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Old 01-20-2014, 04:10 PM   #1
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HopSong's Avatar
Sep 2011
Santa Rosa, CA
Posts: 1,945
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When checking the FG of a beer with a hydrometer.. besides checking it at the proper temperature (or using a calculator).. Should you de-gas the beer?

So far, I've never done that.. exceptt, on a past brew, besides twirling the hydrometer to release bubbles from it, I also shook it in the testing tube a few times, and, IIRC, there was a significant difference.. i.e.. it was lower than with the gassed beer straight from the fermenter.

What say you seasoned scientists. It makes sense to remove the gas.. but it is never covered in the literature I've seen. Nor have I seen it discussed here.

Cheers, Bill
Hop Song Brewing

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Old 01-20-2014, 05:13 PM   #2
Nov 2013
Oklahoma City, Oklahoma
Posts: 371
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I'm an engineer, not a scientist, but I always de-gas it. I suppose it depends on if you are accounting for the dissolved gas in your calculations.

Interested to hear the consensus on this.

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Old 01-21-2014, 02:54 PM   #3
Aug 2010
McLean/Ogden, Virginia/Quebec
Posts: 9,197
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Yes, absolutely. If you do not thoroughly degass the sample bubbles of CO2 will come out of solution and adhere to the hydrometer bulb rendering it more buoyant. This causes it to rise further out of the test jar so that you read a higher gravity than the actual one.

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