During the first weeks of 2016 we filled several beautiful Bordeaux wine casks with our Edradour spirit.
The spirit comes into the filling vat at around 70% abv (alcohol by volume) and is then reduced to the ideal fill strength of 63.6% abv by adding water. Here at Edradour, we simply test the alcoholic strength and the temperature of the spirit and then use a pocket calculator to determine the amount of water needed.
After the water is in, we mix the liquid, using a wooden paddle. The cask we want to fill is put into its place, the spout put into the bung hole and then the tricky part begins: since there is not automatic cut-off we have to listen carefully to the gurgling sound as the spirit runs into the cask. As the pitch of that sound becomes higher and higher we guesstimate how far the level of the liquid is from the bung hole and when the gurgling stops altogether we quickly shut the valve on the filling vat.
Finally, we put a poplar wood plug – called the bung – into the filling hole, bang it in with a heavy hammer, and tataaah: another cask filled to perfection!
Using this old-fashioned and labour intensive method we obviously can’t fill thousands of casks but since we are only distilling about 130,000 litres of pure alcohol per year that is not a problem. Just as a comparison: Glenfiddich, the largest malt whisky distillery in Scotland, has a capacity of 14 million litres per year!
NB: In 2015 we filled 437 casks here at the Edradour Distillery.