charcoal filtration

charcoal filtration is a method of removing substances from a liquid by exposing it to charcoal, a porous black material comprised of carbon and ash that is obtained by the controlled slow burning of wood or other organic matter in a low-oxygen environment. As liquid flows into the charcoal, certain molecules bond with and are trapped by the carbon at the surface through a process known as adsorption. Because it works primarily through chemical attraction, charcoal filtration is effective at removing some substances but not others, depending on their molecular properties. Once all the available surface binding sites have been used up, the charcoal medium is no longer effective at filtration and must be replaced.

In the production of spirits, charcoal filtration may be used prior to distillation to purify water. It may also be used after distillation of unaged spirits such as vodka, prior to barrel aging as in the Lincoln County process used to make some Tennessee whiskies, or after aging in order to produce a lighter flavor and remove color from spirits such as white rum. The effect of charcoal filtration can be different depending upon the source material and the form and purity of the charcoal (e.g., the birch charcoal traditionally favored by Russian vodka distillers, or the maple charcoal used by Jack Daniel’s Tennessee whisky), as well as the chemical properties of the liquid undergoing treatment and the filtration procedure itself. Even aging in charred-wood barrels may be understood as including an element of charcoal filtration, as the spirit interacts with the carbonized material created by the charring process.

Pokhlebkin, William. A History of Vodka. Translated by Renfrey Clarke. London: Verso, 1991.

By: Samuel Lloyd Kinsey