What is a pot still rum?

A pot still is a closed kettle, usually made of copper, which is filled with wash each time, heated and then emptied again.

The vapour rises, passes through the neck to the condenser and becomes liquid again there. What comes out changes from the start to the end of the run, so the distiller makes the cuts at the right time: first the head, then the heart, then the tail. Only the heart goes into the cask. Afterwards the still is emptied, cleaned and refilled, and the same series of choices begins again.

A pot still has only one charge per run, whereas a column is fed at the top and keeps running off at the bottom as long as mash goes in.

In a pot still the composition of the vapour shifts during the run, so the separation happens over time and depends on the cut points the distiller chooses. In a column the separation is fixed in place: the lightest substances at the top, the heart in the middle, the heaviest at the bottom. With the same settings a column therefore delivers the same distillate day after day, whereas two runs in the same pot still never turn out exactly alike.

A pot still lets more congeners through than a tall column, so the distillate turns out heavier in aroma and flavour.

Congeners are all substances other than water and ethanol: esters, higher alcohols, aldehydes and acids. The more a distillate is purified, the less of them remains. The review article in Fermentation from 2021 gives a range of 60 to 94% vol for the heart, depending on the type of still, and reports that distilling in a pot still raises the furfural content, among other things. A pot still ends up lower in that range than a tall column and therefore retains more. What an individual bottle ultimately delivers then still depends on fermentation, maturation and blending.

Pot still rum is mainly associated with Jamaica, Barbados, Guyana and Trinidad and Tobago, where the heavier English-speaking style comes from.

The overview article in Fermentation from 2021 places the pot still with the heavier, more strongly perfumed rums from the English-speaking Caribbean and the column still with the lighter rums from the former Spanish colonies. Many distilleries have both and blend the result. The country on the bottle therefore does not automatically say which type of still is behind it: it is a custom that grew out of the history of an island, not a rule.

EU Regulation 2019/787 sets no requirement on the still type for rum and only regulates the raw material, the distillation strength and the strength in the bottle.

Annex I, category 1 requires that rum comes from molasses or syrup from cane sugar manufacture or from cane juice itself, that it is distilled below 96% vol so that the character of rum remains noticeable, and that the bottle contains at least 37.5% vol at bottling. Adding alcohol is not allowed, flavoring is not allowed, caramel is only allowed for color and sweetening is limited to 20 grams per liter. Nothing is said about copper, stills or columns. In the United States it is regulated in the same way: 27 CFR 5,147 specifies less than 95% vol when distilling and at least 40% vol at bottling, without a word about the equipment.

On the label, look for the words pot still or pot stilled, because there is no legally protected designation for the type of still.

Nobody is obliged to state it, so the absence of those words proves nothing. If nothing is said about it, you get further with the distillery: a house that only has pot stills can deliver nothing but pot still distillate, and a house with both often states itself whether the bottle comes from one run or from a blend. Also look at the strength, because a bottling at 37.5 or 40% vol has been diluted more with water than a bottling at cask strength. If you are in doubt, ask in the shop; we look it up at the distillery rather than guess.