To distil a liquid one simply brings it to the boil and condenses the vapour on a cold surface. To remove the hardness from water it is boiled in a kettle and the steam which is produced condensed against a cold surface to give a pure water free of minerals and all other types of impurity. The calci um and magnesium salts which constitute the hardness are non-volatile and remain behind in the kettle. Nature carries out her own distillation in the form of rain — the sun evaporates water from the surface of lakes and oceans leaving salt and impurities behind. Clouds form, condense, and a close approximation to distilled water falls to earth.
So distillation is not a mysterious subject, nor is it threatening. Nor is it something to be furtive about, something to discuss with your friends in hushed tones. It is as commonplace as a rain-shower or a tea-kettle boiling and causing condensation on a nearby window. And as innocuous.
As you can imagine, the actual practice of distillation is a little more complicated than this although the principle is exactly the same — boil the liquid and condense the vapour — and later chapters will provide an exact description of the equipment required and the procedures involved. Emphasis will be placed on the production of high purity alcohol such as used in vodka and gin, but alcohol containing congeners for providing flavour, both good and bad, can be produced if that is what you want.
There are actually two different types of still, the choice of which to use depending on the level of purity required in the product. Whisky uses one type, rather simple in design since only a modest level of purity is required. Furthermore, if all the "impurities" were removed there would be no taste and you would have produced vodka and not whisky. The other type of still is more elaborate in design and used for making pure alcohol. A brief description of the two types will be provided in this chapter dealing with beverages because it is quite important for the reader to appreciate the differences right at the outset.
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