What qualifies as a 'stuck' fermentation?

[DeadGuyNick]

I just went to check on a stout I made a month ago. The expected FG was supposed to be about 1.017 according to BrewSmith. It came out to about 1.026. Is that considered stuck? Should I try to get it going again with more yeast in a starter?

I tasted it. It's got a bit of a sweet taste, but not overly sweet. It's about 7.35% ABV (expected 7.7%).

What would you do? Call it good and keg it, or try and get that extra gravity point down?

Edit: I'm also not sure if this'll help at all, but during the boil, for some reason I couldn't get a hard rolling boil to go. Used a burner outside. Never had that problem before. It was a low rolling boil, and I boiled a little longer to compensate.

 

[Silver_Is_Money]

I'm not sure if there is an official means by which to definitively proclaim a stuck fermentation, but for me the flag would begin to go up whenever my apparent attenuation was less than 90% of a given yeasts nominal mid-range attenuation rating.

Example using Fermentis W-34/70 lager yeast:
----------------------------------------------------------
Apparent attenuation is factory rated at 83%
0.90 x 83% = 74.7% low range attenuation acceptability
Therefore, fermentation is "potentially" stuck if apparent attenuation is below 74.7%

Example continued:
--------------------------
OG = 1.060
FG target = 1.010 (rounded, for 83% apparent attenuation)
FG for low end of acceptability = 1.015 (rounded, for 74.7% attenuation)

For this example if the actual FG is 1.016 when the "ideal" target is 1.010 you might just begin to start suspecting a stuck fermentation.

https://mashmadeeasy.yolasite.com/

 

[DeadGuyNick]

...less than 90% of a given yeasts nominal mid-range attenuation rating.

I used WLP001, the website says attenuation for that is 73-80. I'll go in the middle and say 76.5.

I found a site that will tell me my attenuation from entering my OG and FG.

OG: 1.082
FG: 1.026
Apparent Att.: 68.3%
90% of 76.5% is 68.85% attenuation.

So if I'm doing this all right, then I'm right about 90% of the avg attenuation of WLP001?

I'll also bring my carboy upstairs from the basement, and carefully swirl it a bit. Maybe I can get it to start up a little bit more, but otherwise, if I did my math right, I guess I can just go ahead and keg it?

 

[Kee]

I used WLP001, the website says attenuation for that is 73-80. I'll go in the middle and say 76.5.

I found a site that will tell me my attenuation from entering my OG and FG.

OG: 1.082
FG: 1.026
Apparent Att.: 68.3%
90% of 76.5% is 68.85% attenuation.

So if I'm doing this all right, then I'm right about 90% of the avg attenuation of WLP001?

I'll also bring my carboy upstairs from the basement, and carefully swirl it a bit. Maybe I can get it to start up a little bit more, but otherwise, if I did my math right, I guess I can just go ahead and keg it?

It won't hurt to let the temperature rise and give it a few more days. I'd hesitate to try anything too drastic, especially if the taste is only slightly sweet.

 

[DeadGuyNick]

It won't hurt to let the temperature rise and give it a few more days. I'd hesitate to try anything too drastic, especially if the taste is only slightly sweet.

Yeah, I'll give it a couple of days and measure again. See if there's an improvement.

 

[Silver_Is_Money]

I used WLP001, the website says attenuation for that is 73-80. I'll go in the middle and say 76.5.

I found a site that will tell me my attenuation from entering my OG and FG.

OG: 1.082
FG: 1.026
Apparent Att.: 68.3%
90% of 76.5% is 68.85% attenuation.

So if I'm doing this all right, then I'm right about 90% of the avg attenuation of WLP001?

I'll also bring my carboy upstairs from the basement, and carefully swirl it a bit. Maybe I can get it to start up a little bit more, but otherwise, if I did my math right, I guess I can just go ahead and keg it?

To find your apparent attenuation just use your OG and FG readings fractions above 1.000 as if they were whole numbers, and do this:

(82 - 26)
----------- x 100 = 68.3%
.....82

I agree that you are within the realm of where (by my unscientific and unofficial criteria) it does not appear to be a stuck fermentation.

https://mashmadeeasy.yolasite.com/

 

[PADave]

I had the same thing happen today. A stout that finished at 1.026. I was going to bottle, but instead put it into a keg. Was afraid of making bombs if it wasn't finished. Going to let it sit for a while, see what happens.

 

[DeadGuyNick]

I agree that you are within the realm of where (by my unscientific and unofficial criteria) it does not appear to be a stuck fermentation.

Thanks, Silver_Is_Money. Finding the attenuation in my beers isn't anything I've ever done before, so this has been a good lesson!

 

[DeadGuyNick]

I had the same thing happen today. A stout that finished at 1.026. I was going to bottle, but instead put it into a keg. Was afraid of making bombs if it wasn't finished. Going to let it sit for a while, see what happens.

I'm going to do the same. I'll let it sit for a couple more days to see if anything happens. Then I was planning to keg anyways, since I'm pretty much over bottling, ha!

Now that I have it sitting for a bit longer, I might look into adding a bit of coffee to it. Maybe that will help out with the extra tiny bit of sweetness in the stout.

 

[RM-MN]

Once fermentation slows down, usually after day 4 or 5, warming the beer can often get the yeast to finish lower without giving you esters or fusels. I start my beers in the 60's and at the end of the week I bring them to the low 70's to finish up.