Any method to actually determine ABV %...

...instead of using a hydrometer to get a potential ABV%? Just curious.

Hopefully there is a way other than using equipment at the local university chem lab.

Chug a 12 ounce glass on and empty stomach.

Honestly, $8.00 for a hydrometer is the simplest method.

Quikfeet509 said:

...instead of using a hydrometer to get a potential ABV%? Just curious.

Click to expand...

You can also use that hydrometer to get a reading after fermentation, and then calculate the % ABV using SG - FG *131

The potential ABV scale on the hydrometer is to give you an idea of your potential based on initial gravity (but it really only works for wine) - but if you subtract your final gravity from your initial gravity and multiply the results by 131, you'll have your actual ABV (assuming your hydrometer is correct and you corrected for temperature).

example: SG = 1.062 FG = 1.015
.062 - .015 = .047 * 131 = 6.157% ABV

That ones a real figure, not a "potential". You can't get the real ABV of course until it's done. And once it's done the potential scale means nothing.

if you have a chem lab i would think taking a sample. measure its volume. burn off as much of the the alcohol as possible then measure volume again. though likely not as accurate as a good og-fg calcuation.

probably other more sophisticated ways but this sounds pretty simple if you dont have a good og/fg

The hydrometer is simply measuring the density of the sample. If you have a good scale and a way to measure the volume accurately, you can do the same thing as a hydrometer.

My hydrometer cost me less than ten bucks and about the same for the test tube. Use the formula (SG-FG) x 131=ABV.

So WHY are you afraid of using a hydrometer....the majority of us do...so what's wrong with us???



When we get done ribbing you for being afraid of a 10 dollar precision instrument...read my blog. http://blogs.homebrewtalk.com/Revvy/Think_evaluation_before_action/

The simple, cheap methods are no more accurate than a hydrometer. To get an accurate value, you'll need a good graduated cylinder or a precision scale and a way to boil off the alcohol without losing water.

Like the other said, take a gravity reading before fementation (original gravity or OG), then you go back and measure it AFTER it is done fermenting (final/finished gravity or FG). Make sure you keep note of the temperature of the wort/beer at time of the reading. Plug the numbers into a formula, beersmith or the many calculators on the internet.

That will give you a very accurate measure of ABV. That number is not an estimate, since the formula is calculating the fact that as sugars get converted to alcohol, the density of the sample will drop. They have figured out via calculations how much alcohol that drop in density corresponds to %alcohol.

Hope that was helpful. Don't use the potential ABV on your hydrometer. If you want a good guesstimate, get beersmith. It will tell you potential alcohol based on its calculation of what your OG and FG SHOULD be.

Excellent info. For some crazy reason, I wanted to find a way to double check the accuracy and precision of the hydrometer [if I have to retake O Chem to make up for a C a decade ago, I might see if I can double check it in the lab], but it looks like that is probably not necessary.


This thread would be finished if there were more pics.

I guess if you wanted to double check you could perhaps weight a sample of beer, keep it at 173 degrees for a long while then measure it again to see how much alcohol boiled off, the problem being you may boil off some water as well, so I'm not sure how to account for that.

My LHBS is primarily a winery. In order to sell his wine, the owner has to have a very precise measurement of the alcohol content in his product. He uses a Ebulliometer.

I don't know the whole process of how it's used.

ebulliometers: Ebulliometer Dujardin Salleron Alcohol Burner @ Wine-Testing-Supplies.com

What is an Ebulliometer?

I don't know if it could be used on beer.

BierMuncher said:

Chug a 12 ounce glass on and empty stomach.

Honestly, $8.00 for a hydrometer is the simplest method.

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Holy cow, are they that expensive nowadays?

I concur, buy one of them thar hydros

Quikfeet509 said:

Excellent info. For some crazy reason, I wanted to find a way to double check the accuracy and precision of the hydrometer [if I have to retake O Chem to make up for a C a decade ago, I might see if I can double check it in the lab], but it looks like that is probably not necessary.


This thread would be finished if there were more pics.

Click to expand...

"Gravity" is just a measure of density, so assuming you have a good enough way to measure volume and mass, you can get the original density and final density of the beer.

I mean, if you take a 100 ml sample, and the mass is 105.5 grams, then you have a density of 1.055 g / ml. Notice that since water has a density of 1 g / ml, that this density is the exact same as "gravity". You can get your final density (gravity) the same way, and use the formula that's already been posted in this thread.

The downside is you can see how accurate you have to be with samples even as large as 100 ml.

Is there a formula to determine abv with just f/g? brix and hydro reading? I believe there is just want to make sure. ?

DKJeremy said:

Is there a formula to determine abv with just f/g?

Click to expand...

Nope.

Actually the OG-FG method using a hydrometer is NOT completely accurate. Just so close to right that nobody needs to worry. The reason it's not completely accurate is because as has already been mentioned you are measuring the total density of the wort/beer not just that of the water and sugar(OG) and then the same water minus the sugar(FG). Other compounds which can affect the density of your sample also drop out of suspension over time as well as the fact that alcohol has a different specific gravity compared to water which throws your calculation off because the FG isn't just water minus the sugar of the OG, it's water and alcohol minus sugar. But everybody is right in that it's the way to go. It's cheap and as accurate as homebrewers need to be, even for competitions. Ie if measure and calculate a brew to 5% and it really turns out to be 5.09, do you think anyone can tell or will even care?

fermentedhiker said:

Actually the OG-FG method using a hydrometer is NOT completely accurate. Just so close to right that nobody needs to worry. The reason it's not completely accurate is because as has already been mentioned you are measuring the total density of the wort/beer not just that of the water and sugar(OG) and then the same water minus the sugar(FG). Other compounds which can affect the density of your sample also drop out of suspension over time as well as the fact that alcohol has a different specific gravity compared to water which throws your calculation off because the FG isn't just water minus the sugar of the OG, it's water and alcohol minus sugar. But everybody is right in that it's the way to go. It's cheap and as accurate as homebrewers need to be, even for competitions. Ie if measure and calculate a brew to 5% and it really turns out to be 5.09, do you think anyone can tell or will even care?

Click to expand...

The state of TX does!

More seriously though, the 131 thing is a very crude linear approximation and one that was fit using data from wine (the homebrewing literature borrowed it from the home wine making literature, rather non-critically).

There is a better approximation due to Balling (via Fix). Anyone interested can find it in posts by Fix on HBD or posts by me here.

If you have access to a GC, that would work very nicely. Much more accurate than a hydrometer. Make sure they don't mind you using their 5 figure piece of equipment to test your beer.

Look here's one for only $7,000! I'm definitely getting that next time I break my hydrometer!

A quality refractometer is also a good alternative. Make sure and adjust for ambient temp. $30-$80. Palmer's authorized carryover for ABV estimation (estimation emphasized):

(OG-FG) * 131.25 = ABV