fix stuck ferm by transferring onto another yeast cake?

Ingredients
1

[crossposted from another forum where it did not get any response…]

Hello,

Got a question that I hope I will not need an answer to, but figured I’d ask it, get some responses, and be ready to act if I need to:

I made a 10 gal batch of 1.054 Budvar clone (Czech Pils) and as usual with my 10 gal batches, split it into two fermenters to fit in my fridge. I pitched two 11g packs of S-189 dry Swiss lager yeast into each fermenter (I did not rehydrate it, but I’ve been using US-05 in this way for a while and never had problems.) I pitched at 52F, and aerated with a mixstir after pitching. I usually go for 4 minutes in each fermenter, with my cordless drill on HI to get a good vortex going. Here is where the problem came in. While aerating the 2nd fermenter, the battery started dying and I just kind of let it run out, therefore aerating the 2nd fermenter only about 90 seconds, maybe 2 minutes max. I figured it would be OK.

Anyways, after 8 days of fermentation at 52F, the second fermenter has clearly been lagging, at least judging by airlock activity. I checked the gravity and the 1st fermenter was down to 1.032 but the second is only 1.042. Today, after 10 days fermenting, the 1st ferm is still bubbling away and the 2nd one is just dead.

So here is the question: assuming, after I let them both ferment another week or so in primary, and assuming that the one fermenter is down to where I want my FG (maybe 1.012-1.014) and the bad batch is stuck around 1.020 or 1.025 or even higher, can I do the following: rack the good beer into a secondary for lagering, and rack the stuck beer onto the good yeast cake left from the first?

I don’t want to get into adding Beano, or making a big starter (I don’t have any liquid yeast on hand). But I thought this might be a good way of firing up the second batch again: I know there will be fermentables in there, because the wort was the same in both fermenters, in fact everything is identical except the “bad” fermenter was not aerated nearly as much as the “good” one.

The other thing I thought of was just blending the two batches at kegging time. Of course I’ll wait a week and see what develops, but I thought I’d toss the question out and solicit some answers.

Enjoy the holiday weekend!

2

Yeah, that would be worth a try once you determine that corrective action is actually needed.

3

As long as you have sufficient residual sugars for the yeast that IMHO would be the best way to go.  If you question the amount of sugars left just add a cup of sugar and you should be good to go.

Fred

4

Is there the possibility of maybe mixing the batch now? Transfer the good one to two fermenters, then top them off with the slow batch…

This way the yeast would not be dormant in the good batch you have now such as it will if you were to let it completely ferment out… You will want good healthy active yeast.

5

I could mix them now… but why would the yeast in the good batch be dormant when it’s done fermenting?  People often repitch just a cup or so of slurry from a completed fermentation into a new beer…  why is this case any different?

6

True, but you are not putting a new beer on that yeast, you are putting partially fermented beer, with a good percentage of alcohol my friend… If at all possible, you might want some very active yeast to finish what remaining sugars you might have…

7

In that case, though, you also aerate to promote yeast growth.  In this case, you don’t want to do that so you need to pitch enough yeast that growth won’t be an issue.  The general recommendation to try to restart a stuck fermentation is to use a qt. of slurry.

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Use more if you can,  LOTS of healthy active yeaast.  My prefered source is a growler FULL of yeast from the active tank at your friendly neighborhood brewpub.  That’s for 5 gallons of beer.

True “Stuck” fermentations are not something to be trying half-measures with.

Fred

9

Thanks for the advice and tips, esp Denny and Fred. I usually have well over a quart, closer to half a gallon, of slurry in the bottom of my fermenters. So I will check my gravities at 14 days, and if everything works out as I suspect it will, I’ll rack my “good beer” to a carboy for lagering, swirl up the yeast in it, and dump it into my stuck fermenter, and hope it kicks off again. Sound reasonable?

10

Go for it

let us know how it goes

Fred

11

OK, what I learned is that RDWHAHB is good advice. I took gravity readings yesterday (at 14 days) and the “good” fermenter was down to 1.011, and the “stuck” fermenter was down to 1.015.  All airlock activity had ceased on both fermenters at 12 days. So after a 24hr diacetyl rest at 60F, today I blended them 50/50 and transferred to carboys to lager. Should get a beer around 1.013, or lower.

Another question: I got 6 cups of nice yeast slurry off this, this is S-189. I want to do a Negra Modelo clone soon - would this yeast be in style for that, or not?