Help! Big imperial stout fermentation stuck at 1.09!

[73standard]

I am making a big, big imperial stout and the fermentation is really giving me trouble. The gravity has only gone from 1.13 to 1.09 and now it's been stuck for the last week.

----HERE ARE THE DETAILS----

HERE'S WHAT WAS IN THE BOIL:

5 gal spring water
16 lb light malt extract for 60 minutes
hops - 5 oz of various hops at various times
2/3 stick brewer's licorice for 30 minutes
2 oz cocoa nibs at end of boil, steeped while cooling

HERE'S WHAT WENT INTO THE FERMENTER:

1. Wort: SG 1.135. Oxygenated with pure O2 for 30-60 seconds before pitching yeast.

2. Yeast starter: 3/4 gallon starter with one vial of White Labs super high gravity yeast (WLP099), let it ferment to completion, refrigerated, and decanted the liquid. Then I warmed the yeast slurry slowly over a few hours during the whole boiling process and introduced it to the wort by getting some room temperature wort into the starter, swirling it around, then pitching it. I pitched it at 70-75°F. This was all at the advice of my LHBS.

3. Fermaid K yeast nutrient. It was a tiny amount. If it's important, I can look it up.

HERE'S WHAT HAS HAPPENED IN THE FERMENTER:

Vigorous fermentation started in < 7 hours. I don't know how quickly exactly because I pitched the starter before bed and when I woke up it was going nuts. But after 5-7 days, it has slowed and stopped at a gravity of 1.09. It has held 1.09 for the past week.

After 2 weeks in the fermenter I added 2 packets of US-05 and gave it 30 more seconds of pure O2 before adding the yeast. My LHBS suggested that this wouldn't be an oxidation issue since the fermentation is nowhere near completion.

2 days later there is no new activity. What should I do? Could it be a pH issue?

I've brewed several beers at SG 1.100 but this is my first venture much above 1.100.

 

[Cyclman]

Is your ferm temp in the yeast's range? Did you use a stirplated starter, if no, you may have pitched too low.

I would do a large stirred starter, pitch it at high kraeusen, keep it at the top end of the yeast temp range, and see what happens.

 

[peterj]

Are you taking the readings with a refractometer or a hydrometer?

 

[73standard]

I'm taking the readings with a hydrometer. I just bought a thief too to make it quicker and easier.

My room temp for the last few weeks has been 70-74°F, which seems like it shouldn't hinder yeast activity, right?

 

[73standard]

Is there any chance something in the wort is making the environment bad for the yeast? Has anyone ever seen pH be an issue?

My starter was made by frequently shaking it.

I remember now that the starter smelled sour when it was done. Is that strange? Never done a starter before.

 

[FatDragon]

Is there any chance something in the wort is making the environment bad for the yeast? Has anyone ever seen pH be an issue?

My starter was made by frequently shaking it.

I remember now that the starter smelled sour when it was done. Is that strange? Never done a starter before.

The sour smell should be the CO2 in the headspace of the starter, or that's my experience with taking a whiff off the top of my fermenters at least. Did you steep some dark grains for color, or is it just dark from carmelizing 16lb of extract in a 60 minute boil? I believe that carmelization (some certainly occurred in a 60 minute boil with that much extract) would make your wort less fermentable, but 1.090 is almost certainly a stuck fermentation regardless of how much carmelization occurred.

 

[73standard]

The sour smell should be the CO2 in the headspace of the starter, or that's my experience with taking a whiff off the top of my fermenters at least. Did you steep some dark grains for color, or is it just dark from carmelizing 16lb of extract in a 60 minute boil? I believe that carmelization (some certainly occurred in a 60 minute boil with that much extract) would make your wort less fermentable, but 1.090 is almost certainly a stuck fermentation regardless of how much carmelization occurred.

I did have a few pounds of grains that were steeped in the beginning.

