rectification is the process of removing congeners from a spirit by redistillation, filtration, or precipitation or of masking their flavor with other compounds. See congeners. Some rectification is integral to the process of making most spirits: in the double distillation that is used for so many pot-stilled spirits, the second distillation can be viewed as process of rectification, and it is worth noting that of the two columns that made up Aeneas Coffey’s revolutionary continuous still, the second was identified as the “rectifier.” See Coffey, Aeneas; distillation, process; and still, continuous. But rectification also has a tradition outside the primary distillery, with independent rectifiers reworking spirits to meet market needs as they perceive them. As the English rectifier William Betts testified before a parliamentary commission in 1848, “The grain distiller manufactures the spirit, and the rectifier purchases it from him, to render it fit for the public.”
We shall return to that “fit for the public,” but let us first examine the various means of rectification. The first is straight redistillation, where the rectifier takes a fairly low-proof spirit, full of impurities, and distills it again, making it purer, stronger, and—for better or worse—less flavorful. Sometimes that redistillation includes adding botanicals, as in the manufacture of gin, aquavit, or anise spirits. See anise spirits; aquavit; botanical; and gin. Here the redistillation both removes flavors from the original distillation and adds new ones from the botanicals.
Filtration, usually with charcoal, also removes impurities (and in particular oils) and can be used on its own or combined with redistillation for a very pure product—indeed, they give us modern vodka, which represents the commercial triumph of rectified spirit. See charcoal filtration; filtration; and vodka. There are also chemical means of rectification, including passing the spirit through petroleum byproducts, which will absorb many of the impurities and are easily separable from the spirit, or using various chemicals to imitate the flavor of some other spirit. Some of these chemical methods of rectification were rather frightening, which brings us to that rendering of the spirit “fit for the public.”
Rectification was a particularly large and important part of the spirits market in Britain, which from the 1730s used the excise laws to keep original distillers and rectifiers strictly separate (as William Betts detailed). Those who fermented and distilled grain were not allowed to also retail it, while rectifiers were allowed to buy and sell spirits but not distill them from scratch. See excise, taxes, and distillation. At best, this system yielded high-quality gins such as those sold by Philip Booth & Sons or Benjamin Hodges & Son. See Old Tom gin. But it also yielded other “compound spirits,” including things such as “British brandy,” which was the same Scottish or English grain spirit that was rectified into gin but artificially flavored and colored to present some resemblance to French brandy. This was used to meet the market needs of those who could not afford real brandy from the early eighteenth century until the early twentieth. Britain was not alone in making such things: in the United States, there was “Duffy’s Pure Malt” whisky, which was merely rectified American grain spirit, neither pure nor made from malt.
Legislation such as the American Pure Food and Drug Act of 1906 put an end to the worst of these products, but flavored neutral spirits are still with us. We no longer hear much about petroleum-byproduct rectification and the like, but neither are those processes necessary: using modern, multiple-column fractional distillation and charcoal filtration, it is possible to make a spirit that has virtually no congeners—that is perfectly rectified, being merely ethanol and water, and precious little of the latter. See azeotrope.
See also distillation, history, and spirits trade, history of.
Royal Commission on Whiskey and Other Potable Spirits. Interim Report. London: HM Stationery Office, 1908.
Select Committee on Sugar and Coffee Planting. Sixth Report. London, HM Stationery Office, 1848.
By: David Wondrich