What is Barrel Entry Proof

When whiskey is entered into the barrel, it undergoes many changes. There are many factors in these changes, and barrel entry proof is an important factor. This proof has changed over the past two centuries, and these changes affect the flavour of the Bourbon we drink. The Bourbon of James Crow would have a very different flavour than the Bourbon of the 21^st century. To best understand these changes, we should look at the Bourbon of the 1830s when Crow was distilling his legendary whiskey.

The 19th century was a time of many technological advancements, but it was not until the end of the century that technology made glass bottles affordable for distillers, and distillers began bottling their own product. In Crow’s time in the 1830s, whiskey was sold by the distiller in barrels. Consumers would purchase the whiskey from the liquor store or tavern, and most often they would bring their own flask or jug to hold the spirit. These flasks and jugs were filled straight from the barrel, so the distiller wanted a whiskey that was considered palatable straight from the barrel. They filled their barrels with whiskey that was 100 to 103 proof. The proof could go up or down with aging, depending on the barrel's storage conditions, so the consumer was getting whiskey somewhere between 95 and 105 proof.

This higher concentration of water meant that the natural sugars in oak staves dissolved quicker into the whiskey. Most whiskey barrels were sold by the distiller at no more than two or three years of age, so it was important to get the sweeter flavours from the wood at a younger age. At the end of the century, when bottling became an affordable practice for the distiller, they would increase the entry proof, sometimes to as high as 107 proof, to ensure the proof stayed above 100 for bottling purposes.

Prohibition ended consumers' ability to purchase their Bourbon directly from the barrel. With repeal came increased regulations for Bourbon. There came an official “Barrel Entry Proof” range of 100-110 proof. The lower limit of 100 was set because the tax was based on 100-proof alcohol. The upper limit was set because of tradition. Barrels were still relatively inexpensive, and the flavour profile was important. That would change in the next two decades. It was determined that people wanted lighter-flavoured whiskey, and one way to do that was to increase the barrel entry proof.

In 1962, the barrel entry proof was increased to today's 125 proof limit. This was done to save on the number of barrels needed to age whiskey and to lighten the flavour of the end product. It would take almost two more decades before the new maximum entry proof became the standard in both practice and regulation, but it has done so. The resulting whiskey was lighter in fflavourafter 4 years of aging. It would take 8 years or more to achieve the richer, bold flavours of the post-Prohibition products.

The craft distilling movement is seeing a swing back to lower entry proof for whiskey. It costs more because it takes more barrels to mature the whiskey, but some distillers are seeing that offset by a richer-tasting product at a younger age. That means they lose less to evaporation during aging, and they hope the cost of the barrels will be offset by a better-tasting product and more bottles to sell.