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Way low FG - Why?

Northern Brewer General
#1

Okay, I just ended up bottling my eighth batch of beer, but for some reason the FG was WAY off 1.029 versus 1.012.

I was brewed a MW Dark Maple Ale extract kit, OG 1.052 (just a little higher then estimated), 5 gal batch (full boil). Based upon the age of my Wyeast and using Mr. Malty’s yeast calculator, I pitched 3 packs of London Ale 1028.

The batch spent two weeks in the primary at around 68 degrees and an additional two weeks in the secondary before bottling. I did not take gravity reading before racking to the secondary (my bad), but in all fairness everything “looked” good.

So why did I end up with a 3% versus 5% beer? What could/should I have done differently?

#2

Tough to say. My style is to leave in the primary for a month mininum, take a gravity reading to ensure completness before transfering. Then you could try to remedy the high FG by swirling the carboy gently to stir it up a bit or pitch more yeast.

You used a lot of yeast. Possibly all 3 of your 1028 were past their fresh date, not as viable as thought. Possible hydrometer reading error.

I’d be carefull if you’re bottle conditioning. That’s a lotta sugar if you toss in fresh yeast.

#3

Hard to say without tasting it myself. It sure seems like 3 packs of yeast would be enough. But did you smack them first? Or did you skip the smacking and just pour them in? It’s possible that the yeast was not perfectly viable. But if you did smack and the packs did swell, then I’m really at a loss. Could be really poor extract. Or maybe if there was a yeast issue, there could have been a significant lag time. Do you know on which day after pitching you began to see signs of fermentation (bubbling airlock, bubbles on surface)? If it started right up within 18 hours, it should have been fine, but if for some reason fermentation was delayed until like day 3 or 4 or more, then who knows what really got in there to ferment your wort.

One other thing – are you absolutely sure that all your gravity readings are 100% correct? If you thought your OG was 1.052 but it was really 1.070 or something, this could explain part of the issue as well, but maybe not all of it.

This is a tough one. Need more info.

#4

Dave - I very confident in my gravity readings, so I don’t think that’s an issue. I did smack the packs about five hours before pitching and they expanded to max possible (Always wonder why they don’t explode!). I had active and regular bubbling in the airlock within twelve hours and it remained very active for about two days. There was enough activity in the airlock after a week, that I waited one more before racking to the secondary. Everything was looking good, hense not taking a reading like I should have when racking. I guess the yeast could have been bad - I did use yeast from two different dates, but didn’t think that would matter. Hate brewing and waiting six weeks just for a small beer… :frowning:

#5

Well, whatever it is we all make mistakes at some point. And when we don’t make mistakes, sometimes things just don’t work out.

How does it taste? Small beers are nice to have around and if it tastes alright at least you can take solace in the fact that it’s drinkable.

#6

Would you mind posting the recipe? Maybe there was just way way way too much crystal malt in there or something. And if anything other than light extract was used, the amber and dark malt extracts contain crystal malt as well. Crystal malt is not very fermentable. So that could be part of the problem if true.

#7

If you do the math on the readings correctly you may be surprised, You stated FG to be 1.012 and OG to be 1.052. If these figures are correct, your beer has 8.30% ABV and 6.67% ABW.

The extra low FG means the yeast was very efficient in eating sugars to make alcohol, Which shows by the High alcohol content.

Don’t try to session this beer…lol

Cheers!

#8

On a lesser note if the FG was the 1.029 & OG was 1.052 then the ABV is 4.89% & the ABW is 3.93%…
jus sayin…

#9

[quote=“Shanhorn”]If you do the math on the readings correctly you may be surprised, You stated FG to be 1.012 and OG to be 1.052. If these figures are correct, your beer has 8.30% ABV and 6.67% ABW.

The extra low FG means the yeast was very efficient in eating sugars to make alcohol, Which shows by the High alcohol content.

Don’t try to session this beer…lol

Cheers![/quote]

I’m sorry but those numbers aren’t right. 1.052 to 1.012 gives 5.2% abv. Those are kind of the classic pale ale numbers. I’m not sure where you’re getting your numbers from but maybe there is a decimal point askew…

To the OP, what was your pitch temperature and fermentation temperature? Temp toward the end of fermentation? To me this is the most likely cause for poor attenuation given the circumstances you describe.

