percolation , or the filtering of liquid or vapor through a porous object, is one of the essentially five means to flavor a spirit that distillers have at their disposal, along with compounding, maceration, infusion, and distillation. Perhaps most associated with a classic campfire coffee brew or traditional Italian “macchina” for stovetop espresso, the concept of percolation is quite simple: the liquid is heated and either bubbles directly through the substance intended to flavor it or its vapor does. It is most commonly featured in gin production, where botanicals are suspended in a basket or other perforated container (rather than in direct contact with neutral spirit) so that as alcoholic vapors rise in the still, they pass through the botanicals, extracting their essential oils and absorbing flavors and aromatic characteristics as they go. See gin.
Of note is the type of still employed for percolation: the Carter-head still, where the botanicals are put in a basket contained in an extra chamber that is interposed between the head of a pot still or a rectifying column and its condenser. This was invented in the mid-nineteenth century by a pair of brothers who worked for none other than Aeneas Coffey, inventor of the Coffey still. See Coffey, Aeneas. The Carter brothers’ invention was one of many fanciful developments of the era that fell out of favor by the middle of the twentieth century, until it was revived to make Bombay Sapphire gin in the 1980s.
The technique of percolation results in more delicate flavors and aromas than one gets from adding the botanicals to the still itself. Relatively few gin brands feature percolation or vapor infusion techniques on their own. Rather, is it often utilized in combination with traditional pot still or “one-shot” distillation, the most notable proponent of this style being Hendrick’s gin. See Hendrick’s Gin. Some vodka distillers also use Carter-head stills for percolating their distillate through charcoal. See charcoal filtration.
See also compounding; distillation; infusion; and maceration.
By: Allen Katz