The boiling and curing house
Contemporary engraving of interior of boiling house with sugar pots. From Diderot's Encyclopédie, 1762, Reference affinerie_des_sucres, as shown on www.slaveryimages.org, sponsored by the Virginia Foundation for the Humanities and the University of Virginia Library. Courtesy of authors Jerome S Handler and Michael L Tuite Jr.
From the mill the raw cane juice was channelled to the boiling house, where it flowed into clarifiers - large metal pans. Here lime and ashes were added to the juice and it was heated to remove impurities. The juice was then ladled into the first of a series of five or more large metal basins called 'coppers' (although in fact usually made of iron), which were heated to drive off the moisture. The juice was heated and moved successively down the line of coppers, progressively reducing and thickening.
Row of sugar boiling coppers at New River plantation, Nevis
In the last of the train of coppers, when the syrupy sugar was close to crystallising, it was poured off into hogsheads (large wooden barrels) or conical clay moulds set over pots, in a dry building called the curing house. Water was poured in the top of the mould and for at least a month, the syrupy molasses drained slowly through into the vessel below leaving behind golden-brown muscovado sugar.
A pottery sugar mould and syrup jar (right), and the finished cone of refined sugar
The hogsheads of muscovado were then usually shipped to Europe for further refining. Larger plantations also had a distillery for making rum which was distilled from molasses. Rum and molasses were shipped in small quantities from the West Indies to New England by 1650. By 1670 these by-products became commercially lucrative(Bridenbaugh and Bridenbaugh 1972, 296) and larger plantations had a distillery expressly for making rum which was distilled from molasses. The cost of building a distillery was comparable to that of constructing a boiling or curing house so only the larger plantations had them.
Making sugar was a highly specialised process. It was critical to know the precise moment when the sugar was ready to set. The boiler, a highly skilled slave, would test the sugar with his elbow or by rubbing the hot sticky syrup between the fingers. His was one of the most important jobs on the plantation and a skilled boiler was a valuable slave. After the French raid of 1706 Ann Hackett, a plantation owner in St Kitts, made an insurance claim for the large sum of £60 for the loss of her slave called Jack, "a good boyler and clayer of sugar".