Alcohol proof and percentage. What’s the difference and purpose?

Question

Alcohol proof and percentage. What’s the difference and purpose?

In: 4

Answer 1

Back in the olden days liquor was taxed based on the alcohol content, but there wasn’t a good way of testing that. The best method we had was to drip the liquor on some gunpowder and try to set it on fire. If it burned, that was “proof” that it contained alcohol. The bare minimum alcohol content that would still burn was defined as 100 proof, which turns out to be about 57% alcohol by volume. Using this scale, pure alcohol would be about 175 proof and 40% alcohol would be 70 proof, for example.

Later, we developed more scientific tests to measure alcohol content by measuring things like specific density and specific gravity, and the laws changed so that alcohol was now regulated in terms of alcohol by volume (ABV) instead of proof. The term “proof” stuck around as a customary measure, but was simply redefined to be exactly double the ABV, e.g. 40% ABV equals 80 proof. These days labelling laws in virtually all countries require listing the ABV; if you see the proof, it’s just redundant for marketing purposes.

Answer 2

Back in the olden days liquor was taxed based on the alcohol content, but there wasn’t a good way of testing that. The best method we had was to drip the liquor on some gunpowder and try to set it on fire. If it burned, that was “proof” that it contained alcohol. The bare minimum alcohol content that would still burn was defined as 100 proof, which turns out to be about 57% alcohol by volume. Using this scale, pure alcohol would be about 175 proof and 40% alcohol would be 70 proof, for example.

Later, we developed more scientific tests to measure alcohol content by measuring things like specific density and specific gravity, and the laws changed so that alcohol was now regulated in terms of alcohol by volume (ABV) instead of proof. The term “proof” stuck around as a customary measure, but was simply redefined to be exactly double the ABV, e.g. 40% ABV equals 80 proof. These days labelling laws in virtually all countries require listing the ABV; if you see the proof, it’s just redundant for marketing purposes.