80 Proof?

[Dravin]

Okay, I know that this means the drink is 40% Alcohol by volume, by why is proof used instead of (and many times alonge side) alcohol by volume?

And when and why did it start being used? I was chatting with a friend in Norway and it got brought up.

[Happy_Lendervedder]

From here: http://www.ex.ac.uk/cimt/dictunit/notes6.htm

What is Proof?

Proof is another (older) measure of the strength of an alcoholic liquid.
It had its origins in days when a simple test was needed that the liquor did indeed contain a correct measure (or more) of alcohol. And it was indeed a simple test.
Some of the liquor was poured over a little gunpowder and ignited. If the alcohol content was adequate, then it would burn ‘just right’ with a steady blue flame and eventually ignite the gunpowder. If there was insufficient alcohol then it would fizzle out and the gunpowder would be too wet to burn. The ‘just right’ condition ‘proved’ the liquor and it was declared to be ‘100% proof’.
This simple test was clearly cumbersome to perform and was later replaced by using a specially graduated hydrometer to measure the specific gravity. This was far more objective and allowed precise statements to be made as to how much different it was from being 100% proof. This gave rise to “under-proof” and “over-proof” measures.

Happy

[samclem]

The OED lists it first from 1705. It seemed to relate to Brandy and showing that it was above the alcohol level of mundane spirits, which

All the Liquors under the Proof of common Spirits, freeze to a State perfectly solid(1747)

Also, it was implied in one early quote that it was “proof” that the brandy was the real stuff.

[Dravin]

Cool, thanks a bunch.