Even single malt Scotch whiskies bottled with a particular age statement are blended from dozens of different casks from the same distillery. Blending (or vatting) different casks of whisky together adds complexity and balance to the finished whisky, and most importantly helps ensure consistency from batch to batch and year to year. Blending is an art mastered only with years of experience.
Blenders play a crucial role throughout the whisky making process, not just at the blending stage. In order to ensure styles of whisky are produced to fulfil sales projections into future decades, blenders regularly communicate requirements to distillers. The type of cask used for maturation is also determined by the master blender, who is seeking a particular character and consistency for the whisky that will emerge after aging. That whisky may be used in a single cask bottling but it is far more likely to be blended with other casks and styles of whisky to become part of a blend.
Whisky colour is measured using a tint meter (Tintometer), usually referencing the Lovibond Series 52 Brown colour scale. This is also used for grading honey and similarly coloured liquids and syrups.
Spirit caramel (E150-a) may be added at the blending state to adjust a whisky's colour and help ensure a consist appearance form batch to batch. Spirit caramel is highly concentrated and a small drop is sufficient to influence the colour of a litre of whisky. Called 'tinting', it is widely claimed that adding caramel does not affect the flavour or aroma of whisky as it is "organoleptically inert", an assertion fervently disputed by purists. Consequently, more single malts are being released at their "natural colour" with labels declaring "no added colour" or suchlike.
It is said by some that the addition of spirit caramel not only aids colour correction but also helps different whiskies merge harmoniously when blended.
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