More than just a number, a variety of phrases and terms can be used to describe proof, many of which have a rich history in their evolution over time. In this week's post we take a deep dive into these terms and phrases in hopes of arming Bourboneurs everywhere with a greater appreciation for the many nuances of "proof."
What is Proof in Bourbon?
Proof is a way to describe the overall strength of your bourbon and measures how much alcohol is contained in the spirit. The higher the proof, the higher the alcohol content. The proof of your bourbon can vary wildly from 80 proof all the way up to 120 proof and, for some bottles, even higher - more on than that after bit.
Barrel Entry Proof
Prior to the advent of many of the rules that govern today's modern bourbon industry, barrel entry proof ranged around 100 to 110 proof. Following Prohibition, the maximum barrel entry proof that was allowed was set to 110 proof. In 1962, the federal government shifted to a 125 proof maximum standard for barrel entry proof. Interestingly, the higher the proof of entry, the less barrels are required to mature the bourbon in, driving some cost savings for the industry at large. Following the 1962 shift, the Federal Bureau of Alcohol, Firearms and Tobacco (ATF) also developed an official rule galvanizing the term barrel entry proof in statute. Under the ATF's 79-9 rule, the terms "original proof," "original barrel proof" and "entry proof" are considered as one in the same.
Minimum Bottling Proof of Bourbon
The lowest proof you'll see on a bottle of bourbon is 80 proof simply because this is the minimum level allowed by law in the United States. This, like so many other nuances to bourbon, however, holds historical significance. Historically, distilled spirits were measured by the English through alcohol by weight as opposed to alcohol by volume (ABV). Back then the minimum proof by weight was 30 degrees, which is roughly equivalent to 39.9 percent ABV. For many distilleries, higher alcohol content simply meant higher taxes so bottling at the minimum provides an opportunity to save money. Further, as you dip below this line the spirit gets a bit watery. As the U.S. passed the Federal Alcohol Administration Act in 1936, this benchmark likely guided them as they landed on 40 ABV as a minimum, or 80 proof.
Bottled-in-Bond
The Bottled-in-Bond Act of 1897 states that all American whiskey (e.g., bourbon) labeled as "bottled-in-bond" must be bottled at exactly 100 proof and lays out a number of other standards. Prior to the Act's passage, many whiskeys were adulterated with flavoring and coloring additives and the passage of the Bottled-in-Bond Act provided a type of quality assurance about what it was that you were in fact drinking.
Prohibition Strength Bourbon
Prior to Prohibition, bottles of bourbon had no age statement, and the typical bourbon was bottled at 90 to 100 proof. Consumers would also buy their bourbon straight from the barrel, bringing a flask or jug to their local liquor store or saloon. This would have of course been of the uncut and unfiltered variety of brownwater.
Post-Prohibition Strength Bourbon
Prohibition ended the widespread practice of getting your bourbon straight from a barrel at your local watering hole and with it brought forward a number of restrictions and regulations. When Prohibition ended in 1933, the majority of bourbon produced in the United States was bottled at or around 90 proof. At this time blended whiskey from Canada was beginning to flood the market which was bottled around 80 proof. Additionally, with the onset of World War 2 from 1934-1946 many distilleries were required to stop making alcohol for public consumption and turn their focus on high proof grain alcohol for the war effort.
In making their stocks go a bit further, given limited production at the time, American distillers began cutting their mature bourbons for blends, and by the 1950's it became hard to sell bottled-in-bond style bourbons, with the general populous favoring lower proof, lighter whiskies. Distillers didn't want to take on the 80 proof standard of Canada and began marketing an 86 proof bourbon referred to as "Kentucky Proof." Of course, not all brands followed along, with Julian Van Winkle refusing to sell anything that wasn't bottled-in-bond. He was attributed with saying that "if folks wanted a lower proof, they could add their own water -- why should they pay him to add the water for them?" In general, however, the bourbons of the time were within the 84 to 90 proof range.
Cask Strength and Barrel Proof
Bourbon's that are referred to as cask strength or barrel proof are bottled at the same proof that the bourbon is at in the barrel. The whiskey is generally filtered prior to bottling, and importantly, no water is added to cut the product.
Is Full Proof the Same as Barrel Proof?
Many folks think that full proof is the same as barrel proof (or cask strength) but in fact it is not. When the bourbon that leaves the barrel is cut with water to lower the proof down to that which it was when it went into the barrel (Barrel Entry Proof) then the distillery may choose to refer to the resultant spirit as "full proof."
Hazmat Bourbon
Sometimes you may hear someone call a bottle of bourbon a "hazmat bottle." Rest assured, these bottles have not been exposed to some level of nuclear radiation and are in fact, completely safe to drink. Hazmat is a term used to signify that the bottle is above 140 proof. Not many bourbons reach what my friends and I reference as "jet A" status, but high-octane bottlings include such things as George T. Stagg and Jack Daniels Coy Hill (though alcohol by volume varies on either side of the hazmat line). Interestingly, hazmat bourbon is illegal to fly with given the proof point, just one of a number of Fun Bourbon Facts to Impress Your Friends.
How to Choose the Right Proof for Your Bourbon?
There are many different proof points for bourbon on the market today, and one can certainly take the lazy river approach or ride the lightning. Some Bourboneurs will prefer a bourbon with a lower proof for its smooth flavor, whilst other Bourboneurs may like their bourbon a bit on the higher proof side because of the more dramatic flavor profiles. At the end of the day, we all have unique preferences and experimenting with different bourbons will help you hone on in what suits your palate the best.
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