Author Topic: Question about high final gravity  (Read 1629 times)

Offline christophercoll

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Question about high final gravity
« on: February 13, 2015, 01:51:06 PM »
Hi,  I'm wondering if someone can provide some advice...

My first all-grain batch has been in the fermenter for 3 weeks and my gravity readings have come in higher than expected at a consistent gravity of 1.015 for the last two days.  The beer smells and tastes good, but I'm worried that I won't be able to hit the projected ABV (was 5.1%, coming in now at close to 4%).

OG of 1.045
Projected FG of 1.05
Gravity reading has been at 1.015 for 2 days.

Grain Bill:
7  lbs Pale
3  lbs Victory
.5 lbs Chocolate
.75 lbs Crystal 60

Yeast: Irish Ale Yeast

My strike water was 5.6 gallons at a temp was 160, dropped to a consistent 152 when grain was added.  I added another 3.5 gallons to sparge with.

The first week in the fermenter, I kept the temp at 70 and have dropped it down to 65 for the last two weeks. The krausen dropped after 2 days.

My first thought was that this could be a stuck fermentation, but I'm not sure.


So I'm wondering:
-could the volume of sparge water have impacted the level of fermentability?
-is there anything that I could do to increase the ABV at this point?  Pitch more yeast?  Add some kind of sugar to the fermenter?   I just don't want to ruin the beer.

I can live with a lower ABV, but I want to understand what went wrong.  I also don't want to try to fix it and wind up ruining it.

Thanks
Chris








Offline bboy9000

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Re: Question about high final gravity
« Reply #1 on: February 13, 2015, 02:50:05 PM »
1.  temperature swings are never good,  the lower temperature may have caused active yeast to flocculate out.

2.  By expected FG "1.05" I think you meant 1.005.  I don't put much into expected FG calculations.  This is a pretty low FG, especially for the Irish Ale yeast IME.  Still, I think you could have gotten lower than you did had you not dropped the temperature.

3.  That's an awfully high amount of specialty malt as a percentage of your total grain bill. I'm not sure how fermentable victory malt is so someone else can chime in.

As to your questions, yes you could pitch more yeast buy I'd make sure it's an active starter- but at this point you are at 66% apparent attenuation so I'd just leave it. 

You could add a simple sugar to raise ABV but it would mess up the flavor and body for this style and I the yeast aren't active it wouldn't get fermented anyway.

Finally, I don't think the volume of sparge water would effect fermentability, just the original gravity.  Fermentability has more to due with the grain bill, mash temp and technique.

I'd try swirling the fermentor gently a bit to rouse the yeast and move it back to 70F for a week.  If that doesn't help I'd just leave it and enjoy a lower abv beer.
Brian
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Re: Question about high final gravity
« Reply #2 on: February 13, 2015, 02:56:41 PM »
Did you aerate the wort?

Offline Stevie

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Re: Question about high final gravity
« Reply #3 on: February 13, 2015, 02:57:54 PM »
1.045 down to 1.005 is 90% ADF. That is an unreasonable expectation for most grain bills and yeasts. I think it's as low as it will go.

Offline HoosierBrew

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Re: Question about high final gravity
« Reply #4 on: February 13, 2015, 03:12:49 PM »
1.045 down to 1.005 is 90% ADF. That is an unreasonable expectation for most grain bills and yeasts. I think it's as low as it will go.

Yep.
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Offline brewinhard

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Re: Question about high final gravity
« Reply #5 on: February 13, 2015, 03:18:07 PM »
+1 to too much specialty malt.  The 3# of victory probably added at least a few gravity points there of unfermentables. 

Offline HoosierBrew

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Re: Question about high final gravity
« Reply #6 on: February 13, 2015, 03:19:21 PM »
+1 to too much specialty malt.  The 3# of victory probably added at least a few gravity points there of unfermentables. 

Yeah, and 3 lbs of Victory is a lot of Victory. I normally use more like 3- 5 %.
« Last Edit: February 13, 2015, 03:21:03 PM by HoosierBrew »
Jon H.

Offline Joe Sr.

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Re: Question about high final gravity
« Reply #7 on: February 13, 2015, 03:59:46 PM »
All of the above plus I would mash lower than 152 if I wanted to wind up at 1.005.
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Offline bboy9000

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Question about high final gravity
« Reply #8 on: February 13, 2015, 04:24:32 PM »
plus I would mash lower than 152 if I wanted to wind up at 1.005.

Which would be a decent FG for a saison but not an Irish Ale.

Edit:  to OP, how did you come up with 1.005 as the FG?
Brian
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Offline denny

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Re: Question about high final gravity
« Reply #9 on: February 13, 2015, 04:45:46 PM »
1.045 down to 1.005 is 90% ADF. That is an unreasonable expectation for most grain bills and yeasts. I think it's as low as it will go.

Yep.

Double yep.  I wish people would learn to ignore FG predictions.
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Offline kramerog

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Re: Question about high final gravity
« Reply #10 on: February 13, 2015, 04:46:20 PM »
Irish Ale yeast is very flocculent; I wouldn't expect it to get to low gravity levels.

Offline christophercoll

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Re: Question about high final gravity
« Reply #11 on: February 13, 2015, 11:45:30 PM »
Thanks everyone, I appreciate the feedback.   

I hadn't thought about the implications for the volume of victory malts, and I hadn't worked with the irish ale yeast before either.  It sounds like those are the main culprits.   



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Re: Question about high final gravity
« Reply #12 on: February 14, 2015, 05:14:22 AM »
Irish Ale yeast is very flocculent; I wouldn't expect it to get to low gravity levels.

The OP should have achieved better than 67% AA.  My bet is on insufficient aeration.  That is one of the major problems that new brewers encounter when they move from partial-boil extract to full-boil all-grain.


Offline zorch

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Re: Question about high final gravity
« Reply #13 on: February 15, 2015, 05:28:15 PM »
The first week in the fermenter, I kept the temp at 70 and have dropped it down to 65 for the last two weeks. The krausen dropped after 2 days.

This is pretty much the exact opposite of what I would do.   Rather than start at 70 then drop to 65 after a week, you will probably have better results if you started at 65 then ramped up to 70 after a few days to finish fermentation. 

Starting cool then raising the temp after a few days helps control esters and encourages the yeast to clean up diacetyl precursors at the end of fermentation.
Starting relatively warm then dropping the temp 5 degrees is a good way to get your yeast to drop out early and leave a lot of diacetyl behind, especially with an Irish strain.

Offline erockrph

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Re: Question about high final gravity
« Reply #14 on: February 15, 2015, 05:55:45 PM »
The first week in the fermenter, I kept the temp at 70 and have dropped it down to 65 for the last two weeks. The krausen dropped after 2 days.

This is pretty much the exact opposite of what I would do.   Rather than start at 70 then drop to 65 after a week, you will probably have better results if you started at 65 then ramped up to 70 after a few days to finish fermentation. 

Starting cool then raising the temp after a few days helps control esters and encourages the yeast to clean up diacetyl precursors at the end of fermentation.
Starting relatively warm then dropping the temp 5 degrees is a good way to get your yeast to drop out early and leave a lot of diacetyl behind, especially with an Irish strain.
+1 - I ruined my first batch of homebrew doing this. Complete butterbomb.
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