reduction is the process by which the alcoholic content of a spirit is lowered to its bottling proof. When a distillate is fresh out of the still, it usually contains 70–96 percent alcohol. When barrel aged, depending on the climate, a spirit typically loses some of its alcohol through the wood, generally 1 percent per year. See angel’s share.
Ideally, the proof, or the percentage of alcohol at which a spirit is bottled and sold, is defined by the master blender, who chooses the perfect proof at which a spirit will show its best organoleptic characteristics, although often taxes, marketing, and tradition also figure into or even drive the choice.
Generally, a spirit is sold between 40 percent and 50 percent alcohol. To reach this point or to adjust it to the perfect proof, the master blender uses a method called “reduction” or “hydration,” a process by which a certain quantity of water is added to the spirit in order to lower its percentage of alcohol to the desired proof. Ideally, this is done incrementally in several stages—a process called “progressive reduction”—to avoid “shocking” the spirit.
Until the nineteenth century, producers used rainwater or distilled water for the reduction. Nowadays, most use water that has been purified through reverse osmosis.
As for ageing, time is the best friend of a good reduction. A very progressive reduction will result in a fully integrated spirit, an essential taste and mouthfeel characteristic referred to as le fondu by the cognac master blenders.
In the Cognac region, where reduction is practiced in its most developed, elaborate form, it is usually done in a minimum of three to four stages, starting at least six months before bottling and ideally years before. This being said, each house has its own reduction method, some of them fine-tuned for centuries. Some prefer to hold their spirit at full proof as long as possible, thus also saving much space and time in the process. Others prefer to start their progressive reduction early on. Also, the reduction can be applied to individual lots or the pre-blended ones known as “coupes.” See élevage. Some combine these two methods.
Old master blenders will explain that there is a rhythm to reduction, every three months or six months or every year. The first reductions can be more substantial (dropping the alcohol by as much as 10 percent at once) and more spaced in time. However, as bottling time approaches, the reduction steps must be done in smaller steps of no more than 3–4 percent alcohol reduction at a time. Otherwise it would “drown” the spirit, which would lose its most interesting organoleptic characteristics and be aggressive on the palate.
Often a reduction step is done right after a small chosen blending step assembling a few matching barrels in a bigger vat. It is also a time at which a master blender can decide to take a spirit from a drier to a more humid cellar or the other way around, depending on the desired style. Once “married,” the resulting spirit is re-dispatched in barrels for further maturation.
The resting time (temps de marriage) between two reductions is extremely important. If the time between two progressive reduction steps is not sufficient, it is said that the spirit smells like “fresh blend,” a feeling of unsettlement, aggressiveness, and wateriness.
Once the reduction is done, the master blender will often homogenize and oxygenize the spirit with a slow pump that is used as a closed circuit in the reduction vat.
The last step of the reduction occurs generally when the spirit is 2 percent alcohol above the desired bottling proof. This is when a slight filtration or chill filtration is done. Then the spirit is adjusted one last time to be at the final bottle proof.
An ancient reduction method in cognac called la méthode des petites eaux (literally “the small-waters method”) requires the master blender to mature pure water in used cognac barrels for several months, thus seasoning the water before using it for a progressive reduction. Indeed, with time, the used barrel will impart some of the cognac and tannic elements of the wood to the pure water, preparing it to be integrated into the spirit that will be diluted. This time—and space—consuming method is now only used by a handful of small producers worldwide.
Admittedly, the system used for cognac is reduction at its most elaborate. Elsewhere, some spirits producers will use parts of this system—many of the most carefully made whiskies, for instance, are reduced in stages—while other producers, and in particular the ones working with highly filtered or rectified spirits, have found it acceptable to dispense with the whole system.
By: Alexandre Gabriel