Triple distilling typically means using a set of stills each dedicated to one particular distillation, with the first distillation in a wash still, the second in a feints still, and the third in a spirit still. The wash still is 'charged' with the wash which typically has an alcoholic strength of around 8-10% abv. Once distilled this results in low wines, with a strength of around 25% abv, or higher.
Distilling the low wines in the feints still entails three distinct phases. The first and final phases, known as the heads and tails respectively, are of an unsuitable character and quality, and are collected to be redistilled in the next distillation run within the feints still. The middle phase of the distillation run, known as the 'spirit cut,' is collected separately, and typically has an alcoholic strength of around 70% abv. "This distillate has quite a full-bodied character, with fruit, cereal and spicy notes. Distilling it for a third time means a longer production schedule and higher costs compared to double distilling, but it produces the style of spirit that we want," says David Quinn, master of Whiskey Science, Irish Distillers.
The third distillation repeats the same process as the second, with the heads and tails collected separately, to be redistilled in the next distillation run within the spirit still. The middle phase of the distillation run yields another 'spirit cut,' collected separately as new make spirit with a strength of around 80% abv, or higher. This is effectively a spirit cut from a previous spirit cut, allowing the distiller to further refine the profile of the new make spirit, by retaining certain characteristics and either reducing or removing others.
"The third distillation produces new make spirit which has a summer fruit character, with peaches and pears. These fruit notes are present all the way through, but are masked by heavier notes until the third distillation separates the fruit notes and leaves behind the heavier character," says Colum Egan, master distiller, Bushmills.
Reducing some of the heavier cereal notes is also a key factor for Woodford Reserve Bourbon, which is distilled from a mash bill (recipe of grains) comprising corn, rye and malted barley.
"We remove corn notes during the second distillation. As these are quite earthy with a farm note, there's an element of unmasking the lighter notes, and in the third distillation we capture amazing floral aromas that would otherwise not show in the spirit. We also get a wonderful spicy character and fruit notes such as grapefruit and lemon," says Chris Morris, master distiller, Woodford Reserve.
The higher the strength of the new make spirit the greater the proportion of lighter notes, including citrus fruityness, and consequently the more elegant the spirit. Correspondingly, the lower the strength the greater the proportion of richer, heavier characteristics such as grain and cereal notes, and the fuller-bodied the spirit. "Even a difference of 2-3% abv in the strength of the new make spirit can significantly change the character, and adjusting the strength is one way that we can produce various styles of new make spirit, either more elegant or fuller-bodied, using the same set of stills," adds David Quinn.
Distilling three times provides certain opportunities, it's important to see the regime in a broader context.
"We can't just give all the credit to the number of distillations, as we wouldn't get the result we want without all the other aspects of the production regime also playing their part. The choice of yeast, for example, helps to promote a particular range of characteristics during fermentation. This creates a large canvas of flavours that we can choose from," adds Chris Morris.
Ageing Triple Distilled Spirit
The ageing process comprises three elements. Additive maturation sees the spirit gaining flavour and colour from the oak cask. Subtractive maturation means the spirit loosing pungency and immaturity, partly through evaporation of alcohol and water from the cask. Interactive maturation refers to other complex reactions including oxidation (see separate article), which develops additional characteristics.
"As triple distillation produces a more refined spirit than double distillation, it doesn't need as much subtractive maturation. The effect of additive maturation is also perceived more quickly, such as the classic vanilla note that a Bourbon barrel adds. This works very well with Auchentoshan, which is a very fresh, vibrant spirit with citrus notes that are more zesty than they would be with double distillation. Vanilla has a great synergistic influence, underlining the orange notes and evolving the lemon notes to create the softness of lemon meringue pie, for example, while also enhancing the characteristic sweetness of the Auchentoshan spirit," says Rachel Barrie, master blender, Morrison Bowmore Distillers.