Water and plain caramel colouring may be added to Scotch whisky before bottling.

However, a whisky maker will sometimes bottle a single cask without diluting it. This whisky may be labelled as Cask Strength, making it clear that the whisky’s ABV was reached naturally during maturation.

Plain caramel colouring or ‘spirit caramel’ is a food-safe additive known by its E number (E150a). It has a very dark brown colour and a bitter taste, but it’s used in such small proportions when colouring whisky that it only tints the colour and does not noticeably change the flavour or aroma. No other additives are permitted by the laws governing Scotch whisky.