Home Brew Forums > Home Brewing Beer > Beginners Beer Brewing Forum > Any method to actually determine ABV %...
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Old 09-24-2008, 09:58 PM   #1
Quikfeet509
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Default 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.


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Old 09-24-2008, 10:00 PM   #2
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Chug a 12 ounce glass on and empty stomach.

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


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Old 09-24-2008, 11:42 PM   #3
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Quote:
Originally Posted by Quikfeet509 View Post
...instead of using a hydrometer to get a potential ABV%? Just curious.
You can also use that hydrometer to get a reading after fermentation, and then calculate the % ABV using SG - FG *131
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Old 09-24-2008, 11:43 PM   #4
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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.

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Old 09-24-2008, 11:45 PM   #5
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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

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Old 09-25-2008, 12:05 AM   #6
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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.
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Old 09-25-2008, 12:12 AM   #7
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My hydrometer cost me less than ten bucks and about the same for the test tube. Use the formula (SG-FG) x 131=ABV.
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Old 09-25-2008, 12:22 AM   #8
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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/...before_action/
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Old 09-25-2008, 02:44 PM   #9
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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.
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Old 09-25-2008, 02:59 PM   #10
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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.


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