Bottle size and ageing

The starting point

A standard bottle of champagne gains about 9 g of CO2 during the second fermentation.³ During ageing on lees the bottle is usually closed with a crown cap. No closure is perfectly gas-tight. Over many years a small flow of CO2 escapes, and the wine slowly loses the pressure and the bubbles it was made with.

At the start of ageing, a standard champagne holds about 12 g/L of dissolved CO2.⁴ How much stays dissolved depends on the CO2 pressure in the headspace, following Henry's law.⁵ Any gas that leaks out lowers that pressure, and with it the dissolved CO2 that later forms the bubbles in the glass.

The study

Liger-Belair and colleagues published the results in ACS Omega in 2023 under the title "Losses of yeast-fermented carbon dioxide during prolonged champagne aging: yes, the bottle size does matter!".⁶ They analysed 13 successive vintages that had aged on lees for 25 to 47 years, in 75 cL bottles and in 150 cL magnums, all closed with crown caps.¹ The same team presented the shelf-life model as a poster at the OENO Macrowine 2023 conference.¹

The result

The vintages aged in magnums kept their dissolved CO2 much more efficiently than the same vintages in standard bottles.^1,2

Shelf-life estimates

The authors built a model to predict how long a bottle keeps enough CO2. The figures below come from the publisher's own summary of the paper, not from the full text, and they are model estimates, not measurements.²

These shelf-life figures are taken from a summary and could not be checked against the full paper. Treat them as orders of magnitude for wines aged on lees under crown cap.

Context

The study concerns long ageing on lees before disgorgement, not bottles kept at home after release. It also says nothing about taste. The names and volumes of these formats are on bottle sizes; for how pressure and dissolved CO2 relate, see CO2 and pressure.