1. The harvest

The grapes are picked by hand between August and October, the harvest time depends on how ripe the grapes are. The wine producers, such as Champagne Roger Constant-Lemaire in Villers-sous-Châtillon, are not allowed to pick the grapes with a machine. The grapes have to be picked by hand so that only the best and ripened grapes are contributed to the Champagne.

After picking the grapes, they are pressed carefully to keep the juice clear white.

2. The First fermentation

The juice is put into a tank and the first fermentation takes place. The result is an acidic still wine that has been fermented dry completely. (The wine producer sees to it that all the natural sugar present in the grapes is fermented out of the wine). Some wine producers, like Champagne Alfred Gratien in Epernay, choose for fermentation in a barrel, a technique that is more difficult to master with sparkling wine.

3. The Assemblage

This is the art of blending. Still white wines combined with some reserve wines to create the base wine for Champagne; Pinot Noir, Pinot Blanc and Chardonnay are combined together.

The assemblage starts in the early spring, about 5 months after the harvest.

4. The Second fermentation

A mixture of yeast, yeast nutrients and sugar (liqueur de tirage) that is added to the wine in the second yeasting, the wine is put in a thick glass bottle and sealed with a bottle cap. The wine bottles are placed in a cool cellar to ferment slowly and to produce alcohol and carbon dioxide.

This is the most important part; the carbon dioxide cannot escape from the bottle and solves in the bottle; you will get the sparkling wine because of the carbon dioxide.

5. The Aging

As the fermentation proceeds, yeast cells die and after several months, the fermentation process is complete. However, the Champagne continues to age in the cool cellar for several more years resulting in a toasty, yeasty character. During this aging period, the yeast cells split open and spill into the solution imparting complex, yeasty flavours to the Champagne. The best and most expensive Champagne is aged for five years or more. This process completes the second fermentation.

6. The Riddling

After the aging process is completed, the dead yeast cells are removed through a process known as riddling. The Champagne bottle is placed upside down in a holder with a 75-degree angle. Each day, the riddler gives the bottle a 1/8th of a turn whilst keeping it upside down. This procedure forces the dead yeast cells float into the bottleneck where they are subsequently removed.

The bottles are placed in racks with the bottlenecks facing downwards. Madame Veuve Cliquot is the inventor of the bottle rack in which the bottles are put downwards.

7. The Disgorging

The disgorgement is the final step in the production of Champagne. The Champagne bottle is kept upside down while the neck is frozen in an ice-salt bath. This procedure results in the formation of a plug of frozen wine containing the dead yeast cells. Finally, the bottle cap is removed and the pressure of the carbon dioxide gas in the bottle forces the plug of frozen wine out (“disgorging”) leaving behind clear Champagne. By doing so, a little bit of wine gets spilled out of the bottle.

8. The Dosage

A mixture of white wine, brandy and sugar (Liqueur de tirage/Liqueur d’expédition) is added to adjust the sweetness level of the wine and to top up the bottle. This procedure decides whether the Champagne will be Brut Nature, Extra Brut, Brut, Extra Dry, Dry, Semi Dry or Doux.

This mixture is differs per Champagne House and is a well-kept secret.

9. The Corking

The bottle is corked and the cork is wired down to secure the high internal pressure of the carbon dioxide in the Champagne.

Link: https://www.champagne-booking.com/en/p/the-production-process-of-champagne