Charcoal mellowing refers to a process used to make Jack Daniel's Tennessee Whiskey. Charcoal Mellowing is what makes Jack Daniel's a smooth sippin' Tennessee Whiskey instead of a bourbon. The process involves slowly dripping the newly made whiskey through giant containers hard-packed with 10 feet of sugar maple charcoal. The process takes ten days, and during this time the Jack Daniels Tennessee Whiskey absorbs the essence of the charcoal, refining the spirit and giving it a unique flavor and aroma.
Sour Mash is not the designation of a special type of whiskey, as most people think. Instead, the name refers to the similarities between making whiskey and making sourdough bread. In both processes, a portion of the previous batch is used to start the next batch in order to promote consistency. Every bourbon and Tennessee whiskey is made using the sour mash process. As the whiskey ages, the whiskey barrels breathe. Because of this phenomenon, somewhere between eight to ten percent of the alcohol volume will be lost to evaporation in the first year. Evaporation continues over subsequent years at a rate of four to five percent per barrel. A good whiskey is likely to lose approximately thirty percent of its original volume by the time it is ready for bottling.
Whiskey barrels are assembled from American White Oak, a wood which carries the right combination of compounds to create the tastiest whiskey. These compounds are exposed when the insides of the barrels are charred by open flame. As the whiskey ages inside the barrel, the wood contracts and expands with changes in the surrounding climate. The whiskey is allowed to move in and out of the wood as this happens, and the exposed compounds mix with the whiskey. The mixing gives the whiskey a smoky flavor and an amber tint.