“Char #4” sounds precise, but the actual burn time behind that number varies by cooperage, by how green the wood was, even by humidity in the char house that day. We’ve had barrels nominally spec’d identically that colored a full year apart from each other at the same fill date, purely from variance in how deep the char actually penetrated.
That’s part of why we buy direct from two cooperages we’ve worked with for over a decade rather than shopping barrel brokers for the best price — consistency in char depth is worth more to us than a few dollars a barrel, because it’s the difference between a twelve-year release that tastes like last year’s and one that doesn’t.