#10

Remember this is an extract kit from Midwest:

  • 8 oz Caravienne Malt - 60 Min
  • 8 oz Carapils - 60 Min
  • 6 lbs Briess Dark LME - 60 Min
  • 12 oz Pure Maple Syrup - 15 Min
  • 1 oz Northern Brewer Hops - 60 Min
  • 1 oz Cascade - 2 Min

Boil size 5.75 gal, batch size 5 gal

Pitched the yeast at 67 degrees.
Estimated OG: 1.050, Estimated FG: 1.012
Actual OG: 1.052, Actual FG: 1.029

On the plus side, it does taste good…

#11

[quote=“Shanhorn”]On a lesser note if the FG was the 1.029 & OG was 1.052 then the ABV is 4.89% & the ABW is 3.93%…
jus sayin…[/quote]

Interesting - BrewMaster is giving me a calculation of 3.01% ABV with the above numbers…

#12

I have been using this SG converter from Brewmasters warehouse. Fill in the blanks & bam figures for ABW & ABV & ACTUAL Final Gravity are given.

http://www.brewmasterswarehouse.com/pro ... h-sg-scale

When I use the paper scale from my broken Hydrometer the figures come out as 1.052=6.8%, 1.029=3.8% leaving only 3%ABV.

Now I thought I read it wrong, The FG the OP has given is actually high for a FG, the low reading of 1.012 is a good FG. Why would the converter link I posted be so far off??

#13

[quote=“Shanhorn”]I have been using this SG converter from Brewmasters warehouse. Fill in the blanks & bam figures for ABW & ABV & ACTUAL Final Gravity are given.

http://www.brewmasterswarehouse.com/pro ... h-sg-scale

When I use the paper scale from my broken Hydrometer the figures come out as 1.052=6.8%, 1.029=3.8% leaving only 3%ABV.

Now I thought I read it wrong, The FG the OP has given is actually high for a FG, the low reading of 1.012 is a good FG. Why would the converter link I posted be so far off??[/quote]

I think you’re misunderstanding how to use the BMW calculator. It is meant for correcting a refractometer FG reading, where the alcohol content and the sugar content of the sample both affect the refraction. The calculator corrects by subtracting the alcohol effect out. When you input 1.052 as the SG and 1.012 as the FG, that calculator is assuming you actually read a refractometer at 1.012 and then taking that FG number and converting it to an actual FG of 0.9886. Going from 1.052 to 0.9886 would in fact produce an 8.3% ABV. If one had a beer finish at 1.012 on a hydrometer, the refractometer would read 1.027.

#14

[quote=“cskollmann”][quote=“Shanhorn”]I have been using this SG converter from Brewmasters warehouse. Fill in the blanks & bam figures for ABW & ABV & ACTUAL Final Gravity are given.

http://www.brewmasterswarehouse.com/pro ... h-sg-scale

When I use the paper scale from my broken Hydrometer the figures come out as 1.052=6.8%, 1.029=3.8% leaving only 3%ABV.

Now I thought I read it wrong, The FG the OP has given is actually high for a FG, the low reading of 1.012 is a good FG. Why would the converter link I posted be so far off??[/quote]

I think you’re misunderstanding how to use the BMW calculator. It is meant for correcting a refractometer FG reading, where the alcohol content and the sugar content of the sample both affect the refraction. The calculator corrects by subtracting the alcohol effect out. When you input 1.052 as the SG and 1.012 as the FG, that calculator is assuming you actually read a refractometer at 1.012 and then taking that FG number and converting it to an actual FG of 0.9886. Going from 1.052 to 0.9886 would in fact produce an 8.3% ABV. If one had a beer finish at 1.012 on a hydrometer, the refractometer would read 1.027.[/quote]

I do see this now, I did the math on the hydro paper & got 3% so I must be doing it correct manually! lol

#15

[quote=“cskollmann”][quote=“Shanhorn”]I have been using this SG converter from Brewmasters warehouse. Fill in the blanks & bam figures for ABW & ABV & ACTUAL Final Gravity are given.

http://www.brewmasterswarehouse.com/pro ... h-sg-scale

When I use the paper scale from my broken Hydrometer the figures come out as 1.052=6.8%, 1.029=3.8% leaving only 3%ABV.

Now I thought I read it wrong, The FG the OP has given is actually high for a FG, the low reading of 1.012 is a good FG. Why would the converter link I posted be so far off??[/quote]

I think you’re misunderstanding how to use the BMW calculator. It is meant for correcting a refractometer FG reading, where the alcohol content and the sugar content of the sample both affect the refraction. The calculator corrects by subtracting the alcohol effect out. When you input 1.052 as the SG and 1.012 as the FG, that calculator is assuming you actually read a refractometer at 1.012 and then taking that FG number and converting it to an actual FG of 0.9886. Going from 1.052 to 0.9886 would in fact produce an 8.3% ABV. If one had a beer finish at 1.012 on a hydrometer, the refractometer would read 1.027.[/quote]

Now this is interesting… I’m using a refractometer for my gravity readings. Using the above link It indicates a 4.89% ABV - much coser to what I was expecting… Perhaps I’ve found my answer? If so, I will not be able to use iBrewMaster for my calculations in the future. Hmmm.

#16

How cool is this?, that the simple use of a form has solved the issue @ hand!

#17

Glad to hear you figured it out, cheers!

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