The short answer: Some words on a bourbon label are legal standards with exact rules: bourbon, straight and bottled-in-bond. Others, like small batch, have no legal definition at all. Single barrel and cask strength sit in between: they describe how the bottle was made, but the details are up to the distillery.
Bourbon
To be called bourbon, a whiskey has to be:
- Made in the United States
- Distilled from a grain mix that is at least 51% corn
- Aged in new, charred oak containers
- Distilled to no more than 160 proof, and put into the barrel at no more than 125 proof
- Bottled at 80 proof or higher
It does not have to come from Kentucky, and there is no minimum aging time for plain "bourbon".
Straight bourbon
"Straight" means the bourbon was aged at least two years, with nothing added for color or flavor. If it's younger than four years, the label has to state the age.
Bottled-in-bond
A rule from the Bottled-in-Bond Act of 1897, and still one of the strictest on any label. A bonded whiskey must be:
- Made by one distillery, in one distilling season
- Aged at least four years in a federally bonded warehouse
- Bottled at exactly 100 proof
The label also has to name the distillery where it was made. That makes bottled-in-bond a good sign of a straightforward, honest pour, often at a fair price.
Cask strength (or barrel proof)
Bottled at, or very close to, the proof it came out of the barrel, with little or no water added. Expect anywhere from about 110 to over 130 proof. A splash of water opens these up.
Single barrel
Every bottle comes from one barrel rather than a blend of many. Two bottles of the same single barrel bourbon can taste noticeably different, which is the point. Private barrel picks are single barrels chosen by a group or a store.
Small batch
No legal meaning. It usually signals a blend of a smaller number of selected barrels, but how small is up to the producer.
Age statements
An age on the label is the age of the youngest whiskey in the bottle. "10 years" means nothing in it is younger than ten.
FAQ
Is bottled-in-bond better than other bourbon?
Not automatically, but the rules guarantee age, proof and a single source, so it's a reliable place to start.
Does bourbon have to be made in Kentucky?
No. It has to be made in the United States. Most of it is made in Kentucky.
What's the difference between cask strength and barrel proof?
In practice, nothing. Both mean bottled at or near the proof it came out of the barrel.