The reduction of alcohol from cask to bottling strength should always be done slowly, with the water and the spirit at the same temperature. Because of the hundreds of components in the alcohol, the assemblage—or blend—needs time to absorb the water and to be married. This discipline from the master blenders illustrates a commitment to quality, consistency and the seriousness to all stages of production.

It is extremely important to never reduce the eau de vie (EDV) bluntly or quickly. For example, when the alcohol content of the spirit is 70% abv or greater, you should not bring it down to 40% abv at one time, even if you are using pure water. This causes hydrolysis of the esters, resulting in a saponification of the spirit. In other words, it will taste like soap. The EDV becomes cloudy. This effect is exaggerated with spirits distilled on the lees, in which case you will notice a blue haze. After such a shock, the spirit becomes flat and has lost a good portion of its complexity and balance. It will never completely recover from this violent transmutation.

You can make the final reduction from 41.5 to 40% abv using spirits that are already cut to no less than 20% abv—already aged for at least the same time as the youngest EDV in your blend. This method allows a faster integration but requires more storage vessels, like neutral vats or casks.

Depending on the aging conditions of your cellar and the size of the barrels, a spirit just distilled will need about 45 to 50 years for the alcohol to drop from 70 to 40% abv without the addition of pure water. The volume will drop from 92.5 gallons at 70% abv to 26 gallons at 40% abv.

During the aging period, the cellar master reduces his or her EDV step by step, or blends to prepare them gradually for bottling.

A lot of water is necessary to monitor these slow but punctual operations. The importance of the water’s quality and origin are of primary concern to achieve the level of quality you want to achieve.

  • The choices of water available are:
    Distilled water—neutral, dry, dead, with no volume
  • De-ionized water—neutral, with a little more volume
  • Spring or well water—the mineral sediments will over time settle down in the bottles even with tight and cold filtration. It usually happens under 55% abv.
  • Rainwater—round, sweet, soft, with volume and a nice flesh. This is the best choice by far. I experimented and created the same blend, one reduced with distilled water and the other with rainwater. The result was like night and day in terms of quality, fullness, and mouth feel.

Before using water from the sky, the cellar master has to send samples of water to a lab for traces of pollution. Purity will differ depending on your geographic location, time of year, direction of the wind, and level of industrialization in your area. It is important to address these problems earlier rather than later to avoid potential lawsuits due to allergies or physical reactions by the consumer.

How to Process and Collect Rainwater

At the beginning of the rainy season, clean the roof of your distillery or cellar thoroughly of debris, dust and leaves, especially in the gutters and drains. Let the rain rinse the rooftop for a few hours.

Collect the rain in a tank. Filter it immediately with a household water filter and store it in a plastic or stainless steel tank in a dark and cool place. You will be able to use it for a few weeks.

Each time before using it, you should inspect and taste it: 1) Visually—check it by very slowly pouring the water. If it starts to become a bit oily, either re-filter it or discard it. 2) Smell and taste—look for a moldy or stagnant smell.

Take a sample in a glass and agitate it, then let it rest for a few minutes. Then re-smell and re-taste it. Usually, odors from the tank dissipate with aeration.

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Master Distiller & Master Blender Hubert Germain-Robin, is the creator of world-renowned brandies and author of Traditional Distillation: Art & Passion and Maturation of Distilled Spirit: Vision & Patience. Germain-Robin’s family history goes back centuries in Cognac, where his family had been producing brandies under the name Jules Robin and Company since the 18th century. He came to California in the 1980s and single-handedly changed the way brandy is produced and perceived by using Cognac techniques with California grape varietals.