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Old 04-18-2013, 10:52 PM   #1
Apr 2013
Posts: 7

I have been making some ferments with wild symbiotic yeast/bacteria blends like water kefir and ginger beer (using sugar water recipes).

I want to measure the alcohol content and read online that it's not really possible if there is carbonation involved. ??

I am not sure if that's true or not but I figure there must be a way to measure because the process is so similar to making beer and I assume you all figured a way to measure alcohol in beer by now obviously.

Any special way I need to go about measuring? I want a very accurate reading. Thanks for your thoughts.

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Old 04-18-2013, 11:02 PM   #2
May 2011
Stow, MA
Posts: 18,853
Liked 3367 Times on 2509 Posts

De-gas the brew via agitation, then test the SG...


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Old 04-20-2013, 06:04 PM   #3
Apr 2013
Posts: 7

oh ok cool that easy huh? good to know

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Old 04-24-2013, 05:16 PM   #4
TopherM's Avatar
Mar 2011
St. Petersburg, FL
Posts: 3,974
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You want to measure the FG of a beer that's already been carbonated, or you are worried about the de-gassing of CO2 in primary/secondary when you take hydrometer readings?

If you want to measure the FG of a beer that's already carbonated, just degas it, like suggested above. If you are worried about the slight bit of residual CO2 in primary/secondary when you take your FG reading, just make sure you spin your hydrometer so it doesn't have any CO2 bubbles on it.

Even easier: Do you have an OG measurement for this brew? You could get pretty close on estimating the FG and then ABV by just using the expected attenuation rate of the yeast you used without having to measure FG. For example an S-05 yeast (and most ale yeasts) has a 70-75% attenuation rate, so your FG is going to be 70-75% of your OG. You can then use that estimate to estimate the ABV with a margin of error of about +/- 0.2-0.3 or so.

Don't overthink it. I can't think of many good reasons why a home brewer would need an EXACT ABV measurement, and you can estimate it pretty easily.

Also, long run, spend $22 and get BeerSmith. Among the 50+ other brewing calculations it automates for you, it does a OG estimate, FG estimate, attenuation estimate, and ABV estimate based on your ingredients. You can then manually enter OG and/or FG actual readings to automatically fine tune the ABV measurement, among countless others.

Good luck!
Primary #1 - Midnight Ryeder (Midnight Wheat and Rye)
Primary #2 - Florida Weiss
Primary #3 - Kane-DOH APA (Honey Citra APA)
Secondary #1 - Downtown Flanders Brown (brewed August 2012)
Keg #1 - Raspberry Florida Weiss
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Keg #3 - NONE!
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