that most commonly refers to the headspace of air between the wine and the top of its container, whether barrel or bottle. In a bottle, it specifically describes the gap between the wine's surface and the bottom of the cork, also called the fill level. The word traces back to the Latin oculus, meaning eye, which the Romans used as a colloquial term for the bung hole of a barrel. This passed into medieval French as oeil, giving rise to the verb ouiller, meaning to fill a barrel to the bung, and then to the noun ouillage, from which the English ullage derives. By extension, ullage came to describe any amount by which a vessel falls short of being full.

• In Neck (IN) or Base Neck (BN): fill at or above the base of the neck, ideal for any age of wine
• Top Shoulder (TS) or Very Top Shoulder (VTS): normal and acceptable for a quality wine 15 years or older
• Upper Shoulder (US): acceptable and common for wines 20 or more years old, with minimal cause for concern
• Mid-Shoulder (MS): more common in wines exceeding 30 to 40 years of age; carries higher risk and warrants careful evaluation before purchase
• Low Shoulder (LS) or Below Shoulder (BS): considered high risk; auction houses generally only accept such bottles if the wine or label is exceptionally rare

The greater the ullage, the greater the potential for the wine to have been exposed to harmful levels of oxygen, since cork is not a completely airtight seal and allows slow diffusion over time. Wine stored on its side also loses volume through absorption into the cork itself, with longer corks absorbing more wine and thus creating more ullage than shorter ones. Abnormally low fill levels relative to a wine's age often indicate poor storage conditions, such as elevated temperatures or low humidity, both of which accelerate evaporation and cork shrinkage. That said, ullage is one indicator among several; provenance, capsule condition, and label state all contribute to a full condition assessment, and even mid-shoulder bottles occasionally prove sound on tasting.

• Wines stored at steady temperatures of 13 to 15 degrees Celsius with humidity around 70 percent develop ullage most slowly
• Excessive oxygen entering through the headspace can interact with Acetobacter in the wine, beginning the process of converting it to acetic acid (vinegar)
• Vintage Port is slightly less susceptible to ullage-related damage due to its higher alcohol content from fortification
• Madeira is uniquely immune to further oxidative damage from ullage because it has already undergone deliberate oxidation during its production process

Assessing ullage requires holding the bottle up to a consistent light source, such as a penlight or LED flashlight positioned behind the neck, to identify the meniscus where wine meets headspace. For Bordeaux-style bottles with distinct shoulders, fill level is described using the standardised shoulder terminology established by Michael Broadbent's guide. For Burgundy-style bottles, which have a more gradual shoulder curve, ullage is measured in centimetres from the bottom of the foil to the top of the wine. Auction houses and fine wine retailers include fill-level notes in condition descriptions for all bottles from approximately the 1990 vintage and older, as younger wines should show negligible ullage.

• Dark glass in Bordeaux bottles can make the meniscus harder to see; tilt the bottle slowly under direct light for the clearest view
• Comparing multiple bottles from the same case is useful, as inconsistent fills across a case may signal variable storage or individual cork failure
• Capsule condition and evidence of seepage around the cork should be assessed alongside ullage as part of a full condition review
• Professional auction houses use standardised photography from consistent angles to document fill levels in catalogue condition notes

The standardised terminology for ullage assessment used across the global fine wine trade was developed in the late 1980s by Michael Broadbent, MW and senior consultant at Christie's, with a primary focus on Bordeaux bottle shapes. His framework has since been widely adopted and adapted by auction houses including Sotheby's, Hart Davis Hart, Zachys, and WineBid, though each house applies its own slight variations in language. Christie's published updated guidance in 2013 clarifying expected fill levels by wine age: top shoulder is normal for any claret 15 years or older, and mid-shoulder is not abnormal for a 30 to 40-year-old wine. For Burgundy, Christie's considers ullage of up to 7 cm relatively normal in a 30-year-old bottle, noting that Burgundy is less affected by ullage than its Bordeaux equivalent.

• Low shoulder fill in a Bordeaux bottle is considered risky and is generally only accepted for auction if the wine or label is exceptionally rare or historically significant
• Zachys and other leading auction houses provide fill-level notes for all bottles from the 1990 vintage and older, as the assumption is that younger wines should have no meaningful ullage
• Ullage assessment is considered one of the most important pre-purchase checks alongside provenance documentation, seepage, and label condition
• A mid-shoulder bottle can still surprise on tasting; experienced buyers weigh fill level alongside all other available evidence rather than treating it as a definitive verdict

In the winery, ullage does not only apply to bottles. As wine matures in oak barrels, natural evaporation causes alcohol and water vapour to escape through the wood, a loss romanticised as the angel's share. If the barrel is not airtight, these departing vapour molecules are replaced by oxygen, which can trigger oxidation and acetic acid development if left unchecked. To prevent spoilage, winemakers regularly top up barrels with the same wine, refilling them to the very brim so that reinserting the bung causes slight spillage. How frequently topping up occurs varies by producer and wine style, ranging from once a week to every six weeks.

• Barrels stored bung-side up allow more rapid aeration and evaporation than those stored bung-over, where wine keeps the seal moist
• Excessive oxygen in the barrel headspace can interact with Acetobacter, converting the wine toward acetic acid, which is why topping up is a fundamental cellar practice
• The liquid lost through barrel evaporation is sometimes called the angel's share, a term borrowed from the whisky industry
• Stainless steel tanks eliminate wood-based evaporation and are sometimes blanketed with inert gas to further protect wine from oxygen during elevage

Traditional natural cork remains the dominant closure for fine wines intended for long ageing, but its inherent variability in oxygen transmission rate (OTR) means that ullage development can differ substantially from bottle to bottle in the same case. Technological closures such as Diam, which processes cork granules using supercritical CO2 via the Diamant process to eliminate TCA contamination, offer winemakers a choice of calibrated OTR values; for example, Diam 10 and Diam 30 are engineered for long-term bottle ageing with the lowest transmission rates in the Diam range. Screwcap closures, which dominate markets such as New Zealand and Australia, introduce minimal oxygen and essentially eliminate the natural ullage development seen in cork-sealed bottles, making fill-level grading irrelevant for wines sealed this way. For fine wine professionals, understanding ullage remains indispensable for evaluating any cork-sealed bottle with meaningful bottle age.

• Diam's agglomerated corks are produced via the Diamant supercritical CO2 extraction process, which removes TCA and other unwanted compounds while allowing for controllable OTR settings across product tiers
• Natural corks show the widest variability in long-term OTR of any closure type, which directly contributes to bottle-to-bottle variation in ullage within the same case
• After approximately 25 to 30 years, natural corks begin to lose elasticity and can allow oxygen to pass between the cork and the glass rather than through the cork itself, accelerating ullage development
• Many top Burgundy and Bordeaux Grand Cru estates continue to use traditional natural cork despite the availability of technological closures, reflecting both tradition and the belief that cork's interaction with wine contributes positively to long-term development