# Why are most liquors 80 proof? **URL:** \ **Category:** Factual Questions\ **Created:** [May 15, 2012, 5:49pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004 "2012-05-15T17:49:12Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [May 17, 2012, 3:50pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/21 "2012-05-17T15:50:25Z")
> [@am77494](#): > > This maybe explained by Game Theory ( Nash Equilibrium - Competitive Strategy). How? ---
**Author:** ![Kinthalis](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kinthalis/32/16084_2.png) [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)\ **Post date:** [May 17, 2012, 4:03pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/22 "2012-05-17T16:03:22Z")
> [@kenobi\_65](#): > > The term came from the U.K., and was based on the spirit’s ability to sustain the combustion of gunpowder. 100 proof was the amount of alcohol in the beverage which was needed to do so – it was actually ~57% alcohol by volume, though the U.S. definition of proof is somewhat different. > [Alcohol proof - Wikipedia](http://en.wikipedia.org/wiki/Alcohol_proof) So cool. So kind of like “bullet Proof” and armor back in the 15th century! I’m totally going to start demanding this test from my local liquor store. ---
**Author:** ![Gagundathar](https://avatars.discourse-cdn.com/v4/letter/g/a183cd/32.png) [@Gagundathar](https://boards.straightdope.com/u/Gagundathar)\ **Post date:** [May 17, 2012, 7:30pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/23 "2012-05-17T19:30:44Z")
> [@Kinthalis](#): > > A related question: > > Why proof? Who came up with this measurement? It looks like proof = twice the percent of alcohol by volume right? Why not just use alcohol by volume? I have often wondered the same myself. According to this relatively reliable source (Wikipedia): > [@](#): > > From the 18th century until 1 January 1980, the United Kingdom measured alcohol content in terms of “proof spirit”, which was defined as the most dilute spirit that would sustain combustion of gunpowder.[1] The term originated in the 18th century, when payments to British sailors included rations of rum. To ensure that the rum had not been watered down, it was “proved” by dousing gunpowder in it, then tested to see if the gunpowder would ignite. If it did not, then the rum contained too much water and was considered to be “under proof”. Gunpowder would not burn in rum that contained less than approximately 57.15% ABV. Therefore, rum that contained this percentage of alcohol was defined to have “100° (one hundred degrees) proof”. Drats! Did not read far enough in the dang thread! Sorry. Kenobi is right as far as I can tell. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [May 17, 2012, 8:25pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/24 "2012-05-17T20:25:14Z")
This sounds like a great opportunity to hijack the thread to ask something that I’ve been wondering for a while. Suppose I poured a glass of whiskey, and let the glass out at room temperature for while – say several weeks. Long enough for it to evaporate by about half. Will it get stronger or weaker? ---
**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\ **Post date:** [May 17, 2012, 8:36pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/25 "2012-05-17T20:36:41Z")
> [@tdn](#): > > Suppose I poured a glass of whiskey, and let the glass out at room temperature for while – say several weeks. Long enough for it to evaporate by about half. Will it get stronger or weaker? [This article](http://bayblab.blogspot.com/2009/01/evaporation-rates-of-ethanol-solutions.html) has the answer to your question. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [May 17, 2012, 8:43pm UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/26 "2012-05-17T20:43:37Z")
> [@DCnDC](#): > > [This article](http://bayblab.blogspot.com/2009/01/evaporation-rates-of-ethanol-solutions.html) has the answer to your question. Thanks! I’m putting the cap back on… ---
**Author:** ![Floater](https://avatars.discourse-cdn.com/v4/letter/f/dc4da7/32.png) [@Floater](https://boards.straightdope.com/u/Floater)\ **Post date:** [May 18, 2012, 10:10am UTC](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004/27 "2012-05-18T10:10:31Z")
> [@tdn](#): > > Suppose I poured a glass of whiskey, and let the glass out at room temperature for while – say several weeks. Long enough for it to evaporate by about half. Will it get stronger or weaker? Anecdotal evidence. I had once made me a batch of wormwood flavoured vodka which I kept in a vessel similar to [these](http://www.google.com/imgres?start=17&num=10&hl=en&as_st=y&biw=1024&bih=619&tbm=isch&tbnid=0CxEUMrIZzM4hM:&imgrefurl=http://www.auction2000.se/ADA/%3FinA%3D20110704_0908&docid=ZSpaSC6uGagJZM&imgurl=http://pic01.auction2000.se/aukpic/ada/20110704_0908/23012_1.jpg&w=800&h=600&ei=xh22T_ols9LhBIm__KMJ&zoom=1&iact=rc&dur=444&sig=107821222095641573253&page=2&tbnh=125&tbnw=176&ndsp=22&ved=1t:429,r:18,s:17,i:44&tx=94&ty=78). Unfortunately the glaze was porous enough to emulate the situation you describe, so in the end all I had was bitter water. [Previous page](https://boards.straightdope.com/t/why-are-most-liquors-80-proof/622004.md?page=1)