Quikfeet509

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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.

conpewter

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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.

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FatDuc

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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.

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zoebisch01

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Holy cow, are they that expensive nowadays?

I concur, buy one of them thar hydros

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rocketman768

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"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.

DKJeremy

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

jaobrien6

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Nope.

fermentedhiker

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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?

remilard

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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.

JKoravos

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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!