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

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

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?

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.

What's your recipe, how big of a batch, and what where your measurements.

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.

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!

mjkinne23 said:

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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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?

Yooper said:

Did you use a hydrometer?

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I used a refractometer to take all my readings.

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?

Did you use the refractometer tool to adjust your final gravity reading??? Alcohol throws off your readings considerably, Beersmith (I'm sure elsewhere does also) has a correction calculator for this... for instance, my IIPA that I just kegged, started out reading 1.087 with my refractometer (correct), and the FG read something like 1.038, but when you factor in the alcohol, and run your correction the ACTUAL FG was like 1.010.

Just a thought.

mjkinne23 said:

I used a refractometer to take all my readings.

Click to expand...

That explains it, then. A refractometer is great for pre fermentation readings, but alcohol skews the light refraction (which is what a refractometer measures), so you should take the FG with a hydrometer.

There ARE calculators to guestimate the "real" reading if you enter the original reading, but they are not all that accurate.

Next time you open a beer, pour some in a testing flask and shake it to decarb. Let it warm, and then take the SG when it's flat. That will be the correct reading.

Yooper said:

That explains it, then. A refractometer is great for pre fermentation readings, but alcohol skews the light refraction (which is what a refractometer measures), so you should take the FG with a hydrometer.

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So I clearly made a rookie mistake when calculating my post fermentation gravitates but is it really as simple as not having let it ferment long enough? I know readings are the only true way to know when it is over but it had been two weeks of very active fermentation and the foam had fallen back in on itself. It was as least as active as all my extract batches. Hard to imagine it still had that far left to go.

mjkinne23 said:

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!

Click to expand...

You say the gravity when racking was 1.032. If you were using raw wort (i.e. no alcohol) conversions, that would translate to a brix reading of 8.25

If you started with an OG reading of 1.054 (brix 13.75), then a brix reading of 8.25 after 2 weeks of fermentation would indicate a SG of 1.020 according to Promash.
However, as Yooper said, the conversions from brix to SG after fermentation has started are not necessarily accurate, and it could be a few points higher or lower than 1.020, but 1.020 is certainly closer to the mark than 1.032.

-a.

ajf said:

1.020 is certainly closer to the mark than 1.032..

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Thanks a. So other than correct readings, any suggestions on what to do differently with the next batch to produce some actual alcohol?

If the beer is good just drink it with you favorite shot I have tried to do opposite buy mashing hotter on my last batch. I am a light wight and love sweeter beer.

I'm no expert on wheat beer, but isnt there another step with wheat? I'm pretty sure you need to "cook" the wheat first so it will release the starches to be converted by the enzymes in your malts. Also I think your mash time needs to be extended?

make sure you have a good mash tun and make sure you take into account the temp absorption that your tun is going to take out of your mash water. i have taken heating my mash tun to the approximate temp by putting hot water in it. this will help with temp control. my tun drops 1 or 2 degrees over an hour.

oh, and you probably do have ok abv - off the top of my head, probably 4.5% or so

mjkinne23 said:

Thanks a. So other than correct readings, any suggestions on what to do differently with the next batch to produce some actual alcohol?

Click to expand...

What do you mean? You started with an OG of 1.054 and the FG is less than 1.020 (but we don't know the exact reading until you take one). Remember that your last refractometer reading is useless, but since it was post-fermentation and it probably calculates to less than 1.020, that's the figure we can use for sure.

That's at least 4.5% ABV and it is probably higher, depending on the actual FG reading.

mikee said:

I'm no expert on wheat beer, but isnt there another step with wheat? I'm pretty sure you need to "cook" the wheat first so it will release the starches to be converted by the enzymes in your malts. Also I think your mash time needs to be extended?

make sure you have a good mash tun and make sure you take into account the temp absorption that your tun is going to take out of your mash water. i have taken heating my mash tun to the approximate temp by putting hot water in it. this will help with temp control. my tun drops 1 or 2 degrees over an hour.

oh, and you probably do have ok abv - off the top of my head, probably 4.5% or so

Click to expand...

No, you just mash wheat malt just like any other malt.