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Another Stuck Fermentation Topic

Instead of highjacking the “add more yeast” thread, I’ve decided my situation is different enough to justify it’s own topic. I brewed an all grain, sweet stout about 12 days ago. I was lazy and didn’t make a starter for my Wyeast 1084. This is the first time I didn’t make a starter in a few years, and it will be the last. I received the yeast from NB during a particularly hot week, but pretty good inflation of the pouch, so I skipped the starter. I mashed at about 154* and hit my OG of 1.060 dead on. I aerated the wort for about 10 minutes or so(the foam fro aeration was beginning to creep up the neck of the carboy) and the temp was below 75* when I pitched. Fermentation began very slow, taking almost 48 hours before there was an inch of kreusen. At that time there was solid airlock activity, but that, and the kreusen, only lasted about a day.

Normally I have great fermentations that end quickly because I have strong yeast from a stater, nutrient in a well aerated wort. I checked the gravity on the fourth day out of curiosity and it was only 1.032. I decided to let it go a full week, figuring it would slowly fall. It didn’t, it was still 1.032. At this point I agitated the carboy to get the yeast back in suspension. Waiting another few days I measured again. 1.032. At this point grabbed some dry yeast I keep on hand, hydrated it, and pitch it. Nothing. The yeast is kid of old, but has been refrigerated the entire time, and showed moderate signs of life when I stirred it up. I tried agitating one more time, swirling strong enough to get the whole yeast cake in suspension, without splashing. Today it’s still at 1.032, where it’s been for the past week.

I’m at a loss guys, any ideas other than throwing in the vanilla beans and cacao and kegging it? My recipe is below. Thanks.

7 lbs Pale Malt, Maris Otter (3.0 SRM) Grain 1 63.6 %
1 lbs Carafa III (525.0 SRM) Grain 2 9.1 %
1 lbs Chocolate Wheat Malt (400.0 SRM) Grain 3 9.1 %
1 lbs Oats, Flaked (1.0 SRM) Grain 4 9.1 %
1 lbs Milk Sugar (Lactose) (0.0 SRM) Sugar 5 9.1 %
2.00 oz Goldings, East Kent [5.80 %] - Boil 60.0 min Hop 6 40.9 IBUs
1.0 pkg Irish Ale (Wyeast Labs #1084) [124.21 ml] Yeast 7 -
4.00 oz Cacao Nibs (Secondary 14.0 days) Spice 8 -
2.00 Items Vanilla Bean (Secondary 14.0 days) Spice 9 -

I’m guessing you have a lot of unfermentables that add weight and body but the yeast won’t eat. The Lactose and Oats for sure, the Carafa and probably the wheat malt are all going to be unfermentable.

I’m not an expert on the brew math, but if you assume that those don’t ferment at all (and some 75% attenuation of the Maris Otter), then what sort of FG would you end up with? Can you calculate the gravity contribution from just the unfermentables, and then add in a calculation on the MO? At 1.032 I’ll bet it is done.

Well, Beersmith, which I understand isn’t perfect, is telling me my FG should be 1.014. That does seem a bit low, but I’m typically within a few points of BS estimates. I’ve brewed a similar recipe before and the FG wasn’t even close to 1.032. I don’t recall ever having one higher than 1.022.

What did you measure the OG and FG with? I had issues using a refractometer post ferment before I knew they weren’t really accurate once alcohol was present. Any chance you used one for the FG measurement?
Assuming 1.032 is accurate that is definitely way high even for a brew with more unfermentables. Your 10 minutes of aeration, how was that done? I’m thinking if it was under oxygenated and underpitched, you may simply have gotten too little yeast growth to ferment properly. Adding dry yeast with no additional oxygen would probably not help if I am correct. You may have to aerate again, or get a well aerated starter going and pictch it at high kruesen…

^This is my best advice although I just read something (I think in BYO) that said not to aerate again. Get a yeast with a higher attenuation than the one you used. I’ve heard of people using champagne yeast or the high gravity yeast but that sometimes they ferment way too low with that stuff. There is a French Saison yeast that Wyeast says is good for restarting stuck fermentations although I’ve never used it or actually heard of people doing it. You could look it up on their website.

The program has no idea what your FG should be…it makes a WAG based on the attenuation rating of the yeast. That’s only for comparing one yeast to another, not to predict what you’ll get. The wort fermentability determines that. Beersmith doesn’t take into consideration the unfermentables. I agree that that’s the issue here.

Thank you everyone for the replies. Denny, just to clarify, you think I have enough unfermentables to have a final gravity at 1.032 and ABV under 4%? To be honest, my samples taste fine, so that may be the case. Or is it worth tracking down some fresh yeast, aerating a starter and pitching?

To answer another question, I’m using calibrated hydrometers. I’ve retired my refractometer for the time being.

[quote=“novabulldog”]Thank you everyone for the replies. Denny, just to clarify, you think I have enough unfermentables to have a final gravity at 1.032 and ABV under 4%? To be honest, my samples taste fine, so that may be the case. Or is it worth tracking down some fresh yeast, aerating a starter and pitching?

To answer another question, I’m using calibrated hydrometers. I’ve retired my refractometer for the time being.[/quote]

I think it’s very possible, but not a given. You can certainly try more yeast, but remember that it takes a LOT of yeast to restart a fermentation. Like a qt. of fresh slurry. And 12 days isn’t very long. I’d give it at least another week before doing anything other than checking the gravity. I’ve riuned too many batches trying to “save” them.

I put in the four ingredients (Lactose, Carafa III, Chocolate Wheat, and the Oats) into Hopville’s beer calculus, and it calculates an OG of 1.022. Definitely lactose is not fermentable, so I bet a lot of the calculators are not going to get these right if all they do is calculate the O.G. and then assume 73% attenuation on the whole thing.

If you then run the calculations on the Maris Otter alone, you’d have an OG of 1.039 and estimated FG of 1.010 (73% attenuation).

Treating them separately:
O.G. Maris Otter 1.039 + unfermentables: 1.022 = 1.061 (est’d).
F.G. Maris Otter 1.010 + unfermentables: 1.022 = 1.032 which is what you’re getting.

With the lactose I would definitely expect to see a higher FG than you’re used to.

The most important thing to me is how do the gravity samples taste? In the end we’re shooting for a flavor, not a number. If it tastes fine, then the FG number doesn’t mean much.

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