rectifier (device) is a general name given to any device that works to purify a spirit during or after distillation. Some rectifiers rely on reflux and are thus built into the distillation process. Of the two columns that constitute the Coffey still, the ancestor of most modern continuous or column stills, one is the “analyzer,” where the wash drips down over perforated plates as steam rises through them and strips off the alcohol. The other column is the “rectifier,” where that alcohol-rich vapor rises over a descending serpentine pipe carrying the cold wash to the analyzer; in the process, the vapor is cooled to the point that the heavier compounds condense and drop out. See Coffey, Aeneas; reflux; and still, continuous.
Other rectifiers use chemical means to purify the spirit; these are generally deployed post-distillation. The oldest, most reliable, and by far the safest of these filter the spirit through a layer of charcoal, which will remove some of the heavier, oilier congeners and render a lighter, cleaner spirit. Charcoal rectifiers go back at least to the beginning of the nineteenth century. In 1809, Samuel McHarry, a Pennsylvania distiller, described a simple rectifier made from a wooden barrel with a perforated false bottom inside that was covered with two inches (5 cm) of “ground maple charcoal and burnt brick dust, made to the consistence of mortar with whisky.” The rectified spirit would be drawn off at the bottom. By the end of the century, numerous variations of this simple device had been patented, and charcoal rectification was a common part of distilling, particularly for Russian vodka and some types of American whisky and Caribbean rum. Of the twenty-eight anonymous whiskies analyzed in the landmark 1908 study of whisky production and maturation by Charles Crampton and Lucius Tolman of the United States Bureau of Internal Revenue, all three of the corn whiskies and one of the fourteen ryes were run through in charcoal “leach tubs”—rectifiers—after distillation. One of those corn whiskies was most likely from Jack Daniel’s, which called its product a corn whisky at the time. The distillery still rectifies its new-make spirit before barreling it. See Jack Daniel’s.
For most modern spirit rectification, gravity rectifiers have been replaced by pressure filters, but the bulk of these are still filled with “activated carbon” (basically, charcoal).
See also vodka.
Crampton, C. A., and L. M. Tolman. “A Study of the Changes Taking Place in Whiskey Stored in Wood.” Journal of the American Chemical Society 30 (January 1908): 98–136.
McHarry, Samuel. The Practical Distiller, Harrisburg, PA: 1809.
By: David Wondrich