(Fusel is the German for “rotgut.”) A small
dose of fusel oils gives a distilled alcohol
character; too much makes it unpleasant.
Concentration by Freezing
Distillation is the most common way of
making concentrated alcohols, but it’s not
the only way. Freezing also concentrates
the alcohol in fermented liquids, by
causing the water to form a mass of solid
crystals from which an alcohol-enriched
fluid can be drained. (Alcohol freezes at –
173ºF/–114ºC, far below water’s freezing
point of 32ºF/0ºC.) In the 17th century,
Francis Bacon noted Paracelsus’s claim
that “if a glass of wine be set upon a
terrace in bitter frost, it will leave some
liquor unfrozen in the center of the glass,
which excelleth spiritus vini [spirit of
wine] drawn by fire.” The nomads of
central Asia apparently applied “freezing-
out” to their alcoholic mare’s milk,