When is a bourbon not a bourbon?When it’s a Tennessee whiskey.And depending who you’re talking to and where you’re doing the talking, the likes of Jack Daniel and George Dickel are either barred from the bourbon club because they’ve messed with the rules, or they have added a quality process that makes their spirit better than that produced by the boys up in Kentucky.The key difference between the two is a process known as the Lincoln County Process which Tennessee law insists on and is frowned upon in Louisville.Known also as charcoal mellowing or leaching, the Lincoln County Process has been used in the State of Tennessee for generations, and its exact origins are not totally clear, though it is often attributed to Alfred Eaton, a distiller operating in the region in the early 1800s.It’s the process of passing the new make spirit – known as white dog in America – through three metres of hardwood charcoal before it can be filled in the barrel. It’s a process that requires great care. Quality wood, often from the maple tree, is used to ensure the best mellowing and a great deal of effort is put in to burning the wood just so to produce the right level of charcoal.This process is not used when making bourbon, though you will find bourbon bottles with the words ‘charcoal filtered’ on them. In these cases the whiskey is filtered through charcoal after it has matured in the barrel, removing impurities and debris from the finished whiskey. In the Lincoln County Process the charcoal process is carried out before the whisky goes to cask, and it impacts directly on the flavour.Its purpose is to ensure a smoothness in the whiskey that its supporters say is not replicated anywhere else.GLOSSARY KKieve An old Irish name for the mash tun Kilning After the barley has been tricked in to growing by soaking the grain in water, the process has to be halted. This is done through heating in a process known as kilning. Kilns can be directly or indirectly fired and a range of different fuels can and are used. These include peat, which can be used for direct firing, imparting to the barley the smoky flavour that can influence the final spirit.L Leaching American term for the charcoal mellowing process in the production of some American whiskey – see main feature Liquor Name for the hot water in the mashing process Low wines After the first distillation has taken place in the wash still the liquid produced is known as low wines. It has an alcoholic strength of about 23% ABV and is mixed with the rejected spirit from the last second distillation before it goes forward to the spirit still.Lyne arm At the top of a pot still is an armthat connects the still to the condenser and through which evaporated spirit must pass. This is known as the lyne arm and its size, position and the angle it is connected at will all affect the amount of spirit that can pass through it and therefore the taste of the recondensed spirit.