Here's another thing that was different about this batch: I tried to boil all 5 gallons but I had to do it in 2 separate pots. It turns out that my stovetop can't boil 2 2.5 gallon brews at once so I had 1 at a rolling boil and the other nearly boiling for an hour. Then when the first one had done its time I switched the other to the good burner and added the malt extract to it (1/2 the total batch amount). Is there anything wrong with keeping 2.5 gallons of grain flavored water very near boiling for an hour (grains removed) before actually boiling it and adding the fermentables?

I may take another user's advice on here and try to make another big starter. What is your recommendation for volume, yeast type, and amount of yeast?

 

[73standard]

Here is the advice from my LHBS:

1. Dilute it with 1 gallon of water to reduce the gravity and make it easier for the yeast to do their job.

2. Make another starter and pitch at high krausen

3. Move it and the yeast to another fermenter. He said some times that can get it active again.

What do you guys think about those? Someone has already recommended another starter pitched at high krausen, which sounds like a good idea to me. What about diluting it? That wouldn't cost me anything up front and also sounds reasonable. I assume I could build it up step-by-step once it's active again and closer to the finish, right?

 

[FatDragon]

2 and 3 sound better than 1. The RIS I have bottled was at 1.025 after a month in primary and I figured it was done based on the amount of roasted malts and the lack of visible fermentation signs for a couple weeks, so I put it in my carboy for a 3-4 month secondary. By the time I bottled, it had dropped to 1.013.

Another idea would be to simply swirl the fermenter a bit to get the yeast back into suspension and raise the temp by a couple degrees to wake them up. That's a common first step for dealing with stuck fermentation.

 

[MrKrinkle151]

The sour smell should be the CO2 in the headspace of the starter, or that's my experience with taking a whiff off the top of my fermenters at least. Did you steep some dark grains for color, or is it just dark from carmelizing 16lb of extract in a 60 minute boil? I believe that carmelization (some certainly occurred in a 60 minute boil with that much extract) would make your wort less fermentable, but 1.090 is almost certainly a stuck fermentation regardless of how much carmelization occurred.

Caramelization shouldn't be happening at boil temps. Maillard reactions, yes, but not caramelization.

 

[dcp27]

WLP099 is a real resource hog so I don't recommend using it as a primary strain, but its such a beast it should have still got you further than that. I'd either make another starter and pitch at high krausen or rack it onto another beers cake. however, before you do anything, make sure u have a way to ferment it colder than you are. a 1.135 OG beer fermented at 70-75F ambient is going to be undrinkable from all of the fusels.
if nothing else works, you can always resort to brettanomyces. won't be the same beer, but it'll certainly get you lower

 

[73standard]

I'm learning a lot about what I should have done with this batch. The guy at the LHBS that recommended the method and yeast I used maybe hadn't had direct experience with it.

 

[73standard]

I swirled it a bit and raised the temperature a couple of degrees and now it seems it's more active. In the last 2 days it's gone from 1.09-1.08-ish to 1.07. The bubbles in the lock are on average about a minute apart. It still tastes way too sweet but I can tell that if it would finish properly it would be pretty great.

I was thinking of taking another reading in a couple of days then if it's not down to 1.06-1.05 I will make another beer and rack this one on the new beer's yeast when it's done. I was thinking I would repeat one of my barleywines that I've made a few times before that I know are less ambitious than this one and have all finished well.

 

[73standard]

Well, I thought I would try the cheaper and quicker things first so I made a 2L starter of WLP099 and it seems to be fermenting now. I didn't add all the stuck wort in at once but it's happily eating it.

With all this taking gravity readings and messing with it, I still don't notice any off flavors developing (knock on wood).

 

[73standard]

Forgot to update sooner but the beer ended up at 1.025. It was stuck at 1.09.

What I did was made the 2L starter of WLP099 then fed it 1L of my stuck beer whenever activity seemed to slow just a little in the new starter fermenter. That turned out to be every few days. When it got too big for the small fermenter I was using for the starter I transferred the contents to my carboy then started feeding it a gallon at a time. It worked very nicely. It didn't carbonate well in the bottles but it tastes really good. I'll look for a way to force carbonate what's left.