Lesson 1 of 9 · 5 minutes

  1. 1. What makes wine sparkle
  2. 2. The life of a bubble
  3. 3. Five ways to make bubbles
  4. 4. The traditional method step by step
  5. 5. Grapes and the blend
  6. 6. Sugar and dosage
  7. 7. Where it sparkles
  8. 8. Reading the label
  9. 9. Serving

What makes wine sparkle

After this lesson you will know where the bubbles in sparkling wine come from, why they stay in the bottle until it is opened, and how EU law sorts fizzy wines by pressure.

  1. 01

    It starts as sweet juice

    Every wine begins as grape juice, called must. Its sugar is the fuel for everything that follows: without sugar there is no alcohol and no gas. In Champagne the grapes are pressed gently, as whole bunches, without crushing.1 The juice then rests so that the solids sink, and the clear juice is drawn off the deposit.2

  2. 02

    Yeast turns sugar into alcohol and CO2

    Add yeast and the sugar starts to disappear. Yeast converts it into alcohol and carbon dioxide (CO2): this is alcoholic fermentation.3,4 In Champagne the first fermentation usually takes place in stainless steel vats.4 The gas from it is not kept, so the result is a dry, still base wine. To get bubbles, the gas has to be trapped.

  3. 03

    A closed bottle keeps the gas

    In the traditional method the base wine is bottled with sugar and yeast and sealed. It ferments again, the gas cannot escape and dissolves in the wine.5 In a calculation from Reims, 24 g/L of added sugar gives about 9 g of CO2 in a 75 cl bottle.6 The amount dissolved follows the pressure of the gas above the wine (Henry's law), so the pressure under the cork rises.7 A closed tank works the same way.8

  4. 04

    About 6 bar in a bottle of champagne

    Pressure is measured in bar. The Comité Champagne gives 6 bar at 20 °C for a finished bottle of champagne.1 The bottles are designed to withstand 12 atmospheres.9 Temperature changes the reading: CO2 dissolves less well in warm wine, so a warm bottle has more pressure than a cold one.6 That is why legal figures are given at one fixed temperature, 20 °C.10

  5. 05

    How the EU sorts wines by pressure

    EU law names the category by the pressure at 20 °C. Semi-sparkling wine has 1 to 2.5 bar. Sparkling wine needs at least 3 bar, and quality sparkling wine at least 3.5 bar.10 In these categories the gas must come from fermentation.10 Protected appellations usually sit in the quality category: Cava, for example, is defined with at least 3.5 bar.11

  6. 06

    Gas added from outside

    A still wine can also be made fizzy with CO2 from an outside source. This is carbonation. EU law puts such wines in separate categories: aerated sparkling wine, with at least 3 bar, and aerated semi-sparkling wine.10 Aerated sparkling wine is made from wine without a protected name of origin (PDO or PGI), and the label must say "obtained by adding carbon dioxide".10,5

Remember

  1. Yeast turns sugar into alcohol and CO2; in an open vat the gas escapes, in a closed bottle or tank it stays in the wine.
  2. The trapped gas builds pressure: 6 bar at 20 °C in a bottle of champagne, by the Comité Champagne's figure.
  3. In the EU, semi-sparkling wine has 1 to 2.5 bar, sparkling wine at least 3 bar and quality sparkling wine at least 3.5 bar, all at 20 °C.
  4. Wine made fizzy with added gas is a separate "aerated" category and must say so on the label.

Check yourself

1Why does the first fermentation give a still wine?

2A wine has 2 bar at 20 °C, all from fermentation. Which EU category fits?

3What makes a wine "aerated" in EU law?

See also

EU categories of sparkling wineMethodsCO2 and pressure in the bottleScienceCarbonationMethodsFirst fermentationMethodsPrise de mousseMethodsbarGlossary

Sources

  1. Comité Champagne (champagne.education). Fiche Élaboration du Champagne (FR) (2024-05)
  2. Comité Champagne (champagne.fr). Settling
  3. Comité Champagne / champagne.education. L'élaboration du Champagne (fiche) (2024)
  4. Comité Champagne (champagne.fr). Fermentation
  5. EUR-Lex. Commission Delegated Regulation (EU) 2019/33 (consolidated text), Articles 47, 48, 49, 53, 54 and Annex III Part A (2023-12-08)
  6. Nature Publishing Group. Liger-Belair G., Cordier D., Honvault J., Cilindre C. Unveiling CO2 heterogeneous freezing plumes during champagne cork popping. Scientific Reports 7: 10938. DOI 10.1038/s41598-017-10702-6 (2017)
  7. AAAS (full text read via Europe PMC, PMC6754238). Liger-Belair G., Cordier D., Georges R. Under-expanded supersonic CO2 freezing jets during champagne cork popping. Science Advances 5(9): eaav5528. DOI 10.1126/sciadv.aav5528 (2019-09)
  8. legislation.gov.uk (The National Archives). Commission Delegated Regulation (EU) 2019/934, Annex II (sparkling wine oenological practices), as reproduced on legislation.gov.uk (2019-03-12)
  9. Union des Maisons de Champagne. Second fermentation (capturing the sparkle)
  10. legislation.gov.uk (The National Archives). Regulation (EU) No 1308/2013, Annex VII Part II (categories of grapevine products), as reproduced on legislation.gov.uk (2013-12-17)
  11. Consejo Regulador DO Cava. Pliego de condiciones DOP Cava

Facts checked on 2026-10-20