The Outcomes
Oak Influence
How much of what you taste came from the cask rather than the spirit itself. Barrel type, whether it's new or previously used, char and toast level, and length of maturation all push this scale.
None
Dominant
I
None
Unaged, or matured in a neutral, non-wood vessel — the raw material stands alone.
II
Light
A short rest or a used, well-worn cask leaves only a gentle trace.
III
Moderate
Vanilla, spice or dried-fruit character clearly present alongside the spirit itself.
IV
Pronounced
Oak is a leading part of the profile — colour, tannin and flavour all show it.
V
Dominant
New, heavily charred or very long-used oak overshadows the base spirit almost entirely.
New charred oak (required for bourbon) drives this scale up fast; a third- or fourth-fill cask can rest a spirit for years while barely moving it.