We have our “spirit” so what makes it into a whisky ? Simple. A wooden oak cask. The spirit has to be left for a minimum of 3 years before it can be called whisky. Once the spirit is inside the cask, the magic begins to happen, the liquid takes natural flavours from the wood as it “breaths”, the term breathing refers to the expansion of the wood as it heats up and cools down with temperature fluctuations, the spirit is drawn into the wood and out again thus giving the spirit it’s colour and flavours. During this process evaporation also happens ( this is known as the Angels share)in the cooler temperatures of Scotland the alcohol evaporates and so reduces the alcohol levels but in hotter climates the water evaporates giving a stronger spirit at the end.
The liquid inside each cask is checked to see if it is maturing well, the whisky will be ready when it’s ready, there is no rushing this process (although there are ways to speed it up) every cask will give the whisky something different from colour to flavours.
So what is the difference in casks ?
Firstly there are several cask types, barrels, hogsheads, butts, port pipes,puncheons and barriques.
So what’s what ?
A barrel usually holds around 195 litres, is made from either American or European oak, this is probably the most common size used. From these you will get flavours like vanilla, toffee, nutty.
A hogsheads usually holds 250 litres, it is also made from American or European oak.
A sherry butt is 500 litres, made from American or European oak, these are primarily made to hold sherry, then reused to mature whisky. These will give you flavours like dried fruits, candied fruits, coffee, chocolates and spices.
A port pipe is 500 litres, also made of oak and used to mature port before being used for whisky. From these you can pick up flavours like dark chocolate and plums.
A puncheon holds around 320 litres, made from oak staves, this is usually shorter and fatter than the butts.
A barrique is 225 litres and is made from European or American oak, they are primarily used to mature wine. Flavours derived from these cask are berries, fresh fruits, figs and spices.
Once the desired cask is chosen you have the choice of Virgin oak, first fill and refil casks.
Virgin oak refers to barrels than have not previously held any liquid. These will give intense flavours like oak and vanilla.
First fill refers to a cask that has previously matured a liquid,(bourbon, sherry, port, wine) but not whisky.
Re-fill is a cask that has already matured whisky. Each barrel can be used a few times, but it will depend on how long each maturation has been, if the average cask matured for 10 years it might be used 3-5 times. Each time the cask is used the flavours and colour become less prominent.