Page 63 - Craft of Whiskey Distilling

52 | CrAFt WHIskEy DIstIllInG
The rate of evaporation is typically about 10% of the remainder per year. So, it would be quite normal for a barrel that’s been aging for seven years to be down to 48% full
The formula for calculating angels’ share is as follows
Final volume = Original volume X (1 ñ percent lost per year)number of years age For 53 gallons aged for 7 years at 10% loss per year it would be
Final volume = 53 gallons X (1 - 0.1)^ = 53 gallons X 0.9^7 = 53 gallons X 0.47 = 25.3 gallons
However, if the whiskey is aged in a hot climate, the lost will be more like 15% per year, but it will age out in only 3 years. The angels’ share under those conditions would be calculated as follows
Final volume = 53 gallons X (1 ñ 0.15)^3 = 53 gallons X 0.85^3
= 53 gallons X 0.614
= 32.5 gallons
Clearly, aging faster in a hotter climate reduces the loss due to angels’ share.
Of course, the final volume must be measured empirically. The calculation is only used to determine if the empirical measurement is roughly where it should be. For example, if a barrel had a slow leak, more whiskey would be lost than would be by angels’ share alone. The calculation would help to spot this inconsistency.
Also during this metamorphosis, the percent alcohol will change. It’ll increase or de- crease depending on the ambient temperature and humidity of the barrel warehouse, so the percent alcohol must be measured as well.
vATTINg:
“Vatting” is when a distiller blends various proportions of the same whiskey from dif- ferent barrels to achieve consistency of quality and flavor. Different barrels will age the whiskey a little differently, and blending the whiskey from numerous barrels is a good way to maintain a uniform brand. Also, the whiskey will vary slightly from batch to batch, and vatting will even out those variations as well.
Vatting is not to be confused with the term “blending”, where the distiller mixes vari- ous different types of whiskey, invariably from different distilleries, to achieve a unique flavor and brand of its own, different from any of the whiskies used in the blend. Also, such blends are often made using Grain Neutral Spirits (GNS) and other types of raw (i.e. un-aged) whiskies in the mix. Some whiskey blenders don’t distill whiskey at all, and just buy whiskey from many dozens of distilleries that they blend together to make their own specific brands. Vatting is only the mixing of the same brand of whiskey from different batches and barrels within the same distillery.