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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Very low ABV despite active fermentation and good BRIX readings
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Old 05-12-2012, 12:56 PM   #1
mjkinne23
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Default Very low ABV despite active fermentation and good BRIX readings

I just brewed my first all grain batch after investing a lot of time and money in building my own system. Despite having a very active fermentation and hitting my OG targets I have almost not alcohol content. I'm not giving up but I need to understand what I did wrong before trying again. I'd be very appreciative for any help anyone can offer.

I had trouble getting the mash temperatures my brewsmith software listed right. I undershot it and tried adding more hot water unsuccessfully. I eventually had to pour off much of the soup and heat it in my brew kettle while stirring continuously so as to not burn the grains. I eventually got the temperature right and the mash seemingly went fine. I took a BRIX reading when transferring to the brew kettle and it appeared correct. The boil went fine and my OG in the carboy was exactly what I was told to expect.

Fermentation started very quickly and was extremely active, lasting a surprisingly long 2 weeks. When I racked to the secondary I took another reading and it indicated almost no alcohol. I let sit for about a month and then bottled. At bottling the BRIX was also telling me the ABV was low, 1.5% and it tasted as such.

After a couple of weeks I tried my first bottle. While the taste was excellent it has almost no alcohol.

How can there be so little alcohol when the fermentation was so active? Any ideas as to what went wrong and how to improve for my next batch?

Thanks for your help
Matt

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Old 05-12-2012, 01:17 PM   #2
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The brix reading is incorrect- sort of. When you take a reading, the brix reading is telling you the amount of potential alcohol remaining. So technically it's correct, but it's useless information.

What you need to do is take the original brix reading, and subtract the current brix reading for the approximate ABV. It's easier to do that in the SG scale, so you'd convert the brix reading to the SG reading first.

The formula for the ABV is (OG-FG) x131 = approximate ABV

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Old 05-12-2012, 01:17 PM   #3
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Maybe I'm wrong, but don't you take your original brix reading, then subtract your final reading to arrive at your actual abv. Is 1.5 your final reading?

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Old 05-12-2012, 01:23 PM   #4
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Sorry, I probably should have been more thorough. I used the BRIX readings and entered that into my software to calculate the OG and FG to then obtain my final ABV. I certainly may have done something wrong with the readings but I'm still struggling to understand how I ended up with almost no alcohol even with such an active fermentation for a long period.

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Old 05-12-2012, 01:27 PM   #5
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What's your recipe, how big of a batch, and what where your measurements.

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Old 05-12-2012, 01:28 PM   #6
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You say you're measuring in Brix, but it isn't clear how exactly you are measuring the gravity. Are you using a hydrometer (I have never heard of one reading in Brix but I'm sure they must exist) or a refractometer? If you're using a refractometer then at least part of the issue is that refractometers are not accurate when there is acohol in the beer/wort.

If you did indeed hit your OG & FG then you almost certainly have the predicted alcohol content. Software predicts the alcohol content specifically from those two numbers. It isn't an independent measurement.

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Old 05-12-2012, 01:36 PM   #7
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I made a 5 gallon Dunkelweizen, the grain bill was:

6lb white wheat
4lb 2 row
8oz caramunich
4oz pale chocolate
4oz carafa special II

My pre-boil gravity was 1.046 and into the carboy it was 1.054, target OG was 1.050-1.052. When I racked it was 1.032 but when I bottled it was 1.40 (one was a bad reading?).

Can't thank all of you enough for your help!

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Old 05-12-2012, 01:39 PM   #8
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Quote:
Originally Posted by mjkinne23 View Post
I made a 5 gallon Dunkelweizen, the grain bill was:

6lb white wheat
4lb 2 row
8oz caramunich
4oz pale chocolate
4oz carafa special II

My pre-boil gravity was 1.046 and into the carboy it was 1.054, target OG was 1.050-1.052. When I racked it was 1.032 but when I bottled it was 1.40 (one was a bad reading?).

Can't thank all of you enough for your help!
Hopefully you didn't bottle it at 1.040! But I'd say it's a bad reading- there is no way for a reading to go UP after fermentation ends.

Did you use a hydrometer?
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Old 05-12-2012, 01:43 PM   #9
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Quote:
Originally Posted by Yooper View Post

Did you use a hydrometer?
I used a refractometer to take all my readings.
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Old 05-12-2012, 01:45 PM   #10
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Could it have been a very very slow fermentation that I should have just let continue longer? The foam had settled back and it had been 2 weeks. Can it take longer with AG?

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