Most amateur distillers are familiar with activated charcoal, using it to remove some of the more noxious substances present in their crude spirit. An ordinary pot still - the standard type of equipment used by amateurs - is incapable of producing pure alcohol so activated charcoal remains the only hope of cleaning it up and producing a palatable beverage.
By contrast, the alcohol produced with the equipment and procedures described in this book should conform to the definition of vodka given by the Bureau of Alcohol, Tobacco & Firearms (the BATF) in the United States, i.e. "a neutral spirit so distilled as to be without distinctive character, aroma, taste or color"*. If properly made, therefore, it should not require a charcoal treatment.
Mistakes can happen, however, particularly in the early days before one has gained experience, and when it does one may be faced with a batch of alcohol which is slightly "off". In such cases a polishing with activated charcoal can be beneficial.
Activated charcoals are 'custom built' for their end purpose, generally involving careful selection of ingredients and very high temperature and gas treatment. They work by physical adsorption (not absorption) on the enormous internal surface area of the carbon, typically 1,000 square metres per gram (hard to believe, but true!). Note that it is a physical and not a chemical effect that makes them work. It pays to be very careful about choosing the source and type of activated carbon you use to clean a spirit. Aquarium carbon will not do! It is an impure substance not designed to be used with products intended for human consumption, and it may well introduce rather nasty trace elements and flavours to your hard won product. Properly sourced activated charcoal is now readily available from winemakers' suppliers, specifically designed for the purpose of cleaning and 'polishing' spirits.
To use it, dilute the alcohol from 96 to 40% (vodka strength) and use about 150 grams of charcoal per 6 litres. Put into a container, stir occasionally over 5 days, allow to settle and then filter. Alternatively, make a continuous filter by clamping filter paper over the end of a length of 11/2 inch pipe (preferably not plastic), add charcoal to a depth of a foot or so, and then pour the alcohol through. It should be completely pure when it emerges.
Used charcoal can be regenerated by rinsing with water, spreading on a metal baking sheet and heating in an oven at 135 oC (275 oF) for several hours. The pungent smell of adsorbed congeners being driven off will be very apparent and will demonstrate that the charcoal has done its job.
* An interesting conclusion to be drawn from this definition is that either:
a) all commercial vodkas are identical, or b) the various brands have been delicately (and differently) flavoured.
(It may be noted that in Russia, hundreds of differently flavoured vodkas are available!)
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