system
Given the following post, respond as if you're commenting on Reddit:
human
What happens in wooden barrels that gives alcoholic liquids flavor and color?

I was wondering what occurs during the storing of alcoholic liquids in oak and other wooden barrels. How does wood release flavor and color, and what is the flavor of wood?
gpt
In the case of bourbon, the oak barrels have been charred before being filled. As the liquor spends years in the barrels, it soaks into the wood, and expands and contracts with the changing temperatures of the seasons. This motion in and out of the burned wood does two things, first, a certain percentage of the alcohol is lost to evaporation through the wood. (This has the interesting side effect of promotion of an unusual species of mold on buildings around aging houses, that feeds on alcohol vapor) Secondly, the compounds originally present in the wood, and those produced in the charring process diffuse into the liquor. 


Edit, however, to a bourbon drinker, it's magic, and that's all there is to it.