My beer started fermenting again.

[johnrm]

I put on a Stout a few (3?) weeks go with US05 yeast.
Activity was slow to start, but took off with a light krausen which subsided after a week.
Still sitting on the yeast in Primary, I noticed activity again about 3 days ago.
The new activity has produced a very thin Krausen with airlock activity.
Infection? I don't think so, I have been meticulous.

I have found a number of reasons why this might be happening...
Change in air pressure.
Solution releasing CO2.
Change in Temperature.
Yeast has reacted to change in Temp and has found sugars to work on.

I may have underpitched initially as the yeast was from trub, and I could not for the life of me see the separation beween Yeast and trub when washing.

Has anone else had fermentation taking off again?

I will take a Gravity reading, sample, smell and taste this evening.

[irish_goat]

Have you a photo of the new krausen?

[Cathal O D]

What was the OG?
I had a high gravity stout that stopped and started again a few days later. It tasted fine. I think high gravity beers can do funny things. It was irish ale yeast though

[DEMPSEY]

Infection is the first thing I though of as well. Lets hope not but keep us posted as regards its journey.

[Eoin]

Temperature has taken an upwards swing recently, I call temps.

Sent using a complex system of semaphore and ninjas.

[Tom]

Temp is my first guess.

As temperature increases, the amount of dissolved carbon dioxide that the beer can support decreases, so CO2 would come out of solution and bubble to the surface. This will look like krausen, and act like krausen

You might find it happens if you lager in demijohns in the fridge. As it warms back up it will release the carbon dioxide that is stored there. It can only go back into solution if the beer gets cooled down and the CO2 couldn't leave the vessel.

[johnrm]

I need to check my recipe for the OG, but It smells perfect and tastes good.
I can just about see yeast activity, so I'm thinking they've woken up for seconds!
I need to get a wee bit of carb into it and serve it through a handpump.

OG 1050
Gravity is currently 1012


BeerSmith 2 Recipe Printout - http://www.beersmith.com
Recipe: The Dark #27
Brewer: John Mangan
Asst Brewer:
Style: Dry Stout
TYPE: All Grain
Taste: (30.0)

Recipe Specifications
--------------------------
Boil Size: 28.04 l
Post Boil Volume: 26.00 l
Batch Size (fermenter): 23.00 l   
Bottling Volume: 21.49 l
Estimated OG: 1.047 SG
Estimated Color: 66.9 EBC
Estimated IBU: 39.1 IBUs
Brewhouse Efficiency: 75.00 %
Est Mash Efficiency: 81.5 %
Boil Time: 60 Minutes

Ingredients:
------------
Amt                   Name                                     Type          #        %/IBU         
2.050 kg              Pale Malt (2 Row) UK (5.9 EBC)           Grain         1        40.7 %       
0.900 kg              Stout Malt (5.9 EBC)                     Grain         2        17.9 %       
0.450 kg              Roasted Barley (591.0 EBC)               Grain         3        8.9 %         
0.301 kg              Barley, Flaked (3.3 EBC)                 Grain         4        6.0 %         
0.300 kg              Brown Malt (430.0 EBC)                   Grain         5        6.0 %         
0.284 kg              Caramunich Malt (110.3 EBC)              Grain         6        5.6 %         
0.257 kg              Golden Naked Oats (11.0 EBC)             Grain         7        5.1 %         
0.250 kg              Aromatic Malt (60.0 EBC)                 Grain         8        5.0 %         
0.147 kg              Wheat, Torrified (3.3 EBC)               Grain         9        2.9 %         
0.100 kg              Black Barley (Stout) (985.0 EBC)         Grain         10       2.0 %         
20.00 g               Bramling Cross [6.00 %] - First Wort 60. Hop           11       13.1 IBUs     
40.00 g               Bramling Cross [6.00 %] - Boil 60.0 min  Hop           12       23.8 IBUs     
0.30 tsp              Irish Moss (Boil 10.0 mins)              Fining        13       -             
10.00 g               Bramling Cross [6.00 %] - Boil 10.0 min  Hop           14       2.2 IBUs     
1.0 pkg               Safale American  (DCL/Fermentis #US-05)  Yeast         15       -             


Mash Schedule: Single Infusion, Full Body
Total Grain Weight: 5.039 kg
----------------------------
Name              Description                        Step Temperat Step Time     
Mash In           Add 14.34 l of water at 76.3 C     68.9 C        45 min       
Mash Out          Add 5.26 l of water at 96.8 C      75.6 C        10 min       

Sparge: Fly sparge with 14.69 l water at 75.6 C
Notes:
------