What Is A Whisky Cask Regauge?
A whisky cask regauge is the process of measuring the contents of a cask to determine the remaining volume of liquid (litres of alcohol and water) and its alcohol by volume (ABV).
A regauge is an essential health check for your cask whisky. It should be conducted every three years once your cask is older than five years, and yearly after it surpasses fifteen years. This process identifies the bulk litres (the volume of liquid in the cask) and the ABV (alcohol by volume) to compute the RLA (regauged litres of alcohol).
What is a Regauge?
A complete cask regauge consists of three steps:
- Sampling and Analysis: A sample is taken and analysed to determine the alcoholic strength, or ABV, which must be over 40% for the liquid to be legally recognised as Scotch whisky.
- Measuring the Bulk Litres: The full cask is weighed, and the weight is documented. The cask is then emptied, and its empty weight is measured. Subtracting the empty cask’s weight from the full cask’s weight gives the volume of liquid in the cask, referred to as the bulk litres.
- Calculating the RLA: The bulk litres and ABV are used to compute the RLA. For example, if you have 400 bulk litres with an ABV of 60%, your RLA would be 240 litres.
Why Do You Need to Regauge Your Cask?
A regauge is vital because both the volume of your cask and its alcoholic strength decrease over time due to natural evaporation (angel’s share). Casks are porous and not sealed, so liquid naturally evaporates, and alcohol evaporates more readily than water, causing the ABV to drop. Regular regauging ensures your whisky does not fall below the required ABV of 40%, allowing you to sell or bottle your whisky at the right time.
Additional Reasons to Re-Gauge:
Angel’s Share Loss
The “Angel’s Share” refers to the natural evaporation of liquid from the cask over time. This loss impacts both the volume and alcoholic strength of the whisky. In most warehouses, approximately 2% of the liquid is lost each year, but this can vary depending on the storage environment, such as temperature and humidity.
Angel’s Share primarily consists of alcohol, which evaporates faster than water, leading to a gradual decrease in ABV. The chemical reason for this is because water molecules exhibit unique cohesion and adhesion properties, unlike ethanol molecules, which lack these characteristics. As a result, ethanol has a lower latent heat of vaporization, causing alcohol molecules to evaporate faster than water.
If left unchecked, this can result in the ABV falling below the legal threshold of 40%, making the whisky no longer eligible for sale as Scotch whisky. Regular regauging helps to monitor and manage these losses effectively, ensuring the whisky remains viable for bottling or sale.
Moreover, understanding the Angel’s Share provides insight into the aging process of your whisky, offering valuable information about how your cask is maturing over time.
Check the Taste of the Whisky
Different whiskies reach their ideal flavour profiles at different times. Regular sampling during a regauge allows you to monitor the development of the whisky’s taste, helping you determine the optimal time for bottling or selling your cask.
Monitor the Cask’s Health
A regauge can help identify problems such as leaks or structural issues with the cask. Detecting and addressing these problems early ensures the whisky’s quality and prevents unnecessary losses.
Determine the Cask’s Value
A cask’s value is directly influenced by its ABV. Casks with an ABV below 40% cannot legally be sold as whisky and will not trade at as high a value. Regular regauging ensures you have accurate data to assess and maintain the worth of your cask.