Cognac is made with only three grape varieties, the Colombard, Folle blanche and Ugni blanc but up to 95% of cognacs use only the Ugni blanc.
The grapes are harvested in the early autumn and pressed using mechanical presses; the grape juice is then fermented. Some distillers will use cultured yeasts but most will use the wild yeast ‘blooms’ on the grapes to ferment the juice. The fermentation will usually take around 24 hours. The wine is not allowed to be preserved with sulphur dioxide and so must be distilled almost immediately to stop the wine fermenting a second time (like champagne) also no sugar is allowed to be added.
Distillation takes place in the pot still known as a Charentais and the spirit is always distilled twice, By French law all Cognac must be distilled by the 31st March of the following year.
The still stills have not changed a great deal in the last two hundred years; they are made from copper and have an onion like shape. The process of distillation is shown in the diagram.
The first distillation produces the ‘brouillis’, a distillate of around 30% which is then re-distilled in a smaller cognac still to a strength of around 70%. The second distillation is monitored by the master distiller who will ‘cut’ the cognac so only the heart is removed and then aged. The heads and tails are re-distilled. It will take up to 11 litres of wine to produce 1 litre of un-aged cognac (eaux de vie).
When the second distillation is complete, the spirit is then siphoned into oak casks where it is left to mature. The oak comes from the forests of Limousin and Troncais, with the majority coming from Limousin as it has a coarser grain and therefore releases less tannin into the new cognac. This oak is cut into staves and then weathered for around four years. This weathering removes a lot of the tannin from the wood as this stops the Cognac becoming bitter it also stops the wood becoming too porous (this stops the spirit evaporating through the wood). The staves are then made into barrels and then toasted (set fire to) to activate the flavours in the wood.
When the spirit (eaux de vie) is drained from the still it is colourless and maturation in the oak draws the tannins from the wood that add the deep colour to the spirit. Most producers leave the spirit in this new oak for up to one year. The spirit is then moved into old casks that halt the absorption of the tannins. The casks are stored in cellars or chais to complete the ageing process. The chais needs to be damp as this lessens the evaporation of the brandy, although it does reduce the alcoholic strength. Most producers will store the cognac in damp cellars for a time and then move them to warm, dry cellars, as this will add complexity to the spirit
The real art of Cognac production is the blending, this blending ensures that each new batch of spirit has exactly the same characteristics as the last batch. To keep the consistency right each new batch is blended with older cognacs some of which can be up to 60 years old. The newly blended Cognac is diluted using distilled water; this reduces the alcoholic content from 70% down to 40%. The Cognac is then returned to wooden barrels where it is left to age, the best cognacs are aged for around 20 years. When the Cognac is transferred into glass bottles for selling, the ageing process stops.
Some blenders will mature very special cognacs in a ‘paradis’ this is an area within the cellar that houses the best cognacs, these cognacs will have been specially selected by the blender as they have developed a extraordinary flavour from an early age. The paradis will house cognacs that will be used for the best blends or for special editions; the blender will decant the cognac from the wood into glass demi-johns (large bottles) to stop the ageing process.
