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whisky glass in a barrel


Here are some technical terms and definitions commonly used in the world of whisky,

which will be useful when understanding about your cask.

OLA (litres)

Original Litres of Alcohol - The original amount of pure alcohol when the cask is first filled.

RLA (litres)

Re-gauged Litres of Alcohol - The amount of pure alcohol in the cask at the points of measurement during the lifetime of the cask.

Angel’s Share

Whilst the spirit matures, loss of both overall volume (including pure alcohol) and alcohol percentage (ABV) will occur  naturally through evaporation. The industry average is 2% per year.


The process of assessing the amount of pure litres of alcohol and ABV % in order to assess the health and maturation quality of the cask on any given date.

ABV (%)

Alcohol By Volume - The standard measure of strength of the alcohol. For example - when the cask is first filled it is 63.5% i.e. for every 1 litre of fluid in the cask there will be 635ml of pure alcohol. The ABV% changes throughout the lifetime of the cask.


Age of Youngest Spirit - The spirit distillation process completion date. This is also the date the cask is filled with  the spirit and therefore the date it begins the maturation process.


In order to be called Scotch whisky a spirit must have aged within a cask for a minimum of 3 years. The distillation date is the date the cask was filled with whisky.

Estimated Number of Bottles

The estimated number of bottles that a cask would yield based on the last known gauge. This is not the estimated number of bottles at bottling.

Cask Sizes

Whisky must be matured in oak casks, which vary in sizes though the most common casks and their capacities are as follows: Barrel - 200 Bulk Litres, Hogshead - 250 Bulk Litres, Butt - 500 Bulk Litres.

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