100
According to McCusker, Jamaica, and, after 1763, Grenada, were the only "real exceptionss" to this rule because they "regularly chose to double-distill" their rum to a high alcohol content.
Understanding the concentration of alcohol in a spirit, however, is more complex than simply knowing the method of manufacture. In the British Caribbean, a proof spirit consisted of equal parts alcohol and water. Thus, a 100 gallon puncheon containing 50 gallons of absolute alcohol and 50 gallons of water was a proof [100 proof spirit, while a 100 gallon puncheon containing 65 gallons absolute alcohol and 35 gallons of water was said to be 130 proof. A single distillation produced a weak spirit called a low-wine. According to McCusker (1989:151-153), who cited the opinion of an anonymous mideighteenth century sugar planter (anonymous 1752:33), low-wine was a proof spirit of equal parts water and alcohol. Yet, this definition does not jibe with other eighteenth century sources, including Edwards' account, the primary source McCusker used to explicate Jamaican rum making. According to Edwards, two 1,200-gallon washes produced 600 gallons of low-wine. Of that, 70 gallons was returned to the low-wine butt for use in the following wash and the remaining 530 gallons of low-wine was re-distilled to produce 220 gallons of "proof' rum. Based on Edwards' observations, therefore, the 530 gallons of low-wine contained only about 21% alcohol making it a spirit of 42 proof. Even if, by the term "proof," Edwards was describing the higher concentrated 130 proof "Jamaican proof'" rum, which became standard in the nineteenth century, the low-wine would still only have contained about 27% alcohol and been a spirit of 54 proof. Thus, Jamaican low-wine was not a proof spirit and McCusker's definition needs some refinement.
Barbadian and Jamaican distillers adopted different methods of rum distilling. In 1765, Antiguan sugar planter Samuel Martin addressed the different techniques in