Cask & Climate

How long does white overproof age? A white rum is usually bottled young. That doesn't mean every white rum is unaged, though: it may have spent time in cask and then been decolourised with activated charcoal. Colour says nothing about age.

Under the rules of the geographical indication, cask ageing must take place in Jamaica, and the oak casks must hold no more than 250 litres. After distillation, only water and caramel colouring may be added. No sweetening is permitted.

If you see an age statement on the bottle, it helps to know what it means under EU law. An age statement must refer to the youngest component in the blend, and ageing must have taken place under the tax supervision of a member state or an equivalent authority.

Caramel colouring, additive E 150a, is permitted to adjust colour. In Germany, drinks without an ingredients list must carry the notice 'contains colouring.' A dark rum, then, can be both young and coloured.

In tropical warehouses, evaporation runs many times higher than what's lost in Scotland, often around eight percent a year. The rule of thumb that one tropical year counts as three European years is often cited. Chemically, it's not an exact match, since evaporation, wood, and oxygen interact in different ways.

For the Royal Navy, maturity was a secondary concern. What mattered was that the rum stayed stable on board and could be poured at a consistent strength, right up to Black Tot Day on 31 July 1970. The diluted grog, moreover, was drunk immediately, not stored.