The following was first published as a box in an article by me published in World of Fine Wine Issue 35 but has been tweaked since:
How Vin Jaune is Made
Vin Jaune is made from 100% Savagnin, in the appellations of Arbois, Côtes du Jura, Etoile and Château-Chalon, the latter AOC being reserved for Vin Jaune only. Savagnin is generally grown on soils of blue or grey marl. It is fairly late-picked, though only rarely with berries affected by noble rot. Ideally the must should be about 13% with chaptalization used in years when necessary, and pH needs to be low (3.0-3.1) to withstand the years of ageing.
The wine is traditionally made with temperature controlled (but not too cool) fermentation in tank and malolactic fermentation in due course.
At some point – usually during the year following vintage, but occasionally in spring 18 months after harvest – the Savagnin wine is transferred into 228-litre (60-US- gallon) Burgundy oak barrels averaging anything from 5 – 50 years old. These are not entirely filled, with the equivalent of about 8-10 litres of ullage or air space. After a time, which varies greatly, a layer of yeast, the voile (veil), appears on the surface of the wine, similar to Sherry’s flor. The best quality voile is grey and quite thin, indicating a living and active yeast mixture. Once the voile has formed, it effectively protects the wine from further oxidation, and it helps promote the aromas and flavours associated with Vin Jaune.
The conditions in which the barrels are stored – which may be at ground level, underground or even an attic – are crucial to the eventual quality of the wine. There are huge variables – indeed, many growers believe that the complexity of Vin Jaune is achieved partly by stocking the barrels in several different locations, all with different conditions. All agree that aerated cellars, with wide temperature variations, are vital, and most prefer dry conditions, where the water content of the wine in the ullaged barrels evaporates slowly, concentrating other substances, including alcohol.
A technician from the official Jura wine laboratory visits most Vin Jaune producers twice a year to test every barrel of Savagnin destined for Vin Jaune, and tests samples to ensure that the level of acetic acid is not too high and that for the first few years the ethanal (acetaldehyde) level is rising. Ethanal, is vital for Vin Jaune and is the most important component for its distinctive oxidative taste. Depending on the lab reports, the producer then decides which barrels should be withdrawn from Vin Jaune ageing, and as long as they are not spoilt, they are used for oxidative Savagnin white wine, or Chardonnay/Savagnin blends.
No racking or any other handling takes place during the minimum six years that the AOC requires Vins Jaunes to remain in barrel. The earliest release allowed is at the start of the 7th year after harvest, so, at the time of writing in 2012, 2005 is the most recent available vintage. Today, the AOC laws insist on approval tests for all Vin Jaune just before bottling; and in Château-Chalon the laws are even stricter with some vintages rejected outright as being unsuitable before the grapes have been picked.
The clavelin bottle
According to the AOC rules Vins Jaunes must be bottled in the squat 62cl clavelin bottle, one of the few non-standard bottle sizes allowed in EU law. A bottle of this shape is said to have been commissioned by growers in Château-Chalon from La Vielle Loye glassworks in the 18th century. It is often described as a bouteille dites anglaise (an “English-style bottle”) the the volume is somewhat more than an English pint, so this is another mystery. What seems more certain is that in 1914 the abbot of Clavelin ordered 30 of these bottles with his own emblem from the glassworks. From around this period, the use of the clavelin for Vins Jaunes became widespread.
The great marketing coup for the clavelin is that 62cl is said to be what remains of a litre of wine after the statutory six years ageing in cask on ullage sous voile (under yeast), certainly it makes the explanation easier. The downside is that US regulations do not allow the importation of this size of bottle into the country though there are some circuitous routes in. Some 37.5cl bottles of similar shape have been produced, but this is not strictly speaking allowed within AOC rules.