If you bought a cognac bottle with marking of XO on the label, consider that you were lucky. Exclusively matured, old noble drink is so marked.
Extra Old
The age of cognac can be recognized by special alphabetic reference on the label. The time frames specified in special classification mean that cognac spirits were sustained in special oak casks during this term. According to the legislation, the minimum age of cognac which can go on retail is two years.
Marking of XO is deciphered by Extra Old, that is "very old" or "extra-old". The alcohols kept in oak casks are a part of cognacs with this marking it isn't less than six years. In some cases (it depends on the specific producer) the endurance of cognac spirits could occur significantly longer.
Sometimes instead of marking of XO on the label of the drink matured for six years and more Napoleon can be written. It depends on the producer too, but in fact there is no difference between the inscriptions XO and Napoleon. It is necessary to understand that marking of Napoleon demonstrates long endurance, but isn't a drink grade. Officially cognacs which were matured more than six years have no classification as it is considered that processes of blending on such terms can't be controlled.
How the taste of cognac is formed?
In the first years of keeping of alcohol in oak casks of its property change as there is an active extraction of tannins, pitches, oils and flying acids from oak wood. Cognac spirits get characteristic golden coloring and are sated with vanilla and wood aromas. In the next years the cognac spirit darkens, is significantly softened and gets additional shades of tastes. The humidity of a cognac cellar influences formation of future cognac. In cellars with low humidity cognac becomes strukturny and to the land, in damp cellars it is even more softened. In the course of long endurance an essential part of alcohol through the porous surface of wood evaporates. Similar "losses" are the excellent environment for reproduction of the special microscopic mushrooms covering cognac cellars with a dense layer. These mushrooms give to walls and ceilings characteristic dark color. Cognac is usually received by means of mixing of cognac spirits of different endurance. In such cases the final aging of cognac is considered on the minimum term of endurance of its components. Thanks to mixing of cognac spirits in mass production of cognacs identical properties of drinks regardless of gustatory qualities of grapes from a harvest of concrete year are maintained.