First, a large part of water and solids is removed from the base, obtaining so-called "low wine", a concentrated wine with 28–30% ABV. In the second stage, low wine is distilled into brandy. The liquid exits the pot still in three phases, referred to as the "heads", "heart", and "tails", respectively. The first part, the "head," has an alcohol concentration of about 83% (166 US proof) and an unpleasant odour. The weak portion on the end, the "tail", is discarded along with the head, and they are generally mixed with another batch of low wine, thereby entering the distillation cycle again. The middle heart fraction, the richest in aromas and flavours, is preserved for later maturation. Distillation does not simply enhance the alcohol content of wine. The heat under which the product is distilled and the material of the still (usually copper) cause chemical reactions during distillation. This leads to the formation of numerous new volatile aroma components, changes in relative amounts of aroma components in the wine, and the hydrolysis of components such as esters. Brandy is usually produced in pot stills (batch distillation), but the column still can also be used for continuous distillation. The distillate obtained in this manner has a higher alcohol concentration (approximately 90% ABV) and is less aromatic. The choice of the apparatus depends on the style of brandy produced. Cognac and South African brandy are examples of brandy produced in batches while many American brandies use fractional distillation in column stills. Aging After distillation, the unaged brandy is placed into oak barrels to mature. Usually, brandies with a natural golden or brown colour are aged in oak casks (single-barrel ageing). Some brandies, particularly those from Spain, are aged using the solera system, where the producer changes the barrel each year. After a period of ageing, which depends on the style, class and legal requirements, the mature brandy is mixed with distilled water to reduce alcohol concentration and bottled. Some brandies have caramel colour and sugar added to simulate the appearance of barrel ageing. Consumption Serving Brandy is traditionally served at room temperature (neat) from a snifter, a wine glass or a tulip glass. When drunk at room temperature, it is often slightly warmed by holding the glass cupped in the palm or by gentle heating. Excessive heating of brandy may cause the alcohol vapour to become too strong, causing its aroma to become