The oak barrel: Critical for Cognac ageing
Maturing is very important for a good Cognac, the slow ageing in oak casks. The used wood for those barrels is selected because of its ability to transfer certain aromas to the spirit. The contact between oak and eaux-de-vie not only gives the Cognac the nice colour but also the bouquet and certain notes. electing the wood
There are several oak producing regions around the world, that are used for barrel production. The French are Argonne, Vosges, Nevers, Tronçais, Allier, Bourgogne, Armagnac (Landes) and Limousin.
Cognac only ages in oak casks made from wood from the Tronçais and more often from the Limousin forests. Two varieties of oak were selected because of their special characteristics: Quersus pedunculata and Quersus sessiliflora. Those wood varieties are hard but at the same time fexible.
The Tronçais forest is situated in Allier and provides slightly softer and grained wood. The wood from the Limousin forest is medium grained, a bit harder and even more porous than the Tronçais. The tannins in Tronçais oak are popular because of their softness – the Limousin oak is more about being strong but balanced. Apparently a Cognac will extract more tanins in a Limousin oak barrel. It’s the most expensive wood for barrels in the world. What’s more, Limousin oak is known for the rich vanilla-like flavor it imparts to eau-de-vie.
Coopers pass on their highly technical procedures, from one generation to another – Coopers still combine their craft and skills ancestral tools. The Seguin Moreau cooperage in Cognac has a very good reputation in being extremely good at Limousin oak. It’s a cooperage which was founded at the house of Rémy in 1971, only for the purpose of providing barrels made of Limousin oak.
Cask making allows absolutely no improvisation. The merrains or boards, which are used to produce the cask are culled between the heartwood and sapwood of oak trees. These oak trees are over hundred years old. These must be split to respect the wood’s grain, afterwards stacked in the open air for about three years (one to three years). This way they lose their bitter flavours.
It is critical for the Cognac production to select the right wood, age and dry it to perfection before starting to make the barrels. After this long period, the boards are shaped into curved staves and the coopers can actually start now with their work. The next barrel making step is toasting.
Toasting the casks
A cooper hoops the staves around a fire, that is made with wood shavings and oak pieces. The wood must be heated to bend the staves into shape.
The amount of toast and the depth of toasting experienced within the stave depends on the heat of the flame, how long it was applied and the moisture content of the stave. While the wood is heated, a wire is placed around the base of the cask – so it can be tightened to bring the staves closer together.
Finally they are joined – without any nails or similar techniques.
The cask must pass several solidity, heat and water tests to detect leaks.
Once the eaux-de-vie is about to be aged in a barrel, oxidation and evaporation plays an important role. In Cognac the evaporation is called the Angels’ share. Evaporation occurs between 1 to 2,5% yearly, it depends on the chai which can be a cellar or storage house.
An example: An evaporation rate of 2.5% over 50 years. A 350 litre barrel of cognac. The barrel will be reduced to 100 litres of 40% of alcohol.
Extraction of wood characteristics from the Limousin oak and concentration of flavours is wanted of course. Newer casks give much more in terms of tannins. This is why, new barrels often are used for newly distilled eaux-de-vie, so the tannins can age and soften. Often Cognac masters blend different barrels in order to create a certain, own style. Some use new barrels to give the cognac a darker and woody flavour.