By Bertille — Millésimes, fine wine merchant since 1984
The magnum is the format of the long table. It is also, less obviously, the format in which wine ages best. The difference is not a matter of prestige. It is physical, and it is measured in years.
What a magnum is
A magnum holds 1.5 litres, the equivalent of two 75 cl bottles. The neck, the cork and the diameter of the bottle opening are identical to a standard bottle. Everything else follows from that.
A magnum pours around twelve glasses. It is stored, carried and served like an ordinary bottle, except that it weighs close to three kilos when full.
Why the wine ages more slowly
Cork is not airtight. It admits a very small amount of oxygen each year, and it is this slow oxidation that makes wine evolve: tannins soften, fruit transforms, tertiary aromas appear.
The key point: a magnum cork admits roughly as much oxygen as a 75 cl cork, because it has the same surface area. But that oxygen is distributed through twice as much wine. Each litre therefore receives about half as much.
The wine develops in the same direction, simply more slowly. A grand cru beginning to tire in 75 cl will still be in full form in magnum, often several years ahead of its standard-format equivalent.
The volume of air left beneath the cork at bottling also represents a smaller proportion of the total. The wine starts with a slight advantage from day one.
A more stable format in the cellar
The second reason is temperature. A larger mass of liquid changes temperature more slowly. In a cellar whose temperature moves with the seasons — which describes most private cellars — a magnum absorbs those swings better than a 75 cl.
Collectors also report greater consistency from bottle to bottle in large format. Across a twenty-year vertical, the variation between magnums is generally narrower than between standard bottles.
Which wines gain most from the format
A magnum adds nothing to a wine meant to be drunk within the year. Its value is proportional to time in the cellar.
It earns its place on:
- Long-ageing Bordeaux vintages, particularly classed growths from strong years
- Grand cru Burgundy, red and white, where a few extra years matter a great deal
- Northern Rhône wines built for keeping, Côte-Rôtie and Hermitage especially
- Vintage Champagne, which gains in complexity and holds its mousse longer
A rosé from the current vintage, an early-drinking white or an everyday wine gain nothing at all.
How long a magnum keeps
There is no arithmetic rule, and the ones you sometimes read are worth treating with suspicion. The format does not double a wine's ageing potential.
The figure generally accepted among merchants and collectors is a few additional years — often three to five on a wine that keeps twenty years in 75 cl. The wine holds its freshness and structure longer, but it remains the same wine, from the same vintage and the same terroir.
What the format costs
A magnum usually costs somewhat more than two 75 cl bottles of the same wine. The difference reflects the cost of the glass, the smaller volumes produced, and steady demand on the great vintages.
On a wine for keeping, that premium is justified by the years gained. On a wine to be drunk within two years, it is not.
Serving a magnum
Three practical points.
A magnum decants like a bottle, but its weight makes the movement less easy. Stand it upright the day before and handle it slowly so the sediment is not disturbed.
It is served at the same temperature as the standard format, bearing in mind that it warms more slowly in the room. Brought up from the cellar, it needs more time.
Finally, an opened magnum gets finished. Twelve glasses is a table of six served twice. This is the format of the shared meal, not the evening glass.
In short
A magnum is not a larger bottle. It is a wine that ages more slowly, in more stable conditions, reaching maturity later and often with greater finesse.
For a vintage you intend to keep, it is almost always the right choice.
Our magnums rest in our cellars at Maussane-les-Alpilles until the day they ship. Discover our magnum selection.
