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

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

In: 4

The proof is double the percentage, so 80 proof means 40% alcohol. I don’t know the purpose.

Proof is the percentage of the alcohol doubled. 100 proof is 50 percent alcohol. I’m not entirely sure of the reason why it’s measured in proof though honestly.

One easy way to tell the alcohol content is to see if it can be set on fire. Any alcohol percentage above 50% is flammable but people back in the days couldn’t measure the alcohol percentage directly.

Thus they set the lower limit of a flammable alcohol beverage (50%) to a proof value of 100. That proof can then be diluted to lower levels. As a coincidence, the proof value is double the alcohol percentage.

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.

Liquor will burn at about 50% ethanol. Or 50%. However, back in the day only scientists would have hydrometers and be able to accurately measure a liquors alcohol percent. So instead, what you would do to make sure your liquors werent watered down is you would burn a few drops as “proof.” If it caught flame it was good liquor. If it didn’t catch flame, your salesman was selling you an inferior product. So the term “proof” started as “this is good liquor”.

Well eventually alcohol became a regulated business. And suppliers had to state how strong it was. But they already had a concept and language for “good” liquor. So the term proof stayed. And they picked 100 proof as 50% ethanol just to put a standard value to proof.

The original, old fashioned proof meant it could spill on gunpowder and not damage the powder’s ability to burn. This was important back in the days when alcohol (rum) was given as part of the navy daily ration. It was stored near the powder and nobody wanted the powder to get f’d up and not work.

today the definition has changed, as I’m sure other posters will point out.

0 views
6 Comments

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

In: 4

The proof is double the percentage, so 80 proof means 40% alcohol. I don’t know the purpose.

Proof is the percentage of the alcohol doubled. 100 proof is 50 percent alcohol. I’m not entirely sure of the reason why it’s measured in proof though honestly.

One easy way to tell the alcohol content is to see if it can be set on fire. Any alcohol percentage above 50% is flammable but people back in the days couldn’t measure the alcohol percentage directly.

Thus they set the lower limit of a flammable alcohol beverage (50%) to a proof value of 100. That proof can then be diluted to lower levels. As a coincidence, the proof value is double the alcohol percentage.

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.

Liquor will burn at about 50% ethanol. Or 50%. However, back in the day only scientists would have hydrometers and be able to accurately measure a liquors alcohol percent. So instead, what you would do to make sure your liquors werent watered down is you would burn a few drops as “proof.” If it caught flame it was good liquor. If it didn’t catch flame, your salesman was selling you an inferior product. So the term “proof” started as “this is good liquor”.

Well eventually alcohol became a regulated business. And suppliers had to state how strong it was. But they already had a concept and language for “good” liquor. So the term proof stayed. And they picked 100 proof as 50% ethanol just to put a standard value to proof.

The original, old fashioned proof meant it could spill on gunpowder and not damage the powder’s ability to burn. This was important back in the days when alcohol (rum) was given as part of the navy daily ration. It was stored near the powder and nobody wanted the powder to get f’d up and not work.

today the definition has changed, as I’m sure other posters will point out.