Stuck Fermentation?

[Lancer X]

We recently made a Russian imperial stout. OG was 1.093, and Beersmith 2 predicted a ABV of 9.2%.

Yeast is Wyeast 1084 Irish Ale. I had made a 2-liter starter on a stirplate (started from one Wyeast smack pack), and it had almost 48 hours to work before we brewed. So, according to Beersmith, our starting pitching rate / cell count (378 billion) should have been sufficient.

Beer was in the primary for about 7 weeks (I know, a little longer than it should have been). Fermentation temp was 68-70F. We just transferred to secondary last night, and measured a gravity of 1.038. Percent alcohol calculator shows us currently at 7.3% ABV, and we'd need to get to about 1.025 to make our ~9.0% ABV goal.

So, if we're only at 7.3% after 8 weeks, does that mean the fermentation stopped? Or will this thing continue working over the coming months? We're at about 70-72F now.

We haven't made many beers this big, so I'm not very confident here. Would really appreciate any advice / info - thanks!

[PorkSlapper]

I think I would put that Imp Stout in the back of the cooler/closet and let it sit for some decent amount of time before you worry about it. I believe that the first time I did an imp. stout it sat in secondary for about 90 days, then after bottling it sat around for about 6 months. I would let it continue to sit in the secondary for a few weeks and take another gravity reading to see if you are getting closer to your 1.025.

-Pork

[Ozwald]

We recently made a Russian imperial stout. OG was 1.093, and Beersmith 2 predicted a ABV of 9.2%.

Yeast is Wyeast 1084 Irish Ale. I had made a 2-liter starter on a stirplate (started from one Wyeast smack pack), and it had almost 48 hours to work before we brewed. So, according to Beersmith, our starting pitching rate / cell count (378 billion) should have been sufficient.

Beer was in the primary for about 7 weeks (I know, a little longer than it should have been). Fermentation temp was 68-70F. We just transferred to secondary last night, and measured a gravity of 1.038. Percent alcohol calculator shows us currently at 7.3% ABV, and we'd need to get to about 1.025 to make our ~9.0% ABV goal.

So, if we're only at 7.3% after 8 weeks, does that mean the fermentation stopped? Or will this thing continue working over the coming months? We're at about 70-72F now.

We haven't made many beers this big, so I'm not very confident here. Would really appreciate any advice / info - thanks!

First off, I wouldn't put too much faith in predicted ABV. From the numbers & assuming this was a 5 gallon batch by your predicted cell count, I would say first of all, your starter was not sufficient & I would highly doubt you got much over 300B cells. I would have let the starter finish out, decant & stepped it up one more time. My rough math sans calculator comes out a little closer to 375-400B cells. That will cause a slower ferment. Don't judge it by the number of weeks, take multiple gravity samples & see what it's actually doing. Beer works on it's own time. Trust me, I bought my little conical a watch & it still can't read the damn thing.

Secondly, my experience with Irish strains is that they work fairly slow & without additional nutrient they like to crap out early. That strain under good conditions & a lower gravity will get you in the low 70's %ADF. That's where BS2 is getting it's 1.025. 71-72%ADF, again I'm not using a calculator, so I might be a point or two off in either direction. With the huge gravity & pitching a little low, you might not see that. You're currently at 58-60%ADF. With only one sample, you don't know if it's still creeping along or not. You also made no mention if you aerated or not, nor the method you used if you did. Big beers need it a lot more.

Keep it at your current temp, take another gravity reading in about a week to see if it's still changing. Irish strains can be diacetyl bombs, so the extended warm rest will be good for it anyhow. Between now & then, the best thing you can do is take notes & learn as much as you can from this beer. Pitch a bit more than BS2 suggests, give it plenty of O2 and add staggered nutrients. I would definitely consider a different strain for the style. For this batch, you'll probably create more problems messing with it than if you just leave it alone & monitor it closely. I'm guessing you'll find that you'll get a few more points out of it, but I don't think you're going to see 1.025. High 20's is my prediction given the information you provided.

[BeaverBarber]

...after 8 weeks, does that mean the fermentation stopped?

Yes. It's over. I can see a way to rescue the situation though, but I don't know how bad you want it. In order to rescue that beer, you need to add yeast that has completed the lag and growth stages and is in the process of fermenting. You could make a starter and when it is at high krausen you could add it to the wort, but for a starter of the size that you need, you'll likely need another beer. So you could maybe make a second batch of beer that you wouldn't mind going into your stout, and when that beer is at high krausen, you could remove about a gallon and add it to the stuck beer. This should be plenty of yeast and the yeast has completed their growth stage and they are actively fermenting the wort. If there are fermentable sugars in the stalled wort this yeast should take care of them.

[EagleDude]

Take a sample of the beer and see how sweet it tastes ... 1.038 probably going to taste too sweet. As others mentioned, add some active yeast that can handle higher alcohol. The Irish esters are already there so don't worry about just using the Irish yeast with this beer ... perhaps SD super strain? I would probably also make very small sugar additions over several days once the new yeast is added to keep it going, drive up the alcohol, and help force it to dry out.

If the beer tastes good but is just too sweet, it is also an opportunity to pitch a brett strain and let it sit for an extended period.

[spiderwrangler]

I'd worry that adding small sugar additions may result in yeast preferentially feeding on that and not touching the remaining sugars in the beer itself. Before getting into adding anything or mucking about with it too much, taking a second data point to see if it is still moving down or not would be good in deciding your next course of action.

[Stinkfist]

Not positive it was the best idea but I brewed up a Belgian quad and it got stuck at 1.020(should be closer to 1.012), so after a week or two with no change sitting at 75f I decided I needed to do something so I bought 2 11gam packets of S-33 and rehydrated and pitched directly into the beer, was fermenting again within a few hours... It was still going last I checked but I haven't done a gravity check yet but it should have done the trick..

[Ozwald]

taking a second data point to see if it is still moving

Exactly.

One data point doesn't tell you if it's finished or not. You only know where it's at, at that specific moment in time. Basic physics. Comparing two data points will tell you what it's actually doing. The reason I suggested separating the measurements by a week is because if it is in fact still fermenting (very likely in my opinion) it will be moving very, very slowly. Without a calibrated lab grade hydrometer that measures in a very narrow range, you won't likely see that change over the course of a day or two. Big beers take time. Assuming that it's done solely based on the fact that it's been 8 weeks is a very stupid & inexperienced assumption (not yours, Lancer) & using desperate measures, such as krausening it with another beer without knowing what's actually going on is extremely poor advice. Get your data points first. I would also go against basing it on the perceived sweetness on something this large. A perfectly fermented beer that started at 1.093 is going to taste too sweet out of the fermenter. So is an under attenuated fermentation. The carbonic acid is going to bring it around, but without experience with this big of a beer, that is going to be very difficult to predict accurately before you carbonate it. Patience is key. And lots of notes so you nail the next one without breaking a sweat & win a couple of medals with it.