Wine Arcana

Concept

Racking and topping

Also known as Soutirage, Ouillage

Racking transfers wine away from a settled deposit into another vessel. Topping adds wine to reduce the space left above the liquid in a storage vessel. Both recur during maturation, but they solve different problems: racking separates wine from solids, while topping manages headspace.

Their place in the cellar sequence depends on what the wine is doing. Fermentation, sediment formation, intended lees contact, and oxygen exposure give the winemaker reasons to act—or to leave a vessel undisturbed.

Drawing wine away from a deposit

Gravity gathers settling particles at the bottom of a tank or barrel. Racking draws off the clearer liquid while leaving that deposit behind. Gravity or a pump can move the wine. The defining feature is the separation, not the source of motive force.

The deposit may follow fermentation, a fining treatment, or tartrate stabilization. Drawing off clear wine removes much of the sediment, but organisms and fine particles can remain suspended. Racking is therefore distinct from filtration designed to remove microorganisms.

Each transfer needs a suitable destination and clean equipment. It also leaves wine mixed into the discarded solids. In work on reducing winery transfers, AWRI identified labour, cleaning water, wastewater, and wine held in lees as practical costs. Its investigation of removing sediment from beneath the wine illustrates the difficulty: liquid can channel through the deposit before the solids themselves have been removed.1. Australian Wine Research Institute, “Reducing wine movements during production,” project summary and results.

Deciding which lees to keep

Lees aging deliberately retains useful sediment. A producer may remove the rapidly settling, coarse fraction and continue ageing with finer yeast lees, or retain a different mixture for the desired style. Keeping lees and stirring them are separate decisions.

The decision to rack follows the condition of both wine and deposit. Their aroma, microbial activity, and intended contact time matter more than a universal monthly schedule. Nor does one racking necessarily end lees contact: sediment can form again, or selected fine lees can accompany the wine.

A transfer also changes oxygen exposure

Racking can be conducted protectively or with deliberate aeration. The OIV recognises both approaches. The choice matters because moving wine exposes fresh liquid surfaces and can change its dissolved-gas content. Reduction, oxidation, and the intended stage of maturation need to be considered together.

One recorded example shows several purposes meeting in a single operation. For its 2015 anniversary Shiraz, AWRI racked barrels into a tank large enough to combine the wine, washed the barrels, and refilled them with dry-ice protection. The transfer allowed blending and vessel cleaning as well as sediment removal.2. Peter Godden, “Racking for the first time,” AWRI, 23 June 2015.

Why the fill level changes

During oak maturation, evaporation, uptake by new wood, and sampling can reduce the amount of wine in a barrel. The growing space above it is called ullage. Topping replaces losses with sound wine suited to the lot, reducing that space. Fill-level inspection and sulfur dioxide checks remain recurring cellar work.

A tank can also be partly empty after wine is withdrawn. A smaller suitable vessel may accommodate the remaining lot more effectively. Where headspace must remain, wineries use gases such as nitrogen, carbon dioxide, or argon to reduce oxygen exposure. The gas, its delivery, and the vessel's subsequent handling all affect protection.

A gas blanket needs management. Turbulent delivery mixes gas with air, and carbon dioxide dissolves readily into wine, changing both the headspace and the wine's dissolved CO₂. Temperature changes also alter liquid volume. Headspace protection is consequently a monitored storage condition, not a permanent result of one gas addition.3. Ben Cordingley, “Gases – we have you covered,” 2023, gas delivery, solubility, and storage-headspace discussion.

Wines deliberately kept below full

Flor maturation uses a yeast film at the wine's surface and requires access to air. Sherry casks intended for biological ageing therefore retain headspace. These conditions support a particular microbial process; an unexpectedly low fill level in an ordinary barrel is not equivalent to a controlled flor maturation.

Sources