Wyeast 1968 stops early?

Ingredients
1

I’m on my second batch using Wyeast 1968 (London ESB). The first was a partial-extract pumpkin porter, and this one is an all-grain ESB. In each case, the fermentation completely stopped long before it should have, at about 60% attenuation, resulting in a stuck fermentation.

For the first one, OG was 1.078, and FG was 1.031, an apparent attenuation of 60%; desired FG would have been 1.024. For the ESB, OG was 1.060, and FG was 1.024, to yield an apparent attenuation of 60%; desired FG would have been in the late teens, say 1.017.

Wyeast claim an attenuation range of 67-71 for this strain, which in each case would have gotten my FG down to the desired spot.

Am I just getting unlucky? I nailed the mash on my ESB, and the pumpkin porter was extract, so I’m pretty confident in the sugar content going in…

I’ve brewed plenty of batches with other Wyeast strains (I use them almost exclusively, save for an occasional Nottingham batch), usually with 1056 and 1272 (American Ales), with a couple batches of 1084 (Irish Ale) as well, and I’ve never had problems with these less-flocculant/higher-attenuating strains.

The ESB is still in primary currently, but it has been 3 days at the same SG, so I’m pretty sure it’s done. I tried a gentle swirl of the fermenter when I first noticed fermentation had tapered off, and have done this twice since, doesn’t appear to help restart.

Should I try pitching a more-attenuative yeast onto this batch, to “finish” it? Maybe 1318 (London Ale III)? Or Nottingham? Or S-04?

2

1968 is a very flocculant yeast. You may need to rouse it a few times to keep it active and in suspension.

3

Kick the fermentor to rouse the yeast.

4

Rousing and warming it up a bit should help. 1968 is definitely a strain that benefits from warming it up a couple degrees after it’s fermented for a couple days. The small temp rise keeps the yeast more active and will prevent the stall from happening.

5

1968 drops like concrete once it starts to floc, so it does require some extra care for the best results. I use it all the time and typically get in the mid-70’s for % attenuation.

I typically swirl my fermenters daily, and I ramp up my fermentation temp as early as the 2nd or 3rd day after pitching. I also tend to pitch 002/1968 on the low side compared to most ales. Big pitches seem to work fast initially, but once it starts to form big flocs I think the yeast tends to drop too quick. And since the flocs are like chunks of clay, you can’t reliably swirl it back into suspension to wake it back up. This can give you low attenuation and diacetyl on occasion.

6

Wow, thanks for the quick replies everyone!  I’ll try rousting the yeast and bumping the ambient temp a bit (I do not have fermenter temp control yet).

Also, I usually do rack to secondary after a week, and stay in secondary for another week or more, but when I did this with my first 1968 batch, and then bottled on 8oz DME, I ended up with a very flat beer after even 2 weeks in bottles.  I’m thinking the high flocculation resulted in no (or very few) yeast in the final bottled beer, so nothing to eat my priming sugar, and thus no carbonation.  How do you all manage priming for bottling with 1968?  Or are most folks who use 1968 doing force-carbed kegging?

7

I force-carb now, but I never ran into any issues with 1968 back when I was still bottle-conditioning everything. But 2 weeks is the bare minimum for acceptable carbonation when bottle-priming under even the best conditions. I usually allow 3-4 weeks before I decide that there was an issue.

It could be that since 1968 is so flocculant that there is less yeast in suspension that makes it through to bottling, which in turn may take longer to finish carbonating. but that’s just a WAG on my part.

8

My first few batches I did as well, until I hit a batch that was WAY over-carbonated, and I’ve been gunshy ever since, trying bottles at 1 week, and every few days after.

My pumpkin stout is still bottle conditioning after 4 weeks, and is still pretty flat.  But it was a complicated little bastard of a beer, with lactose and brown sugar and tons of pumpkin and spices, 2 different LMEs and 3 different steeping grains, and not a lot of hops.  Might be it’s just a wacky beer (it is, and I’m not a huge fan, but some of my porter-loving friends dig it!)…  Might be the lactose…

We shall see how this ESB behaves, once I can get it down to an acceptable FG…

9

I use 002 (White Labs equivalent) as my house yeast, and get 75-85% attenuation with it.  Like Eric above, I don’t pitch the “correct amount”, so maybe that’s why I haven’t had problems?  Also, I usually leave it for three weeks before bottling, and it’s usually about a month in the bottle before both carbonation and taste seem right.
Good luck!