Classic vinification of red bordeaux involves time and, because of the size of most top estates, considerable space in which to house the wine as it slowly makes itself (see red winemaking). The process begins in the vat hall or cuvier, then moves to a first-year chai in which a year’s production is stored in barrel, continues in the second-year chai, and increasingly necessitates an area for bottle storage.
Grapes are almost invariably destemmed before crushing, and fermented in large fermentation vessels, known as cuves in Bordeaux, which may be made of cement, stainless steel, or even wood, for between five and ten or more days. Some form of temperature control was installed at most properties in the 1970s or early 1980s, but is needed for only the hotter vintages; indeed it is increasingly common practice to heat the cuves at the beginning of fermentation. Fermentation temperatures are generally slightly higher in Bordeaux than in the new world, with 30 °C/86 °F being a common maximum during fermentation. The concentration of phenolics in ripe Bordeaux Cabernet Sauvignon grapes is such that the precise techniques of extraction are an extremely important aspect of vinification. Much modern research is concentrated on the relative merits of various pumping over regimes, usually several times a day. The post-fermentation maceration is therefore seen as crucial by most winemakers, who allow the newly made wine at least a week and sometimes much longer ‘on the skins’.