Malt whisky is made by soaking barley in steeps (water cisterns) for two or three days until it swells, after which it is left to germinate for around seven days, during which the starch in the barley seed is converted into soluble sugars – this process is known as malting. The malted barley or “green malt” is then dried in a kiln over a furnace, which can be oil-fired, peat-fired or, more often than not, a combination of the two. Only a few distilleries still do their own malting and kilning in the traditional pagoda-style kilns; the rest simply have their malted barley delivered from an industrial maltings. The first process in most distilleries is therefore milling, which grinds the malted barley into “grist”. Next comes the mashing, during which the grist is infused in hot water in mashtuns, producing a sugary concoction called “wort”. After cooling, the wort passes into the washbacks, traditionally made of wood, where it is fermented with yeast for two to three days. During fermentation, the sugar is converted into alcohol, producing a brown foaming liquid known as “wash”. Distillation now takes place, not once but twice: the wash is steam-heated, and the vapours siphoned off and condensed as a spirit. This is the point at which the whisky is poured into oak casks – usually ones which have already been used to store bourbon or sherry – and left to age for a minimum of three years. The average maturation period for a single malt whisky, however, is ten years; and the longer it matures, the more expensive it is, because two percent evaporates each year. Unlike wine, as soon as the whisky is bottled, maturation ceases.