Upon arrival at the cooperage, the barrels are cleaned to remove the layer of charred wood and are then re-charred by being set fire to from the inside until the correct degree of char (smokiness) is reached, a process called de-char re-char. The barrels must be checked to ensure they are strong and water tight so the coopers replace wooden staves and hammer on new metal hoops, a skilled process requiring a 3 year apprenticeship. The Speyside cooperage makes and repairs about 100,000 barrels, hogsheads, butts and puncheons a year.

After some time in a Bourbon cask, enormous 500 litre sherry butts can be used to mature whisky. This dates back to when fashionable sherry was imported from Jerez in vast quantities along with the wines of Bordeaux, and any barrel available was used to mature whisky. It is only more recently that the effects of different woods has been singled out to produce and market different styles of whisky and it is essential that good quality woods are used for the blender to ensure consistency of style. Style is influenced by many factors. Whether the whisky is blended (a combination of grain and malt whiskies), a vatted malt (malt whisky from several distilleries) or a single malt (the product of one distillery). In grain whisky production, distillation is in a continuous still which produces a more neutral spirit. In malt whisky production, only malted barley is used and the product of fermentation, the wash, is distilled in traditional copper pot stills which produce a spirit with more congeners, the flavour compounds. At the Invergordon distillery I saw the large scale of grain whisky production in the enormous continuous still, and the vast warehouses where barrels can be stored on palettes stacked 6 high and where many processes are mechanised. At the Dalmore distillery I saw small scale malt whisky production, the shining copper pot stills and the spirit safe where the foreshorts and feints are separated by hand.

Variations in flavour of different whiskies also come from the characteristics of the water used in production, which must always be local. The main regions are Highland (including Speyside), Lowland, Campbeltown or Islay. I was very fortunate to taste a huge range of whiskies in the sample room at the Whyte & Mackay headquarters. Richard talked me through the tasting process using a nosing glass called a copita and affter three or four sniffs the flavours start to appear, including the unusual aroma of salty bananas from the 1964 Bruichladdich Isaly Malt. The tasting really highlighted the differences between the peaty Islay whiskies of the west coast of Scotland which are nothing like the lighter more delicate whiskies of Speyside in the north east.

The way whiskies are aged will also greatly affect flavour. Whisky is matured in barrel for 3 years before it can be legally sold as Scotch whisky and it is up to the blender to chose the right wood for the whisky being produced. All barrels are oak which can be of American or French origin. These woods have different porosities allowing the liquid inside to "breath" at different rates. The size of barrel affects the speed at which the wood influences the liquid, the degree of char and how long the whisky is matured for will have different effects on flavour. A used sherry cask can cost up to £350 so choosing the right cask if important. For lighter styles of malt whisky, Fino or Manzanilla sherry casks work well, and for heavier, darker styles, Matusalem or Oloroso casks are suitable.