Cheat sheet on Cognac distillation
The great majority of grapes are harvested mechanically, then pressed and set to ferment. The resulting white wine, pretty weak, around 8-9% alc/vol, is then distilled twice. In the Cognac region, harvest usually begins the 3rd or 4th week of September. Some producers, such as Paul Giraud, Daniel Bouju, Remy Martin or Cartais-Lamaure, still practice harvesting by hand, at least in some of their vineyards.
For distillation, a traditional copper still pot is used. The typically charantaise feature is the s.c. gooseneck. Today, very few stills are still heated with wood (as in Property Guy Gombert). Nowadays, in most cases the distillers use gas. The beginning of Distillation varies, but must by law terminate at midnight on March 31. The distillaton itself is based on the water’s boiling point being higher than that of alcohol.
It takes place in two stages, (hence the term double distillation); in the first, a raw eaux-de-vie known as brouillis is produced. The second, known as bonne chauffe produces a much higher alcohol content and only the middle part of the distilled liquor is saved, poetically called “heart” (the coeur) while the first part (heads) and the last (tails) are either discarded or re-processed.
The clear liquid, eaux-de-vie, which is the end product, the coeur, of distillation, is stored in oak casks. These are largely made with oak from Limousin or Tronçais.
Oak is characterized by its porosity and the high content of tannin, which makes it an ideal wood to begin the next step towards the creation of cognac. The interaction between air, water spirits and tannins is one of the true secrets of cognac.
During the process, each year about 3% of the stock evaporates, what is called "the Angels' share" which inevitably makes the final product more expensive.
Each manufacturer has its own approach for the next steps in the development of cognac. How to mix, maturing, bottling and the final presentation are all part of the characteristic signature of each producer.