A type of distillation process in which the liquids to be separated are placed in a still. During operation, there is no further addition of liquid for separation. Scotch whisky is distilled by this technique. Initially, alcohol-rich vapour known as foreshots is produced and collected before the heart is collected. Feints, which are lean in alcohol, are finally recovered. Both the foreshots and feints are returned to the distillation process for the next batch. The process operates at unsteady state and can be described by the Rayleigh equation.