Wow, that's very high. I'm curious about whether the angels' share noticeably alters the ABV, from the time the distillate is put into the cask, to when it's bottled (as I'm assuming different evaporation rates for water & ethanol).
"Casks stored in humid conditions lose a greater proportion of alcohol than those stored at lower humidity levels. Conditions of low humidity draws more water through the staves - leaving a higher proportion of alcohol in the cask. "
So, in the case of the aforementioned Stagg, the distillate went into the barrels at 125 proof, and came out at 144. Clearly, the angel's share preferred to take water over distillate.
That said, the yield was horrible -- 10-15 gallons of spirit per barrel out of an initial barrel capacity of 55 gallons.
That said, I question whether humidity has as much to do with it as atmospheric pressure does. The benefits of barreling something like bourbon in a place like Kentucky is that they have 4 full seasons, and the variance in atmospheric pressure from cold winter to hot summer creates something of a capillary effect in the distillate -- as the weather gets hotter (and maybe more humid) the distillate pushes into the barrels, but pulls out during the cooler months.
Just putting the barrels in a hot place for its entire aging process might accelerate the aging, or it might mean that because it loses the breathing effect, it might extract more of the tannins and less desirable elements from the barrels.
Wow that's a massive loss though, I hadn't realised it could be that much lost.
That's also interesting regarding a potential for accelerated ageing.
I'm also wondering how oxygen uptake is effected by differing levels of spirit in the cask, I'm assuming that might effect the taste somewhat.
Edit: The thesis 'Aging of whiskey spirits in barrels of non-traditional volume' has lots of interesting information.
"As evaporation occurs and the fill level decreases, oak not in contact with liquid spirit dries, contracts, and becomes
more porous to the entry of outside air (28). Oxygen present in the barrel fuels oxidation reactions that are essential in the production of mature spirits"
Yes, the ABV raises or lowers depending on temperature and humidity. The Stagg almost certainly went in at 125 proof (barrel entry proof), so it got a big boost during the considerable aging process.
I've heard descriptions (from the producers) of barrels that gained / lost proof depending on what floor of the warehouse they were stored on. Pretty neat.
