Cold prefermentary maceration and alcoholic fermentation are carried out together on a monovarietal basis: one vat may only contain the juice of one grape variety and, preferably, of one single plot. At this point, blending has not happened yet. The must (grape juice) and skins (the whole skin mass is also known as pomace or marc) macerates for twenty-one days, sometimes longer, depending on the intended type of wine.
These phases of prefermentary and fermentary maceration allow the extraction of pigments and tannins from the skin to the juice. After a few days in the vat, the must begins to ferment under the natural action of grape yeasts. Alcoholic fermentation starts above 16 to 18 °C (60 to 64 °F) and may reach about 28 to 30 °C (82 to 86 °F; it may be controlled through thermoregulation as necessary), for an average duration of 18 days. Through that process, the sugars contained in the grapes are turned into alcohol while carbon dioxide and heat are also released.
During this stage, the pomace (the skin and pips) converges towards the top part of the vat into a mass that is called a “cap”. Specific techniques are used to facilitate the extraction of the grape components by immersing the cap and preventing the growth of harmful bacteria that are likely to proliferate in the solid parts emerging above the must; pumping-over consists of pumping the juice from the bottom to the top of the vat and pouring it over the cap. Delestage or “rack and return” consists of emptying all the juice from the vat by gravity, at the end of which the cap is pressed by its own weight when it settles at the bottom of the vat.
Then the juice poured out of the vat is poured back in from the top so that the cap is fully immersed. Pigeage, or punching-down, is a very old technique that inspired the two previously mentioned methods: using a pige (pestle) held at arm’s length through the opening of the vat (or using a mechanical pige), the winemaker breaks and immerses the cap. After the first fermentation, an extra postfermentary maceration may follow, also under temperature control, so that the wine’s tannins have a chance to build a complete structure.