of the tank and spraying it over the floating cap; normally this would be done several times per day during fermentation) punching down the cap (either manually or using an automated mechanical system) submerging the cap (the cap is kept beneath the surface of the liquid phase by a physical restraint) drain and return (the above techniques can all be supplemented by a drain and return operation, in which the liquid phase is drained off the skins into another vessel and then pumped back over the skins) Temperature control Fermentation produces heat and if left uncontrolled the temperature of the fermenting may exceed 40°C (104°F), which can impair flavour and even kill the yeast. The temperature is therefore often controlled using different refrigeration systems. Winemakers have different opinions about the ideal temperature for fermentation, but in general cooler temperatures (25-28°C; 77–82.4°F) produce fruitier red wines for early drinking while higher temperatures (28-35°C; 82.4-95°F) produce more tannic wines designed for long aging. Following the fermentation Winemakers will usually check the density and temperature of the fermenting must once or twice per day. The density is proportional to the sugar content and will be expected to fall each day as the sugar is converted into alcohol by fermentation. Pressing Pressing in winemaking is the process where juice is extracted from grapes. This can be done with the aid of a wine press, by hand, or even by the weight of the grape berries and clusters themselves. Historically, intact grape clusters were trodden by feet but in most wineries today the grapes are sent through a crusher/destemmer which removes the individual grape berries from the stems and breaks the skins, releasing some juice, prior to being pressed. There are exceptions, such as the case of sparkling wine production in regions such as Champagne where grapes are traditionally whole-cluster pressed with stems included to produce a lighter must that is low in phenolics. In white wine production, pressing usually takes place immediately after crushing and before primary fermentation. In red wine production, the grapes are also crushed but pressing usually does not take place till after or near the end of fermentation with the time of skin contact between the juice and grapes leaching color, tannins and other phenolics from the skin. Approximately 60-70% of the available juice within the grape berry, the free-run juice, can be released by the crushing process and does