The Lincoln County Process is a traditional element of producing Tennessee whiskey, and refers to filtering freshly distilled spirit through columns of charcoal, prior to aging the spirit in oak barrels. Charcoal acts as a natural filter, with the ability to absorb certain compounds from the spirit, which modifies the spirit character. This in turn has a significant influence on the flavour profile of the mature whiskey. Consequently, the Lincoln County Process is a key stage that differentiates Tennessee whiskies such as Jack Daniel’s and George Dickel from other American whiskies, including bourbon, that don’t use this process.
The first step is selecting hard sugar maple trees to produce charcoal. Being indigenous to the region, and available in plentiful supply, explains why this has always been the traditional choice, and consequently the only type of wood which has been used.
Sugar maple trees are a type of hardwood, as opposed to softwood. This is a primary way of dividing trees, the real difference is structural, as hardwood is porous whereas softwood isn’t, with the further significance being that hardwood burns at a higher temperature which makes it more suitable for producing charcoal.
Felled trees are sawn into sticks which are allowed to air-dry for several months. This is a much slower process than kiln drying wood, which wouldn’t produce the same result.
“Air-drying is best for charcoal production as the wood burns cleaner and hotter, which gives a better conversion rate of wood into charcoal,” says John Lunn, George Dickel’s master distiller.
Once air-dried, the sticks are stacked in ricks and ignited in the open, with experienced staff members waiting for the appropriate time to begin extinguishing the flames (otherwise, the result would be ashes, not charcoal).
“The fire takes about four hours before we start hosing, and the exact time you start adding water is crucial. We’re looking for maximum conversion of wood to charcoal, so you don’t want any of the original wood exposed in the charcoal, but you don’t want to burn it down to dust either. It takes two people about one hour of hosing to extinguish the flames,” adds Lunn.
Once the fire has been extinguished and the charcoal cooled, it can be broken down.
“We grind the charcoal by putting it through rollers, with the spacing between the rollers set at between a quarter of an inch and half an inch, to produce chips of charcoal, rather than square or round pieces. The size of the charcoal pieces influences the filtration process. If the charcoal pieces are too large and dense the spirit finds it harder to work its way through, whereas a smaller size provides an optimum surface area of charcoal to interact with the spirit,” says Jeff Arnett, Jack Daniel’s master distiller.
The charcoal is placed in large vessels referred to as ‘mellowing vats’ or ‘mellowing tanks.’ Pipes that conduct the freshly distilled spirit are positioned above the vats. The spirit then drips slowly from these pipes, and ‘spreads’ evenly across the entire surface of the charcoal filter. The aim is to keep the tanks saturated with alcohol all the time, otherwise the whisky would form little channels through the charcoal, and it could trickle through without actually being filtered.
Filtration is a time consuming process: it takes several days for the spirit to work through 10 feet of charcoal. But when the spirit emerges from the filter the difference is significant.
“When distilling Tennessee whisky you get a grainy character that comes mainly from the corn. Our mash bill has a high corn content, while also including rye and malted barley. Graininess is really prominent in the spirit, and it’s almost completely removed by filtration,” says John Lunn.
Filtered spirit is analysed for consistency, which also confirms the filter is doing its job. A charcoal filter needs to be changed periodically. Exactly when that happens depends on the quantity of spirit that passes through it.
“We have about 50 tasters who sample batches of spirit before and after filtration to ensure the grainyness has gone.
“As filtering removes a lot of grain character, we get even more of the barrel character showing in the mature whiskey, which means the vanilla notes for example are more pronounced, and the taste is much sweeter,” says Jeff Arnett.
Meanwhile, other distillers voice alternative opinions.
“Historically not every whiskey distiller in Tennessee used the Lincoln County Process.
“It’s not compulsory, and we have opted not to use it because our whisky has a bolder flavour without it, which we prefer,” says Phil Prichard, master distiller and president of Prichard’s Distillery, which launched a Tennessee whiskey in 2010.
The Lincoln County Process was originally developed and practiced in Lincoln County, within the State of Tennessee. But exactly when, and how it started is uncertain, as various distilleries in Tennessee used this process from the early 19th century. Meanwhile, there was a precedent for this approach, as the tradition of filtering vodka through charcoal in Russia dates from the 18th century.
An additional point to make is that neither Jack Daniel’s nor George Dickel are located in Lincoln County. George Dickel is in Coffee County, while Jack Daniel’s is in Moore County, although this distillery did experience a certain ‘relocation’ during the 19th century.
When the distillery was established by Jack Daniel in the 1860s it was in Lincoln County. However, the county boundaries were redrawn in Tennessee during the 1870s, which also resulted in new counties being established and new county court houses built. This was done so that the inhabitants of any county were no more than one day’s horse ride from a courthouse, where all business and legal matters were conducted,” explains Jeff Arnett.