Vodka production: Hydration
Water forms some 70% of the contents of a bottle of vodka so is crucial to both its taste and mouthfeel.
Distilleries are usually established in locations where there is a good supply of raw materials such as grain or molasses, good transport for the finished product, a reliable power source and most importantly, a plentiful water supply - ideally soft water which is low in salts and ions. Distilleries use a lot of water.
Distillers favour water naturally low in dissolved salts and ions such as sodium, chloride, calcium carbonate, calcium sulphate and magnesium. It is common to find distilleries supplied by artesian wells or natural springs and much is made by marketing departments about the purity of the water used in their vodka production.
Modern water purification technology allows distillers to demineralise water using reverse osmosis to produce pure, tasteless water which will not affect the flavour of the finished vodka.
To affect reverse osmosis, water is pumped through tubes at very high pressure and then forced through a selective membrane. The larger molecules and ions are unable to pass through the membrane and so are separated from the now demineralised water.
When water is blended with ethanol alcohol there is a reaction generating small amounts of heat. Consequently, some distillers prefer to gradually hydrate their spirit, slowly reducing it to bottling strength. Some choose to let the vodka rest to allow the spirit and water to coalesce, like leaving the molecules in your food to settle down after cooking in a microwave.