Split beer into 2 fermenters - 50% didn't ferment

[notStan]

Hey guys,
I'll try to keep this as short as possible. I normally brew 40-50L batches (a bit over 10 gal). I didn't have enough large fermentation containers as 3 other beers were already fermenting. I decided to use 2 smaller containers to ferment the beer.
These were the steps I took:
0. Created a yeast starter a day in advance on a magnetic stirrer.
1. I brewed an all grain beer, and cooled it to desired fermentation temp.
2. I simply split the beer over the 2 containers 50/50. (about 19L each). The SG and the temp of both containers was the same.
3. I put the stirrer for the yeast starter on 100% for a short period of time to ensure that the yeast would be spread across the liquid in the flask.
4. Took the yeast starter from the stirrer and within 15 seconds poured half into 1 container and the other half into the next.

After about 5 hours, one container started fermenting, and the other didn't ferment at all. I have now bought an extra container and combined the batch again, introducing a lot of oxygen - not ideal!
I'm wondering what possible reasons were for this to happen? And if anyone has got experience with fermenting in more than 1 container.

 

[VikeMan]

How long did you wait before recombining the batch? And how did you decide that the wort in one of the fermenters was not fermenting?

Did this happen to be a fast floccing clumpy yeast strain like Wyeast 1962/WLP002? If so, 15 seconds would be more than enough time for most of the yeast to fall to the bottom of your starter container. I could well imagine one of the fermenters getting a lot more yeast than the other, and thus having visible signs of fermentation sooner.

 

[str1p3s]

It's probably more likely that one container had a leak. Did you check both batches with a hydrometer?

 

[notStan]

How long did you wait before recombining the batch? And how did you decide that the wort in one of the fermenters was not fermenting?

I waited exactly 1 week before combining the batches. I concluded one wasn't fermenting because the airlock wasn't bubbling, something which has never happened to me before.

Did this happen to be a fast floccing clumpy yeast strain like Wyeast 1962/WLP002? If so, 15 seconds would be more than enough time for most of the yeast to fall to the bottom of your starter container. I could well imagine one of the fermenters getting a lot more yeast than the other, and thus having visible signs of fermentation sooner.

I used Wyeast 3787 trappist high gravity yeast. Actually this could be the reason of the process failing.

It's probably more likely that one container had a leak. Did you check both batches with a hydrometer?

Unfortunately I didn't check both batches with a hydrometer. If this ever happens again, I will totally do that, thanks for your comments.

 

[TheMadKing]

It's probably more likely that one container had a leak. Did you check both batches with a hydrometer?

This.. It fermented, you just had a leak so no bubbles

 

[VikeMan]

I used Wyeast 3787 trappist high gravity yeast. Actually this could be the reason of the process failing.

3787 isn't a clumpy strain (i.e. wouldn't fall to the bottom of your starter in 15 seconds), so I don't think it would explain a split starter with big cell count differences. As mentioned, lack of bubbles isn't a good indicator of fermentation inactivity.

 

[TheMadKing]

Can you check the gravity now with a hydrometer?

If half of it didn't ferment your gravity should be about halfway between your OG and your expected FG and your apparent attenuation would be in the 35% ballpark