Rum is distilled in the manner described in the introductory chapter of this book. The choice of stills does, however, have a profound effect on the final character of Rum. All Rums come out of the still as clear, colorless spirits. Barrel aging and the use of added caramel determine their final color. Since caramel is burnt sugar, it can be truthfully said that only natural coloring agents are used.

Lighter Rums are highly rectified (purified and blended) and are produced in column or continuous stills, after which they are usually charcoal-filtered and sometimes aged in old oak casks for a few months to add a degree of smoothness. Most light Rums have minimal flavors and aroma, and are very similar to Vodka, particularly those brands that have been charcoal-filtered. Heavier Rums are usually distilled in pot stills; similar to those used to produce Cognacs and Scotch whiskies. Pot stills are less “efficient” than column stills and some congeners (fusel oils and other flavor elements) are carried over with the alcohol. Some brands of Rum are made by blending pot and column distilled Rums in a manner similar to Armagnac production.

source: tastings.com