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David on Technical Topics – Adding Water to Cognac

We call it dilution in the industry and nearly every cognac needs to have a level of dilution to optimise its qualities.  Some cognacs are superbly smooth and almost too easy to drink whilst others are fiery and aggressive and seem to burn the mouth with every mouthful drunk.  Getting the optimum balance between aggressiveness and flavour is a skill that must be acquired in order to maximise the quality of the cognac.

Adding water to cognac is certainly not just a case of pouring water from the tap into a barrel of cognac.  The water must be pure and not contain any minerals.  Distilled water is the normal choice but there are some special waters supplied in bulk for big blenders.  The addition of this special water is a skill that has been developed over many years of understanding the noble spirit.  In essence, spirit and water do not mix easily and some cognacs have a higher absorption level than others.  A good diluter can taste the water in cognac if it has not been mixed properly.  There are a number of ways that mixing can be undertaken.

Some producers dilute their cognacs whilst they are still hot and fresh from the still but this can be difficult as the strength of the cognac gradually reduces from the start of the distillation to the cut (the point where one stops collecting the water-clear eau de vie because it is too weak to provide sufficient flavour).  Other producers will make a “Petite Eau”, a weak blend of cognac and water which is aged in casks before adding back into the cognac to arrive at the right strength.  When a cognac has been produced and aged for many years most will dilute it gradually, a couple of degrees at a time.  Each step can take many weeks before the correct balance is achieved and usually, the nearer one gets to 40% abv, the longer each step will take.

The speed of dilution depends largely on the speed that the cognac will absorb the water.  A good dilution, where the two components mix without detection, may take several years.  Other factors which may influence the dilution process are the size and shape of the still, the maximum temperature of the hot eau de vie and even the age, toasting and size of the barrels used for storage.

Cognacs should be diluted to a strength that optimises their flavour and so the final abv will vary.  Take a look at our Hermitage 1975 at 47% and Hermitage 2005 at 40%, both of which are beautifully balanced and full of flavour.

You have probably gathered by now that adding a drop of tap water before drinking your cognac is not a good idea!  Go to our Brandy Education Page to read more Technical Topics.