In modern times, most distillers purchase molasses rather than make it themselves. Yeast and water are added to the molasses to create a “wash,” which is then allowed to ferment. Some distillers use wild yeasts, but others use specific cultivated strains. We’ll look a little later at the role yeast plays in the flavor and character of finished rum.
Fermentation, of course, is the process by which yeasts convert sugars into alcohol. In modern spirits production, this process generally takes place in large metal tanks and is carefully monitored. Fermentation lasts from twenty-four hours to several weeks, depending on the type of rum being produced. We’ll look more at these variables a little later.
Depending on the type of rum being produced, distillation can proceed using either a pot still or a column still. Pot stills are more traditional and less efficient—more expensive—than column stills. Generally, heavier rums are produced in pot stills and lighter rums in column stills, although some rums are a blend of pot and column.
