Cask Strength

Where it started

The U.S. defines "barrel proof" and "cask strength" in regulation, and the current rule sits in 27 CFR 5.87.¹ In Scotland, new spirit is usually reduced to a standard 63.5 percent for filling casks,⁴ so a cask-strength release shows what years in wood did from that common starting point.

Where and how it's made

The term "barrel proof" or "cask strength" may be used only when the bottling proof is not more than two degrees lower than the proof of the spirits when they are dumped from the barrels.¹ A separate set of terms, "original proof," "original barrel proof," "original cask strength" or "entry proof," may be used only if the proof going into the barrel and the proof in the bottle are the same.¹ The KDA's plain-language version: barrel proof means within two degrees of the dumped proof, and it is generally understood that no water is added.³

Where the number starts. Bourbon may enter the barrel at up to 125 proof,² and Scotch usually goes in at 63.5 percent alcohol.⁴ Some of every barrel is lost to evaporation over the years, the angel's share,³ and what is left is what you get. The label number is a record of that one batch or barrel.

How to taste it

Small pour, tulip glass, and taste it neat once so you know the baseline. Then add water in drops, not splashes, tasting between additions. A single large ice cube works too, slowly. Food: anything fatty or sweet stands up to it, from a ribeye to pecan pie.