Vodka production: Filtration
Anyone who uses a Brita Filter to make their tap water more palatable will recognise the benefits of activated carbon filtration. Activated carbon filters can be used to remove the organic impurities that affect the colour, smell and taste of vodka, without affecting its alcohol content.
Early separation processes simply involved leaving the spirit to stand until solid particles had fallen to the bottom of the tank. Later fining processes used coagulants such as milk or eggs which solidified around the contaminants so encouraging them to sink.
Russians attribute the invention of charcoal filtration to a chemist by the name of Theodore Lowitz who in 1780 was commissioned by the Tsar to make the national drink more hygienic. He used charcoal made from charred hardwoods to remove fusel oils and other contaminants left by the relatively primitive distillation methods of the time. The Swedes and Poles also lay claim to the invention of the process.
While distillation methods have improved to the extent that it is possible to produce near pure ethanol alcohol, some distillers still choose to use charcoal filtration for to its cleaning and softening effect on the spirit - it is particularly useful for removing oily contaminants.
The use of different charcoals made from different woods has varying effects on the distillate. Birch charcoal remains the most popular but the charcoal recipe used by many distillers is a closely guarded secret. Of course, there are vodka distillers that say, "charcoal is for barbecues."
Over the years many different substances have been used for vodka filtration including cloth, wool, paper, sand and other stone fragments. During the 1990s race to develop vodkas perceived as being ever more premium, filtration materials became ever more exotic, with garnet crystals and even crushed diamonds being used as a filtration medium.
Every bottled spirit should at least pass through a particle filter (usually cellulose). Some producers use cellulose pads impregnated with activated carbon as they claim this helps enhance the visual 'polish' and the shine of the spirit.
It is also common to chill and then filter vodka at low temperatures. During chilling to temperatures between -2°C (28°F) and as low as -12˚C (10°F) long-chain protein molecules precipitate out of the spirit, ie they change from being dissolved in the liquid into solids again and are then filtered out using particle filters. If these long-chain protein molecules are not removed the vodka could become hazy when stored at low temperatures. However, some vodka producers would rather risk precipitation claiming that chill-filtration strips out mouthfeel and flavour provided by the fatty acids.
In his book 'Kindred Spirits 2', drink writer Paul Pacult writes, "How vodkas are filtered also affects their character. Charcoal filtering, the most prevalent, imparts a hint of sweet smokiness, almost a sooty quality. Quartz crystals lend a stony, mineral-like kind of taste while cloth or fibre panel filtering gives off an aroma of parchment or cotton fabric."