CLAY   Humanity’s love affair with the wine extends way back – over 8,000 years ago; when people most likely stored their wine underground, in large, round clay vessels called kvevri or qvevri. 

WOOD  When charring a barrel, you break down hemicellulose into its ten constituent sugars, which caramelize in a very tight layer underneath the char in existing, unburned wood. As heat radiates and cools, you get the breakdown of lignin into vanillin and tannic acid begins to turn into the color red. You get a wide array of effects with Whiskey as the heat passes through the barrel.