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Hey,

So I brewed an Oatmeal Stout on Sunday and I think I have a stuck fermentation. And I need advice on what to do next. there's been no activity in the airlock for the past 24 hours, so I took the gravity this evening and as expected, it's about 6-8 points high. Here are the stats:

OG: 1.058
Yeast: 1 litre starter of Wyeast 1084 (Irish Ale)
Fermenting temp: constant 21C
Gravity now: 1.020 (I was aiming for 1.012-1.014)
Apparent attenuation: 64%

I pitched the yeast Sunday evening and it fermented nicely for just a day, then just stopped. The starter was in good shape when I pitched it, and I used the same equipment and method that I've always used. I mashed at 151F and the temp was 149F at the end.

What should I do? give it a good stir? Re-Pitch? Leave it?

Thanks

So it was brewed this past Sunday? I'd be patient and leave it. It's only been a couple of days. There could still be lots going on even though there's no airlock activity.

I'd say you might need some amalyse. I stopped using 1084 because it was a bad fermenter.

try stirring up the yeast to get some of it back into suspension, then leave it for another couple of day and check it again.

jeffsmith wrote:So it was brewed this past Sunday? I'd be patient and leave it. It's only been a couple of days. There could still be lots going on even though there's no airlock activity.

+1... nothing wrong with rousing the yeast a bit, as mentioned, also.

What was your recipe? Were there a lot of specialty malts or other unfermentables?

Type: All Grain
Date: 10/21/2012
Batch Size: 38.00 L
Boil Size: 46.60 L
Boil Time: 60 min
Brewhouse Efficiency: 73.00

Ingredients

Amount Item Type % or IBU
15.00 lb - Pale Malt (2 Row) - 64.77 %
2.00 lb - Black (Patent) Malt - 8.64 %
2.00 lb - Oats, Flaked - 8.64 %
1.50 lb - Caramel/Crystal Malt - 6.48 %
1.00 lb - Chocolate Malt - 4.32 %
1.00 lb - Victory Malt - 4.32 %
0.66 lb - Roasted Barley - 2.85 %
1.00 oz - Fuggles - 6.9 IBU
1.00 oz - Bramling Cross - 8.6 IBU
1.00 oz - Fuggles - 6.6 IBU
1 Litre Starter of Irish Ale (Wyeast Labs #1084) Yeast-Ale

Beer Profile

Est Original Gravity: 1.058 SG
Measured Original Gravity: 1.058 SG
Est Final Gravity: 1.014 SG
Measured Final Gravity: 1.020 SG
Estimated Alcohol by Vol: 5.61 % Actual Alcohol by Vol: 4.96 %
Bitterness: 22.1 IBU
Est Color: 50.9 SRM

Mash temp?

Three days is not very long, definitely give it more time. Stirring it up can't hurt it too much, sometimes I just pick the carboy up and take it on a walk up and down the hallway, then put it down (just don't rack it too a keg, as I learned the hard way). That does the trick, without too much risk of breaking the CO2 layer.

A one litre starter was pretty small on a 10 gallon batch. I still say AA is what's needed.

Sorry, it was a 2 litre starter, but I split the batch with a friend so I'm only speaking about my 5 gallons when I mentioned the 1 litre starter. I've asked him to check his gravity tonight to see how his half is doing.

We mixed in the yeast prior to the split so they should be at the same point. And if not then it points to temperature or another variable that's specific to my batch.

Do you mean you made a 2 L starter and then mixed it in 10 gallons, and then split the wort into two 5 gallon batches?

You'd need to do a 5.75 L starter for a 10 gallon beer at 1.058, according to mrmalty.com. A 1 L starter for 5 gallons would be fine, but when you increase the volume of the batch (or the OG), the inoculation rate changes, so 2 L isn't enough to get you the yeast count you need for 10 gallons.

Again, time may be all it needs, but I wouldn't be surprised if underpitching is an issue here.

I should clarify...

A 10 gallon batch of 1.058 wort would require about 400 billion yeast cells to ferment well.

A 1 L starter (assuming 100% viability in the smackpack, say manufactured today) would give you about 200 billion yeast cells.

A 2 L starter gives you 250 billion yeast cells... not 400, or even 300, as you may originally think. That's because of the inoculation rate for increasing starter volumes.

Dave,

Update on the other 5 gal batch: My basement is 15-16C so I put the beer belt on when I got back from your place on Sunday night, it has stayed at 24-25C since that time. I checked on the beer Monday evening, the airlock was full of stout and the lid of my bucket was a mess, so my 5 gal was very active in the first 24 hours. I cleaned it up and it has been relaxed since that time, almost no activity this evening. I just took the SG at 1.013, I will probably transfer it to the carboy tomorrow or perhaps Friday night. It seems very strange that my 5 gal batch basically exploded in the first 24 hours and yours did not take off.

The Tankhouse Ale Clone we did on Sunday was also on the beer belt since Sunday evening and it started up exactly as planned, it is still chugging along this evening.

- Greg

LiverDance wrote:try stirring up the yeast to get some of it back into suspension, then leave it for another couple of day and check it again.

Did it, the air lock hasn't moved in the 14 hours since (the inside piece is still resting on the tube, so I know there hasn't been much CO2 produced)

Graham.C wrote:Mash temp?

151F

berley wrote:Do you mean you made a 2 L starter and then mixed it in 10 gallons, and then split the wort into two 5 gallon batches?

Yes

chicanuck wrote:I just took the SG at 1.013, I will probably transfer it to the carboy tomorrow or perhaps Friday night. It seems very strange that my 5 gal batch basically exploded in the first 24 hours and yours did not take off.

Agreed.

Fishdisease wrote:

berley wrote:Do you mean you made a 2 L starter and then mixed it in 10 gallons, and then split the wort into two 5 gallon batches?

Yes

Was it mixed well? If not, he could have gotten the lion's share of the yeast.

Also, it looks like his fermentation temps were on the high side and that would effect the vigorosity of his fermentation.

RubberToe wrote:Was it mixed well? If not, he could have gotten the lion's share of the yeast.

Also, it looks like his fermentation temps were on the high side and that would effect the vigorosity of his fermentation.

Mixed very well, I agree that temperature was the main variable here.

So I can either add amylase or re-inoculate

Amylase seems easier...but I don't have any....

I might have some....