Jamaican master blender Joy Spence. Distillers that make lighter rums, such as Bacardi, prefer to use faster-working yeasts. The use of slower-working yeasts causes more esters to accumulate during fermentation, allowing for a fuller-tasting rum. Fermentation products like 2-ethyl-3-methyl butyric acid and esters like ethyl butyrate and ethyl hexanoate give rise to the sweetness and fruitiness of rum. Distillation As with all other aspects of rum production, no standard method is used for distillation. While some producers work in batches using pot stills, most rum production is done using column still distillation. Pot still output contains more congeners than the output from column stills, so produces fuller-tasting rums. Ageing and blending Many countries require rum to be aged for at least one year. This ageing is commonly performed in used bourbon casks, but may also be performed in other types of wooden casks or stainless-steel tanks. The ageing process determines the colour of the rum. When aged in oak casks, it becomes dark, whereas rum aged in stainless steel tanks remains virtually colourless. Due to the tropical climate, common to most rum-producing areas, rum matures at a much higher rate than is typical for whisky or brandy. An indication of this higher rate is the angels' share, or the amount of product lost to evaporation. While products aged in France or Scotland see about a 2% loss each year, tropical rum producers may see as much as 10%. After ageing, rum is normally blended to ensure a consistent flavour, the final step in the rum-making process. During blending, light rums may be filtered to remove any colour gained during ageing. For dark rums, caramel may be added for colour. There have been attempts to match the molecular composition of aged rum in significantly shorter time spans with artificial aging using heat and light. In cuisine Besides rum punches, cocktails such as the Cuba libre and daiquiri have stories of their invention in the Caribbean. Tiki culture in the U.S. helped expand rum's horizons with inventions such as the mai tai and zombie. Other cocktails containing rum include the piña colada, a drink made popular in America by Rupert Holmes' song "Escape", and the mojito. Cold-weather drinks made with rum include the rum toddy and hot buttered rum. A number of local specialties also use rum, including Bermuda's Dark 'n' Stormy (Gosling's Black Seal rum with ginger beer), the Painkiller from