The original post: /r/askscience by /u/MindOfErick on 2024-11-07 19:42:15.

I’ve tried searching around and others asking similar questions of aging whiskey in barrels, but all the answers only talk about the flavors added by the aging process. What is happening at the molecular level that changes clear liquor brown? Wine does not impart color from oak and neither does beer, but a fortified wine can change color. Does it have to do with the percentage of alcohol or viscosity, or something else?